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Journal of Stored Products Research 59 (2014) 158e166

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Journal of Stored Products Research

journal homepage: www.elsevier .com/locate/ jspr

End-use quality characteristics of hermetically stored paddy

B.D. Rohitha Prasantha a, *, R.F. Hafeel b, K.M.S. Wimalasiri a, U.P.D. Pathirana a

a Department of Food Science & Technology, Faculty of Agriculture, University of Peradeniya, 20400, Sri Lankab Rice Research Station, Department of Agriculture, Ambalantota 82100, Sri Lanka

a r t i c l e i n f o

Article history:Accepted 16 July 2014Available online

Keywords:PaddyHermeticMillingRice weevilNiacin content

* Corresponding author. Tel./fax: þ94 0718075686.E-mail address: rop_bd@yahoo.com (B.D.R. Prasan

http://dx.doi.org/10.1016/j.jspr.2014.07.0030022-474X/© 2014 Elsevier Ltd. All rights reserved.

a b s t r a c t

Four paddy varieties (Bg 352, Bg 300, Bg 358 and Bg 360) were stored in hermetic IRRI bags and commonwoven polyethylene bags (polybags) at room temperature either uninfested or infested with rice weevils(Sitophilus oryzae (L.)). After 9 months of storage, samples were tested for insect mortality, gas contents,moisture content (m.c.), thousand grain mass (TGM), porosity, hardness, whiteness, total milled rice yield(TMR), head rice yield (HRY), gelatinization temperature, amylose (AC), crude protein (CP), crude fat, freefatty acid (FFA), thiamine and niacin contents and sensory characteristics. These properties after storagewere compared with their initial condition. The oxygen content dropped from 21% to 7% and 13.8% forinfested and uninfested IRRI bag samples, respectively. The results showed that m.c., of the IRRI bagsamples increased significantly (P < 0.05) by 5% when compared to the initial sample but it increased by15% in polybag stored samples. After 9 months, dry matter loss (DM) was 65% higher in polybag than IRRIbag samples. Highest DM loss was observed in Bg 300 and the lowest DM loss was observed in Bg 358and Bg 360. Paddy samples stored in IRRI bags showed reduced whiteness compared to polybag storedsamples. Storage in IRRI bags significantly increased (P < 0.05) TMR, HRY, AC and sensory valuescompared to polybag samples. However, paddy samples stored in polybags significantly increased(P < 0.05) their CP and FFA contents while decreasing sensory values, thiamine and niacin contents. TheFFA value of polybag samples was 2.5 times higher than IRRI bag samples. Hermetic storage of dry paddyimproved overall paddy quality but different end-use quality parameters were observed in the twopaddy grain types of short round (Bg 352 and Bg 300) or intermediate bold (Bg 358 and Bg 360).

© 2014 Elsevier Ltd. All rights reserved.

1. Introduction

For a stable supply of rice, it is necessary to increase paddy (rawrice) production and minimize postharvest losses during thehandling process. Nearly 50% of the paddy harvested in Sri Lanka iskept by farmers (Hafeel et al., 2008), for consumption, seeds andfuture sale for a period of 6e12 months. It has been estimated thaton-farm storage loss of paddy in Sri Lanka is about 8% (Adhikar-inayake et al., 2006) due to poor storage, a considerable amountcontributed to the total annual production of approximately 4million metric tons. Current statistics reveal that annual per capitaconsumption of rice in Sri Lanka is approximately 108 kg.

Storage of paddy in woven polyethylene bags (polybags) is acommonly used, inexpensive and convenient storage method.However, it does not provide the required safety for long-termstorage of paddy, especially under humid climatic condition

tha).

(Weinberg et al., 2008). Even where grains are stored in suitablesilos, losses may still occur due to contamination, deterioration,spillage and spoilage. Insect infestation causes significant damageto the quality of paddy during storage (Jood et al., 1993; Trematerraet al., 2004) and tends to speed up undesirable chemical changesamong stored grains and their products (Raj and Singaravadivel,1990; Seitz and Sauer, 1996). Therefore, quality deterioration ofpaddy or processed rice is unavoidable under common storagesystems. Advanced cold storage or controlled atmosphere systemsfor paddy are not practical at the small farm level as the systemsneed large spaces and expensive environment control facilities.

Hermetic storage of paddy or processed rice is considered afeasible alternative method to woven polybag storage, and ad-dresses the major problems of mold and insect infestation (Navarroet al., 1997; Donahaye et al., 2001). Hermetic or airtight storage is anexcellent method to control insects in stored grain, without the useof chemical pesticides (Navarro, 2006). In this method the storageatmosphere is modified by sealing the container hermetically, sothat a low oxygen (O2) and high carbon dioxide (CO2) atmosphere isobtained after a few weeks of storage (Navarro and Donahaye,

B.D.R. Prasantha et al. / Journal of Stored Products Research 59 (2014) 158e166 159

2005). The development of both fungi and insects can be preventedwhen O2 <3% in the hermetic storage container within 30 days(Moreno-Martinez et al., 2000; Adhikarinayake et al., 2006).

Donahaye et al. (1991) first investigated the possibility of storingbagged paddy outdoors in tropical Sri Lanka using hermeticallysealed plastic liners. Adhikarinayake et al. (2006) developed andevaluated an airtight reinforced concrete bin to store paddy in SriLanka. In both trials, paddy was stored within the storage structurefor 6 months, obtaining excellent hermetic conditions of low O2(<5%) and high CO2 (>9%). They recorded better milling outturn,lower changes in moisture content and reduced mass loss (<0.4%)of paddy during hermetic storage. Although hermetic storage iseffective, farmers are reluctant to use the technology due to ma-terial cost and practical difficulties such as handling and main-taining the structures. Therefore, farmers prefer to use methodssimilar to their common polybag storage system. Another disad-vantage of airtight storage is that of moisture rising to the productsurface in response to temperature differences in a large storagesystem (Gough, 1985) which may reduce product quality. Becausefinal quality of rice (milled paddy) is important to consumers, lowfarmer adoption may be due to the uncertainty of the quality of riceunder hermetic conditions after extended storage (between crop-ping seasons). Grain viability, amount of non-reducing sugars,colour, organoleptic qualities and free fatty acid values are some ofthe quality parameters most susceptible to change during storageof paddy due to ageing (Zhou et al., 2002). Tananuwong and Malila(2011) reported that physicochemical properties of organic ricechanged even during storage under vacuum-packed conditions.Most importantly, consumers prefer rice with a white translucentendosperm and good aroma, and will pay a premium price for it. Inorder to increase farmer adoption of hermetic storage systems andfulfil the market demand of quality rice, a thorough investigation ofthe effect of hermetic storage on rice quality should be carried out.

The objective of this research was to determine the effects oflong-term hermetic storage on Sitophilus oryzae (L.) (rice weevil),milling, physicochemical and sensory qualities of different paddyvarieties. Ambient storage (25e32 �C and relative humidity75e85%) is generally used for commercial storage of paddy andother grains in Sri Lanka, and two cropping seasons (9e12 months)is considered a long period for paddy storage under ambient con-ditions. Feasible and easy handling is important to popularize thehermetic storage method among farmers. Hermetic IRRI super bagis another alternative storage technique, similar to common poly-bag storage (Hafeel et al., 2008). Therefore, in this study, polybagsand IRRI bags are used for packing and storage of four differentpaddy varieties commonly grown in Sri Lanka. Results of this studywill help to determine the applicability and suitability of hermeticbag storage over common polybag storage by considering the enduse quality of paddy.

2. Materials and methods

2.1. Sample preparation

Four high yielding paddy varieties (Table 1) of two grain typeswere cultivated at Rice Research and Development Institute (RRDI),

Table 1Paddy varieties according to their grain type.

Paddy variety Grain type Maturity (days)

Bg 352 Intermediate bold 105Bg 300 Intermediate bold 90Bg 358 Short round 105Bg 360 Short round 105

Sri Lanka for the experiment. Paddy was harvested at the physio-logical maturity defined by the RRDI for each variety. Before stor-age, paddy samples were sun dried on a smooth drying floor,without exposure to high temperature, to a final moisture contentof 12 ± 0.6% wet basis (w.b).

In order to control possible pest and microbial attack, each 5 kgsample was cleaned and disinfested using 5 ml of chloroform(CHCl3) vapour for 12 h in a 5 L gastight chamber prior to storageand initial testing.

2.2. Paddy storage

Paddy samples of 2 kg from each variety were stored under twodifferent types of storage materials, polypropylene bags (polybag)as common storage and IRRI super bags (IRRI bag) for hermeticallysealed storage. IRRI bags, obtained from the International RiceResearch Institute (IRRI), Philippines, are highly impermeable to airand moisture diffusion, which has an oxygen permeability of35e55 ml/m2/day and a water vapour transmission rate of 8 g/m2/day (Bakker et al., 2003; Anonymous, 2009). Paddy samples weretightly packed into the bags and the mouth of each bag was closedwith 5 mm wide PVC cable connectors. Prepared samples werestored in a clean, recently fumigated empty room where theaverage ambient temperature and relative humidity (r.h.) were30 ± 2 �C and 80 ± 5%, respectively. All quality characteristics ofpaddy and their milled rice were measured before storage (initialsamples) and after 9 months of storage in the bags.

2.3. Hermetic condition

To evaluate the atmosphere in the IRRI bag, oxygen (O2) andcarbon dioxide (CO2) concentrations were monitored using a gasanalyzer (ICA 15 Dual Analyzer). Two needles (2.5 mm � 5 cm)were inserted through adhesive rubber septa on opposite sides ofan IRRI bag. The needles were connected to the inflow and outflowtubes (5 mm diameter) of the analyzer. Temperature and r.h.,within the bags were monitored in four additional IRRI bags usingT-type thermocouple data loggers (TC08-PicoTech, UK) and relativehumidity sensors (Thermo-hygrometer model: HT-800, UK). Ther-mocouples and r.h., sensors were inserted through the wall of eachbag and silicone rubber gel was used to seal the hole around thecables. The initial O2 concentration of the samples was set to 21%.

2.4. Infestation of insects

Separate sets of experiments were carried out to evaluate themortality of insects under hermetic conditions. Adult S. oryzae (L.)were obtained from a culture maintained for several years at theDepartment of Agricultural Biology, University of Peradeniya, SriLanka. Approximately 3-week old adults reared in paddy were usedfor the infestation experiment. Storage bags were infested with 100unsexed adult weevils. Mortality of insects was determined bysifting the paddy samples 30 days after storage began. In anotherexperiment, inert gas concentrations (%) were evaluated in undis-turbed infested and uninfested samples every 30 days for up to 9months.

2.5. Moisture content, dry matter content and thousand grain mass

The moisture content (m.c.) of the initial and stored paddysamples was determined (%w.b) by forced-air oven drying at 105 �Cfor 24 h (AACC, 2000). Dry matter (DM) was also measured usingmoisture data. DM losses (%) were calculated related to the initialDM contents of paddy samples.

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From each storage type, a random sample of 30 gwas drawn andfed into the digital grain counter (6708-Indosaw, India) and 1000grains were counted precisely. The grain samples were weighed(0.01 mg) using an electronic balance (XP220-Precisa, Italy) toobtain the thousand grain mass (TGM).

2.6. Density and porosity

The true density (DT) of paddy samples (15 g) was determinedby the kerosene displacement method described by Bhattacharyaet al. (1972). The bulk density (DB) of the paddy samples wasdetermined by densely packing a 100 cm3 container with paddyand determining the weight of the sample. The percentage ofporosity ( 3% ¼ (1 e DB/DT) � 100) of the paddy was calculate fromthe true and bulk density data.

2.7. Grain hardness

Fifty undamaged paddy grains without cracks and splits wereselected by using a grain scope (TX 200-KETT, Japan). Thoseselected grains were carefully placed in the hardness tester (StakeNo.174886, Japan) to measure the grain hardness (N). Force at firstrupture was considered as the yield point.

2.8. Grain whiteness

The degree of whiteness (WH) of rice (milled paddy) sampleswas measured using a whiteness metre (C-300 KETT, Japan) havinga standard whiteness plate value of 83.4. At least three readingswere obtained for each sample. The standard plate was used inbetween each sample measurement.

2.9. Milling quality

Milling outturnwas determined from triplicate samples of 150 gpaddy. Pre-cleaned paddy samples were passed twice through alaboratory rubber roll sheller (XXY155-Yanmar, Japan) for de-husking. The weight of the de-husked brown rice was recorded.The resulting brown rice sample was polished for one minute byusing an abrasive type polisher (McGill mill No. 2 TX, USA) to obtaina typical degree of polish of ca. 8%. Total milled rice was passedthrough a sieve to remove broken grains and further separationwasdone manually. Milled rice kernels that were at least two-third ofthe original kernel length were considered head rice. Percentage oftotal milled rice (TMR%) was calculated by comparing the weight ofde-husked and polished samples to the weight of the un-milledpaddy. Head rice yield (HRY%) was expressed as the percentageratio of the weight of unbroken kernel to the weight of un-milledpaddy (Juliano, 1985; Archer and Siebenmorgen, 1995).

2.10. Gelatinization temperature

Time required for cooking is determined by the gelatinizationtemperature (GT) of rice kernel starch. GT was measured by itsalkali spreading value (Perez and Juliano, 1978; AACC, 2000). Aseven-point scale of 1e7 was used to rank the degree of spreadingfrom low to high. Approximate GT values were calculated by usingthe following equation (Bhattacharya et al., 1982) for all four vari-eties stored under different storage conditions.

GT ¼ 74:54� 1:4R (1)

Where GT is the gelatinization temperature (�C) and R is the rankspreading value.

2.11. Proximate composition

Apparent amylose content (AC) of 100 mg rice flour sample(<60 mm) was measured using AACC 61-03 (AACC, 2000) method.AC content of the rice samples and rice standards was measured at620 nm using a UVevisible spectrometer (Jenwaye6305, UK). Floursamples were also evaluated for their percent crude protein(N � 5.95) and percent cured fat contents by using micro-kjeldhaltechnique and soxhlet extraction method respectively (AACC,2000).

2.12. Free fatty acid

Free fatty acid value (mg KOH/100 g of dry weight) was deter-mined by the rapid titrationmethod (AACC, 2000). Ground samples(4 g) of brown rice were extracted with tolue and filtrate wastitrated with 0.01 N potassium hydroxide (KOH).

2.13. Determination of vitamin B content as Thiamine and Niacin

Thiamine and niacin were determined by the method describedby Toma and Tabekhia (1979) using an HPLC system (SHIMATZU,Japan) with some modifications. A 250 mm � 4.6 mm i.d., 5 mmAltra aqueous C18 (Restek 9178575) analytical column was used at27 �C for chromatographic separation of the vitamins. Solvent usedfor the mobile phase at the rate of 1.2 ml/min, was a mixture of25 mM tri-sodium phosphate (Na3PO4) and HPLC grade methanol,95:5 (V/V). The mixture was adjusted to pH 2 using 0.05 M phos-phate buffer. Vitamins were extracted from 2 g of finely ground(<40 mm) brown rice samples in 60 ml of lukewarm 2% acetic acidfor 20 min, and then sonicated for 5 min in an ultra sonic bath.About 25 ml of methanol and 2% acetic acid were added to themixture to increase the volume to 100 ml. After centrifugation,20 ml of the clear supernatant was filtered through a Fluoroporefilter cartridge (0.45 mm) before injection into the HPLC as 10 mlreplicates. Standard solutions of 100 mg/ml niacin and thiamine(BDH, UK) were prepared as above and filtered before injection. Theconcentration of each vitamin was measured by UVevisibleabsorbance maxima of 254 nm.

2.14. Sensory evaluation

Aroma, appearance, taste and stickiness of the cooked rice wereevaluated using 5 point hedonic scale (1 ¼ very poor to 5 ¼ verygood). For stickiness, rank score of “1” was given for very highstickiness and “5”was given to very low stickiness rice kernels. Ricesamples from each treatment were cooked in a 300 ml capacitymini rice-cooker (SR-03GNational, Japan) with rice towater ratio of1:2 w/w. Fifteen grams of each cooked rice sample were served to30 semi-trained taste panellists at RRDI for sensory evaluation.Each panellist received one sample at a time. During the test,temperature of each served sample was maintained between 40and 50 �C.

2.15. Statistical analysis

Data analysis of the measured properties of the paddy/ricesamples stored for 9 months was conducted in a completely ran-domized design. The percent gas concentrations (O2 and CO2) andmortality of insects were transformed using arcsine square rootbefore analysis of variance. Results of this experiment are presentedas a mean of at least three replicates. Sensory evaluation data wereanalysed using Friedman non-parametric test. Duncan's multiple-range test (DNMRT) was used for mean and rank mean compari-sons at P < 0.05 (SAS, 1990).

Table 2Insect mortality (Sitophilus oryzae) and physical quality parameters of four paddyvarieties initially and after 9 months of storage in polybag and IRRI bag.

Paddy &storage

Insectmortality(%)b

True density(kg/m3)

Porosity (%) Grainwhiteness

Grainhardness(N)

Bg 352Initial 1223 ± 3.1 aa 50.3 ± 0.5 aa 51.3 ± 1.8 aa 41.1 ± 1.1 aa

Polybag 0 1190 ± 2.4 b 48.7 ± 0.3 a 34.4 ± 1.2 c 46.2 ± 0.7 bIRRI bag 100 1198 ± 3.5 ab 51.5 ± 0.1 a 36.1 ± 0.5 bc 44.9 ± 0.8 cBg 300Initial 1237 ± 1.1 a 49.2 ± 0.4 a 45.8 ± 1.2 a 27.8 ± 1.8 aPolybag 0 1200 ± 6.4 b 48.3 ± 0.1 b 38.8 ± 0.0 b 45.1 ± 0.5 bIRRI bag 100 1224 ± 7.4 a 49.2 ± 0.2 a 35.4 ± 1.3 c 43.4 ± 0.8 cBg 358Initial 1252 ± 6.5 a 49.3 ± 1.0 a 40.7 ± 2.3 a 26.7 ± 3.1 aPolybag 2 1174 ± 9.2 b 45.3 ± 0.5 b 28.1 ± 2.1 c 42.4 ± 1.3 bIRRI bag 100 1201 ± 4.3 b 49.2 ± 0.3 a 23.6 ± 0.4 b 40.1 ± 0.3 cBg 360Initial 1236 ± 2.6 a 51.0 ± 0.1 a 44.2 ± 1.3 a 35.1 ± 1.0 aPolybag 0 1150 ± 4.8 b 47.0 ± 0.5 c 31.0 ± 1.0 c 43.8 ± 0.5 bIRRI bag 100 1178 ± 6.0 c 47.5 ± 0.5 bc 29.6 ± 0.6 c 41.4 ± 0.4 c

a Mean ± SD; Mean values of each variety within a column with different lettersare significantly different at P < 0.05.

b Estimated after 30 days.

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3. Results and discussion

3.1. Hermetic condition

During the experiments, it was observed that IRRI bags withpaddy samples were compressed, which is an indication of thedevelopment of hermetic condition. There was no significant dif-ference (NS; P ¼ 0.07) between the average temperatures of paddysamples stored hermetically in IRRI bags (31 ± 2 �C) or in polybags(30 ± 2 �C), although temperatures in the IRRI bag were slightlyhigher. Within bag r.h., decreased to 73 ± 1% in IRRI bags and wassignificantly (P < 0.05) different than the ambient r.h., of 75e88%found in polybags. Asanga and Mills (1986) found that temperatureand r.h., did not change appreciably in a hermetic container of pearlmillet.

There was no change over time in O2 or CO2 concentrations inthe polybag stored samples; gas concentrations in the polybagswere more or less similar to atmospheric gas composition. Gasconcentrations in IRRI bags during the 9 months of storage for bothinfested and uninfested paddy is given in Fig. 1. The O2 level in theuninfested samples gradually decreased to 13.8 ± 0.6% after 90 daysof storage. Simultaneously, CO2 concentration increased to amaximum of 3.1 ± 0.2% within 60 days. After about 90 days, CO2

concentration in the uninfested IRRI bag samples did not changesignificantly (NS; P ¼ 0.08). Moreno-Martinez et al. (2000)observed the O2 level of uninfested maize decreased to 13.7%within 24 days and then further dropped to 8.4% after 30 days. Thenumber of insects and other living organisms was very low inuninfested hermetic IRRI bag samples due to the disinfestation ofthe treated paddy at the beginning of the experiment. Therefore,depletion of O2 in the uninfested hermetic condition may beattributed to respiration of paddy and/or use by remaining fungiafter disinfestations but for the infested paddy it was mainly due toinsects. The level of generated CO2 is low in paddy which has m.c.<14% (Caliboso and Sabio, 1998).

After 30 days very lowor no insect mortality (%) was observed inpaddy samples stored in polybag (Table 2), while insect mortality inthe hermetic IRRI bag was 100%. Although no live insects werefound in the infested IRRI bags after 30 days, CO2 had significantly(P < 0.05) increased to 9.1 ± 0.5% and O2 had dropped down to7 ± 0.7% (Fig. 1). Observed compression in the IRRI bag during theexperiment may have created a low O2 tension inside the bagwithin 30e60 days. This situation may have enhanced the mor-tality of S. oryzae. Previous studies have shown that the level of CO2content rising above 12% within 3e4 weeks of hermetic storage ofpaddy (Donahaye et al., 2001; Ferizli et al., 2001) with artificial

Fig. 1. Average O2 and CO2 concentrations (%) of all four paddy varieties with orwithout insect infestation (Sitophilus oryzae) during 9 months of storage in hermeticIRRI bag.

infestations of storage pests. Moreno-Martinez et al. (2000) re-ported 100% control of 20 adult Sitophilus zeamaiswithin 12 days ina 250 ml hermetic container with 150 g of maize. Singh et al. (1976)showed that adult S. oryzae (L.) consumes 100 ml/adult/day of O2.Therefore it could be possible that 100 adult insects be able toconsume all available O2 in an air tight container within 21 days,however they may die earlier than that as a result of low O2

availability or low O2 tension.In the infested samples there was a steady increase of O2 and

decrease of CO2 after 60 days of storage. This could be due to gasdiffusion through the IRRI bags (Anonymous, 2009), a small leak, orsorption of CO2 by the stored paddy. Therefore, it is evident thatIRRI bag may not retain its complete gas tightness throughout thelong term storage of paddy. Similar gas concentration patterns ininfested grains have been observed in hermetically stored pearlmillet (Asanga and Mills, 1986) and paddy treated with high CO2concentrations (Carvalho et al., 2012). Although the observed gasconcentrations in the above studies were different than currentstudy, the pattern of CO2 and O2 change during storagewas more orless similar. However, the extent of O2 and CO2 concentrationschange depends on factors such as storagematerial, product qualityand quantity, m.c., number of insects and type of microorganisms(Cofie-Agblor et al., 1998; Moreno-Martinez et al., 2000).

According to our ongoing field study, repeated use of IRRI bags isnot viable because of the low retention of CO2. This could be due todamage to the inner-layer of the IRRI bag caused by the sharp edgesof long paddy grains. Also, these bags are less resistant to roughhandling. Although farmers were advised to protect the IRRI bag bycovering it with a polybag; they were reluctant to do so due to thecost of extra handling.

3.2. Moisture content

The m.c., of paddy samples (Fig. 2) stored in hermetic IRRI bagwas significantly higher (P < 0.05) than initial m.c., levels andranged from 12.7% to 13.3%. Paddy samples stored under non-hermetic conditions in polybags ranged from 13.8% to 14.4% m.c.,significantly higher (P < 0.05) than in hermetic IRRI bag samples.The highest m.c., was observed in Bg 352 and Bg 300 varietiesstored under non-hermetic conditions. Ben et al. (2006) reported aslight increase in moisture in IRRI bags (1.2%) after 8 months of

Fig. 2. Change of the moisture content of four paddy varieties before storage (initial)and 9 months after storage in common polybag and hermetic IRRI bag.

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storage compared to a greater increase found in control samples(4.7%). In the current study the observed average increase in m.c.,after 9 months of storage was 5.1% and 14.8% in IRRI bag and pol-ybag samples, respectively. Slight increase of m.c., in IRRI bag storedpaddy samples could be due to accumulation of physiologicalmoisture or atmospheric moisture diffused through the IRRI bagmaterial. Contrasting to the above findings, Kyu et al. (1999) re-ported that paddy stored hermetically for 4 years did not increaseits m.c. Different paddy varieties equilibrate to different m.c., underany given environmental condition, depending on the moisturesorption characteristics of the grain (Kunze and Wratten, 1985;Pearce et al., 2001). Our results indicate the importance of usinghermetic storage to avoid moisture diffusion into the storage sys-tem. According to Donahaye et al. (1991) and Adhikarinayake et al.(2006) m.c., of stored paddy does not change in gas tight structuressuch as cubes or bins. Therefore, bulk storage of paddy in her-metically sealed systems has an advantage if there is no adverseeffect on the paddy quality.

3.3. Thousand grain mass

The TGM values (Fig. 3) for paddy stored in polybags showed nodifferences from paddy stored in IRRI bags. However, after 9months of storage, TGM for paddy stored in both decreasedsignificantly (P < 0.05) when compared to initial values. Accordingto the mass loss estimation based on TGM, an average of 3.3% and8% mass loss compare to initial samples was found in IRRI bags and

Fig. 3. Mean thousand grain mass (TGM) and mean dry matter (DM) loss of paddyduring storage in common polybag and hermetic IRRI bag.

polybags, respectively. Absorption of moisture from the environ-ment (Fig. 2) might have kept the TGM in polybags relatively un-changed even after 9 months when compare to IRRI bag samples.Zareiforoush et al. (2009) reported that there was a positive cor-relation between TGM and m.c., of paddy.

The average DM loss was 65% higher (P < 0.05) in polybag thanin bag stored paddy samples (Fig. 3). The highest DM loss was3.7± 0.06%, observed in the BG 300 variety stored in polybagswhileDM loss for this same variety was 1.4 ± 0.05% in IRRI bags. DMlosses in IRRI bag samples were 0.46e1.4%; the highest and lowestvalues were recorded for the two “intermediate bold” varieties ofBg 352 and Bg 300. Based on the results, long grain paddy varietieswith short maturity periods (90 days) such as Bg 300 might havehigher DM losses compared to short grain varieties with longermaturity periods. Donahaye et al. (1991) found 0.33e0.64% loss ofDM due to metabolic activity of long bold rice varieties during 6months of hermetic storage. Adhikarinayake et al. (2006) reportedthat mass loss of long medium paddy variety Bg 94-1 (shortmaturity) based on TGM and DMwere 2.2% and 0.4% after 6 monthsstorage in hermetic ferro-cement bin in Sri Lanka respectively.

3.4. Density and porosity

Average DT value of initial paddy samples was 1237 ± 3 kg/m3

(Table 2). The average DT of IRRI bag and polybag stored paddysamples was found to be 1200 ± 5 kg/m3 and 1178 ± 6 kg/m3,respectively, and were significantly different (P < 0.05). Bg 352,being an intermediate bold variety, had the lowest density valuesthan other varieties and showed the lowest rate of moisture in-crease during hermetic storage. Although the highest DM loss afterstorage was observed in Bg 300, it showed significantly higher DT(P < 0.05) than other varieties. DT indicates the exact materialdensity of the product itself. Therefore changing moisture or drymatter may significantly affect density. Bhattacharya et al. (1972)reported that, for every 1% increase in m.c., the density of thepaddy increased by about 7.5 kg/m3. This increase is due to thepresence of air space between the kernel and the husk, enabling thekernel to hydrate without affecting the paddy kernel volume.

The porosity value ( 3%) increases when DB decreases at constantDT. The 3represents the space left between paddy grains when thepaddy fills a container. The highest (51.0%) and lowest (49.2%)initial 3values were observed in paddy varieties Bg 360 and Bg 300respectively (Table 2). Among local paddy varieties, bold paddyshowed lower 3value than slender paddy varieties (Palipane et al.,1985). Average 3values of initial (50 ± 0.5%) and hermetically stored(49.3 ± 0.3%) paddy samples were showed no differences. However,3values of polybag samples were 5% less (P < 0.05) than IRRI bagstored samples. The increase in 3is related to a decrease in DB ofhermetic samples (Santos et al., 2010). In drying and aeration the 3

values of grain in bulk becomes useful parameter.

3.5. Grain hardness

Hardness of paddy varieties increased significantly (P < 0.05)from that of initial samples during storage but the values weresimilar between the two storage methods (Table 2). The hardnessvalue for the IRRI bag stored paddy was 45e40.1 N, and was46.2e42.4 N for the polybag samples. Polybag stored Bg 300showed the highest percentage increase (38.4%) in hardnesscompare to its initial value. Nagato et al. (1964) reported that thehardness at any specified point within the endosperm increased ordecreased linearly according to changes in its moisture content.Although paddy hardness increases during storage, hardness mayreach a maximum and then begin to decline (Perez and Juliano,1981).

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3.6. Grain whiteness

Table 2 shows that storage methods significantly (P < 0.05)affected theWH of rice from paddy stored at ambient temperaturesfor 9 months. Initial rice samples WH were significantly higher(P < 0.05) than stored samples and was 51.3e40.7. The WH of theIRRI bag stored sample was slightly lower but statistically insig-nificant (NS; P ¼ 0.06) than polybag samples. The reason fordecreased WH in hermetically stored paddy may be related toslight increase of temperature (31 ± 2 �C) during IRRI bag storage.Soponronnarit et al. (2008) reported that initial m.c., storage con-ditions and storage time influenced the WH of rice. Bg 358, a shortround paddy variety, had the lowest WH values (40.7) and Bg 352had the highest initial value (51.3). WH has been found to be animportant factor affecting the quality of cooked rice, and valuesabove 38 or 37 are considered to indicate acceptable quality (Kim,2002; Soponronnarit et al., 2008). The reduction of WH is mainlydue to non-enzymatic browning reactions but diffusion of hullpigments and/or bran into endosperm during storage are also apossible reason for changing WH (Reyes and Jindal, 1989). Weffenand Zuxun (2002) stated that vacuum packed rice developedstrong rancid odour and discolouration after 2 years of storage. Yanet al. (2004) reported that the discolouration of rice packed inperforated pouches was greater than vacuum-packed rice.

3.7. Milling quality

The most significant quality parameters during rice milling arekernel WH, total milled rice yield (TMR) and head rice yield (HRY).These are the most commonly used indicators to determine thequality of rice. Paddy samples stored in the IRRI bag showedsignificantly greater (P < 0.05) TMR and HRY than polybag samples.TMR of IRRI bag stored rice was 4.5% higher and HRY was 6% higherthan that from polybag samples. TMR and HRY for the initialsamples were 70.7e74.3 and 50e59% respectively, in the varietiesused in this study (Table 3). Initial values of HRY were significantlyhigher (P < 0.05) than for stored rice but TMR was significantlyhigher (P < 0.05) in IRRI bag samples than initial samples by0.3e6.2%. For all varieties except Bg 352, paddy stored in IRRI bagsand polybags showed a decrease in HRY values of 2.5 and 7.1%,respectively, when compared to initial samples. Similar to theabove findings, Ben et al. (2006) also found 1.23% lower HRY inpaddy stored hermetically for 8 months using IRRI bags whencompared to initial samples. These results contrast with the find-ings of Adikarinayake et al. (2006) where HRYand TMR percentages

Table 3Milling quality parameters of four paddy varieties initially and after 9 months of storage

Paddy & storage TMR (%) HRY (%) Alkali spreading

Bg 352Initial 71.3 ± 0.1 aa 50.0 ± 1.2 b 4Polybag 73.0 ± 1.0 b 51.3 ± 0.8 b 5IRRI bag 75.5 ± 0.3 c 55.6 ± 1.3 a 5Bg 300Initial 74.3 ± 0.1 a 57.6 ± 0.8 a 4Polybag 70.2 ± 0.7 b 51.0 ± 0.2 b 3IRRI bag 75.3 ± 1.0 c 55.0 ± 0.5 c 3Bg 358Initial 72.5 ± 0.7 a 59.0 ± 1.4 a 3Polybag 70.4 ± 0.3 b 55.2 ± 0.8 b 3IRRI bag 72.7 ± 0.6 a 57.6 ± 1.1 c 2Bg 360Initial 70.6 ± 0.2 b 58.0 ± 1.2 a 2Polybag 70.0 ± 0.4 b 56.0 ± 0.8 b 3IRRI bag 72.8 ± 0.3 a 57.5 ± 0.5 c 3

a Mean± SD;Mean values of each variety within a columnwith different letters are signGT is gelatinization temperature.

of Bg 94-1 were similar to the initial values after 6 months ofhermetic storage. Bakker et al. (2003) stated that there was nodecline in milling recovery and HRY in paddy stored in a hermeticstorage system. This might be explained by grain absorption ofmoisture during storage, causing moisture stress that leads tokernel fissuring and breakage resulting in reduction of the HRY inlong term storage (Donahaye et al., 2001).

The highest and the lowest percentages of increased TMR in theIRRI bags were observed in Bg 352 and Bg 358 respectively. TMR%values for polybag samples decreased by 0.8e5.5% compared totheir initial values except variety Bg 352, in which TMR% increasedby 2.4%. The increase in Bg 352 could be attributed to their highhardness (Table 2) and other varietal characteristics. Paddy vari-eties having high amylose (>20%), low alkali spreading value andhigh protein (>7%) give higher HRY than other paddy varieties(Yadav and Jindal, 2008).

3.8. Gelatinization temperature

The determination of the gelatinization temperature (GT) isessential for cooking and processing operations. Alkali spreadingvalue (AS) varied from 5 to 2 in the selected varieties (Table 3) andthe approximate gelatinization temperature falls in the range of71.74e67.54 �C (Equation (1)). That suggests starch of the testedrice varieties belonged to a high, high-intermediate or intermediategelatinization group. In general, storage method did not show anyeffect on the GT of the tested varieties. However, there was a 1.4 �Cdifference between the GT values for polybag and IRRI bag samplesfor Bg 358. Initial GT of Bg 352 and Bg 300 had intermediate ASscores of 4 and GT of 68.94 �C. After 9 months, AS score of Bg 352increased up to 5 and GT of 67.54 �C but it could be still classified asan intermediate GT value under alkali-digestion test. The changesin these properties indicate that as the storage period increases,lipid oxidation, interaction between amylose-protein and protein-fatty acids continues to progress (Zhou et al., 2002; Sodhi et al.,2003; Soponronnarit et al., 2008) thereby impede starch gelatini-zation, especially under high ambient temperature (>25 �C)storage.

3.9. Proximate composition

The amylose (%), crude protein (%) and crude fat (%) contents ofthe four paddy varieties used in this storage study are presented inTables 3 and 4. Amylose content (AC) is considered the single mostimportant characteristic for predicting rice cooking and processing

in polybag and IRRI bag.

Calculated GT (�C) GT classification Amylose content (%)

68.94 Intermediate 26.2 ± 0.4 a67.54 Intermediate 32.3 ± 0.2 b67.54 Intermediate 32.7 ± 0.3 b

68.94 Intermediate 27.5 ± 1.0 b70.34 High-intermediate 31.1 ± 0.4 a70.34 High-intermediate 31.0 ± 0.5 a

70.34 High-intermediate 28.7 ± 1.0 b70.34 High-intermediate 32.1 ± 0.3 a71.74 High 32.5 ± 0.4 a

71.74 High 28.3 ± 0.6 b70.34 High-intermediate 30.0 ± 0.3 ab70.34 High-intermediate 30.4 ± 0.2 a

ificantly different at P < 0.05. TMR is total milled rice yield, HRY is head rice yield and

B.D.R. Prasantha et al. / Journal of Stored Products Research 59 (2014) 158e166164

(Zhou et al., 2002). Initial samples from all four varieties containedAC in the range 26.2e28.7%. After 9 months of storage, average ACof both polybag and IRRI bag samples increased significantly(P < 0.05) by about 14% compare to their initial AC values. So andKim (1999) reported that rice increased AC even after 4 years ofstorage in ambient atmosphere at 30 �C. However, the AC of paddysamples contained in the polybags was almost similar to the her-metic IRRI bag samples. The AC of polybags samples was 30e32.3%and was 30.4e32.7% in IRRI bag samples. Similarly, Sukprakarnet al. (1989) reported that rice stored for 6 months under a highCO2 atmosphere did not show significant differences in theiramylose content, soluble amylose, and cooking time compare tocontrol samples. The lowest and highest increases of AC in storedrice compared to the initial AC were recorded in Bg 300 (2%) and Bg352 (6.3%). Regardless of the storage condition, amylose increasesduring storage of paddy occurs as a result of starch degradationwith ageing (Villareal et al., 1976).

The changes in crude protein (CP) content was significantlyaffected (P < 0.05) by storage regardless of the storage method.After 9 months, CP content of the 4 varieties had decreased by5e15% but the highest CP loss was recorded in the IRRI bag samples.The CP of paddy decreases as a result of a decrease in the content of“eSH” bonds during prolong storage (Zhou et al., 2002). Compare topolybag samples, IRRI bag stored paddy varieties Bg 352 and Bg 358showed significantly lower (P < 0.05) CP content but Bg 300 and Bg360 showed only slight declines in their CP content. According toDaftary et al. (1970) a progressive increase in protein content ofwheat occurred during prolonged storage due to the loss of car-bohydrates during respiration. This phenomenon could be thereason CP is relatively low in IRRI bag samples because DM loss washigher in polybag samples when compared to IRRI bag storedpaddy (Fig. 3).

The crude fat (CF) content of stored paddy samples was lower(P < 0.05) than that of corresponding initial samples. However, nosignificant differences (NS; P ¼ 0.2) were found between the twostorage methods with regard to CF content. Zhou et al. (2002) re-ported that rice fat content was significantly reduced during stor-age at high temperature due to fat hydrolysis.

3.10. Free fatty acid

Free fatty acid (FFA) value is commonly used as an indicator ofquality deterioration during paddy storage because fat hydrolysisor oxidation is more rapid than that of starch or protein breakdown.

Table 4Nutritional compositions of four paddy varieties initially and after 9 months of storage i

Paddy & storage Crude protein (%) Crude fat (%)

Bg 352Initial 6.6 ± 0.4 aa 2.4 ± 0.1 aPolybag 6.1 ± 0.1 b 1.9 ± 0.1 cIRRI bag 5.8 ± 0.1 c 2.0 ± 0.1 cBg 300Initial 7.3 ± 0.4 a 3.0 ± 0.1 aPolybag 6.9 ± 0.2 a 1.9 ± 0.1 bIRRI bag 6.9 ± 0.1 a 2.0 ± 0.1 bBg 358Initial 8.5 ± 0.3 a 2.4 ± 0.0 aPolybag 7.5 ± 0.3 b 1.6 ± 0.1 bIRRI bag 7.2 ± 0.1 c 2.1 ± 0.1 cBg 360Initial 7.0 ± 0.1 a 2.4 ± 0.1 aPolybag 6.7 ± 0.1 b 2.0 ± 0.2 bIRRI bag 6.5 ± 0.2 b 2.1 ± 0.1 b

a Mean ± SD; Mean values of each variety within a column with different letters are s

Table 4 shows that of both IRRI bag and polybag stored paddysamples changed with respect to FFA content. The FFAvalues of IRRIbag stored samples were significantly lower (P < 0.05) than thepolybag stored samples. Compared to initial paddy samples, FFAvalues increased in stored paddy. The FFAvalues of polybag sampleswere 3.9e4.1 mg KOH/100 g d.b., which was an increase of 156%compared to initial samples. FFA values in samples stored in IRRIbags were 2.5e2.6 mg KOH/100 g d.b., an increase of about 63%from initial samples and 2.5 times less than polybag stored samples.This is due to low O2 concentration that developed in the hermeticIRRI bag during storage which may help to prevent fat fromoxidation. The increase in FFA therefore causes deterioration of ricequality of during storage (Zhou et al., 2002). According to thefindings of Villareal et al. (1976) and Sodhi et al. (2003), increases inFFA content in rice is influenced by the storage period, storagetemperature and the composition of rice.

3.11. Vitamin B content as Thiamine and Niacin

Levels of both thiamine and niacin contents in the initial sam-ples were lower than the levels of Californian brown rice reportedby Toma and Tabekhia (1979). Initial thiamine and niacin contentsof 4 paddy varieties were 3.5e4.4 mg/g and 36.8e41.5 mg/g,respectively (Table 4). According to Juliano (1985), thiamine con-tent decreased during storage, but in this study, there was no sta-tistical difference (NS; P ¼ 0.09) between initial and IRRI bagsamples for thiamine and niacin content. Other than Bg 300, thia-mine and niacin content was comparatively lower (P < 0.05) inpolybag samples compared to IRRI bag samples. Reddy andPushpamma (1986) reported that the loss of thiamin was higherthan that of niacin in rice with or without insect infestation after 12months of storage. Factors other than insect infestation, such asmoisture, temperature, and oxygen fluctuations, processing con-dition and packaging also contribute to vitamin B losses.

3.12. Sensory evaluation

The results of this test showed (Fig. 4) that aroma, appearance,taste and stickiness of cooked rice quality were affected signifi-cantly by storage method (P < 0.05). Although the panelists re-ported little or no difference in aroma and appearance betweeninitial and IRRI bag stored paddy, very poor aromawas noted for allpolybag stored samples. Compared to initial samples, taste ofcooked rice obtained from polybag and IRRI bag stored samples was

n polybag and IRRI bag.

Free fatty acid(mg KOH/100 g d.b.)

Thiamine (mg/g) Niacin (mg/g)

1.6 ± 0.1 a 3.6 ± 1.2 a 41.5 ± 2.0 a4.0 ± 0.1 b 4.1 ± 0.3 a 33.5 ± 0.6 b2.5 ± 0.1 c 4.5 ± 0.3 a 36.8 ± 2.6 a

1.7 ± 0.1 a 4.4 ± 0.4 a 40.6 ± 3.8 a4.1 ± 0.1 b 3.7 ± 0.5 a 39.3 ± 4.8 a2.6 ± 0.1 c 4.0 ± 0.9 a 38.8 ± 2.1 a

1.4 ± 0.1 a 4.2 ± 1.1 ab 38.9 ± 2.6 a4.0 ± 0.1 b 3.0 ± 0.2 a 26.0 ± 0.9 b2.5 ± 0.1 c 4.1 ± 0.4 b 37.0 ± 5.9 a

1.4 ± 0.0 a 3.5 ± 0.3 a 36.8 ± 3.0 a4.1 ± 0.1 b 2.6 ± 0.1 b 27.0 ± 2.3 b2.6 ± 0.1 c 4.4 ± 1.0 c 35.4 ± 3.4 a

ignificantly different at P < 0.05.

Bg 352

012345

Appearance

Aroma

Stickiness

Taste

Bg 300

012345

Appearance

Aroma

Stickiness

Taste

Bg 358

012345

Appearance

Aroma

Stickiness

Taste

Bg 360

012345

Appearance

Aroma

Stickiness

Taste

Fig. 4. Variation of sensory characteristics of cooked rice varieties in polybag and hermetic IRRI bag after 9 months of storage.

B.D.R. Prasantha et al. / Journal of Stored Products Research 59 (2014) 158e166 165

ranked by the panelists as “poor” and “moderate”, respectively.Zhou et al. (2002) reported formation of FFA during storage ofpaddy, increasing the level of acidity and significantly deterioratingthe taste and aroma of cooked rice. This could be the reason forsubstandard taste and aroma of stored paddy compare to initialsamples. Local consumers prefer to consume rice having lowstickiness and separate kernels in their dishes. Our results indicatethat storage in IRRI bag and polybag significantly reduced (P < 0.05)the stickiness (rank z 5) of cooked rice than initial samples. Ac-cording to Perdon et al. (1999), increasing degrees of starch retro-gradation during storage resulted in increased rice firmness anddecreased stickiness. Sensory characteristics of cooked ricechanged with time even when rice is stored vacuum-packed(Tananuwong and Malila, 2011). Paddy ageing during storage un-der ambient condition is a spontaneous phenomenon that changesthe physicochemical characteristics of paddy while modifyingprocessing and cooking qualities. Therefore hermetic storage inIRRI bag provided the best shelf-life and improved the end-usequalities of paddy.

Acknowledgement

We thank D.M.N. Dissanayake (RRDI, Sri Lanka) and Judy John-son (USDA-ARS, CA 93648, USA) for their valuable support. Thisresearch was funded by National Science Foundation, Sri Lanka.

References

AACC, 2000. Approved Methods of the American Association of Cereal Chemists.American Association of Cereal Chemists. Inc., St. Paul, Minnesota, USA.

Adhikarinayake, T.B., Palipane, K.B., Müller, J., 2006. Quality changes and mass lossof paddy during airtight storage in a ferro-cement bin in Sri Lanka. J. StoredProd. Res. 42, 377e390.

Adikarinayake, T.B., Palipane, K.B., Müller, J., 2006. Quality changes and mass loss ofpaddy during airtight storage in a ferro-cement bin in Sri Lanka. J. Stored Prod.Res. 42, 377e390.

Anonymous, 2009. http://www.knowledgebank.irri.org/rkb/grain-storage-systems/hermetic-storage-systems.html (verified 14.02.2014).

Archer, T.R., Siebenmorgen, T.J., 1995. Milling quality as affected by brown ricetemperature. Cereal Chem. 72, 304e307.

Asanga, C.T., Mills, R.B., 1986. Hermetic storage of pearl millet, Pennisetum ameri-canum (L.) leeke; laboratory studies. J. Stored Prod. Res. 22, 211e216.

Bakker, R.R., Rickman, J.F., Kim, O.W., 2003. Rice quality management throughbetter drying, storage and milling practices. In: Mew, T.W., Brar, D.S., Dave, D.,Hardy, B. (Eds.), Rice science Innovations and Impact for Livelihood. Pro-ceedings of the International Rice Research Conference, 16e19 September 2002.China, Beijing, pp. 687e697.

Ben, D.C., Liem, P.V., Dao, N.T., Gummert, M., Rickman, J.F., 2006. Effect of hermeticstorage in the super bag on seed quality and milled rice quality of differentvarieties in Bac Lieu, Vietnam. Int. Rice Res. Notes 31, 55e56.

Bhattacharya, K.R., Sowbhagya, C.M., Indudhara, S.Y.M., 1972. Some physical prop-erties of paddy and their interrelation. J. Sci. Food Agric. 23, 171e186.

Bhattacharya, K.R., Sowbhagya, C.M., Indudhara Swamy, Y.M., 1982. Quality profilesof rice: a tentative scheme for classification. J. Food Sci. 47, 564e569.

Caliboso, F.M., Sabio, G.C., 1998. Hermetic storage of grains in the tropics. In:Nawa, Y., Takagi, H., Oguchi, A. (Eds.), Postharvest Technology in Asia: a StepForwards a Stable Supply of Food Products. The 5th JIRCAS InternationalSymposium, 9e10 September 1998, Japan, pp. 59e72.

Carvalho, M.O., Pires, I., Barbosa, A., Barros, G., Riudavets, J., Garcia, A.C., Brites, C.,Navarro, S., 2012. The use of modified atmospheres to control Sitophilus zeamaisand Sitophilus oryzae on stored rice in Portugal. J. Stored Prod. Res. 50, 49e56.

Cofie-Agblor, R., Muir, W.E., Jayas, D.S., White, N.D.G., 1998. Carbon dioxide sorptionby grains and canola at two CO2 concentrations. J. Stored Prod. Res. 34, 159e170.

Daftary, R.D., Pomeranz, Y., Sauer, D.B., 1970. Changes in wheat flour damaged bymold during storage. Effects on lipid, lipoprotein, and protein. J. Agric. FoodChem. 18, 613e616.

Donahaye, E., Navarro, S., Ziv, A., Blauschild, Y., Weerasinghe, D., 1991. Storage ofpaddy hermetically sealed plastic liners in Sri Lanka. Tropical Sci. 31, 109e124.

Donahaye, J., Navarro, S., Andales, S., del Mundo, A., Caliboso, F., Sabio, G., Felix, A.,2001. Quality preservation of moist paddy under hermetic conditions. In:Donahaye, E.J., Navarro, S., Leesch, J.G. (Eds.), Proceedings of an InternationalConference on Controlled Atmosphere and Fumigation in Stored Products, 29Octobere3 November 2000. Executive Printing Services, Clovis, Fresno, CA,USA, pp. 209e225.

Ferizli, A.G., Navarro, S., Donahaye, J.E., Rindner, M., Azriel, A., 2001. Airtight granaryfor use by subsistence farmers. In: Donahaye, E.J., Navarro, S., Leesch, J.G. (Eds.),Proceeding of International Conference of Controlled Atmosphere and Fumiga-tion in Storage Products. Executive Printing Services, Clovis, CA, USA, pp. 37e43.

Gough, M.C., 1985. Physical changes in large-scale hermetic grain storage. J. Agric.Eng. Res. 31, 55e65.

B.D.R. Prasantha et al. / Journal of Stored Products Research 59 (2014) 158e166166

Hafeel, R.F., Prasantha, B.D.R., Dissanayake, D.M.N., 2008. Effect of hermetic-storageon milling characteristics of six different varieties of paddy. Tropical Agric. Res.6, 102e114.

Jood, S., Kapoor, A.C., Singh, R., 1993. Effect of insect infestation on the organolepticcharacteristics of stored cereals. Postharvest Biol. Technol. 2, 341e348.

Juliano, B.O., 1985. Rice: Chemistry and Technology, second ed. American Associa-tion of Cereal Chemists, St. Paul, Minnesota, USA.

Kim, D.C., 2002. Post harvest technology for high quality rice. Food Preserv. Process.Ind. 1, 35e43.

Kunze, O.R., Wratten, F.T., 1985. Physical and mechanical properties of rice. In:Juliano, B.O. (Ed.), Rice chemistry and Technology. AACC, USA, pp. 207e231.

Kyu, H.S., Young, S.K., Jae, S.H., Ju, Y.J., Jae, M.C., 1999. Studies on the change ofcomponents with long-term storage of paddy. Korean J. Food Nutr. 12,409e414.

Moreno-Martinez, E., Jim�enez, S., V�azquez, M.E., 2000. Effect of Sitophilus zeamaisand Aspergillus chevalieri on the oxygen level in maize stored hermetically.J. Stored Prod. Res. 36, 25e36.

Nagato, K., Ebat, M., Ishikawa, M., 1964. On the formation cracks in rice kernelsduring wetting and drying of paddies. Nippon Sakumotsu Gakki KIji 33, 82e89.

Navarro, S., 2006. Modified atmospheres for the control of stored-product insectsand mites. In: Heaps, J.W. (Ed.), Insect Management for Food Storage and Pro-cessing, second ed. AACC International, St. Paul, MN, USA, pp. 105e146.

Navarro, S., Caliboso, F.M., Sabio, G.C., Donahaye, E.J., 1997. Quality conservation ofpaddy stored under gastight seal outdoors in the Philippines. In: Donahaye, E.J.,Navarro, S., Varnava, A. (Eds.), Proceedings of an International Conference onControlled Atmosphere and Fumigation in Stored Products, 21e26 April 1996.Print Co. Ltd., Nicosia, Cyprus, pp. 159e168.

Navarro, S., Donahaye, E.J., 2005. Innovative environmentally friendly technologiesto maintain quality of durable agricultural products. In: Ben Yehoshua, S. (Ed.),Environmentally Friendly Technologies for Agricultural Produce Quality. CRCPress, Boca Raton, FL, USA, pp. 204e260.

Palipane, K.B., Swarnasiri, D.P.C., Thilakaratne, B.M.K.S., 1985. Physical properties,milling, cooking, eating and nutritive qualities of some recently recommendedrice varieties in Sri Lanka. J. Post Harvest Technol. 1, 31e38.

Pearce, M.D., Marks, B.P., Meullenet, J.F., 2001. Effect of post harvest parameters onfunctional changes during rough rice storage. Cereal Chem. 78, 354e357.

Perdon, A.A., Siebenmorgen, T.J., Buescher, R.W., Gbur, E.E., 1999. Starch retrogra-dation and texture of cooked milled rice during storage. J. Food Sci. 64,828e832.

Perez, C.M., Juliano, B.O., 1978. Modification of the simplified amylose test for milledrice. Starch 30, 424e426.

Perez, C.M., Juliano, B.O., 1981. Texture changes and storage rice. J. Texture Stud. 12,321e333.

Raj, S.A., Singaravadivel, K., 1990. Biodeterioration in rice (Oryza sativa L.) due tolow, medium and high moisture. Int. Biodeterior. 27, 237e248.

Reddy, U.M., Pushpamma, P., 1986. Effect of storage and insect infestation onthiamine and niacin content in different varieties of rice, sorghum, and le-gumes. Nutr. Rep. Int. 34, 393e401.

Reyes Jr., V.G., Jindal, V.K., 1989. Conduction heating of high moisture rough rice III.Changes in milling and cooking qualities. J. Food Process Eng. 11, 103e115.

Santos, B.S., Martins, M.A., Faroni, L.R.D., Rodrigues Jr., V., Dhingra, O.D., 2010.Quality of maize grains treated with allyl isothiocyanate stored in hermeticbags. J. Stored Prod. Res. 46, 111e117.

SAS Institute, 1990. SAS Language and Procedures, Version 6.1st Edition. SASInstitute, Cary, NC.

Seitz, L.M., Sauer, D.B., 1996. Volatile compounds and odors in grain sorghuminfested with common storage insects. Cereal Chem. 73, 744e750.

Singh, N.B., Campbell, A., Sinha, R.N., 1976. An energy budget of Sitophilus oryzae(Coleoptera: Curculionidae). Ann. Entomol. Soc. Am. 69, 503e512.

So, K.H., Kim, Y.S., 1999. Studies on the change of component with long term storageof paddy. Korean J. Food Nutr. 12, 409e414.

Sodhi, N.S., Singh, N., Arora, M., Sing, J., 2003. Changes in physicochemical, thermal,cooking and textural properties of rice during aging. J. Food Process. Preserv. 27,387e400.

Soponronnarit, S., Chiawwet, M., Prachayawarakon, S., Tungtrakul, P.,Taechapairoj, C., 2008. Comparative study of physicochemical properties ofaccelerated and naturally aged rice. J. Food Eng. 85, 268e276.

Sukprakarn, C., Attaviriyasook, K., Khowchainaha, L., Bhuddasamai, K., Promsatit, B.,1989. Carbon dioxide treatment for sealed storage of bag stacks of rice inThailand.In: Champ, B.R., Highley, E., Banks, H.J. (Eds.), Fumigation and Controlled Atmo-sphere Storage of Grain. Proceedings International Conference Held in Singapore,14e18 February 1989, ACIAR Proceeding No. 25, pp. 1188e1196.

Tananuwong, K., Malila, Y., 2011. Changes in physicochemical properties of organichulled rice during storage under different condition. Food Chem. 125, 179e185.

Toma, R.B., Tabekhia, M.M., 1979. High performance liquid chromatographic anal-ysis of B-vitamins in rice and rice products. J. Food Sci. 44, 263e265.

Trematerra, P., Sciarretta, A., Paula, M.C., Lazzari, S.M., 2004. Insect pests infesting apaddy rice storage facility in Brazil: phenology and spatial distribution. Tec.Molit. 55, 103e110.

Villareal, R.M., Resurreccion, A.P., Suzuki, L.P., Juliano, B.O., 1976. Changes in phys-icochemical properties of rice during storage. Starch 28, 88e94.

Weffen, Q., Zuxun, J., 2002. Paddy and rice storage in China. Advances in storedproduct protection. In: Credland, R.F., Armitage, T.M., Bell, C.H., Highley, G.(Eds.), Proceedings of 8th International Working Conference on Stored ProductProtection. CABI Publishers, UK, pp. 26e39.

Weinberg, Z.G., Yan, Y., Chen, Y., Finkelman, S., Ashbell, G., Navarro, S., 2008. Theeffect of moisture level on high-moisture maize (Zea mays L.) under hermeticstorage conditionsein vitro studies. J. Stored Prod. Res. 44, 136e144.

Yadav, B.K., Jindal, V.K., 2008. Changes in head rice yield and whiteness duringmilling of rough rice (Oryza sativa L.). J. Food Eng. 86, 113e121.

Yan, T.Y., Chung, J.H., Rhee, C.O., 2004. Development of an automatic packer usingvacuum packaging and its effects on the rice quality. J. Biosyst. Eng. 29, 131e140.

Zareiforoush, H., Komarizadeh, M.H., Alizadeh, M.R., 2009. Effect of moisture content onsome physical properties of paddy grains. Res. J. Appl. Sci. Eng. Technol. 3, 132e139.

Zhou, Z., Robards, K., Helliwell, S., Blanchard, C., 2002. Ageing of stored rice:changes in chemical and physical attributes. J. Cereal Sci. 35, 65e78.