Crack Development in Individually Quick Frozen Cut and Peel Carrots

E:FoodEngineering&PhysicalProperties

JFS E: Food Engineering and Physical Properties

Crack Development in IndividuallyQuick Frozen Cut and Peel CarrotsPHILLIP JOY AND RAJASEKARAN LADA

ABSTRACT: Crack development during freezing (CDF) is one of the major challenges in individually quick frozen(IQF) cut and peel carrot processing. The effects of processing and freezer storage on crack development were exam-ined on the cut and peel carrot variety, Sugarsnax. Carrot samples were removed from the major processing steps,the trans-slicer, the shaper, the blancher, and the dryer, and examined for crack development by measuring per-centage cracked, crack morphology, total soluble solids, moisture levels, and membrane injury index immediatelyafter processing. These parameters were also examined following 20 wk of standard freezer storage for cut and peels.Approximately 2% of nonprocessed carrots were cracked compared to 45% of carrots after the initial trans-slicingstage. As the processing continued, cracking decreased due to the removal of the outer epidermis to 16% of the fin-ished product. This suggests that CDF was initiated at the 1st processing stage. Crack width and depth were 2.3 and2.6 mm, respectively, at the trans-slicer stage and decreased to 1.1 and 1.8 mm at the end of the line. It was foundthat CDF was further exacerbated by freezer storage due to inefficient water removal at the dryer stage. Crack widthand depth increased to 1.5 and 3.0 mm after 20 wk for freezer storage. Root size also played a role in CDF, suggestingthat larger pieces are more susceptible to crack development. Total soluble solid concentrations did not play a rolein crack formation during cut and peel processing.

Keywords: baby carrots, cracking, freezing, membrane injury index, moisture content

Introduction

The individually quick frozen (IQF) cut and peel carrot industryis rapidly expanding due to growing consumer demands. While

IQF is one of the specialized processing methods for preserving car-rots, certain IQF processing steps and freezer storage conditionscan often markedly reduce the quality of the IQF carrots due tocrack development. Crack development during freezing (CDF) hasrecently become a major quality issue of the IQF cut and peel carrots.Cracks in IQF cut and peel carrots reduce not only visual quality butalso consumer acceptance of the product, leading to a considerableprofit loss. Currently, there is very little or no information on thecausal factors that lead to CDF. Nor is there any scientific study toquantify the damage.

Carrots undergo several postharvest processes before they arefreeze-stored. Carrots are washed, sliced, shaped, blanched, dried,and passed through a freezing tunnel before being stored in a freezerthat is generally maintained at temperatures between −12 ◦C and−10 ◦C. The rate of freezing has been shown to be a critical factorin crack development (Rahman and others 1971). Previous researchhas found that cellular damage and leakage are high when samplesare frozen at slow speeds (Fuchigami and others 1995). In the frozencut and peel industry, a high rate of freezing is employed to minimizethe damage caused by slow speeds. Freezing and blanching, in com-bination, do considerably more damage to the cells than freezingalone (Prestamo and others 1998). These processes destroy cytoplas-mic structure and weaken cell walls, leading to breakdown of proto-plasmic structure, causing turgor loss, accumulation of pectins, andthe softening of tissues (Prestamo and others 1998). One of the ma-jor difficulties is detecting crack development during different steps

MS 20060315 Submitted 6/2/2006, Accepted 9/19/2006. Authors are withDept. of Plant and Animal Sciences, Nova Scotia, Agricultural College, Truro,Nova Scotia, Canada B2N 5E3. Direct inquiries to author Lada (E-mail:[email protected]).

of IQF processing. If membrane damage occurs, then crack devel-opment can be measured by electrolyte leakage, which may serve asa tool for detecting crack development and to identify the process-ing step that may be involved in CDF. This study was conducted toidentify the steps in the IQF processing that may contribute to CDF.

Materials and Methods

Cut and peel carrot production and processingCarrots (Daucus carota L. var sativus) cultivar Sugarsnax were

grown in Annapolis County, Nova Scotia (latitude 45.1 N; longitude64.6 W). Carrots were seeded in May 2004 at a seeding rate of 35to 45 seeds 30/cm. Fertility management was determined from soiltests taken during the fall of the previous year and 500 kg/ha of 10N-10P-30K with 2% Mg and 0.2% B of micronutrients were appliedaccordingly. Plant protection was based on crop scouting for anypest and/or disease thresholds (Ministry of Agriculture and Food1993). Carrots were harvested in September 2004 from a single loca-tion using a 3 row ASA Lift carrot harvester (T-3000EH-1, Paul MillerFarm, Hancock, Wis., U.S.A.). Carrots were transported to the pro-cessing plant by trucks and dumped in the storage facility, whichconsisted of a dark, open ventilated shed at ambient temperature,until processing. Carrots were processed within 24 h. The procedurefor processing cut and peel carrots is described by Lazcano and oth-ers (1998). Briefly, carrot pieces entered the system and were carriedin water throughout the process (fluming). The trans-slicer slicedthe carrots into approximately 3 to 4 smaller pieces. The shaper re-moved the outer epidermis of the carrots and formed them into thecharacteristic shape of baby carrots. The steam blancher, operatingat 110 ◦C for 10 to 15 s, was used for microbiological and enzymaticcontrol. The carrots were then cooled by the flume water to about 10to 15 ◦C and then transferred to the dryer, which lasted for approx-imately 20 s. The dryer consisted of a conveyor belt that shook andremoved the excess water of the flum from the carrot pieces. The

E392 JOURNAL OF FOOD SCIENCE—Vol. 71, Nr. 9, 2006 C© 2006 Institute of Food Technologistsdoi: 10.1111/j.1750-3841.2006.00187.xFurther reproduction without permission is prohibited

E:Fo

odEn

ginee

ring&

Phys

icalP

rope

rties

Crack development in cut and peel carrots . . .

final stage of the product was an air-blast freezing system (IQF tun-nel), operating at−2 ◦C. The air velocity and speed of the tunnel wereprecisely monitored using a computer-controlled program, whichallowed for very little variation of these parameters, as per industrystandards.

Moisture analysesMoisture levels were monitored at each sampling point by a mod-

ified relative water content (RWC) procedure (Barrs and Weatherley1962; Anburani 1993; Caldwell 2001). This consisted of weighing thecarrot piece immediately after sampling (FW), placing it in 50 mL ofdistilled water, and reweighing after 24 h to obtain the turgid weight(TW). The samples were then dried in a forced-air oven maintainedat 80 ◦C for 48 h to obtain the dry weight (DW). RWC was calculatedas (FW − DW)/ (TW − DW) × 100.

Percentage crackedCarrot samples (30 kg) were examined before processing to de-

termine the percentage cracked and the crack morphology. Duringprocessing, samples were removed from each of the major steps,the trans-slicer, the shaper, the blancher, the dryer, and after theIQF tunnel. They were sorted visibly into cracked and noncrackedpieces and the percentage was calculated on a mass-to-mass basis.Percentage cracked was also examined after 20 wk of freezer storage.

Crack morphologyDuring processing, samples were removed from each of the major

steps, the trans-slicer, the shaper, the blancher, and the dryer, andthen passed directly through the IQF tunnel. After removal fromthe IQF tunnel, measurements were taken on 3 sets of subsamplesof 1000 g each. For each morphological measurement, 30 crackedcarrot pieces were chosen at random and examined. Crack dimen-sions (length, width, and depth) were recorded using digital calipers(Harbor Freight Tools Camarillo, Calif., U.S.A.).

Freezer storage and crack developmentThe remaining product was then stored in a freezer facility with

high-velocity fans and automatic defrost in cardboard bins linedwith plastic under consistent standard processing parameters. Theywere maintained at−10 ◦C, the standard storage temperature for IQFcut and peel carrots. Three sets of subsamples, 1000 g each, were col-lected at the end of 20 wk of freezer storage. Crack dimensions weremeasured once again to determine if standard storage conditionsenhanced cracking.

Total soluble solids and membraneinjury index analyses

Total soluble solid concentrations and the membrane injury in-dex (MII) were measured to investigate the relationship betweencrack development and the underlying physiological mechanismsand to determine if these procedures could be used as monitoringtechniques. Samples from the major processing steps were removedfrom the freezing tunnel and used to measure total soluble solidconcentrations using a N-20E Brix meter (Atago Co., Ltd., Tokyo,Japan) on noncracked and cracked samples, immediately after pro-cessing and once again after 20 wk of freezer storage at −10 ◦C.Electrolyte leakage and membrane damage were measured as MII,as described by Rajasekaran and Blake (1999). The procedure con-sisted of submersing carrot pieces from each treatment in 30 mLof water overnight. Electrolyte leakage (ECi) was measured usinga conductivity meter (µS) (Con 5 Acorn Series, Oakton, Singapore).The carrot pieces (in water) were then placed in an oven at 80 ◦C for 4h to fully destroy all membranes. Solutes were once again measured

(ECk) and MII was calculated using the following equation: {(Eck– ECi)/ ECi} × 100%. Once again readings were done on samplesimmediately after processing and after 20 wk of freezer storage at−10 ◦C.

HistologyHistological measurements were also taken every 2 wk in both

cracked and noncracked pieces of the freezer-stored carrots to bet-ter understand the origin and the extent of crack penetration intothe tissues. This consisted of taking 5 thin sections of carrot tissuesof each treatment and capturing the image using a camera (Olym-pus OM-S2) attached to the BHZ microscope (Carsen Medical andScientific Co. Ltd. Markham, Canada), under 10× magnification.

Statistical analysesThe general linear models (GLM) procedure (SAS institute Inc,

Cary, N.C., U.S.A.) was used for ANOVA to test statistical significance.Means were separated using Fisher’s protected LSD (P = 0.05) re-peated measures when F-tests were determined to be significant.

Results and Discussion

Cracking before processingAlthough cracking in fresh market carrots has been well docu-

mented to be due to several reasons, including genetic variations,rapid uptake of water prior to harvest, changes in soil environment,the stage of carrot growth, and the elastic properties of the cell wall(McGarry 1993; Hole and others 1999; Sorensen and Harker 2000;Seljasen and others 2001), little is known on crack development inIQF carrots. Our results, in terms of visual cracking, indicated thatbefore processing there was very little or no visual cracks presenton the carrots sampled prior to processing. A lack of visible cracksprior to processing strongly suggests that the cracks develop dur-ing processing and perhaps are amplified during freezer storage. Inthis study, field parameters were not intensively investigated; how-ever, our previous research has shown significant differences amongfields in terms of crack morphology, indicating that edaphic factorsmay play a role in crack development during processing and freezerstorage (Joy and others 2005).

Percentage crackedAs seen in Table 1, the nonprocessed carrot pieces had only 2%

of the samples being cracked, thus supporting the previous state-ment that the majority of the damage is being produced during theprocessing of the cut and peel carrots and not during harvestingor transportation. However, Mempel (1998) observed that mechan-ical injuries during harvest and preparation, such as impacts onhard surfaces and harsh handling, can increase respiration rates andcause nonvisible, internal damage in carrots. Ethylene production

Table 1 --- Percentage cracked of cut and peel carrot va-riety Sugarsnax at different steps of processing. Meanswith the same letters are not significantly different atP = 0.05.

Stage of Percentageprocessing cracked (%)

Nonprocessed 2d

Trans-slicer 45a

Shaper 10cd

Blancher 2d

Dryer 3d

After freezing tunnel 16bc

20-wk freezer storage 23b

URLs and E-mail addresses are active links at www.ift.org Vol. 71, Nr. 9, 2006—JOURNAL OF FOOD SCIENCE E393



has also been shown to increase due to harsh mechanical techniques(Seljasen and others 2001). Such factors may play a role not only innegative sensory qualities like taste but also in other biochemicalchanges that affect cracking later in the processing of the IQF car-rots.

The highest percentage of cracks was observed immediately fol-lowing the trans-slicer stage, suggesting that this initial step is thecause of the cracks. The percentage of cracks decreases as the car-rots were passed through the remaining stages due to the removal ofthe uppermost layers of epidermis by the shaper and contraction oftissues due to heat of the blancher, causing many of the cracks not tobe visible and therefore not apparent. The percentage of cracks onceagain increases after the carrots were passed through the freezingtunnel as seen from the increased visible cracks. Freezer storage for20 wk also significantly increased the percentage of cracked carrots(Table 1).

Weight of cracked piecesThe mean weight of cracked pieces was significantly higher than

the mean weight of noncracked pieces (Figure 1), indicating a strongrelationship between size of the carrot piece and crack formation.While the exact reason is not known, it is possible that large piecesmay have been overmatured and perhaps be less elastic, preventingtissue expansion during processing or freezer storage, contributingto CDF. Heat transfer rates and thermal stress during processing areother mechanisms that may explain this relationship. The shape and

0

2

4

6

8

10

12

Trans-slicer

Shaper Blancher Dryer

Car

rot

Wei

g ht

(g)

Noncracked

Cracked

bc bc

ded

bcc

e

a

Figure 1 --- Weights of noncracked and cracked individualcarrot pieces from various treatments immediately afterIQF process. Means with the same letters are not signifi-cantly different.

0

5

10

15

20

Trans-slicer


Cra

ckLe

ngth

(mm

)

Week 1

Week 20

bcd

aabccd

dcd

d

ab

00.5

11.5

22.5

33.5

Trans-slicer


Cra

ckW

idth

(mm

)

Week 1

Week 20

b

cef

df

cde

a

A) B)

0

1

2

3

4

5

Trans-slicer


Cra

ckD

epth

(mm

)

Week 1

Week 20

bcb

ed

e

c

e

a

C)

Figure 2 --- Crackmorphology of carrotpieces removed fromvarious treatments overfreezer storage time. (A)Crack length, (B) crackwidth, and (C) crack depth.Means with the sameletters are not significantlydifferent at P = 0.05.

size of the carrot pieces will determine the rate and extent of heattransfers within them (Grandison 2006). The smaller the carrot piecethe lower the heat transfer rate, resulting in less thermal stress andlower cracking.

Crack morphologyCrack length showed very little difference among treatments (Fig-

ure 2A). In general, cracks following 1-wk freezer storage were longerin samples obtained from the trans-slicer than the cracks obtainedfrom the shaper and blancher but it was not different from the cracksobtained from the dryer (Figure 2A). In terms of crack width anddepth, the trans-slicer significantly increased cracks compared tounprocessed samples, confirming that the trans-slicer is the initialsource of damage seen in IQF carrots (Figure 2B and 2C). The trans-slicing operation is a quick and abrupt process that is very hard onexternal carrot tissues. Changing the speed, angle of blades, num-ber, and sharpness of blades may reduce the damage caused by thisstep. During the shaping and peeling, process, a significant por-tion of the damage caused by the trans-slicer is removed from thecarrot. This would be the reason for the decline in crack dimensionseen between these 2 steps (Figure 2B and 2C). Shaping and peeling,however, is not enough to remove the cracks entirely; rather it couldcontribute to microcrack formation because of the rough, abrasivenature of the rollers involved in this step. The blancher treatment hadsignificantly lower crack widths compared to the shaper treatments(Figure 2B), suggesting that the blanching treatment may limit crackdevelopment. This may have been accomplished in 2 ways: the cellsmay have stretched more and enzymes such as pectinase, cellulose,and ligase, which dissolve membranes, may have degraded, provid-ing a stronger cell allowing cell expansion without rupturing duringfreezing (Uemura and Yoshida 1986; Fuchigami and others 1995).The dryer stage did not show any reduction in crack width or depth.Although a reduction in moisture content of the carrot pieces wasobserved, from 100% to 98.7%, it appears that the carrots are stillfully saturated with water and that the dryer was of limited effi-ciency and/or the duration of the dryer application was insufficientto remove enough water to prevent cracking during the freezing pro-cess. Excess water carried through microcrevices with the tissue mayhave caused the expansion and crack development when frozen.

E394 JOURNAL OF FOOD SCIENCE—Vol. 71, Nr. 9, 2006 URLs and E-mail addresses are active links at www.ift.org

E:Fo

odEn

ginee

ring&

Phys

icalP

rope

rties


Cracking during freezer storageAlthough crack length did not increase following 20 wk of freezer

storage in any treatment (Figure 2), an increase in crack width anddepth was observed in all treatments over the 20 wk, indicating thatthe storage conditions, including temperature, air velocity, humid-ity, and time, could also play a role in enhancing cracks (Figure 2Band 2C). Due to constraints of the processing plant and the inabil-ity to change environmental conditions, all of these variables werenot able to be fully investigated. Freezing over an extended periodof time, as in storage, can cause the formation of small numbers oflarger crystals in the extracellular locations (Goodenough and Atkin1981; Hung and Kim 1996). The ice crystals may then puncture thecell walls and membranes, causing high electrolyte loss and pro-moting membrane leakage during thawing. Such slow freezing alsocauses irreversible damage to cell structure and texture (Guadalupeand others 1998). This suggests that the cracks observed in IQF cutand peel carrots may have formed during processing and then havebeen exacerbated by freezer storage. This theory is supported by thatdata gathered over this study. Samples taken from the dryer stagebegan with an average crack width of 1.1 mm, but at the end of thestudy in week 20 the width was 1.5 mm (Figure 2B).

The enhancement of cracks during freezer storage may be dueto several reasons. First, the volumetric changes associated withthe water–ice phase transition. Water expands when it is frozen.This model may be very similar to the model described by Kimand Hung (1994): if the internal portions of the carrot are notfrozen immediately in the freezing tunnel but later on during stor-age, it is possible that stresses caused by the volume changes cancause the existing cracks to become more severe, as observed in alltreatments.

Second, moisture content and density increase the possibility offreeze-cracks (Kim and Hung 1994). The moisture content of carrotsincreased from 94% before processing to 100% when placed withinthe processing line, ensuring they are fully saturated throughoutthe entire process until they reached the dryer. A small reductionof moisture (1.3%) was accomplished by this process but was in-sufficient to prevent cracking. A more effective dryer or a longerprocess may be one way to limit CDF in cut and peel carrots duringprolonged freezer storage.

It has been well documented that storage and freezing bringsabout multiple changes in the biochemistry of plant cells and theircell walls (Rahman and others 1971; Uemura and Yoshida 1986;Fuchigami and others 1995; Galindo and others 2004). Cellulosemircofibrils, pectins, and structural proteins are the major com-ponents of the cell wall, which provides the protection from injuryfrom freezing. Changes in any of these components can have con-sequences on the integrity of the plant cell and may contribute tothe deterioration of sensory quality of the product. Rahman andothers (1971) documented cell separation and cell wall disruptionin raw frozen carrots but suggest that the lack of them in blanchedcarrots are caused by physical and chemical changes. Peroxidase,which has detrimental effects on flavor, texture, color, and nutri-tional value, has been documented to be affected by freezer storage(Marin and Cano 1993). Small changes in carbohydrates may oc-cur as biochemical processes are slowed due to lower temperatures,and in particular, water-soluble carbohydrates may be reduced infreezer storage due to water dip loss during thawing (Kidmose andMartens 1999). Carotene concentrations, on the other hand, remainrelatively stable during freezer storage (Kramer 1979; Dutta and oth-ers 2005). There is little data available as to what extent such physicaland biochemical changes in carrots due to freezer storage will haveon the extent of cracking. Tissue structural weakness may triggercracking. The cell walls are connected by calcium (Ca) bonds. Lower

tissue Ca concentration or exceedingly high Ca concentration (thatcause rigidity of cells to expand) would lead to breakage of bonds,thus allowing cracks to develop when stress occurs. Previous un-published research suggests that calcium levels, however, are notchanging during the cut and peel process but further investigationinto these parameters will be needed to fully understand the causesof cracking in IQF carrots.

Total soluble solids analysesTotal soluble solids concentrations of both noncracked and crack

pieces were examined to determine the relationship, if any. Sugarsare thought to lower intermembrane stresses, inhibit protein de-naturation in membranes, and increase membrane stability by in-creasing hydrophobic interactions (Tregunno and Goff 1996). Withrespect to total soluble solids concentration (%), there was no dif-ference between noncracked and cracked carrot pieces in any ofthe treatments (P = 0.7823 at 5% level), suggesting that crack devel-opment is independent of tissue sugar concentration. A slight de-crease in total soluble solids was observed during the trans-slicingprocedure but it had no correlation with crack development and,therefore, cannot be used as a monitoring tool to assess CDF (Table2). An increase in sugar concentration was seen over freezer stor-age. Total soluble solids increased from 7.2 in week 1 to 7.8 in week20 (P = 0.0001 at 5% level). This corresponds well with studies byKidmose and Martens (1999), who also found increases in sucroseconcentrations during freezer storage. They suggest such increasesare due to the reactivation of enzymes during storage that catalyzethe hydrolysis of starch to free sugars, and not to water loss duringstorage and thawing.

Membrane injury indexMII revealed that the highest amount of damage and solute leak-

age occurs at the beginning of processing line, trans-slicing (Ta-ble 2). The carrots sampled immediately following the trans-slicingshowed the highest amount of membrane damage correspondingwith the largest cracks. The subsequent processing steps are still de-structive to the carrot membranes, as shown by the low MII values.The shaper may remove the major portions of the cracks producedby the trans-slicer but is still damaging to the carrots on a cellularlevel, inducing further leakage and suggesting considerably moredamage happening other than visible cracking. MII also increasedsignificantly over freezer storage by 28% (P < 0.001 at 5%), furthersupporting our hypothesis that cracking is enhanced by extendedperiods of freezer storage.

Histological analysesHistological studies have revealed that most cracks seem to orig-

inate in the upper layers of tissues and appear to be caused byphysical damage done during the processing of them. This can beobserved in all treatments, suggesting that it is happening at theinitial trans-slicer stage (Figure 3). These microscopic studies havealso shown that both cracked and noncracked carrot pieces have

Table 2 --- Total soluble solid concentrations and mem-brane injury index of cut and peel carrot variety Sug-arsnax at different steps of processing. Means with thesame letters are not significantly different at P = 0.05.

Total soluble Membrane injurysolids (% Brix) index (%)

Trans-slicer 7.2c 15.1b

Shaper 7.4a 23.2a

Blancher 7.3bc 22.7a

Dryer 7.4ab 23.7a




Figure 3 --- Microscopicobservation of cracksin carrot samplesfollowing 20 wk offreezer storage from(A) trans-slicer, (B)shaper, (C) blancher,and (D) dryer.Magnification 10×.

Figure 4 --- Microscopicobservation reveal icecrystals at theintercellular spacesand tearing of cellularstructure following 20wk of freezer storagefrom (A) trans-slicer,(B) shaper, (C)blancher, and (D)dryer. Magnification10×.

E396 JOURNAL OF FOOD SCIENCE—Vol. 71, Nr. 9, 2006 URLs and E-mail addresses are active links at www.ift.org

E:Fo

odEn

ginee

ring&

Phys

icalP

rope

rties


pores or empty spaces in their tissues (Figure 4). These spaces arefilled with ice when frozen and may be beneficial, allowing for thedissipation of stress and decreasing crack severity. Previous stud-ies by Rahman and others (1971) have shown that definite changesin carrot cells take place during blanching and freezing processesthat affect the texture of the product. Blanching showed no tissuedisruption, suggesting that physiological and chemical rather thanphysical changes cause the loss in cell viability. Freezing, on theother hand, did reveal tissue disruption, suggesting that freezingtemperature is a major cause of cell disruption. Our studies show thatcracking in cut and peel carrots is initiated by physical causes andmost likely enhanced by physiological and chemical changes duringfreezing.

Conclusion

CDF is one of the major challenges in IQF cut and peel process-ing. Cracks in IQF cut and peel carrots appeared to have been

initiated at the 1st step in processing, trans-slicing. MII revealed thathighest amount of damage and solute leakage occurred at the endof processing line, suggesting that the damage begun during trans-slicing was enhanced throughout the remaining steps and furtherexacerbated by freezer storage. Root size also played a role in CDF inthat the mean weight of cracked pieces was significantly higher thanthe mean weight of noncracked pieces. There was no relationshipbetween total soluble solids and crack development. High levels ofmoisture within carrot tissues also play a role in CDF. A more effi-cient drying process may be required to limit CDF.

Acknowledgment

We thank Ms. Janice Sherrard, Mr. Brian Williams, Hillaton FoodLimited, and Mr. Angus Ells, Bragg Lumber Company Lim-

ited, for their technical assistance. Funding support by TechnologyDevelopment, NSDA, and Oxford Frozen Foods Limited is gratefullyacknowledged.

ReferencesAnburani A. 1993. Mechanisms of flower drop in water stressed tomato (Lycopersicon

esculentum Mill.) [master’s thesis]. Annamalai Univ., India.Barrs HD, Weatherley PE. 1962. A re-examination of the relative turgidity technique

for estimating water deficits in leaves. Aust J Biol Sci 15:413–28.Caldwell TJ. 2001. Quaternary ammonium compounds and their roles in enhancing

drought tolerance in carrot, onion, and tomato seedlings [MSc thesis]. DalhousieUniv., Canada.

Dutta D, Raychaudhuri U, Chakraborty R. 2005. Retention of β-carotene in frozen car-rots under varying conditions of temperature and time of storage. African J Biotech4:102–3.

Fuchigami M, Hyakumoto N, Miyazaki K. 1995. Programmed freezing affects tex-ture, pectin composition and electron microscopic structure of carrots. J Food Sci60(1):137–41.

Galindo FG, Brathen E, Knutsen SH, Sommarin M, Gekas V, Sjoholm I. 2004. Changesin the carrot (Daucus carota L. cv. Nerac) cell wall during storage. Food Res Inter37:225–32.

Goodenough PW, Atkin RK. 1981. Quality in stored and processed vegetables and fruit.New York: Academic Press. p 398.

Grandison AS. 2006. Food processing handbook. KGaA, Weinheim: Wiley VCH VerlagGmbH & Co. p 35.

Guadalupe P, Fuster C, Risueno MC. 1998. Effects of blanching and freezing on thestructure of carrot cells and their implications for food processing. J Sci Food Agric77:223–9.

Hole CC, Drew RLK, Smith BM, Gray D. 1999. Tissue properties and propensity fordamage in carrots. J Hort Sci Biotech 74(5):651–7.

Hung YC, Kim NK. 1996. Fundamental aspects of freeze-cracking. Food Tech 50(12):59–61.

Joy PR, Lada RR, Fullerton C, Williams B, Ells A. 2005. Edaphic factors on crack devel-opment of cut and peel carrots. Hort Sci 40(4): 1004.

Kidmose U, Martens HJ. 1999. Changes in texture, microstructure and nutritionalquality of carrot slices during blanching and freezing. J Sci Food Agric 17:1747–53.

Kim NK, Hung YC. 1994. Freeze-cracking in foods as affected by physical properties. JFood Sci 59:669–74.

Kramer A. 1979. Effects of freezing and frozen storage on nutrient retention of fruitsand vegetables. Food Tech 33:58–61.

Lazcano CA, Dainello FJ, Pike LM. 1998. Seed lines, population density, and root sizeat harvest affect quality and yield of cut-and-peel baby carrots. Hort Sci 33(6):972–5.

Marin MA, Cano MP. 1993. Effects of freezing preservation on mango (Mangifera indicaL.) peroxidase. Z Lebensm Unters Forsch 197:537–40.

McGarry A. 1993. Influence of water status on carrot (Daucus carota L.) fracture prop-erties. J Hort Sci 68(3):431–7.

Mempel H. 1998. Washed carrots—quality from harvest to consumer. Gemuse-Munchen 34(7):400–04.

Ministry of Agriculture and Food. 1993. Integrated pest management for onions, car-rots, celery and lettuce in Ontario. Ontario, Canada: Ministry of Agriculture andFood.

Prestamo G, Fuster C, Risueno MC. 1998. Effects of blanching and freezing on thestructure of carrot cells and their implications for food processing. J Sci Food Agric77:223–9.

Rahman AR, Henning WL, Westcott DE. 1971. Histological and physical changes incarrots as affected by blanching, cooking, freezing, freeze drying and compression.J Food Sci 36:500–2.

Rajasekaran LR, Blake TJ. 1999. New plant growth regulators protect photosynthe-sis and enhance growth under drought of jack pine seedlings. Plant Growth Regul18:175–81.

Seljasen R, Bengtsson GB, Hoftun H, Vogt G. 2001. Sensory and chemical changes infive varieties of carrot (Daucus carota L.) in response to mechanical stress at harvestand post-harvest. J Sci Food Agric 81:436–47.

Sorensen L, Harker FR. 2000. Rheological basis of splitting in carrot storage roots. JAmer Soc Hort Sci 125(2):212–6.

Tregunno NB, Goff HD. 1996. Osmodehydrofreezing of apples: structural and texturaleffects. Food Res Inter 29:471–9.

Uemura M, Yoshida S. 1986. Studies on freezing injury in plant cells. Plant Physiol80:187–95.


Documents

Crack Development in Individually Quick Frozen Cut and Peel Carrots