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TRIBHUVAN UNIVERSITY

INSTITUTE OF ENGINEERING

THAPATHALI CAMPUS

A Seminar paper on

Effect of Storage Time and Type of Conditioning on Filling Value of Cut

Rolled Stem of Tobacco

By

Bikram Dahal

A SEMINAR PAPER

SUBMITTED TO THE DEPARTMENT OF INDUSTRAIL ENGINEERING

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE

DEGREE OF BACHELOR IN INDUSTRIAL ENGINEERING

DEPARTMENT OF INDUSTRIAL ENGINEERING

KATHMANDU, NEPAL

SEPTEMBER 22, 2014

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Abstract

Stem of tobacco has to be conditioned either with steam/water or water only

depending on bulking time available and best utilization of machines. Different type

of conditioning have effect on filling value so it’s necessary to find out if there is

significant effect of type of conditioning on filling value. Some batch of CRS are keep

in advance for processing next day in CRS bin. Storage time also effect filling value.

This research paper discuss about effect of storage time and type of conditioning on

filling value Filling power of tobacco has great economic important in tobacco

industries as well as affects every parameter of final cigarettes produce like losses end,

firmness, density, burning rate etc. so the effect of time of storage and type of

conditioning was studied. Result show that type of conditioning have no significant

difference in filling value for two grade of stem whereas remaining one grade’s filling

value is significantly higher when cold conditioned than hot, whereas storage time has

significant effect on filling value. Filling value of CRS kept in advance have greater

filling value than CRS proceed on same day.

Keywords: filling power, CRS, Tobacco Stem.

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1. Introduction

Tobacco leaf is separated into two parts lamina and stem. Stem is the midrib of leaf

and remaining portion is known as lamina. Most cigarette contains approximately 20%

stem by weight. The material is low cost and has a potential, through processing, to

give a high filling value. However, when smoked, stem is typically described as woody,

cellulosic, burnt and acrid with more irritating properties than lamina (Stephenson,

1994). So stem are processed in tobacco industries, first conditioned, bulked, cut into

small piece in 140-160CPI, expanded and then rapidly dryer and mixed with lamina at

ratio of 20:80 to reduce its irritating property. (ITC)

Filling value is define as the ability of a unit weight of the material to occupy space.

Applied to cigarettes, the filling value of tobacco blend is its ability to ‘fill out’ or ‘firm

up’ a cigarette of constant volume i.e. circumference and length constant (Akehurts,

1968). Filling power is intrinsic property of material Firmness is define as a cigarette

rods resistance to compression. Each Manufacture established an internal standard of

firmness of his cigarette brand. One of studies conducted by (Wong, 1976) concluded

that the relationship between cigarette firmness, in term of weight savings, and tobacco

filling power was highly significant (R=0.83). Other researcher also support this facts

(Walker, 1974). To illustrate: The effect of Filling value and cost , Assuming a finished

blend cost of Rs. 2000 per kg, a 4 percent increase in bland filling power will save

manufacturer approximately RS 3.4 crore per billion of cigarettes sold (Semfie ld,

1973). Considering average weight of cigarette of 850mgms per cigarette. And 2%

Increase in filling power is claimed for the Water Treated Stem process compared to

CRS when incorporated at 20% in cigarettes (Grandpre, 1887).

Conditioning is the process of spraying steam/water or water only on dry stem or

lamina to increase moisture for cutting. Conditioning can be done by two method hot

and cold. In hot conditioning steam/water is sprayed over stem in closed chamber at

fixed temperature and pressure and for certain time (as per the standard protocol of

company). And in cold conditioning only water is used instead of steam and water. For

cold conditioning stem has to be bulked for 12 hours and for hot conditioning 2 hours.

(ITC)

If stem has to process next day they are cold conditioned earlier day. So that whole

machines can be fully utilized. I.e. if conditioning is not carried out the day before,

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cutter has to be in ideal time till conditioning and bulking time of CRS. Total of eight

operation can be cold conditioned in Surya Nepal. Presently mostly only two-three

operation are cold conditioned as this two-three operation can be cut during same time,

as hot conditioning and bulking is carried out next day. In similar way CRS are stored

in advance for next day so that lamina dryer line can be operated along with lamina

conditioning line. As conditioned lamina are also kept in advance. So that no machines

are ideal.

So due to these reason it is necessary to know the effect of type of conditioning

and storage time on filling value. So that process variation of filling value can be

explained and best type of conditioning can be found. This help to make necessary

adjustment in program of conditioning type such that most of batch of stem can

conditioned in best conditioning type of conditioning process. Knowing the effect of

storage time will help to explain variation of CRS filling value between two operation

to some extend and make procedure to store cut tobacco at least 12 hours before

processing.

.

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2. Limitation

Filling value where measured at different moisture using moisture

correction factor. Moisture correction factor was best 12%-15%. Few

sample had filling value larger than 15%.

Process variation can be observed so large data were collected to reduce

error.

Temperature of samples were different.

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3. Objective

To find effect of conditioning on filling value.

To find effect of storage time on filling value.

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4. Methodology

CRS’s filling value of two month was collected from data daily report of QUAS of

Surya Nepal. Data collected were categorized as type of stem along with time of

storage and type of conditioning. Addition 10 operation were tracked of GRADE 3

stem. Sample where taken after CRS bin and their filling value were measured and

some portion of same small were kept in humidity cabin, maintained at 21+1 C and

HR 62+2 for two days and it filling value were measured. Filling value of CRS cutter

is measured using MC and height of sample in densimeter. Moisture Content was

measured by weighting 10±0.005 gram of sample in tin box and then keeping tin box

in oven for 3hours.followed by half an hour in silica jell compartment. Finally net

weight of sample was taken.

Moisture content= 10- Net weight of tin after keeping in oven and silica jell.

Height was measure using densimeter. Densimeter consist of graduated cylinder of

radius(R) with a closely fitting plunger and weight. The procedure for measuring

height is a known weight i.e. 20 ±0.05 gm. weight is place in cylinder and plunger is

inserted into cylinder gradually weight of 3 kg is applied. After 30 sec height (H) of

plunger is measure from based of cylinder.

Volume occupied by sample= πR2H.

Filling value = volume* moisture correction factor.

For study of effect of hot conditioning and cold conditioning, effect of storage time

on measure filling value of CRS, first normality of data was tested using Shapiro-wiki

test than for equality of variation Levene test was carried out followed by t-test to find

if two series of data had significant difference.

Shapiro-Wilk test was carried out in each data series to find out if data series were

normal disturbed or not. The null-hypothesis of this test is that the population is

normally distributed. Thus if the p-value is less than the chosen alpha level, then the

null hypothesis is rejected and there is evidence that the data tested are not from a

normally distributed population. In other words, the data are not normal. On the

contrary, if the p-value is greater than the chosen alpha level, then the null hypothesis

that the data came from a normally distributed population cannot be rejected. E.g. for

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an alpha level of 0.05, a data set with a p-value of 0.05 rejects the null hypothesis that

the data are from a normally distributed population (Shapiro, 1965). However, since

the test is biased by sample size, the test may be statistically significant from a normal

distribution in any large samples. Thus a Q–Q plot is required for verification in

addition to the test (Markowski, 1990).

And Levene test for equality of variation was used to test whether variation

between sample were equal or not. Levene's test is an inferential statistic used to assess

the equality of variances for a variable calculated for two or more groups. Levene's test

assesses this assumption. It tests the null hypothesis that the population variances are

equal. If the resulting P-value of Levene's test is less than some significance level

(alpha value), the obtained differences in sample variances are unlikely to have

occurred based on random sampling from a population with equal variances. Thus, the

null hypothesis of equal variances is rejected and it is concluded that there is a

difference between the variances in the population (Levene, 1960).

For normal population, when the sample sizes n1 and n2 are not large and σ1≠ σ2.

We purpose

Null hypothesis H0= there is no significant difference between two mean.

Alternative hypothesis H1= there is significant difference between two mean.

Test statistic “t” = (x̅1−x̅2)−𝛿

√(𝑆1

2

𝑛1−

𝑆22

𝑛2)

Where

x̅1and x̅2 are means of population

s1 and s2 are standard deviation of population.

If calculated p-value is less than significance level α. Null hypothesis H0 is rejected.

If calculated p-value is more than significance level α we fail to reject Null hypothesis.

For comparison of two significant different mean bar graphs are used.

All analysis of tests where were carried out using SPSS tool.

(Rice, 2006)

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5. Literature Review

Stem expansion is favored at high temperatures (up to 250°C) and high moisture

levels (up to 30% m .c.). These factors lead to an increase in the water vapor pressure

inside the cells of the stem and to a more elastic cell structure (Grandpre, 1887).At

these temperatures, heat enhances the production of water from the decomposition of

low molecular weight polysaccharides and sugars so more water is available for

expansion (Reynard, 1985). A high internal pressure in stem is necessary to have good

expansion and, in the build-up of this pressure, the stem cell structure plays an

important role. Four types of cell structure are present in stem: epidermis cells,

collenchyma cells, parenchyma cells and vascular bundle cells. The structure of the

epidermis cells which are circularized and covered with wax, and the collenchyma

cells which are thickened with cellulose, restrict the loss of water during heating, thus

contributing to the build-up of the internal pressure. After expansion the walls of these

cells are rigid enough to keep their new structure. Stems expanded in a vacuum oven

at room temperature showed the same behavior as conventionally expanded stem

indicating that expansion is mainly due to the build-up of internal gas pressure in the

cell walls (Reynard, 1985).Stem are heated in hot conditioning as heating open the

capillary’s that have shrink during drying so moisture can easily penetrate. Hence

bulking time is less for hot conditioning. (ITC)

Longer stem expand more than shorter stem due to pressure drop. (Grandpre, 1887).

Temperature 85 0F at 21.5 % MC of tobacco is best environment for cutting lamina, if

temperature is increase 90-95 there is 0.6-1.2g/cc loss in filling value. Or else MC of

22-22.5% at 110 0F to 115 0F is best for cutting (Morris, 1984).

Each stem have its own instinct property to absorb water. For example consider a

blend made up of equal quantities of two types; one able to absorb water quickly and

the other absorbing more slowly. If we assume that each stem had the same opportunity

to absorb water and that the average moisture of the blend is correct, then we are forced

to accept that 50% of the blend is drier than Intended and 50% wetter than intended.

Steam are passed over series of vibrating conveyer so that they roll. The advantage of

rolling is that enables a better cheese formation at the cutter. The better cheese

formation, the fewer heavies’ pullouts (winnows) and the lower the cheese pressure

which can be used. Lower cheese pressure usually results in higher filling power and

cleaner cutter operation. The disadvantage of rolling is the danger of damage to the

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stem fiber and cell structure. Damage will occur if the stem does not have a sufficient ly

high penetrated moisture content. Any cracking, rupturing or fibrillation of the stem at

rolling is an indication of inadequate conditioning and will lead to loss of filling power

and yield potential, Cutting moistures have in the past been set somewhat arbitrarily

Today the philosophy would be to use as high a penetrated moisture content as possible.

The use of water sprays to lubricate and clean the rollers will impart some surface

moisture to the stem and in effect reduce the penetrated moisture associated with an

out moisture test (Solm, 1993).

t-test is used widely in comparison between two means in physiology to weapons

(Onlinestatbook, 2014).

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6. Result

Following is the result of normality test all data series used for t-test. As significant

value or p-value is greater than 0.05 we failed to reject null hypothesis i.e. data are

normal.

Tables 6.1 p-value of Shapiro-wilk Test

* S = Sample processed on same day A =Sample processed advance

CC =Cold Conditioning HC = Hot Conditioning

Lavene test result show that all value except GRADE 2 after and same have equal

variation. As p-value for all other data series is more than 0.05.

Table 6.2 Levene-s test p_value along with t-test p_value

Grade Stem

Shapiro-Wilk Type Of Conditioning

Shapiro-Wilk

p_value p_value

Filling

value

GRADE 1 "A" 0.353 GRADE 1 "CC" 0.15

GRADE 1 "S" 0.353 GRADE 1 "HC" 0.934

GRADE 2 "A" 0.619 GRADE 3"CC" 0.432

GRADE 2 "S" 0.426 GRADE 3"HC" 0.98

GRADE 3"A" 0.438 GRADE 2 "CC" 0.392

GRADE 3"S" 0.717 GRADE 2 "HC" 0.889

Levene's Test for

Equality of Variances

t-test

F p_value p_value

Filling

value

GRADE 1 "A"/

"S"

Equal variances

assumed

0.02 0.89 0.004

GRADE 2 "A" /"S"

Equal variances not assumed

4.75 0.03 0.019

GRADE 3"A"

/"S"

Equal variances

assumed

0.58 0.45 0.196

GRADE 3"A" /"S" “My samples”

Equal variances assumed

0.07 0.8 0.022

GRADE 1 "CC"/"HC"

Equal variances assumed

0 0.96 0.008

GRADE 3"CC"/"HC"

Equal variances assumed

0.17 0.68 0.417

GRADE 2

"CC"/"HC"

Equal variances

assumed

1.78 0.19 0.092

GRADE 2 "CC"/"HC" "A"

Equal variances assumed

0.02 0.9 0.555

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t-test result between hot and cold conditioning for different grade of stem shows

that there is no significant different between hot and cold conditioning for GRADE

3and GRADE 2 and for GRADE 1 filling value differ significantly for type of

conditioning. Average filling value of cold conditioning is always greater than that of

hot conditioning.

t-test result of same day and advance show that there is significant difference when

CRS are proceed same day or kept for next day. FV of CRS advance is always greater

than CRS of same day.

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7. Analysis and discussion

From t-test it can be observed that type of conditioning has no significant effect on

filling value from GRADE 3and GRADE 2 but has significant effect on filling value

of GRADE 1. Possible theory for this is that, this is due to size of stem. One type of

stem used in GRADE 1 are longer so it takes more time for water to penetrated as

moisture mostly penetrated through capillary action. As it can be observed that cold

conditioning always has higher filling value than cold conditioned stem this is due to

high temperature can damage some cells and if there is already cracks, holes in stem it

can further damage it. As stem have their own intrinsic property to absorbed water and

blend of steam is mixture of many grade it is possible that for some grade of stem hot

conditioning followed by two hours of bulking is not enough. But cold conditioning

and twelve hour of bulking is enough. Other factor effecting filling value may be

temperature of sample while cutting as hot conditional same have few degree Celsius

higher temperature than cold conditioned sample.

From t-test it is observed that storage time has significant effect on filling value of

CRS. The theory is that once expanded cell need certain time to form rigid structure

that can withstand pressure applied to CRS during measurement of height. As cell

membrane is made of polysaccharides which need time to form a rigid shape. The

temperature of sample where also different as advance sample are process at morning

time when temperature is low. As cell with lower temperature have more rigid cell

wall structure than cell at higher temperature. (Waikato, 2014).

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8. Conclusion

Filling Value of tobacco stem is not effected by type of conditioning process from

all grade except that for GRADE 1 stem. This grade of stem have longer stem size so

cold conditioning provides enough time for penetration of moisture. Time of storage

effect the filling value as expanded tobacco need time to for rigid cell structure. Due

to rapid evaporation tobacco don’t loses their expanded structure but if force is applied

on them their structure collapses. Storage for day provides time for these structure to

be rigid and permanent. Hence the filling value of higher of CRS kept in advance is

higher than filling value of CRS processed same day.

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References

Akehurts, B. M. (1968). Tobacco.

Grandpre, D. Y. (1887). A Review of Firmness and Tobacco Properties. Montreal:

Imperical Tobacco Limited, R&D Division.

ITC. (n.d.). Standard Operating Procedure . Indian Tobacco Company Limited.

Levene, H. (1960). Contributions to Probability and Statistics: Essays in Honor of

Harold Hotelling. Stanford University Press. pg 278-292.

Markowski, C. A., & Markowski, E. P. (1990). Conditions for the Effectiveness of a

Preliminary Test of Variance. The American Statistician, 44.

Morris, P. (1984). Aspects of Tobacco Processing . Phillips Morris.

Onlinestatbook, (2014). Onlinestatbook Retrieved from the case studies:

http://onlinestatbook.com/2/case_studies/case.html

Reynard, R. J. (1985). Wetting, Heating and Drying Single Tobacco particles, Part II.

British American Tobacco RD. 1994.

Rice, j. A. (2006). Mathematical Statistics and Data Analysis. Duxbury Advanced.

Semfield, D. M. (1973). Tobacco filling Power: part 1. Cigarettes Maufacturing

Techonolgy , 46.

Shapiro, S. S., & Wilk, M. B. (1965). An analysis of variance test for normality

(complete samples). Biometrika, 52.

Solm, E. J., O'connor, L. H., Young, H. J., & Beeson, D. (1993). Drying and

Moisturing of Tobacco Stems. BAT, product Development.

Stephenson, T. A. (1994). Investigation Into the Effect of Stem Moisture Content on

Process & Product Performance. Southampton : British-American Tobacco Co. Ltd.

The University of Waikato, (2014, 20 9). Plant Structure and function. Retrieved from

Science on the Farm: http://sci.waikato.ac.nz/farm/content/plantstructure.html

Walker, E. K., & Voisey, P. W. (1974). Measurement of Cigarette Firmness and Its

Relationship to Filling Value of cut Tobacco. Tobacco 176(2T).

Wong, J. S., & Wilson, T. L. (1976). A Study of Variation in Tobacco Filling Power

and Cigarette Firmness. Amatil Report .

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Appendix 1: Normality Test Result

Grade Stem Shapiro-Wilk

Df p_value

Filling value

GRADE 1 "A" 14 0.353

GRADE 1 "S" 36 0.353

GRADE 2 "A" 48 0.619

GRADE 2 "S" 67 0.426

GRADE 3"A" 11 0.438

GRADE 3"S" 14 0.717

Type_Of_Conditioning Shapiro-Wilk

df p_value

Filling values

GRADE 1 "CC" 19 0.15

GRADE 1 "HC" 17 0.934

GRADE 3"CC" 23 0.432

GRADE 3"HC" 19 0.98

GRADE 2 "CC" 44 0.392

GRADE 2 "HC" 22 0.889

Shapiro- Wilk Statistics of Type of Conditioning Samples

Shapiro- Wilk Statistics of Same Day and Advance Samples

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Appendix 2: t-test statistics

Levene's Test

for Equality of

Variances

t-test for

Equality of

Means p_value (2-

tailed)

Mean Differ

ence

95% Confidence

Interval of the

Difference F

p_val

ue t df

Lower Upper

Filling value

GRADE 1

"A"/ "S"

Equal

variances

assumed

0.02 0.89 3.03 48 0.004 2.01 0.68 3.35

GRADE 2 "A" /"S"

Equal

variances not

assumed

4.75 0.03 2.28 85.96 0.025 0.88 0.11 1.64

GRADE

3"A" /"S"

Equal

variances

assumed

0.58 0.45 1.33 23 0.196 0.79 -0.44 2.01

GRADE

3"A" /"S"

Equal

variances

assumed

0.07 0.8 2.47 23 0.022 1.47 0.24 2.71

GRADE 1

"CC"/"HC"

Equal

variances assumed

0 0.96 2.83 34 0.008 1.85 0.52 3.18

GRADE

3"CC"/"H

C"

Equal

variances

assumed

0.17 0.68 0.82 40 0.417 0.39 -0.57 1.36

GRADE 2

"CC"/"HC

"

Equal

variances

assumed

1.78 0.19 1.71 64 0.092 0.76 -0.13 1.66

GRADE 2

"CC"/"HC" "A"

Equal

variances assumed

0.02 0.9 0.59 47 0.555 0.38 -0.92 1.69

t-test Statistics of Type of Conditioning and Time Difference Samples