erh studies of papaya cheese-libre

8/12/2019 ERH STUDIES of Papaya Cheese-libre

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J. Adv. Sci. and Tech.,7 (l and ll), June, Dec., 2004'12'16. ISSN:0971-9563

EQUTLIBRIUM REIATIVE HUMIDITY (ERH) STUDIES OFPAPAYA CHEESE

SURABHI RAI, VIJAY SETHIAND K.S. JAYACHANDRANDivision of Post harvest Technology, l.A.R.l., Pusa, New Delhi - 1 10012'

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ABSTRACT

Measurement of water activity (aw) is important to determine theoptimum storage conditions of any product. ERH studies of papayacheese revealed optimum RH for storage was 68.3%. The criticalmoisture content of the product was 23.5 per cent having 79.6% RHand beyond this point the quality of the product deteriorated as itbecome soft, darker and mould growth began.Keywords : ERH, water activity, a*, fruit cheese.

INTRODUCTION

The shelf life of processed products is determined by a variety of factors that includes

temperature, pH, relative humidity, moisture content etc. While all these factors can influence

the chemical reactions and microbial activity water activity (aw) is one of the most critical

factors that controlling chemical and biological spoilage of product. Thus it is important to

determine the water activity (aw) refers to the available water in any product and is calculatedby dividing vapour pressure of solution (of solutes in water in most foods) by the vapourpressure of the solvent, usually water (Frazier and Westhoff; 1995). The water activity of a

product can be determined from the relative humidity of the air surrounding the sample when

the air and the sample are at equilibrium. Therefore, the sample must be in an enclosed space

where this equilibrium can take place. Once this occurs, the water activity of the sample and

the relative humidity or ERH. ln the present study the ERH studies of papaya cheese were

carried out to determine the optimum storage RH to as calculate the packaging materialrequirements.

MATERIAL AND METHODSpapaya cheese prepared as per the procedure given by Jain (1954) was used in the present

investivation. Equilibrium relative humidity of guave cheese was determined by the weight

equilibrium method (Wink, 1946). Two grams of cheese was weighed in small aluminiumdishes and these dishes were exposed to different relative humidities, ranging from 0-100%

at ambient temperature. The gian or loss in weight of the product under each humidity was

determined at 24 hours intervals. The observations were recored for product appearance'

discolouration and presence of mold growth etc to determine the critical moisture content,

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13al. ,Aor- Sci. and Tech., 7 (l and ll), June, Dec', 2004

danger point and ideal RH for storage. The selection of packaging materialwas done as per

ffie required quantity of the material to be packed for a certain period of storageat a particular

iernperature and relative humidity as per the standard procedure (Ranganna'1997)

.REVIEW OF LITERATURE

Products equilibrating with a relative humidity of less than 50 per cent are termed

hygroscopic and those with relative humidity above 50 per cent are termed ashygroemmesive

(Landrockand procter, 1951). Various considerations involved in the selection of the

right type

of package are the initial moisture content, ERH of the product, the critical moisture content

above which the product becomes unusable, premissible moisturepickup' size and shape of

the container, desirable shelf life of the product and climatic conditions prevailingduring

storage and transport (Mulikrishna, 1964). The ERH curve for osmoticallydried papaya slices

strowed that finat product has on ERH of 59 per cent. The water activity(aw) achieved was too

low(0.59)forthegrowthofmicroorganisms(AhmedandChoudhari'1995)'sagarandMaini{1992) observed that the critical point and danger

point of dehydrated guava power to be 1 1 '26

and 8.40 percent respectively. Mould growth occurred al21'5 per cent equilibriummoisture

content.

RESULTS AND DISCUSSION

The relationship between the equilibrium moisture content, number of days theproduct took

to equilibriate at a particular relative humidity and the general condition of theproduct at

different relative humidities for the papaya cheese is presented in Table 1 ' The initialmoisture

content of papaya cheese was 1 7.42%.lt can be seen from the moisture equilibrium curve

(Figure 1), that mould growth'commenced at relative humidity of 92 per cent and above'

Aspergitus spp and Penicillium spp were found to be the predominant moulds' The critical

moisture content of the product was 21.4 per cent having 79'6% RH and beyond thispoint the

quality of the product deteriorated as the product became soft, darker and mould growth

began. Danger point was less by 5% relative humidity (19.75"/"\.The optimum relative humidityfor the storage of papaya cheese was found to be 68'3%'

The calculations (Table 2) revealed that the permeability limit (water vapour transmission)

of the packaging material required for storage of papaya cheese was 26.42 X 10-6 cclcmzlsecl

cm of Hg at 250c. The permeability limits indicated that papaya cheese could be safelypacked

in awide range of packaging materials like low-density polyethylene, high-density polyethylene,

polyproPylene etc.

CONCLUSION

The present study predicted that papaya cheese shows best stability at a relative humidity

of 6g.3 per cent, as storage at higher relative humidity condition would result in deteriorationof the product. Moreover the cheese can be safely packed in a wide range of packaging

materials like low-density polyethylene, high-density polyethylene, polypropylene etc'


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J. Adv. Sci. and Tech., 7 (l and ll), June, Dec., 2OO4

REFERENCES

Ahmed, J. and Choudhary, D.R. (1995). Osmotic dehydration of papaya. Ind. Fd. packer.49:5-9-

Frazier, W.C. and Westhoff, D.C. (1995). Food Microbiology. Edn.4ih. Tata McGraw Hill publishingCompany Limited, New Delhi.

Jain, N. L; Das, D. P. and Lal, G. (1954). Preparation of guava cheese. Chem. Age of lndia Series9:88.

Landrock, A.R. and Proctar; B. E. (1951). A new graphical interpolation method for obtainnghumidity equilibrium data with special reference to its role in food packging studies. FoodIech.5:332-335

Ranganna, S. (1997). Handbook of Analysis of Quality Control for Fruit and Vegetable products.

Edn. 2d. Tata McGraw Hiil Pubtishing Company Limited, New Dethi.Sagar, V. R. and Maini S.B. (1992). Economic utilization of rainy season Guava:drying aspects. lncl

Fd. Packer.6:19-22.

Wink, W. A. (1946). Determinig the moisture equilibrium curves of hygroscopic materials. tnd. Eng.Chem. Anal.18:251.

11.1 32.4 43.7 52 68.3 71.4 79.61Equilibrium relative humidity(%)

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Figure 1 : Humidity moisture equilibrium curve for papaya cheede.

MG: MOULDGROWTH

CP: CRITICAL POINT

DP: D.TNGER POINT


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J. Adv. Sci. and Tech., 7 (l and ll), June, Dec.' 2004

Table 1 : Relationship between the equilibrium moisture content and time for equilibration atditferent relative humidities for papaya cheese at embient temperature (11.5 to 12.50c)

(lnitial moisture cpmtemt 19.36%)

Equilibruimrelative

humidity(%)

Equilibriummoisturecontent

(%)

Number ofdays required

to reachequilibrium

Remarks

11.1

32.4

38.0

43.7

52.0

68.3

71.4

79.61

100

3.82

5-30

6.30

7.82

12.1

18.2

19.3

21.4

52

47

42

38

31

26

18

13

Product very hard, brittle, cracks allaround, colour became lighter.

Product very hard, brittle, cracks all around,very light colour



Product had good texture and very lightcolour.

Product had good texture.

Product had good texture but there wasdarkening of product.

Product hecame very soft and mould growthoccurred after 7 days.

Product became semisolid after 2 days and

mould growth occurred after 7 daYs

erh studies of papaya cheese-libre

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