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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 OF PAPAYA CHEESE

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

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ABSTRACT (aw) is important to determine the activity water Measurement of

optimum storage conditions of any product. ERH studies of papaya cheese revealed optimum RH for storage was 68.3%. The critical moisture content of the product was 23.5 per cent having 79.6% RH and beyond this point the quality of the product deteriorated as it become soft, darker and mould growth began. Keywords : ERH, water activity, a*, fruit cheese.

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( 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 calculated by dividing vapour pressure of solution (of solutes in water in most foods) by the vapour pressure 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 material requirements. MATERIAL AND METHODS papaya 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 aluminium dishes 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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,Aor- Sci. and Tech., 7 (l and ll), June, Dec', 2004

packaging material was done as per danger point and ideal RH for storage. The selection of period of storage at a particular ffie required quantity of the material to be packed for a certain procedure (Ranganna' 1997) iernperature and relative humidity as per the standard .REVIEW OF LITERATURE

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50 per cent are termed Products equilibrating with a relative humidity of less than termed as hygroemmesive hygroscopic and those with relative humidity above 50 per cent are of the right type (Landrock and procter, 1951). Various considerations involved in the selection product, the critical moisture content of package are the initial moisture content, ERH of the moisture pickup' size and shape of above which the product becomes unusable, premissible conditions prevailing during the container, desirable shelf life of the product and climatic for osmotically dried papaya slices storage and transport (Mulikrishna, 1964). The ERH curve The water activity (aw) achieved was too strowed that finat product has on ERH of 59 per cent. low(0.59)forthegrowthofmicroorganisms(AhmedandChoudhari'1995)'sagarandMaini point and danger point of dehydrated guava power to be {1992) observed that the critical

1 1 '26 moisture equilibrium per cent and 8.40 percent respectively. Mould growth occurred al21'5 content.

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RESULTS AND DISCUSSION number of days the product took The relationship between the equilibrium moisture content,

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

Table 1 ' The initial moisture different relative humidities for the papaya cheese is presented in equilibrium curve content of papaya cheese was 1 7.42%.lt can be seen from the moisture per cent and above' (Figure 1), that mould growth'commenced at relative humidity of 92 predominant moulds' The critical Aspergitus spp and Penicillium spp were found to be the beyond this point the moisture content of the product was 21.4 per cent having 79'6% RH and growth quality of the product deteriorated as the product became soft, darker and mould point was less by 5% relative humidity (19.75"/"\.The optimum relative humidity began. Danger

for the storage of papaya cheese was found to be 68'3%' transmission) The calculations (Table 2) revealed that the permeability limit (water vapour was 26.42 X 10-6 cclcmzlsecl of the packaging material required for storage of papaya cheese could be safely packed papaya cheese cm of Hg at 250c. The permeability limits indicated that polyethylene, high-density polyethylene, in awide range of packaging materials like low-density polyproPylene etc. CONCLUSION

relative humidity The present study predicted that papaya cheese shows best stability at a would result in deterioration of 6g.3 per cent, as storage at higher relative humidity condition packed in a wide range of packaging the cheese can be safely

of the product. Moreover polypropylene etc' materials like low-density polyethylene, high-density polyethylene,


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

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REFERENCES Ahmed, J. and Choudhary, D.R. (1995). Osmotic dehydration of papaya. Ind. Fd. packer.49:5-9Frazier, W.C. and Westhoff, D.C. (1995). Food Microbiology. Edn.4ih. Tata McGraw Hill publishing Company Limited, New Delhi.

Jain, N. L; Das, D. P. and Lal, G. (1954). Preparation of guava cheese. Chem. Age of lndia Series 9:88.

Landrock, A.R. and Proctar; B. E. (1951). A new graphical interpolation method for obtainng humidity equilibrium data with special reference to its role in food packging studies. Food

Iech.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.

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Fd. Packer.6:19-22. Wink, W. A. (1946). Determinig the moisture equilibrium curves of hygroscopic materials. tnd. Eng. Chem. Anal.18:251.

Figure 1 : Humidity moisture equilibrium curve for papaya cheede.

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MG: MOULDGROWTH

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CP: CRITICAL POINT

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DP: D.TNGER POINT

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11.1

32.4

43.7 52

68.3 71.4

Equilibrium relative humidity(%)

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Table 1 : Relationship between the equilibrium moisture content and time for equilibration at ditferent relative humidities for papaya cheese at embient temperature (11.5 to 12.50c) (lnitial moisture cpmtemt 19.36%) Equilibruim relative humidity

Equilibrium moisture

content

Number of days required to reach

(%)

(%)

equilibrium

11.1

3.82

52

Product very hard, brittle, cracks all around, colour became lighter.

32.4

5-30

47

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

38.0

6.30

42

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

43.7

7.82

38

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

52.0

12.1

31

Product had good texture and very light colour.

68.3

18.2

26

Product had good texture.

71.4

19.3

18

Product had good texture but there was darkening of product.

79.61

21.4

13

Product hecame very soft and mould growth occurred after 7 days.

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

Remarks

Product became semisolid after 2 days and mould growth occurred after 7 daYs

Erh studies of papaya cheese libre  
Erh studies of papaya cheese libre  
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