PRESERVATION OF GUAVA PULP USING OHMIC HEATING
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Date
2016
Authors
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Journal ISSN
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Publisher
AAU, Anand
Abstract
Guava (Psidiumguajava L.) is one of the most tropical fruit, rich in high-profile
nutrients with its unique flavour, taste and health-promoting qualities. The guava fruit
fits in functional food category, often called ‘super fruit’. It is rich in lycopene and
ascorbic acid; especially it contains ascorbic acid (100-200 mg/100 g) higher than a
fresh orange juice (60-80 mg/100 ml). Guava has excellent digestive and nutritive
value, pleasant flavour, high palatability and availability in abundance at moderate
price. Guava pulp is used in preparation of jams, mixed fruit drinks, baby food,
confectionary and ice-cream. Conventionally, it is being obtained by washing, peeling,
pulping and thermal processing of fully ripened guava fruit at 90±2°C for minimum 4
min., for acceptable sterility. Overheating is in general practice to meet the safety
requirements. This results in great loss of heat sensitive nutrients. Ohmic heating is
considered as a better and promising alternative over the conventional heating process;
in which rapid and volumetric uniform heating is possible. Therefore, this study was
undertaken with the primary objective of enhancement of shelf life of guava pulp
through ohmic heating. Process parameters considered for the study were: voltage (120-
180 V), temperature (70-90°C) and holding time (2-6 min.) for maximum reduction in
enzyme activity and total viable counts, and minimum reduction in ascorbic acid.
Factorial design was adopted for the study of effect of these variables on the shelf life
of guava pulp and for optimization of the process parameters. . Electrical conductivity
of the pulp ranged from 8.5664 - 17.8321 mS/cm. The specific heat of the pulp was
ranges between 90.3851 to 741.5922 J/kg °C.
ii
The optimized studied parameters for maximum reduction in total viable count,
enzyme activity and maximum retention of ascorbic acid were: 120 V, 90°C and 4 min.
for voltage, temperature and holding time, respectively. The optimized results for
ascorbic acid, enzyme activity and total viable count were 214.61 mg/100gm, 3.11 PE
units/g and 2.05 logCFU/ml respectively. The results showed that the ohmically heated
processed pulp was stable and acceptable upto ninety days under refrigerated condition
at ± 7°C. As compared to ohmically heated pulp the conventionally heated pulp was
stable and acceptable upto 60 days under refrigerated condition at ± 7°C.
Description
Keywords
Food Processing Technology, Bio Energy, method