Prakash Kumar Nayak

Quality comparison of elephant apple juices after high‐pressure processing and thermal treatment

BACKGROUND In the present work, the effect of high pressure processing (HPP) on the quality parameters (pH, °Brix, total acidity, viscosity, colour, antioxidant activity, total phenols, total flavonoids, microbial flora, and sensory analysis) of elephant apple (Dillenia indica) juice was investigated. The juice samples were analysed periodically (0, 1, 2, 5, 10, 20, 30, 40, 50 and 60 days) during 60 days of storage period and results were compared with thermally processed as well as with untreated (fresh juice) samples. RESULTS Slight variations had been observed in the quality parameters like pH, °Brix and total acidity. Other parameters like colour values, antioxidant activity, total phenols and total flavonoids were varied significantly (P < 0.05) in between the treated (HPP and thermal) and untreated juice samples. The microbial counts of the HPP treated samples were lower than the other samples. Sensory results also showed similar results to those of the other analyses that the treated samples were better for consumption rather than the untreated samples. The shelf-life of the HPP processed elephant apple juice was established as 60 days at 4 °C. CONCLUSION This study showed that application of HPP effectively maintained quality attributes and extended shelf life of the elephant apple juice. It may be suggested that application of HPP could be considered for commercial application during storage and marketing.

Effect of microwave pretreatment on the color degradation kinetics in mustard greens (Brassica juncea)

ABSTRACT In the present work, the impact of microwave pretreatment on the thermal degradation of color (chlorophylls) in mustard greens was studied. The drying experiments were conducted in the range of temperatures from 50 to 80°C. The degradation in the levels of chlorophylls has been quantified using Hunter color values (L*, a*, and b*) and calculating total color difference (ΔE). From the color results, the changes in color values (L*, a*, and b*) were observed as inappreciable, and changes in ΔE were found to be increased during drying. Analysis of kinetic data displayed a first-order reaction kinetics for chlorophyll degradation. Arrhenius equation was used to calculate the activation energies for rate constants, and it has been varied from 13.3 to 27.4 kJ/mol. Thermodynamic parameters, enthalpy of activation (ΔH#), and entropy activation (ΔS#) were found to be in the range of 1.40–2.63 J/mol and −293 to −305 J/mol · K, respectively. The data from the present work revealed that the microwave pretreatment of mustard greens remarkably influenced the retention of chlorophylls in the final dehydrated powder.

Effect of Microwave Blanching on Slice Thickness and Quality Analysis of Star Fruit

Star fruit (Averrhoa carambola L.) is one of the underutilized tropical fruits and is a good source of vitamins and minerals. Peroxidase (POD) is the most heat stable enzyme which is used as an indicator for adequacy of blanching process. Blanching is a prerequisite for the preservation of fruits and vegetables. Hot water blanching is having disadvantages like wastewater production and loss of valuable nutrients by leaching. Microwave blanching is one of the emerging and clean technology which seems to provide a better nutrient retention due to shorter heating time and zero wastewater production. Therefore, the present investigation was carried outto identify a suitable blanching method (hot water blanching and microwave blanching)for different slice thickness (5, 10 and 15 mm) of star fruit that ensures enzyme inactivation and maximum retention of therapeutic value (ascorbic acid and oxalic acid). It was observed that blanching at 600, 480, 240 and 120 W power level for aslice thickness of 5, 10 and 15 mm required blanching time of 30-60s, 40-70s, 60-80s, 80-150s and 300-720s respectively. For a given slice thickness, the moisture content of samples decreased with increase in power level. The moisture content was reduced to 84-88 % w.b. from an initial value of 90 % w.b. depending on power level and blanching time combinations. At the same time, the oxalic acid decreased significantly with increase in slice thickness and adecrease in power level. The change in ascorbic acid also showed a similar trend but the influence of slice thickness was not significant (p>0.05). Current research in nutrition and Food Science Journal Website:www.foodandnutritionjournal.org ISSN: 2347-467X, Vol. 5, No. (3) 2017, Pg. 274-281 COnTACT Prakash Kumar Nayak pk.nayak@cit.ac.in Department of Food Engineering and Technology, Central Institute of Technology, Kokrajhar, Assam-783370, India.