PRESERVATION OF JAMUN JUICE THROUGH SONICATION ASSISTED OHMIC HEATING

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Date
2023-05-19
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ACHARYA NG RANGA AGRICULTURAL UNIVERSITY
Abstract
Indian blackberry (SyzygiumcuminiL. Skeels/ Eugenia Jambolana Lam) is commonly known as “Jamun” in Indian sub-continent. India contributes a higher production of jamun. Jamun is taken mostly for medicinal purposes than a normal fruit. It is a rich source of anti-oxidants, anthocyanins, phenols, vitamin and minerals. As most of the Jamun production is being neglected, unutilized and wasted due to lack of processing technologies. Processing jamun fruit into juice will be a better option as the fruit juice can attract more consumers and gains market space. In general to preserve fruit juices, thermal processing along with chemical preservatives is widely used. Thermal processing of juices causes unwanted changes in taste and odour with damage to bio-active components and functional properties. Sonication assisted ohmic heating is a good alternative technique to replace the conventional heat treatment process. Sonication is considered a suitable technique for treatment of liquid foods due to the fact that transferring of acoustic energy to food is instantaneous and throughout the whole product, with reduction of the processing time, higher throughput, and lower energy consumption in succeeding treatment. Ohmic heating contributes quick and uniform heating, resulting in less thermal damage to the foods. In addition, as there is no hot surface, fouling problems and heat damage to the product can be reduced. Therefore, a high-quality product with minimal structural, nutritional or organoleptic changes can be manufactured in a short operating time. The ohmic heating of jamun juice was carried out at voltage gradient (20-40 V cm-1), temperature range (40-75 ˚C) and treatment time range (2-4 min). Response surface methodology following Box- Behnken design (BBD) was used to optimize the response parameters i.e., pH, TSS, anthocyanin content and total phenolic content. Significant changes were observed in pH, TSS, anthocyanin content and total phenolic content during ohmic heating treatments. The optimized condition for ohmic heating of jamun juice was observed at 30 V cm-1, 57.5 ˚C and 3 min. The sonication of jamun juice was carried out at amplitude range (40-100 %) and treatment time range (5-15 min). Response surface methodology following Central Composite Design (CCD) was used to optimize the response parameters i.e., pH, TSS, anthocyanin content and total phenolic content. Slight significant changes were observed in pH and TSS during sonication treatments. Anthocyanin content and total phenolic content showed a significant change during sonication treatments. The optimized condition for sonicated jamun juice was observed at 28% amplitude and treatment time of 10 min. The optimized sonicated sample was ohmic heated at different ohmic heating conditions. The ohmic heating of sonicated jamun juice sample was carried out at voltage gradient (20-40 V cm-1), treatment range (40-75 ˚C) and treatment time range (2-4 min). Response surface methodology following Box- Behnken design (BBD) was used to optimize the response parameters i.e., pH, TSS, anthocyanin content and total phenolic content. Slight significant changes were observed in pH and TSS during ohmic heating treatments. Significant changes were observed in anthocyanin content and total phenolic content during ohmic heating treatments. The optimized condition for ohmic heating of jamun juice was observed at 30 V cm-1, 75 ˚C and 4 min. . Both the non-sonicated and sonicated optimized samples were kept for storage studies at ambient condition (28±2 ˚C) and refrigerated condition (4±2 ˚C). During the storage period the pH, TSS, anthocyanin content, total Phenolic content, ascorbic acid and total soluble sugars of fresh jamun juice stored at ambient and refrigerated condition were reduced from 3.43 to 3.33, 13.13 to 11.13 ºBrix, 79.18 to 61.81 mg/100mL, 146.79 to 125.06 mg/100mL, 12.34 to 10.11 mg/100mL and 8.64 to 8.41%, 3.43 to 3.43, 13.13 to 12.50 ºBrix, 79.18 to 60.30 mg/100mL, 146.79 to 123.30 mg/100mL, 12.34 to 11.11 mg/100mL and 8.64 to 8.63%. The maximum total plate count, yeast count and mould count of 11 x 103 CFU/mL, 12 x 102 CFU/mL and 3 x 102 CFU/mL were observed in fresh juice sample on 14th day of storage at refrigerated condition. During the storage period the pH, TSS, anthocyanin content, total Phenolic content and ascorbic acid of optimized ohmic heated juice sample stored at ambient and refrigerated condition were reduced from 3.63 to 3.43, 13.63 to 7.43 ºBrix, 65.47 to 46.01 mg/100mL, 192.83 to 166.30 mg/100mL and 12.25 to 10.23 mg/100mL, total soluble sugars increased from 7.51 to 7.53%, 3.63 to 3.30, 13.63 to 12.00 ºBrix, 65.47 to 41.88 mg/100mL, 192.83 to 99.44 mg/100mL and 12.25 to 8.16 mg/100mL, total soluble sugars from 7.51 to 6.13% and optimized ohmic heated sonicated jamun juice sample stored at ambient and refrigerated condition were reduced from 3.57 to 3.33, 13.33 to 11.97 ºBrix, 61.53 to 43.07 mg/100mL, 227.57 to 183.77 mg/100mL and 14.05 to 11.48 mg/100mL, total soluble sugars changed from 8.55 to 8.54%, 3.57 to 3.10, 13.33 to 11.77 ºBrix, 61.53 to 40.06 mg/100mL, 227.57 to 121.91 mg/100mL and 14.05 to 9.92 mg/100mL, total soluble sugars from initial 8.55 to final 6.88%. The maximum total plate count, yeast count and mould count of 14 x 103 CFU/mL, 11 x 102 CFU/mL and 4 x 102 CFU/mL were observed in ohmic heated juice sample on 21st day of storage at ambient conditions. The maximum total plate count, yeast count and mould count of 13 x 103 CFU/mL, 7 x 102 CFU/mL and 8 x 102 CFU/mL were observed in ohmic heated juice sample on 35th day of storage at refrigerated condition. The maximum total plate count, yeast count and mould count of 10 x 103 CFU/mL, 14 x 102 CFU/mL and 5 x 102 CFU/mL were observed in sonication assisted ohmic heated juice sample on 28th day of storage at ambient condition on 28th day of storage. The maximum total plate count, yeast count and mould count of 13 x 103 CFU/mL, 11 x 102 CFU/mL and 8 x 102 CFU/mL were observed in sonication assisted ohmic heated juice sample on 35th day of storage at refrigerated condition. The shelf life of the fresh jamun juice was observed as 7 days at refrigerated storage, ohmic heated juice sample was observed as 14 days at ambient storage, ohmic heated juice sample was observed as 91 days at refrigerated storage, sonication assisted ohmic heated juice sample was observed as 21 days at ambient condition and sonication assisted ohmic heated juice sample was observed as 119 days at refrigerated storage. Keywords: Jamun, ohmic heating, sonication, sonication assisted ohmic heating, anthocyanins, phenols, optimization of process variables, microbial inactivation and shelf life.
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PRESERVATION OF JAMUN JUICE THROUGH SONICATION ASSISTED OHMIC HEATING
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