Effect of combined preservation techniques on the stability and microbial quality and retention of anthocyanins in grape pomace stored at low temperature.

Studies were carried out with an objective to assess the effect of various post harvest treatments with chemical preservative, ionizing radiation doses and low temperature (LT) storage on the storability and the microbial quality of the grape pomace and retention of anthocyanins in it. The grape pomace collected after processing of fully matured grape berries (var.Bangalore blue) was treated with 0.1% sodium benzoate(0.1% SB), packed and sealed in LDPE film pouches and exposed to γ-irradiation(0, 2, 4 and 6 kGy) and stored along with untreated control at LT (4 ± 1 °C, 90-95% RH)conditions. During storage, changes in physico-chemical and microbial quality attributes of these treated grape pomace were recorded. Among the treatments, combination of 0.1% sodium benzoate and 2.0 kGy dose of γ-irradiation (0.1% SB +2.0 kGy) was found to be more effective in improving the storability of grape pomace and in retention anthocyanins (34.70 mg/100 g) during storage. The storage life of above treated grape pomace stored at LT could be extended up to 16 days as compared to 8 days of control grape pomace (31.8 mg/100 g). Results on microbiological studies indicated that 0.1% SB +2.0 kGy reduced the total aerobic bacterial count (1.4 log CFU/g) and the yeast and mould count (1.6 log CFU/g) in the treated grape pomace during 16 days of storage as compared to the total aerobic bacterial count (6.5 log CFU/g) and the yeast and mould count (6.3 log CFU/g) in control. Sodium benzoate and low irradiation (0.1% SB +2.0 kGy) was significant in controlling the multiplication of coliforms in grape pomace during LT storage and thus finds potential for commercial application in ensuring the microbiological safety and quality of grape pomace during its bulk storage at low temperature (4 ± 1 °C; 90-95% RH) conditions. This preservation method could be used by the wine making industries for bulk storage of grape pomace after processing of colored grapes during peak harvesting season for further end uses.