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.