Sterilization of pickled ginger in retort pouch

Abstract

This research aims to develop a suitable sterilization process for pickled ginger in retort pouch. The microbial analysis results showed that number of bacteria in untreated pickled ginger enumerated using total plate count (TPC), Escherichia coli and yeast and mold were 1.6×10⁶ CFU/g, 43 MPN and 2.04×10² CFU/g, respectively. Therefore, in order to comply with Thailand’s community standard of pickled ginger, the pickled ginger should be thermally treated to limit the number of bacteria to 1.0×10⁴ CFU/g. Retort pouch was chosen as a packaging material due to its lightweight and flexibility. Each pouch was filled with 250 g of pickled ginger. The pouch was either treated at 100°C for 3 minutes (HTST) or 65°C for 15 minutes (LTLT) to satisfy lethality level of 3.0. The numbers of TPC, Escherichia coli and yeast and mold of the treated ginger were 3.9×10³ (HTST) (3.75×10³ CFU/g for LTLT), MPN <3 (both HTST and LTLT) and 70 (HTST) (75 CFU/g (LTLT)), respectively. The hardness values of untreated sample, HTST-treated, and LTLT-treated were 42.14, 50.96 and 48.02 N, respectively. The color values (L*, a*, b*) of control sample, HTST-treated, and LTLT-treated were L* 61.20, a* -1.34, b* 20.66; L* 53.83, a* 3.00, b* 21.76; and L*61.68, a* -1.36, b* 20.43, respectively. It can be concluded that both HTST and LTLT treatments could be used to reduce the number of microorganisms in pickled ginger. However, LTLT-treated sample was brighter than HTST process. On the other hand, the hardness value of HTST was higher than that of LTLT. In summary, the investigated optimal heating condition could potentially reduce the risk of foodborne outbreaks caused by pickled ginger.