Effects of Thermal Processing and Food Additive on Shelf Life of Grass Jelly in Syrup Product

Abstract

The short shelf-life of the 7-day problem of grass jelly in syrup products has been seriously concerned by the small business operators who are the local food producers. Hence, this research was aimed to investigate the effects of thermal processing (pasteurization) and food additives on the shelf-life of grass jelly in syrup products. Grass jelly extracted solution was prepared from jelly grass and split into 7 portions and kept in fridge until usage for further treatments. These 7 portions were processed to achieve the 7 grass jelly samples of control, sodium benzoate and sodium sorbate added in grass jelly pulp at 500 ppm (J500), sodium benzoate and sodium sorbate added in syrup at 500 ppm (S500), glycerol added in grass jelly pulp at 2.5% (G2.5) and 3.5% (G3.5), and pasteurized at 100°C for 10 minutes (H10) and 20 minutes (H20). Later, samples were stored at 4 °C for 28 days with the interval of 7 days for quality assessments. The results revealed that every experimental sample sets showed reductions of L*-a*-b*-values, pH, and TSS when stored for a long period of time while the a_w presented increasing after 7 days and gradually decreased after 21 and 28 days of storage, respectively. The texture profile analysis (TPA) (Hardness, cohesiveness, springiness, adhesiveness, chewiness, gumminess) were analyzed and the results showed that most of the experimental samples presented the increasing trends from day 0 to day 14 followed by gradually decreased from day 14 to day 28. Considering the microbial quantity criteria for shelf-life assessment, the total microbial amount must not exceed than the standard of grass jelly products (Thai Industrial Standards Institute (157/2547)). This study observed that the control sample had a shelf-life of 7 days, while the J500, S500, G2.5, and H10 samples could be stored for up to 14 days. Furthermore, the G3.5 and H20 samples had the longest shelf-life at 4 °C of 21 days. To conclude, it could be suggested that applying the glycerol for 3.5% and thermal processing of pasteurizing grass jelly in syrup at 100°C for 20 minutes could extend shelf-life of the grass jelly in syrup product for up to 21 days at 4°C or 3 times longer when comparing with the traditional practice. These observations could assist the small business operators the valuable chance to expand the market as well as to enhance the profit.