Optimization of calcium alginate gel hardening process for red-raspberry and analysis of its canned quality

Red-raspberry was mainly processed into cans. Response surface methodology was employed to optimize the technological parameters of calcium alginate gel to harden red-raspberry grain. The optimum conditions of test:sodium alginate was 1.24%, pumping time Ⅰ was 41 min, CaCl₂ was 0.32% and pumping time Ⅱ was 31 min. The hardness was the maximal (451.18 g), the sensory evaluation was the highest (90.23). Through comparing the quality of canned red-raspberry, blueberry and strawberry, the results showed that the content of V_C was significantly different in canned goods of three different species (p<0.05), the decreasing order was canned strawberry, canned red-raspberry and canned blueberry. There was no significant difference in the contents of total phenolic between canned red-raspberry and canned blueberry (p>0.05), but was obviously higher than canned strawberry. There was significantly higher retention rate of V_C and total phenolic in canned red-raspberry (p<0.05).The content of reducing sugar, soluble solids and total acid in canned red-raspberry were significantly lower than other canned goods (p<0.05). Under the condition of hardening, the fresh fruit nutrients can be retained in the canned red-raspberry more effectively.