Optimization of thermal sterilization process for low-acid and acidified instant laver

In order to optimize the sterilization process of laver (Porphyra spp.) and develop high-quality instant wet laver products, we measured the heat penetration curves during high-pressure heat treatment (110, 115, 121 ℃) and normal pressure heat treatment (85, 90, 95 ℃) for low-acid and acidified lavers (pH≤4.6). Combined with preservation experiment and microbial analysis, we determined the F-value (Safe sterilization heating time) corresponding to the two sterilization methods, and explored the effects of different temperature-time combinations on the sensory and nutritional quality of laver with the same F-value. Results show that low-acid laver could reach commercial sterility when F₀ was 3 min under high-pressure heat sterilization, and acidified laver could also reach the preservation requirements when ${F\,}_{93.3}^{8.89}$ was 5 min under normal pressure heat sterilization. Compared with high-pressure heat sterilization, acidification combined with normal pressure sterilization could obtain better texture and color. The toughness, hardness and sensory score of laver increased with the increase of sterilization temperature with the same F-value. In terms of nutrients, the total soluble sugar and free amino acids decreased with the increase of temperature in the high-pressure group. The highest free amino acids content was obtained at 90 °C in the normal-pressure group. In general, the texture, sensory and nutritional quality were better when the sterilization parameters were 90 °C, 11.5 min (Acidified group) and 115 °C, 8 min (Low-acid group).