适宜添加剂预处理提高罗非鱼片冻融-热泵干燥品质

Improving quality of tilapia fillets freeze-thaw combined with heat pump drying using suitable additive pretreatment

为了获得添加剂预处理对罗非鱼片冻融-热泵干燥品质的综合影响,并为真空冷冻干燥提供常压低温干燥的替代比较,以罗非鱼片为试验材料,选取海藻糖、山梨醇和麦芽糊精3种添加剂,进行了不同质量分数的添加剂浸渍预处理对罗非鱼片冻融结合热泵干燥过程影响的系列试验,获得了干燥曲线,品质指标变化规律和试验条件下的最佳工艺条件,并与热风干燥,热泵干燥和真空冷冻干燥所得样品性能进行了对比试验。结果表明:合适的预处理添加剂及其质量分数能对冻融结合热泵干燥方式产生有利的促进作用,能取得提高干燥速度和改善干燥品质的双重效果,且以质量分数为15%的海藻糖溶液浸渍处理获得的效果较佳,在较佳工艺下获得的罗非鱼片的干燥品质综合评分比热风干燥和常规热泵干燥分别提高了40.18%和33.57%,相比于不经添加剂预处理的对照组有25.41%的提高,与真空冷冻干燥比仅低了4.39%,但其常压干燥条件比真空冷冻干燥的真空条件有较大程度的改善,研究结果能为水产品的常压低温干燥提供参考。

In order to obtain the combined effects of additive pretreatment on the quality of freezing-thawing and heat pump drying of tilapia fillets, and to provide an atmospheric cryogenic drying method which can substitute vacuum frozen drying method, a series of tests of freezing-thawing process combined with heat pump drying for tilapia fillets were conducted in the laboratory, and the best experiment processes obtained were as followed：freezing-thawing pretreatment （conditions： freezing at -32℃ for 1.0 h, melting at 20℃ for 1.5 h）, hot pump drying （conditions：Temperature 45℃,wind speed 2.5 m/s for 4 h）, freeze and thaw imbedding （conditions：freezing at-40℃for 1.5 h, melting at 25℃for 1.0 h）, hot pump drying （conditions：Temperature 45℃,wind speed 2.5m/s for 3 h）, freeze and thaw imbedding （conditions：freezing at-30℃for 1.5 h, melting at 25℃for 0.5 h）, heat pump drying （conditions：Temperature 45℃,wind speed 2.5 m/s） to dry basis moisture content 0.30±0.02 g/g. In order to further shorten the drying time and improve the quality of the dried products, on the basis of the previous studies, this paper chose three different types of additives including trehalose, sorbitol and maltodextrin to be used on tilapia fillets under the condition of ice-water bath for 1 h before freezing-thawing process combined with heat pump drying. Drying curves and quality indexes variation of different types and concentrations of additive treatments were obtained by the experiments, and the best additive impregnation conditions were obtained through the comprehensive score of dried product’s quality index. Contrast tests were carried out using three methods including hot air drying, heat pump drying and vacuum freeze drying under the condition of trehalose solution （mass fraction of 15%） impregnation. The results showed that suitable pretreatment additive and its mass fraction was beneficial to the method of freezing-thawing combined with heat pump drying, and could shorten the drying time and effectively improve the comprehensive quality of tilapia fillets after the process of freezing-thawing and heat pump drying. Within the scope of this study, trehalose solution （mass fraction of 15%） immersion treatment obtained the best results. The comprehensive score of tilapia products’ drying quality under the optimum processing conditions increased by 25.41%than that without additive processed, increased by 40.18%and 33.57%respectively compared with hot air drying and conventional heat pump drying, yet was 4.39%lower than vacuum freeze drying, but its drying condition had a greater degree of improvement because of its atmospheric condition compared with vacuum freeze drying. The results can provide a reference for the atmospheric pressure low temperature drying of aquatic products.