【作者】 何学连；

【导师】 过世东；

【作者基本信息】 江南大学 ， 食品科学， 2008， 硕士

【摘要】 近年来,虾干制品以其营养丰富、风味独特、耐贮存、携带方便等特点受到广大消费者的欢迎,但目前世界范围内白对虾的加工还处于初级阶段,加工环节的滞后已经成为其进一步发展的瓶颈。本论文以白对虾为试验原料,系统地研究白对虾的干燥工艺。为了使产品的品质更好,在优化干燥工艺之前,发现烫漂对其产品品质有很大的影响。本论文研究了烫漂工艺对白对虾PO活力、失重率、色泽、质构、烫漂残液和细菌总数的影响。研究得出:在100℃条件下,烫漂1min就能使PO的活力大大降低,且能改善产品的品质。采用2%NaCl溶液烫漂1min,失重率高,营养流失少,对虾的组织状态、色泽和气味好,此时为最佳烫漂工艺条件。本文对几种常见的干燥方法进行分析和比较,目的是寻找到适合白对虾的干燥方式,从而也为后期联合干燥工艺的运用提供理论支持。本文研究了几种常见的干燥方法对白对虾干燥特性、质构、水分活度(Aw)、L值、超微结构和复原率的影响,发现冷冻干燥的白对虾综合品质最佳,真空干燥、微波干燥次之,热风干燥最差。真空干燥产品的综合品质仅次于冷冻干燥。所以,本文对白对虾真空干燥进行深入研究,分析了真空干燥参数对白对虾干燥特性、质构和复原率的影响。建立了白对虾的真空干燥模型,并确定了白对虾在不同真空干燥条件下模型中的参数。初步研究发现,三种联合干燥产品的组织结构优劣顺序为:冷冻干燥-真空干燥>冷冻干燥-微波真空干燥>微波干燥-真空干燥。在此基础上,为了进一步提高产品的品质、降低干燥成本,本实验将冷冻干燥分别与微波真空干燥、真空干燥进行联合,探索白对虾的最佳联合干燥工艺。为了实现微波真空干燥与冷冻干燥的优势互补,本文采用L9(34)正交优化试验研究了白对虾冷冻和微波真空最佳联合干燥工艺。各因素对复原率影响主次顺序为转换点水分含量>微波功率>微波时间>微波真空度;最佳组合为转换点水分含量50%、微波时间25s、微波功率330W、微波真空度0.07MPa。方差分析表明,转换点水分含量、微波时间、微波功率对复原率都有显著影响,而微波真空度效果不显著,方差与极差分析结果一致。同时,为了获得真空冷冻和真空干燥联合干燥白对虾的最佳工艺,本文设计了一个三元二次旋转回归试验方案,采用响应面分析得到真空冷冻和真空干燥联合干燥白对虾的最佳工艺条件范围:温度(48-53℃)、真空度(0.066-0.073MPa)、转换点水分含量(44.6-47.7%),在此条件下,硬度绝对差、复原率和弹性分别接近于47g、71.81%和0.831g。更多还原

【Abstract】 In recent years, the dried shrimp was welcomed by consumers because of its high nutritive value, special flavor, storage stability and portability. However, the processing level of white shrimp was still at an initial stage all over the world at present. The lag of processing link had become a bottleneck to its development. The objective of this paper was to study its drying technologies of white shrimps systematically.In order to make its qualities better, the great effects of blanching on the white shrimps were found before drying. The method was applied to investigate the effects of blanching technology on the qualities of white shrimp such as PO activities,the rate of weight loss, color, texture, remanent blanching liquid and total bacteria. The results showed that blanching at 100℃for 1 minute could reduce PO activities badly and improve the qualities of dried shrimp. When white shrimps were blanched for 1 minute in the 2% NaCl solution at 100℃, the rate of weight loss was high and nutrition loss was little. Meanwhile, the ideal color and tissue state could be achieved.Analysis and comparison of some usual drying methods was conducted in order to obtain the suitable one and consequently provide theoretical supports for combination dryings of white shrimps. The effects of different drying methods on qualities were studied including drying characteristics, texture, water activity (Aw), L value, superstructure and recovery rate. The results showed that white shrimps treated by vacuum freeze drying were the best, vacuum drying and microwave secondary, air drying the worst.The results showed the white shrimps treated by vacuum drying were better than other drying methods except vacuum freeze drying. So, it was necessary to make a further study on vacuum drying. The effects of vacuum drying parameters on drying characteristics, texture and recovery rate were studied. The vacuum drying model of white shrimp was established. It was found that model was the most suitable to describe the kinetics of vacuum drying. And the parameters of vacuum drying model under different conditions were determined.On the basis of a previous pilot study, it was shown that the organizational structures of the dried shrimps decreased successively as follows: a combination drying of vacuum freeze and vacuum drying > vacuum freeze and microwave vacuum drying > microwave and vacuum drying. In order to further improve product quality and reduce costs, freeze vacuum drying was combined with vacuum drying and microwave vacuum drying respectively. In order to realize mutually complementary, the optimal drying conditions of microwave vacuum drying combined with vacuum freeze drying were studied in the paper by adopting the L9(34) orthogonal experiment. It was found that the capability of effects of factors on the recovery rate: the conversion point of water content > microwave power > microwave time > microwave vacuum. The optimum compounding was composed by follows: conversion point of water content 50%, microwave time 25s, microwave power 330W, microwave vacuum 0.07MPa. The variance analysis showed that the recovery rate was significantly influenced by the conversion point of water content, microwave power, microwave time except microwave vacuum. The result of the variance analysis was the same as the range analysis. Meanwhile, the ternary quadratic rotary recursive design was chosen to attain the best technology of drying white shrimps by vacuum freeze drying combined with vacuum drying in the paper. The optimal conditions of the combination drying were determined by response surface analysis. When temperature, vacuum pressure of vacuum drying and the water content of white shrimp were 48-53℃, 0.066-0.073MPa and 44.6-47.7%, these were obtained as follows: the absolute hardness difference close to 47g, the recovery rate 71.81% and springiness 0.831g.更多还原