【作者】 徐侃；

【导师】 孟岳成；

【作者基本信息】 浙江工商大学 ， 食品科学， 2011， 硕士

【摘要】 本论文通过对冷冻米饭的品质评价方法、基本生产工艺及产品品质特性的研究,为冷冻米饭的开发提供了理论参考,对优化产品生产工艺和保证最终产品品质具有实际指导意义。本论文的主要研究内容及结论如下：通过对十种不同原料大米制作的冷冻米饭的感官评价指标与质地指标的相关性分析结果表明,质构仪TPA模式下测定的硬度指标与感官综合得分有极显著的负相关性(P<0.01)；粘着性指标与感官综合得分有极显著的正相关(P<0.01),因此可以将质构仪TPA模式下测定的硬度与粘着性指标作为评价冷冻米饭品质的推荐指标。通过测定十种原料大米的直链淀粉与蛋白质含量,并与冷冻米饭的品质评价指标的相关性分析发现,直链淀粉含量与硬度有极显著的正相关(P<0.01),与粘着性有极显著的负相关(P<0.01)。而原料米的总蛋白质含量与冷冻米饭的品质指标没有显著的相关性,在试验基础上发现直链淀粉含量在17%左右的原料大米较适合生产冷冻米饭。对冷冻米饭的生产工艺研究表明,大米的吸水率受到温度、pH和米水比的影响,不同的浸泡时间和浸泡温度对冷冻米饭的硬度和粘着性的影响均显著(P<0.05),经过高温浸泡的大米,其制作的冷冻米饭品质要优于常温浸泡的大米。不同的蒸煮工艺对冷冻米饭的品质影响较大,采用均匀加热的电磁感应蒸煮方式和使用能均匀传导热力、保温性能良好的内锅蒸煮出的米饭品质较好,同时保持沸腾阶段时间和保温时间也是影响冷冻米饭品质的重要参数。通过测定米饭的冷冻曲线发现,冷冻温度、米饭的质量、形状和包装形式对冻结速率影响较大,而冻结速率对冷冻米饭的水分、硬度和粘着性均有显著影响(P<0.05),同时冻结速率与米饭的老化焓变也有较明显的负相关性。为减少冷冻米饭饭粒之间的粘连结块现象,选定SSPS、米糠油、柠檬酸为品质改良剂进行响应面试验,得到一个最佳配方：SSPS为0.48%、米糠油为0.44%、柠檬酸为0.005%。以糊化度、水分、硬度、粘着性、白度和菌落总数为评价指标,对-18℃、4℃和25℃存放下的米饭品质进行分析,发现-18℃存放下米饭品质下降最慢,并可有效抑制微生物的生长。4℃存放下米饭品质下降最快,而25℃存放时米饭中微生物的生长最快。通过分析糊化度与米饭硬度和粘着性之间的关系,发现米饭的糊化度与其硬度和粘着性分别存在明显的负线性和正线性相关趋势。同时发现米饭的老化过程对米饭的白度没有影响,而米饭的冻结状态对米饭的白度影响很大。通过研究微波复热过程中冷冻米饭的温度变化和水分迁移情况发现,不同的微波加热功率和米饭的质量均会对冷冻米饭的升温情况和含水量产生影响。微波加热时冷冻米饭的表面和中心会出现温度的不连续分布,随着微波加热时间的推移,温度梯度会发生转换,并导致其表面与中心的含水量也存在一定的差异。以新鲜米饭作对比,对冷冻米饭和复热米饭进行体外消化试验发现,新鲜米饭的体外消化液中无论是还原糖和葡萄糖含量的增加速率,还是最终含量均要大于冷冻米饭和复热米饭。对米饭蛋白质体外消化试验发现新鲜米饭体外消化液中的可溶性蛋白质含量要明显高于冷冻米饭和复热米饭。对新鲜米饭、冷冻米饭和复热米饭体外消化液中游离氨基酸含量的分析,共发现15种游离氨基酸,三种米饭总游离氨基酸含量分别为1.24mg/g、0.62mg/g和0.59mg/g。采用SPME技术富集,GC/MS分离检测,得到新鲜米饭的挥发性风味成分33种,冷冻米饭和复热米饭的挥发性风味成分分别为20种和18种,这些组分主要有醛、醇、酮、酯等4大类。更多还原

【Abstract】 The main work in this paper includes:establishe a method to evaluate the quality of frozen cooked rice, study on material adaptability for frozen cooked rice, determine the best production technology and research on quality characteristics of the product. Through those study can provide a theoretical reference for the development of frozen cooked rice, and a practical guide for production optimization and the final quality of the product. The main conclusions of this paper are listed as follows:10 kind of rice were selected to be made into frozen cooked rice, and the correlation coefficients between sensory evaluation and instrumental measurement indexes were analyzed. The result showed that hardness measured by TPA mode of Texture Analyser was significantly negatively correlated to total score of sensory evaluation(P<0.01). And adhesiveness was significantly positively correlated to total score(P<0.01). So hardness and adhesiveness measured by TPA mode of Texture Analyser could be used as recommend indexes for evaluating the quality of frozen cooked rice. After analyzing the relationships between the content of amylose and total protein of 10 kind of rice and the qualities of frozen cooked rice, significant positive correlation between amylose content and hardness(P<0.01), significant negative correlation between amylose content and adhesiveness (P<0.01) were found. But the total protein content and the product quality were uncorrelated. At last, it has been found that the rice with about 17% amylose content is adequate for producing frozen cooked rice.The research on the production technology of frozen cooked rice indicated that the water absorption of rice was under the influence of temperature, pH and the ratio between water and rice. The hardness and adhesiveness of frozen cooked rice were both significantly correlated to the soaking temperature and time(P<0.05), and the quality of frozen cooked rice with high temperature socking was better than low temperature. The quality of frozen cooked rice was also affected by different cooking conditions, better product quality was made by electromagnetic induction heating which can distribute heat evenly, and the cooker with good thermal insulation properties. Furthermore, boiling time and holding time were also important factors. The studies on analysing the freezing curves of cooked rice showed that freezing temperature, weight, shape and package had a great influence on freezing rate. And the freezing rate significantly affected on hardness, adhesiveness and retrogradation enthalpy of frozen cooked rice. In order to reduce the possibility of adhereing each other, chosen SSPS, rice bran oil and citric acid as quality improver, and were analyzed by experiment of response surface analysis, found the optimal formula was:SSPS 0.48%, rice bran oil 0.44%, citric acid 0.005%.Under the three different storage temperature -18℃,4℃and 25℃, the qualities of cooked rice were analyzed by evaluating the gelatinization degree, water content, hardness, adhesiveness, whiteness and aerobic bacterial count, found that -18℃was a better storage temperature for keeping the quality of cooked rice from decreasing, and inhibiting microorganism from growth. The quality degradation of cooked rice at 4℃was serious, while less serious at 25℃, but at 25℃the growth trend of total bacteria was obvious. Through analysing the Correlation coefficients between gelatinization degree and hardness and adhesiveness, found that gelatinization degree respectively negatively and positively correlated to hardness and adhesiveness. Other result showed the process of retrogradation had no affect on whiteness of cooked rice, while frozen situation made the whiteness increasing obviously.Temperature profile and moisture immigration of frozen cooked rice through microwave reheating were studied. It showed that microwave power and the weight of frozen cooked rice both had an effect on the temperature rising and moisture immigration. Moreover, the conversion of temperature gradient existed during microwave reheating and that the temperature rising and moisture loss were different among surface and inner.An in vitro digestion method was used to investigate the difference between fresh cooked rice, frozen cooked rice and reheated frozen cooked rice. Results showed that in vitro digestive juice of fresh cooked rice, both the increasing rate and final content of reducing sugar and glucose were more than other two cooked rice. The content of soluble protein in vitro digestive juice of fresh cooked rice was also more than other two cooked rice. Through the determination of free amino acid in vitro digestive juice of fresh cooked rice, frozen cooked rice and reheated cooked rice, found the content of total free amino acid was respectively 1.24mg/g,0.62mg/g and 0.59mg/g, including 15 kind of free amino acid.The volatile aromatic components in cooked rice were extracted by solid-phase micro-extraction(SPME) and were analyzed by GC/MS. The results showed that total 33 different compounds were isolated and identified from fresh cooked rice, and respectively 20 and 18 different compounds were isolated and identified from frozen cooked rice and reheated frozen cooked rice. These compounds were mainly aldehydes, alcohols, ketones, esters etc.更多还原