【作者】 余世锋；

【导师】 马莺； 孙大文；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2010， 博士

【摘要】 大米淀粉凝沉是制约大米类食品行业发展的瓶颈问题。大米淀粉凝沉在很大程度上决定了大米类食品的凝沉性质和品质劣变。温度是影响淀粉凝沉的主要因素,人们对常温和普通低温下大米淀粉凝沉性质已经有较多的认识,但在低温和超低温预冷下大米淀粉凝沉性质方面研究较少,低温和超低温预冷处理对大米淀粉及其制品凝沉抑制作用尚不清楚。因此,本论文从以下几方面展开研究:(1)大米淀粉及米粉物理化学性质及其相关性,(2)低温和超低温预冷下大米支链淀粉、淀粉和米粉凝沉性质及其凝沉机理,(3)低温和超低温预冷对米饭品质及其凝沉性质的影响。本文研究目的是为工业化生产高品质即食米制品提供理论基础。根据大米中直链淀粉的含量将大米分为中直链淀粉含量大米(SM)、低直链淀粉含量大米(DH)、极低直链淀粉含量大米(TML)和糯性大米(SN2)。本文系统地研究了四类大米淀粉及米粉物化性质,X衍射表明大米淀粉及大米粉特征图谱为A型,2θ在15°、17°、18°和23°有较强衍射峰;扫描电镜(SEM)证实了大米淀粉及大米粉颗粒形状为多角形,粒径为2~8μm。大米淀粉及米粉的膨润性、溶解性、浊度、糊化性质、质构及凝沉性质与大米直链淀粉/支链淀粉比例有关,直/支链比越高,大米淀粉及米粉浊度、糊化温度、硬度及糊化焓变越大,膨润性、溶解度及黏性越小。通过差示扫描量热仪(DSC)对低温(-20、-30和-60℃)和超低温(-100℃)预冷下大米支链淀粉凝沉性质研究发现,预冷后的新鲜支链淀粉没有明显凝沉现象发生。低温和超低温预冷处理大米支链淀粉,在4℃冷藏下1 d内迅速凝沉,1~11 d凝沉焓变持续增长,11 d大米支链淀粉凝沉焓变值分别达到最大11.0 J/g(SM),7.0 J/g(DH)和10.0 J/g(TML),14~21 d支链淀粉凝沉焓变基本不变,21 d大米支链淀粉完成凝沉过程。大米支链淀粉冻藏1~5月凝沉没有发生。低温(-20和-30℃)预冷下大米淀粉有轻微凝沉,低温(-60℃)和超低温(-100℃)预冷下大米淀粉DSC扫描曲线上没有凝沉现象发生。大米淀粉冷藏4℃初期淀粉凝沉发生,1~7 d淀粉迅速凝沉,7~14 d淀粉凝沉焓变缓慢上升,21 d大米淀粉凝沉过程完成。低温和超低温(-100℃)预冷-冻藏方法能有效抑制大米淀粉凝沉。大米直链淀粉-脂类复合物在冷藏或冻藏期间性质稳定,热特性参数没有变化。采用DSC和质构仪对低温和超低温预下大米粉凝沉性质研究发现,低温(-60℃)和超低温(-100℃)快速预冷-冻藏可以抑制大米粉凝沉。DSC扫描发现大米粉冷藏初期重结晶现象开始发生,1~7 d大米粉迅速重结晶,7~14 d大米粉凝沉焓变缓慢上升,21 d大米粉凝沉过程完成。大米粉糊硬度和黏性在0~7 d变化最大,14~21 d基本不变。超低温(-100℃)预冷处理的米粉冻藏1~5月期间没有凝沉现象发生,冻藏期间米粉质构性质变化不大。大米粉中直链淀粉-脂类复合物的在冷藏或冻藏期间性质稳定。通过对大米支链淀粉、淀粉及米粉动力学研究发现,大米支链淀粉、淀粉及米粉凝沉动力学遵从Avrami方程,凝沉成核方式分为三种类型:SM支链淀粉、淀粉及米粉为瞬间成核;SN2支链淀粉、淀粉及米粉成核方式为自发成核;DH和TML支链淀粉、淀粉及米粉成核方式具有自发和瞬间成核共同作用,成核方式随预冷速率增加而从瞬间成核向自发成核转变。淀粉及米粉凝沉主要表现为支链淀粉凝沉,直链淀粉对支链淀粉凝沉起协同作用,淀粉和米粉凝沉是直链淀粉和支链淀粉凝沉共同作用的结果。采用DSC和质构仪研究米饭品质影响因素,结果表明大米淀粉凝沉导致了米饭硬度上升和黏性下降,高直链淀粉含量大米米饭硬度高、黏性低,快速预冷可以抑制米饭短期的凝沉和品质劣变。冷冻速率和贮藏温度对淀粉凝沉和米饭质构性质有重要影响,米饭硬度和黏性与冷冻速率和淀粉凝沉成相关性,快速冷冻(1.45℃/min)的米饭硬度值低、黏性高,缓慢冷冻(0.09℃/min)处理过程加剧了米饭的凝沉。快速冷冻米饭的优良品质会在冷藏过程中逐渐失去,而快速冷冻结合冻藏处理可以有效抑制米饭凝沉和米饭品质劣变。因此,快速冷冻-冻藏是米饭品质最佳处理条件,这些发现有助于工业化生产加工出高品质、长货架期的即食米饭。更多还原

【Abstract】 Rice starch retrogradation restrict the development of food industry. Rice starch is the major components of rice foods, the retrogradation and textural properties of rice foods are depended upon rice starch retrogradation. Up to now, a lot of works were focused on rice starch retrogradation at low and room temperature, however, the rertogradaion of rice starch precooling with low and ultra-low temperatures has not been studied in detail. Therefore, in this paper, these projects will be investigated: (1) Physicochemical properties of rice starch and rice flour, (2) The retrogradation properties and retrogradation mechanism of rice amylopectin, rice starch and flour by low and ultra-low temperature precooling, (3) The effects of low and ultralow temperature precooling on the quality and retrogradation properties of cooked rice. The work in this dissertation is devoted to help the food industry to produce high quality instant ready meal.We investigated the physicochemical properties and correlation of starch and flour of intermediate amylose content rice (SM), low amylose content rice (DH), very low amylose content rice (TML) and waxy rice (SN2). The results of SEM indicated that the granule of rice starch and flour was polygonal shape, the size was 2~8μm. The X-ray results indicated that the rice starch and flour was A pattern, the strong peak of 2θwas 15°, 17°, 18°and 23°. The results of swelling power, solubility, turbidity, pasting properties, gel textural properties and retrogradation enthalpy were correlated to the ratio of rice amylose to amylopectin.The higher the ratio value, the higher of the turbidity, pasting temperature, hardness and gelatinization enthalpy, however, the lower of swelling power and solubility. The retrogradation properties of rice amylopectin precooling with low and ultra-low temperatures were investigated by Differential Scanning Calorimeter (DSC).Rapid cooling can retard amylopectin retrogradation effectively, and the rice amylopectin didn’t retrograde after precooling immediately. However, the rice amylopectin retrograded rapidly within 1 day, the retrogradation enthalpy continuely increased from 1~11 days, and the rice amylopectin of SM, DH and TML reached the highest retrogradation enthalpy values of 11.0 J/g (SM), 7.0 J/g (DH) and 10.0 J/g (TML) in the 11th day, respectively. From 14 to 21 days, the retrogradation enthalpy of rice amylopectin changed slowly during chill storage. The retrogradation process of waxy rice (SN2) amylopectin was very different with SM, DH, and TML. The SN2 amylopectin retrograded slowly in 0~11 days, increased rapidly from 11 to 14 days, and reached the highest retrogradation enthalpy value of 9.0 J/g in the 21th day of chill storage. Furher study indicated that low and ultralow temperature precooling and frozen effectively retrard amylopectin retrogradation, there was no amylopectin retrogradation when amylopectin frozen for 1~5 months. The retrogradation properties of rice starch precooling with low and ultralow temperatures were investigated by DSC and texture analyzer (TA). Rice starch retrograded rapidly from 1 to 7 days, increased slowly from 7 to 14 days, and the retrogradation process finished within 21 days during chill storage. Low and ultra-low temperature precooling and frozen effectively retrard rice starch retrogradation, there was no starch retrogradation when frozen for 1~5 months. The textural properties of rice starch increased rapidly from 1 to 7 days, increased slow from 7 to 21 days, and the textural properties changed slowly during frozen storage. The amylose-lipid complex was not changed during chill or frozen storage, and the properties of rice amylose-lipid complex were related to amylose variety and molecule structure.The retrogradation properties of rice flour precooling with low and ultra-low temperatures were investigated by DSC and TA. The rice flour retrograded rapidly from 1 to 7 days, retrogradation enthalpy increased slowly from 7 to 14 days, and the retrogradation process was finished within 21 days during chill storage. The hardness and adhesiveness of rice flour paste changed rapidly from 0 to 7 days, changed slowly from 7 to 14 days, and changed slowly from 14 to 21 days. The resuts indicated that low and ultra-low temperature precooling combined with frozen method can effectively retard rice flour retrogradation, there was no starch retrogradation when frozen for 1~5 months. The amylose-lipid complex in rice flour was not changed during chill or frozen storage.Rcie amyloepctin, rice starch and flour retrogradation kinetics were accorded with Avrami equation. The SM amylopectin, rice starch and flour retrogradation were instant crystallization. The SN2 amylopectin, rice starch and flour retrogradation were spontaneous crystallization process. The DH and TML amlopectin, rice starch and flour retrogradation were both instant crystallization and spontaneous crystallization, which were depended upon freezing or cooling rate. The retrogradation of rice starch and flour mainly caused by amylopetin and amylose retrogradation, the two process contributed to rice starch and flour retrogradation.The effects of low and ultra-low temperature precooling on the eating quality and retrogradation properties of cooked rice were investigated. Rice starch retrogradation contributed to hardness increase and adhesiveness decrease of cooked rice, higher amylose content of cooked rice had higher hardness and low adhesiveness value. The textural properties of cooked rice were related to starch retrogradation and cooling rate. Rapid precooling could effectively retard cooked rice staling and textural properties loss during a short time chill storage. Freezing rate and storage temperature showed significantly effects on retrogradation and textrual properties of cooked rice, the textural properties of cooked rice were positively related to freezing rate and starch retrogradation. Rapid freezing (1.45℃/min) can produce a high quality of cooked rice, i.e. lower hardness and higher adhesiveness value, however, slow freezing increased the staling of cooked rice. The advantages (lower hardness and higher adhesiveness, less starch retrogradaton) of cooked rice gained by rapid freezing, were lost quickly within 3 days of storage at 4℃. However, rapid freezing combined with -18℃frozen storage can effectively retard starch retrogradation and maintain the textural properties of cooked rice for at least 7 months. Therefore, high quality cooked rice can be produced by combined rapid freezing with frozen storage. The work in this dissertation is devoted to help the food industry to produce high quality instant cooked rice.更多还原