【作者】 梁兰兰；

【导师】 宁正祥；

【作者基本信息】 华南理工大学 ， 食品科学， 2010， 博士

【摘要】 传统的米排粉加工工艺选用储存了一年以上的早籼稻谷作为原料,生产出来的米排粉不断条、不糊汤。近年来由于市场情况变化,一年以上的陈粮供应紧张。且陈粮普遍存在黄曲霉毒素污染的问题。而用储存期一年以下的新粮生产的米排粉容易粘连、断条、糊汤。稻谷的品种差异对米排粉的品质也有影响。早籼稻由于品种、种植区域的差异,导致稻谷品质不同。如果品种选择、搭配不恰当,生产出来的米排粉就容易断条、糊汤,品质低下。因此,研究早籼稻储存期和品种对米排粉品质的影响机理显得很有必要。针对米排粉的挤丝过程,研制了二步法米粉挤丝机设备,并研究了米粉挤丝条件对米排粉品质的影响。结果表明:米粉加水量对米排粉的容积密度、蒸煮重量、蒸煮损失均有影响,米排粉加水量的最适宜区域在45%附近。挤丝机出丝板孔径小于0.6mm会导致粉条的蒸煮时间减少、蒸煮重量降低、蒸煮损失增加。但出丝板孔径的大小不会改变米排粉的糊化度。糊化度随加水量增加而增加。米排粉糊化度与蒸煮时间、蒸煮重量、蒸煮损失之间并无显著相关性。分析测定了稻谷在18个月储存期间的直链淀粉含量、脂肪酸值等理化特性、热特性以及米淀粉晶体特性变化,以及用这些稻谷制作的米排粉的质构特性变化,并研究特性间的相关性,探讨稻谷特性变化影响米排粉质构的机理。研究结果表明:用经过18个月储存的稻谷制作的米排粉的质构特性发生了变化。总体而言,稻谷储存时间延长可以改善米排粉质构特性,表现在拉伸特性和抗剪切性能、弯曲特性都更好,并且表面粘性、碎粉率、断条率、汤汁沉淀和吐浆量均呈现降低的趋势。延长稻谷储存期可以降低米排粉的粘性,增加硬度和筋道感。在稻谷储存期间,稻米的直链淀粉总量并没有显著的变化,稻谷的脂肪酸值在18个月的储存期间几乎呈线性地增长。直链淀粉含量与米排粉质构特性之间不存在显著相关性(P>0.05),稻谷脂肪酸值和剪切粘性、柔韧性、碎粉率呈极显著相关(P<0.01),与其他特性指标之间没有显著相关性(P>0.05)。不同储存时间稻谷的米粉热特性均发生了明显的变化。米粉热特性与米排粉拉伸特性显著相关(P<0.05)。稻米淀粉的相对结晶度与米排粉的质构特性(包括拉伸特性、剪切特性、表面粘性、弯曲特性与理化特性)间存在普遍的显著或极显著的相关性。在反映米排粉质构特性的14项指标中,有13项与稻米淀粉的晶体特性显著(P<0.05)或极显著相关(P<0.01)。测定了145份广东省2008年早籼稻谷的直链淀粉含量等理化特性、热特性、晶体特性,以及以其中27份不同品种稻谷样品为原料制作的米粉凝胶的质构特性,并分析了理化特性、热特性、晶体特性与米粉凝胶质构特性之间的相关性。结果表明:早籼稻谷直链淀粉含量、胶稠度和食味品质是影响米粉凝胶质构特性的理化特性参数,而垩白度、垩白粒率与粒型是与米粉凝胶质构无关的描述稻米外观的参数。米粉凝胶最大剪切力与米粉直链淀粉含量极显著正相关(n=27, r=0.536,P<0.01),与胶稠度极显著负相关(n=27, r=-0.584,P<0.01),与米饭食味品质显著负相关(n=27, r=-0.471,P<0.05)。米粉凝胶硬度与米粉直链淀粉含量无显著相关性(P>0.05),但和米饭的食味品质显著负相关(n=27, r=-0.479,P<0.05)。早籼稻谷热特性显著影响米粉凝胶的质构。籼稻米粉热焓与米粉凝胶咀嚼性显著负相关(n=27, r=-0.392,P<0.05)、与最大剪切力极显著负相关(n=27, r=-0.638,P<0.01)。早籼稻米淀粉相对结晶度虽然与米粉凝胶质构间并无显著相关性(P>0.05),但是其中存在的少量V型晶体造成了米粉凝胶最大剪切力下降。更多还原

【Abstract】 Paddies stored for over one years are traditionally used for processing Cantonese rice noodles, which provide good textural properties of rice noodles, such as low breaking ratio and low soup sediments. However more paddies stored for less than 1 year have to be used in Cantonese rice noodles processing, because of changes of market circumstance and aflatoxin pollution problem. Unfortunately these noodles made by newly paddies have poor textural properties, such as high breaking ratio and high soup sediments, under same processing conditions. Furthermore, textural properties of Cantonese rice noodles are also affected by varieties of paddies. It seems that studies on the effect of paddies storage and varieties on the textural properties of Cantonese rice noodles are necessary.A two steps single extruding machine was made. And the effect of extruding conditions on textural properties of Cantonese rice noodles was studies. Results showed that water ratio significantly affected the bulk density, cooking weight and cooking loss of Cantonese rice noodles. And the best water ratio was around 45%. Aperture of extruding machine had no effect on gelatinization degree, but had effect on cooking time, cooking weight and cooking loss. Gelatinization degree increased with water ratio, and showed no significant relations with cooking time, cooking weight and cooking loss.Chemical, thermal and crystal properties of paddies were determined during 18 months storage. Textural properties of rice noodles made by these paddies were also determined. Results showed that rice noodles made by longer stored paddies had better textural properties, including stretching, cutting, bending and were low in adhesiveness, fragment ratio, breaking ratio, soup sediments et al. Amylose content had little changes during 18 months storage, while fat acid value increased with storing time. No significant relationships was found between amylose content and textural properties of rice noodles (P>0.05). Adhesiveness, bending ratio and fragment ratio of rice noodles were significantly affected by fat acid value of paddies(P<0.01). Thermal properties of paddies changed a lot during storage, which showed a significant relationship with stretching properties of rice noodles(P<0.05). Crystal properties of paddies showed popular relationships with textural properties of rice noodles. It was significantly related with 13 of 14 indexes of textural properties of rice noodles.Chemical, thermal and crystal properties of 145 samples of early long-grain paddies harvested in Guangdong province in 2008 were determined. And textural properties of rice gels made by 27 different varieties of paddies out of 145 ones were determined too. Results showed that amylose content, gelconsistency and taste score were indexes affecting textural properties of rice gels, while chalky percentage, chalky kernels percentage and kernel form were indexes showed no effects. Firmness of rice gels was extremely affected by amylose content of paddies (n=27, r=0.536,P<0.01), gelconsistency (n=27, r=-0.584,P<0.01) and taste score (n=27, r=-0.471,P<0.05). Hardness of rice gels showed no relationship with amylose content of paddies, but with taste score (n=27, r=-0.479,P<0.05). Furthermore, textural properties were affected thermal properties of early long-grain paddies.ΔH negatively affected chewiness (n=27, r=-0.392,P<0.05) and firmness (n=27, r=-0.638,P<0.01) of rice gels. No significant relationship was found between crystal degree of early long-grain paddies and textural properties of rice gels (P>0.05). The existence of V style rice starch crystals caused the decreasing of firmness of rice gels.更多还原