自然发酵对大米理化性质的影响及其米粉凝胶机理研究

通过对整粒大米 (籼米 )自然发酵过程中理化性质变化的研究 ,探讨传统自然发酵米粉的凝胶机理。研究发现发酵过程中总淀粉及直链淀粉含量并无显著变化 ,蛋白、脂肪和灰分含量随着发酵的进行而明显减少 ,而游离脂肪酸的含量呈上升趋势。流变学测定发现 ,发酵法生产的米粉相对于对照样品最大破断应力减小而最大应变增加。感官评定结果表明发酵法生产的米粉柔韧筋道 ,品质更好。笔者认为自然发酵虽然未影响总淀粉和直链淀粉含量 ,但降解了蛋白和脂肪而改变了大米粉的流变性质。另外灰分的降低赋予米粉洁白的外观 ,带给产品更好的透明感     

自然发酵对阴米淀粉物化性质的影响

研究大米在生产阴米自然发酵过程中,阴米米粉和发酵液中主要化学成分的含量变化,探讨传统自然发酵对阴米淀粉的颗粒性质、消化性和特征黏度的影响。研究表明：在自然发酵过程中,阴米米粉中粗脂肪、粗蛋白含量随发酵时间的延长而减少,最大降幅分别为22.95%和63.10%,游离氨基酸总量与原米相比有不同程度的降低,其中发酵5d的样品降幅最大达54.31%。发酵液pH值在发酵初期随发酵时间的延长而降低,从第1天的6.44降低到第4天的4.44,第5天达到3.90左右后趋于平衡;随着自然发酵的进行,发酵液可滴定酸度和游离氨基酸总量逐渐增大,可溶性糖含量逐渐减小。在对阴米淀粉的研究中发现,可消化淀粉含量有所提高;各样品溶解度和膨润力变化趋势类似,均随温度升高而增加;扫描电镜观察到阴米淀粉颗粒相互黏连,结合紧密;与原米相比,阴米淀粉的结晶度和特征黏度都有所降低。     

自然发酵对米粉力学性质的影响

通过对整粒大米(籼米)自然发酵，探讨传统自然发酵法对米粉力学性质的影响。研究发现随着发酵时间的增加，米粉的硬度和最大破断应变及塑性呈递增趋势，杨氏模量与最大破断应力随着发酵时间的增加先增加而后减少，屈服强度呈减少趋势。而不同发酵时间、浓度为5％大米粉的糊化流体都属于非牛顿假塑性流体，在相同温度下，剪切应力随剪切速率的增加而增大，表观粘度随剪切速率的增加而减少。发酵7天的大米粉糊化流体的剪切应力和表观粘度在不同温度和剪切速率下都较其他样品大。     

自然发酵对米粉RVA黏度性质及米粉拉伸性质的影响

研究了发酵时间对米粉RVA黏度性质及所制作的米粉的拉伸性质的影响。结果表明,发酵使米粉的RVA峰值黏度、低谷黏度及最终黏度上升,胶凝值下降,而崩溃值先上升然后下降。发酵提高了米粉的拉伸性质,改善了米粉的质地和口感;综合分析后认为,大米30℃左右发酵2d比较适宜。     

发酵鲜湿米粉的优良菌种选育及品质研究

从大米发酵液中分离得到一株优势菌株,命名为S2219。经形态学特征、生理生化特性及16S r DNA基因序列分析鉴定其为乳酸乳球菌(Lactococcus lactis),进而比较纯菌种发酵、自然发酵及不发酵米粉的蛋白质、脂肪、淀粉含量、质构及感官品质。结果显示,纯菌种发酵米粉的蛋白质和脂肪质量分数均低于自然发酵和不发酵米粉,但其直链淀粉质量分数高于自然发酵和不发酵米粉;质构感官方面,纯菌种发酵明显改善了米粉的咀嚼性、弹性和回复性。米粉制备的最佳发酵方式是纯菌种发酵,其获得的米粉具有柔韧劲道、口感滑润的特点。     

微生物强化发酵对米粉品质的影响

研究目的及方法：采用接种植物乳杆菌（L.p-35）、发酵乳杆菌（L.f-7）、热带假丝酵母（C.t-3）、枯草芽孢杆菌（B.s-14）进行强化发酵制作米粉,通过测定发酵后大米及米粉的蛋白、淀粉、直链淀粉含量,采用扫描电镜观察发酵对大米籽粒外观结构的影响,并从米粉产品质构、感官品质两方面,对比研究了强化发酵与传统自然发酵的差别。结果：强化接种L.p-35+L.f-7+C.t-3+B.s-14（第4组）四种微生物发酵制得的米粉与其他强化发酵组相比,蛋白含量明显降低,淀粉、直链淀粉含量明显增加。通过扫描电镜观察,强化发酵组明显改变了大米颗粒表面结构。结合质构及感官评定,第4组及自然发酵组制得的米粉品质在弹性、咀嚼性、爽滑感等方面优于其他强化发酵组。结论：综合各方面评分,第4组在优化大米结构、提高米粉品质方面存在明显优势,并结合pH、微生物变化情况,强化发酵有利于加速发酵过程。为开发米粉发酵剂提供了理论支持。     

微生物强化发酵对米粉品质的影响

采用接种植物乳杆菌(L.p-35)、发酵乳杆菌(L.f-7)、热带假丝酵母(C.t-3)、枯草芽孢杆菌(B.s-14)进行强化发酵制作米粉,通过测定发酵后大米及米粉的蛋白、淀粉、直链淀粉含量,采用扫描电镜观察发酵对大米籽粒外观结构的影响,并从米粉产品质构、感官品质2方面研究了强化发酵与传统自然发酵的差别。强化接种L.p-35+L.f-7+C.t-3+B.s-14(第4组)4种微生物发酵制得的米粉与其他强化发酵组相比,蛋白含量明显降低,淀粉、直链淀粉含量明显增加。通过扫描电镜观察,强化发酵组明显改变了大米颗粒表面结构。结合质构及感官评定,第4组及自然发酵组制得的米粉品质在弹性、咀嚼性、爽滑感等方面优于其他强化发酵组。综合各方面评分,第4组在优化大米结构、提高米粉品质方面存在明显优势,并结合pH、微生物变化情况,强化发酵有利于加速发酵过程。     

磨粉工艺对大米粉品质特性影响

选用干法和湿法两种磨粉工艺研究磨粉技术对大米粉品质特性的影响。通过分析大米粉的色泽、粒径分布、破损淀粉含量和糊化特性等性质,结合米粉的蛋白质二级结构、质构和感官评价,筛选出较好的制粉工艺。研究结果表明:与干法工艺相比,湿法制粉大米粉破损淀粉含量有所下降,低至8%以下; L*值升高, b*值降低;粒径减小,其范围在53.8～112.1μm之间。就米粉糊化特性而言,湿法工艺糊化温度相对较高,达到79.85℃,但衰减值和回生值有所降低。两种工艺条件对蛋白质二级结构产生了一定影响,湿法工艺下β-转角含量高,α-螺旋和无规则卷曲含量低,β-折叠含量相差不大。感官评价发现,采用湿法工艺生产的米粉品质更好。     

自然发酵对糙米煎饼理化性质的影响

通过对自然发酵煎饼不同时期的常规营养成分、pH值、RVA特征值、色差、糊化度、剪切力等指标的测定,研究自然发酵的煎饼的营养成分、质构性质、老化性质、感官品质、保藏品质的变化规律。研究表明经过自然发酵的煎饼蛋白质含量增加,蛋白质和脂肪经过微生物的作用更加容易被人体吸收利用,提高了煎饼食品的营养价值;外观颜色更加丰富饱满,感官品质提高;发酵后的煎饼抗老化能力增加,保藏期间的质量得到改善。通过对煎饼糊发酵过程中的理化性质及煎饼质构性质的变化的研究,探讨其发酵机理,从而为发酵煎饼的工业化生产奠定基础。     

发酵碎米理化性质的变化及与米粉品质的关联性

为了提高碎米的利用率,以籼碎米为原料,利用自然和植物乳酸菌发酵碎米,研究发酵对碎米理化性质的影响,探索碎米理化性质变化与米粉品质的关联性。结果表明,碎米发酵后,发酵液的pH值降低、固形物含量升高;淀粉、脂肪酸值和白度升高,而蛋白质、脂肪和灰分下降,且植物乳杆菌发酵时比自然发酵的作用更好。碎米的理化指标中淀粉、蛋白质、脂肪、脂肪酸值、白度和灰分与其米粉品质都有较显著的关联性。     

Effect of fermentation metabolites on rheological and sensory properties of fermented rice noodles

BACKGROUND: Considering the effect of natural fermentation on the textural improvement of fermented rice noodles in China and South Asia, and given the lack of reports concerning the roles of fermentation metabolites (enzymes, organic acids, glucose and maltose), this study aims to determine fermentation metabolites produced during fermentation of raw milled rice grains, and investigate their effects on rheological and sensory properties of rice noodles. RESULTS: α‐Amylase activity was correlated with reducing sugar content significantly in the supernatant during fermentation process (r = 0.76, P < 0.05). Lactic acid was the dominant organic acid produced by fermentation. Protein and lipid content decreased significantly by fermentation. Treating the rice grains with trypsin, lipase or lactic acid could modify the rheological characteristics and improve the sensory properties of rice noodles. Removal of protein and lipid by physical extraction confirmed the results. The residue of glucose and maltose in rice flour weakened the noodle texture. CONCLUSIONS: Fermentation of raw milled rice decreased protein and lipid content, increased the purity of rice starch, and thus improved the texture of fermented rice noodles. The low molecule weight sugars produced during fermentation should be removed for their negative effect on texture. Copyright © 2008 Society of Chemical Industry     

籼米陈化对鲜湿米粉品质的影响

为明确原料对鲜湿米粉品质的影响,对比研究了室温放置0~2个月和12~16个月籼米(浙富802)经自然发酵后鲜湿米粉品质及其理化指标的变化。结果表明,鲜湿米粉的硬度、回复性和咀嚼性等质构特性及拉伸力、白度均随发酵时间的延长而增加,且陈米米粉的相应指标值显著高于新米(P0.05);黏性、断条率和蒸煮损失率随发酵时间的延长而降低,陈米米粉的相应指标值显著低于新米(P0.05)。说明籼米陈化有利于鲜湿米粉品质的提高。理化性质分析表明,陈化降低了米粉的蛋白质、脂肪和灰分含量,但提高了米粉的淀粉和直链淀粉含量,改变了产品中淀粉-蛋白质的相互作用,从而引起产品品质发生变化。     

发酵对鲜湿米粉品质影响研究进展

米粉发酵后可获得更好的口感和品质。了解发酵对米粉理化性质的影响,不仅可以为传统米粉发酵工艺的改良提供理论依据,还可促进现代生物技术的介入和应用。本文综述了发酵米粉的微生物及工艺,以及发酵对大米的淀粉、蛋白质、脂肪和最终米粉产品品质影响方面的研究进展,对于选育出优良发酵菌种,改善米粉发酵品质进而可以进行大规模的工业化生产起到重要的作用。     

Noodle quality affected by different cereal starches

To investigate the effects of starch characteristics on the quality of noodle making, white salted noodles (WSN) made from reconstituted flours, in which the wheat starch was substituted by different cereal starches, including waxy and non-waxy rice starches, waxy wheat starch and waxy corn starch, were prepared. The rheological properties of raw WSN were mainly influenced by the size of starch granules, where the small starch granules, such as for rice starches, exhibited high amounts of water absorption during dough preparation and a dense packing of starch granules inside a thin gluten-strand network. The rheological properties of cooked WSN were mainly dominated by the amylose content and fine structure of the amylopectin, which resulted in the differences in water absorption and cooking time required for cooked WSN.     

自然发酵对淀粉凝胶的改性机理及发酵菌株的筛选

采用凝胶过滤层析法研究整粒大米自然发酵后淀粉分子质量分布的变化 ,探讨发酵对淀粉凝胶改性的机理。发现发酵后淀粉大分子降解 ,中等及小分子质量淀粉比例增加 ,分子质量大小趋于均匀 ,从而使淀粉分子易于接近聚合而增强了淀粉凝胶性能。对发酵样品的显微观察发现 ,淀粉粒结构并未破坏 ,因而淀粉溶出损失很小 ,初步认为是微生物所产酶和酸渗入颗粒内部作用的结果。通过对自然发酵菌株的分离筛选获得 3株酵母、5株细菌、2株霉菌。经过工艺试验认为 ,自然发酵主要是酵母菌作用的结果。研究结果可为进一步提高传统发酵类淀粉凝胶食品如馒头、发酵型米粉的品质、改良产品工艺开拓新的途径。     

Functional and multiple end‐use characterisation of Canadian wheat using a reconstituted dough system

Three Canadian wheat cultivars representing the Canada Western Red Spring, Canada Western Extra Strong and Canada Prairie Spring classes, varying in protein content yet containing similar high‐molecular‐weight glutenin subunits, were evaluated for dough functionality and multiple end‐use properties. The effect of protein content on dough properties and end‐product quality was also studied. Gluten, starch and water‐soluble components were extracted from the flours and reconstituted to make up three samples for each variety to match the protein content of the three parent flours. Empirical and dynamic dough rheological properties, baking (bread and tortilla) performance and noodle‐making properties of the flours were determined using small‐scale techniques. Results indicated that protein content had a significant effect on rheological and end‐use quality of wheat flours. Increase in protein content (of the reconstituted dough) increased mixograph peak height (r = 0.761), peak width, maximum resistance to extension and end‐product quality characteristics such as loaf volume (r = 0.906), noodle firmness and cutting force and decreased storage and loss moduli. Reconstituted flours from the three varieties at the same protein content also showed significant differences in mixing time, mixograph peak height, maximum resistance to extension, composite fineness of pan bread, tortilla diameter, cooked noodle hardness, gumminess and dynamic viscosity of dough. This study indicates that a simple reconstituted dough system can provide an unambiguous assignment of the quantitative and qualitative effects of dough components on dough properties. It has the advantages that any aspect of flour composition can be manipulated and details of the relation between composition and functional behaviour can be obtained for any end‐product. Copyright © 2003 Crown in the right of Canada. Published by Society of Chemical Industry     

Effect of dry- and wet-milled rice flours on the quality attributes of gluten-free dough and noodles

The rheological and cooking properties of gluten-free noodles prepared with dry- and wet-milled rice flours were characterized. Dry-milled rice flour with a higher degree of starch damage exhibited greater water hydration properties than wet-milled rice flour at room temperature. However, the pasting results of rice flour suspensions demonstrated that wet-milled rice flour showed a higher value of peak viscosity due to its great swelling power upon starch gelatinization. The similar thermo-mechanical tendency was observed in a rice dough system by Mixolab. In the planar extensional test, the noodle dough sample prepared with dry-milled rice flour exhibited higher elongational viscosity which could be favorably correlated to more resistance of dry-milled rice noodle strands to extension. When rice noodles were cooked, increased cooking loss was observed in dry-milled rice noodles which was attributed to great water solubility derived from a higher degree of starch damage.     

生米发酵食品的研究进展

生米发酵食品是一种重要的米制品种类,在我国具有悠久的发展历史。本文阐述了几种生米发酵食品的特点及大米在发酵过程中的微生物的变化情况及发酵对化学组成和理化性质的影响。发酵过程中微生物对大米中的物质进行降解,形成发酵制品的特殊风味,其中优势菌种为乳酸菌。发酵后淀粉的含量有所增加,脂肪、蛋白质和灰分的含量逐渐减少,但游离脂肪酸的含量增加。发酵有利于淀粉的糊化,较大地改变了大米制品的质地。随着对发酵米制品的制作机理的深入研究,生米发酵制品在食品工业中的应用将越来越广泛。     

Effect of starch and non-starch components on water migration,microstructure, starch retrogradation and texture of flat rice noodles made from different rice varieties

Effects of starch and non-starch components on rice noodle quality, water migration during rehydration, texture, microstructure and starch retrogradation of dried rice flour and rice starch noodles made from five rice varieties with similar high amylose contents were examined. Rice noodle qualities depended mainly on starch properties and to a lesser extent on the presence of non-starch components. Elongation of rice flour noodles was lower than rice starch noodles due to the presence of non-starch components that interrupted the starch network. Non-starch components reduced cooking loss of flour noodles in some varieties. Water migration in rice flour noodles with a looser microstructure was faster than in rice starch noodles. Nuclear magnetic resonance imaging revealed different water migration speeds in rice flour noodles among varieties, related to noodle microstructure and retrogradation properties. For production of good quality rice noodles, manufacturers should consider not only amylose content but also non-starch components.