酵母菌发酵对小米淀粉分子结构及糊化特性的影响

研究自然发酵及其优势菌(酵母菌)对小米淀粉分子结构及糊化特性的影响,为剖析不同菌属在小米自然发酵中的改性机理及发酵对小米淀粉性质的影响奠定理论基础。采用0.2 g/100 m L的Na OH提取发酵后的小米淀粉,研究自然发酵及优势菌发酵后对小米淀粉颗粒特性、结晶度、官能团、分子量、糊化及老化特性的影响。结果如下:酵母菌发酵后,淀粉颗粒表面有明显的侵蚀迹象,而自然发酵淀粉颗粒表面侵蚀迹象较轻;酵母菌发酵后小米淀粉的结晶度较自然发酵减少0.33%;发酵并未改变小米淀粉官能团区的峰位,但特征峰强度减弱,酵母菌发酵后小米淀粉指纹区图谱消失;未发酵小米淀粉重均分子量为1.5×10~4~5.9×10~5g/mol~(-1),自然发酵分子量在2.1×10~4~5.4×10~5 g/mol~(-1)间,酵母菌发酵后支链淀粉长链及直链淀粉比例减少而中间及短支链淀粉的比例相对增加;酵母菌发酵96 h糊化温度较自然发酵下降1.07℃,热焓值较上升0.78J·g~(-1);回生值较自然发酵下降471 m Pa·s。自然发酵的优势菌(酵母菌)使小米淀粉的分子结构、糊化及老化特性发生明显变化,并在小米自然发酵过程中起主导作用。     

生物发酵处理对小米淀粉分子结构及糊化特性的影响

采用0.2 g/100 m L NaOH溶液提取发酵后的小米淀粉,研究自然发酵及优势菌(乳酸菌、酵母菌)发酵后对小米淀粉颗粒特性、结晶度、官能团、分子质量、糊化及老化特性的影响。结果如下:乳酸菌、酵母菌发酵后,淀粉颗粒表面有明显的侵蚀迹象,而自然发酵淀粉颗粒表面侵蚀迹象较轻;乳酸菌发酵后小米淀粉的结晶度较自然发酵增加1.49%而酵母菌发酵减少0.33%;发酵并未改变小米淀粉官能团区的峰位,但特征峰强度减弱,乳酸菌、酵母菌发酵后小米淀粉指纹区图谱消失;未发酵小米淀粉重均分子质量为1.5×10~4~5.9×10~5 g/mol,自然发酵分子质量在2.1×10~4~5.4×10~5 g/mol,乳酸菌发酵分子质量为1.6×10~4~5.3×10~5 g/mol,酵母菌发酵分子质量为1.6×10~4~4.7×10~5 g/mol,乳酸菌、酵母菌发酵后支链淀粉长链及直链淀粉比例减少而中间及短支链淀粉的比例相对增加;乳酸菌、酵母菌发酵96 h糊化温度较自然发酵下降0.84℃和1.13℃,热焓值上升1.00 J/g和0.78 J/g;二者的回生值较自然发酵分别下降743、471 mPa·s。自然发酵的优势菌(乳酸菌、酵母菌)使小米淀粉的分子结构、糊化及老化特性发生明显变化,并在小米自然发酵过程中起主导作用。     

直投式发酵辣椒复合菌剂的制备

为开发发酵辣椒复合菌剂,提高发酵辣椒工业生产效率,对从自然发酵辣椒中筛选鉴定出的菌株进行产酸能力、耐酸性、耐盐性和安全性等发酵能力测定,选择出发酵菌剂的备选菌株为植物乳杆菌、乳酸乳球菌和枯草芽孢杆菌。通过接种配比试验和对发酵条件的优化,得出复合菌剂的最佳配方:菌液(枯草芽孢杆菌乳酸乳球菌植物乳杆菌)体积比为141,接种量6%,发酵时间66h,盐浓度4%。该条件下得出的发酵辣椒产酸量为0.77%;感官评定分数17.525。     

自然发酵优势菌对小米淀粉物化性质的影响

小米自然发酵过程难控制,研究自然发酵液分离并鉴定出的优势菌(乳酸菌、酵母菌)对发酵小米淀粉物化性质的影响,可更好地剖析小米自然发酵的机理,为掌握并控制自然发酵提供理论依据。采用质量浓度为0.2 g/100 mL的NaOH溶液提取发酵后小米淀粉,并测定自然发酵、乳酸菌和酵母菌发酵小米淀粉溶解度、膨润度、透明度、热特性、黏度特性。结果表明,随发酵时间的延长,3种发酵方式所得小米淀粉的溶解度、膨润度和透明度均降低,且乳酸菌和酵母菌发酵小米淀粉的透明度较自然发酵下降1.4%和1.0%;乳酸菌和酵母菌发酵96 h时糊化温度较自然发酵下降1.84℃和1.13℃,峰值温度较自然发酵下降1.04℃和0.43℃;终止温度降低3.69℃和2.85℃;热焓值较自然发酵相比上升1.00 J/g和0.78 J/g;而乳酸菌和酵母菌的衰减值、回生值较自然发酵分别下降978 mPa·s和400 mPa·s、743 mPa·s和471 mPa·s,峰值黏度较自然发酵相比上升185 mPa·s和103 mPa·s。自然发酵的优势菌(乳酸菌、酵母菌)使小米淀粉发生改性,且发酵后的物化性质较自然发酵发生显著变化。     

强化发酵对小米淀粉分子结构及老化特性的影响

利用自然发酵液中对淀粉老化特性起主要作用的菌种(乳酸菌:戊糖片球菌、植物乳杆菌、屎肠球菌,酵母菌:酿酒酵母,芽孢菌)强化发酵,研究强化发酵对小米淀粉分子结构及老化特性的影响,为剖析自然发酵对淀粉老化特性的改性机理提供理论基础及数据支持,为开发发酵小米新途径、生产小米发酵剂提供依据。采用0.2 g/100 m L的Na OH提取发酵后的小米淀粉,研究强化发酵对小米淀粉颗粒特性、红外光谱、分子量及老化特性的影响。结果如下:发酵并未改变淀粉的偏光十字;自然发酵后小米淀粉表面被侵蚀,强化发酵后淀粉颗粒表面侵蚀迹象变重,孔道加深且数量增多;自然发酵后小米淀粉官能团区的峰位未变,强化发酵小米淀粉指纹区图谱部分消失,且自然发酵及强化发酵小米淀粉的特征峰强度减弱;强化发酵后I区的重均、数均分子量升高,而自然发酵重均、数均分子量略有降低,但II区二者的重均、数均分子量均降低;自然发酵及强化发酵后淀粉的回生值及最终黏度降低。发酵使淀粉的分子结构发生改变,短期抗老化性能提高。     

酵母菌与乳酸菌发酵对小米淀粉粘度的影响

自然发酵受环境和微生物的影响大,难实现发酵产品的大规模生产。故研究自然发酵优势菌对小米淀粉的影响很有必要。选取内蒙古赤峰生产的黄金苗小米为原料,利用自然发酵纯化的酵母菌与乳酸菌为菌种进行纯种发酵96 h,并且与自然发酵后的小米淀粉比较,分析淀粉的粘度、衰减值和回生值的变化。采用0.2 g/100 m L的Na OH溶液提取3 h的方法来提取发酵后小米中的淀粉,并对其发酵液中固形物的含量、p H、淀粉的粘度特性、偏光十字进行测定。结果表明,三种发酵方法所得的发酵液中总固形物的含量都增加;较自然发酵相比,发酵前24 h乳酸菌和酵母菌发酵液中的p H下降迅速,之后变化缓慢;淀粉粘度特性表明,乳酸菌和酵母菌发酵终止时,其粘度的起始温度、衰减值、回生值较自然发酵相比都下降,峰值粘度较自然发酵相比都上升,乳酸菌发酵和酵母菌发酵的最终粘度与自然发酵相比有所增加,偏光十字显示无论是自然发酵酵母菌发酵还是乳酸菌发酵,发酵后的淀粉颗粒仍具有偏光十字,说明发酵未改变淀粉的结晶结构。      

乳酸菌发酵大米工艺优化制备米发糕研究

以米发糕感官评分为考核指标，利用响应面法优化乳酸菌发酵大米工艺，并对制作的米发糕与市售米发糕进行对比分析。结果表明：最佳发酵工艺参数为乳酸菌发酵温度26℃、发酵时间23 h、菌液接种量1.4%(以大米质量为基准),在此条件下制作的米发糕感官评分为84.6,口感柔软细腻，有柔和的发酵香气，内部气孔均匀致密，品质优于市售米发糕。     

自然发酵对小米淀粉分子结构及凝胶特性的影响

研究自然发酵对小米淀粉凝胶特性及分子结构的影响,旨在为发酵小米淀粉改性机理的研究提供理论基础,为实现机械化、产业化生产发酵小米制品提供科学依据。采用内蒙古黄金苗小米自然发酵144 h,研究发酵对小米淀粉分子结构的影响,分析小米淀粉凝胶特性的变化,结果:自然发酵使小米淀粉的颗粒表面遭到侵蚀,但发酵未改变淀粉的A型结晶;发酵后淀粉的基团峰位未发生变化,但峰强减弱;发酵后Ⅰ区(支链淀粉)、Ⅱ区(直链淀粉)的重均分子质量降低,数均分子质量升高,未发酵小米淀粉的重均分子质量为2.5×10~4~5.9×10~5 g/mol,发酵后小米淀粉重均分子质量为2.2×10~4~5.4×10~5 g/mol。发酵后小米淀粉的回生值、最终黏度较未发酵小米淀粉降低425、470 m Pa·s;糊化温度、热焓值分别上升1.62℃、7.05 J/g;发酵后淀粉凝胶的硬度降低60.735 g,弹性降低0.707,且发酵96 h后,淀粉的凝胶特性基本趋于平稳。自然发酵后小米淀粉的分子结构发生变化,淀粉的凝胶特性改变,更适宜生产利用淀粉抗老化特性制得的产品。     

湿热处理和发酵对小米营养素生物可给性及淀粉消化性的影响

目的：为提高小米的营养价值和改善淀粉的消化性,研究湿热处理和发酵对小米中氨基酸、矿物质、酚类的生物可给性和淀粉消化特性的影响。方法：将湿热处理和发酵单独或组合作用于小米,通过氨基酸分析仪、ICP-OES、Folin-酚法分别测定不同处理样品的氨基酸、矿物质、总酚在体外模拟胃、肠道消化过程中的释放量,用体外酶解技术测定淀粉的消化性,并用ORAC法比较不同处理样品抗氧化活性的变化。结果：湿热处理可显著增加小米中锌的生物可给性,降低铁的生物可给性,使慢消淀粉（SDS）和抗性淀粉（RS）的含量分别从20.1%和13.3%升至26.8%和17.1%。发酵显著降低了蛋白质的体外消化率,增加了铁锌元素的生物可给性,提高了SDS的含量。湿热处理的小米经发酵后,赖氨酸和总氨基酸的生物可给性分别提高74.4%和41.5%,RS的含量较湿热样品进一步增加,铁的生物可给性下降。此外,小米样品经体外模拟胃、肠道消化,游离酚较消化前提高19～22倍,湿热-发酵样品表现出最高的抗氧化活性。结论：在无麸质小米食品的加工中,湿热处理与发酵的组合在改善营养成分生物可及性方面有望成为一项有前景的技术方案。     

小米酸粥自然发酵工艺优化及其挥发性风味物质分析

以小米为原料自然发酵制备小米酸粥,以感官评分为指标,在单因素试验的基础上通过响应面法优化小米酸粥的发酵工艺,并对其挥发性风味物质进行分析。结果表明：最佳发酵工艺条件为米与汤质量比1∶4、发酵温度34℃、发酵时间30 h,在此条件下制得的小米酸粥营养丰富,风味独特,其感官评分为91.74。在小米酸粥中共检测出36种挥发性风味物质。     

不同酿造过程中醪糟淀粉的结构与消化性能的变化

为探讨醪糟淀粉的分子结构与消化性能关系,通过控制糯米原料用量,得到不同的醪糟淀粉。在糯米原料适量的情况下,酿造后的醪糟淀粉表面有一定的破损,但其A型结晶结构保持不变,同时淀粉颗粒内部的紧密程度有所提升。此外,醪糟淀粉分子量及分子半径缓慢下降,形成带有一定支叉结构的淀粉链段。在消化性能上,部分醪糟经蒸煮后模拟人体消化,约有37.86%的淀粉在消化20 min后消化,在20～120 min之间有34.56%淀粉消化,其葡萄糖释放速度适中,作用类似于慢消化淀粉,对控制人体血糖水平等有重要意义。所以,对醪糟酿造过程进行控制,调控醪糟淀粉分子结构,可影响其消化性和营养价值。     

微波复合酶解改性对小米淀粉结构表征及其理化特性的影响

本文以小米淀粉为原料，采用微波、酶解、微波复合酶解三种方法改性淀粉。从淀粉颗粒形貌、偏光特性、结晶结构、短程有序性、粒径分布等方面对小米淀粉进行结构表征，测定其直链淀粉含量、溶胀力与透明度等指标以分析小米淀粉的理化特性。结果表明：改性后，小米淀粉的颗粒结构被破坏，偏光十字特性消失，结晶结构发生改变，但三种改性方法均不影响小米淀粉的基本官能团。其中，微波改性小米淀粉为A型晶体，酶解和微波复合酶解改性淀粉结晶型为B型，微波复合酶解改性淀粉的相对结晶度提高了35.32 %。改性淀粉的粒径、直链淀粉含量均有所提高，与原淀粉相比，微波复合酶解改性淀粉的直链淀粉含量增加了49.03 %。综上所述，与单一法相比，微波复合酶解法对淀粉颗粒结构和理化性质的改善效果最佳，这对于小米淀粉基食品的开发应用具有重要意义。     

In vitro batch fecal fermentation comparison of gas and short-chain fatty acid production using "slowly fermentable" dietary fibers

Abstract: Sustained colonic fermentation supplies beneficial fermentative by‐products to the distal colon, which is particularly prone to intestinal ailments. Blunted/delayed initial fermentation may also lead to less bloating. Previously, we reported that starch‐entrapped alginate‐based microspheres act as a slowly fermenting dietary fiber. This material was used in the present study to provide a benchmark to compare to other “slowly fermentable” fibers. Dietary fibers with previous reports of slow fermentation, namely, long‐chain inulin, psyllium, alkali‐soluble corn bran arabinoxylan, and long‐chain β‐glucan, as well as starch‐entrapped microspheres were subjected to in vitro upper gastrointestinal digestion and human fecal fermentation and measured over 48 h for pH, gas, and short‐chain fatty acids (SCFA). The resistant fraction of cooked and cooled potato starch was used as another form of fermentable starch and fructooligosaccharides (FOS) served as a fast fermenting control. Corn bran arabinoxylan and long‐chain β‐glucan initially appeared slower fermenting with comparatively low gas and SCFA production, but later fermented rapidly with little remaining in the final half of the fermentation period. Long‐chain inulin and psyllium had slow and moderate, but incomplete, fermentation. The resistant fraction of cooked and cooled potato starch fermented rapidly and appeared similar to FOS. In conclusion, compared to the benchmark slowly fermentable starch‐entrapped microspheres, a number of the purported slowly fermentable fibers fermented fairly rapidly overall and, of this group, only the starch‐entrapped microspheres appreciably fermented in the second half of the fermentation period. Practical Application: Consumption of dietary fibers, particularly commercial prebiotics, leads to uncomfortable feelings of bloating and flatulence due to their rapid degradation in our large intestine. This article employs claimed potential slowly fermenting fibers and compares their fermentation rates with a benchmark slow fermenting fiber that we fabricated in an in vitro simulation of the human digestive system. Results show a variety of fermentation profiles only some of which have slow and extended rate of fermentation.     

纯种发酵对小米淀粉分子结构及老化特性的影响

利用自然发酵液中对淀粉老化特性起主要作用的菌种发酵,研究发酵对小米淀粉分子结构及老化特性的影响。采用0.2 g/100 m L的NaOH溶液提取发酵后的小米淀粉,研究不同菌种发酵后对小米淀粉颗粒特性、官能团、分子质量、糊化及老化特性的影响。结果表明:发酵未改变淀粉的偏光十字;植物乳杆菌、戊糖片球菌和屎肠球菌发酵后小米淀粉表面被侵蚀,酿酒酵母及芽孢菌发酵后淀粉颗粒表面侵蚀迹象变重,孔道加深且数量增多;酿酒酵母及芽孢菌发酵后小米淀粉官能团区的峰位未变,但特征峰强度减弱,植物乳杆菌、戊糖片球菌及屎肠球菌发酵后小米淀粉指纹区图谱部分消失;植物乳杆菌发酵后Ⅰ区、Ⅱ区的重均、数均分子质量较小米淀粉降低。戊糖片球菌、屎肠球菌、酿酒酵母发酵后Ⅰ区的重均分子质量升高,数均分子质量降低,Ⅱ区重均、数均分子质量降低。芽孢菌发酵后Ⅰ区的数均分子质量略有升高,Ⅱ区重均、数均分子质量降低。植物乳杆菌、戊糖片球菌及屎肠球菌发酵后淀粉的糊化温度、回生值及最终黏度降低,热焓值升高。酿酒酵母发酵后糊化温度及回生值降低,最终黏度及热焓值升高。发酵使淀粉的分子结构、支链淀粉及直链淀粉分子发生改变,短期抗老化性能提高。     

中度嗜酸放线菌YY21液体发酵产纤溶酶条件的研究

为了提高中度嗜酸放线菌YY21产纤溶酶的产量,本文通过单因素实验对其液体发酵培养基和培养条件进行了研究。结果表明:发酵培养基组成为小米粉1.7%,葡萄糖2%,碳酸钙0.2%,氯化钠0.5%,蛋白胨0.6%;发酵条件为250 m L三角瓶装培养基50 m L,接种量5%,在22℃、转速160 r/min的条件下振荡培养4 d。在最适条件下,放线菌YY21液体发酵产物在血纤维蛋白平板上形成溶圈面积可达到164.38 mm~2,较初始产酶活力(溶圈面积87.58 mm~2)提高了88%,发酵时间缩短了3 d。通过对液体发酵培养基和培养条件的研究有效地提高了中度嗜酸放线菌YY21产纤溶酶的产量。      

Characterization of lactic acid bacteria isolated from a Thai low-salt fermented fish product and the role of garlic as substrate for fermentation

Lactic acid bacteria (LAB) isolated from raw materials (fish, rice, garlic and banana leaves) and processed som-fak (a Thai low-salt fermented fish product) were characterized by API 50-CH and other phenotypic criteria. Lactococcus lactis subsp. lactis and Leuconostoc citreum were specifically associated with fish fillet and minced fish, Lactobacillus paracasei subsp. paracasei with boiled rice and Weisella confusa with garlic mix and banana leaves. In addition, Lactobacillus plantarum, Lactobacillus pentosus and Pediococcus pentosaceus were isolated from raw materials. A succession of aciduric, homofermentative lactobacillus species, dominated by Lb. plantarum/pentosus, was found during fermentation. In total, 9% of the strains fermented starch and 19% fermented garlic, the two main carbohydrate components in som-fak. The ability to ferment garlic was paralleled by a capacity to ferment inulin. An increased percentage of garlic fermenting strains was found during fermentation of som-fak, from 8% at day 1 to 40% at day 5. No starch fermenting strains were isolated during fermentation. Three mixed LAB cultures, composed of either starch fermenting Lc. lactis subsp. lactis and Lb. paracasei subsp. paracasei, or garlic fermenting Lb. plantarum and Pd. pentosaceus, or a combination of these strains were inoculated into laboratory prepared som-fak with or without garlic. In som-fak without garlic, pH was above 4.8 after three days, irrespective of addition of mixed LAB cultures. The starch fermenting LAB were unable to ferment som-fak and sensory spoilage occurred after three days. Fermentation with the combined mix of starch and garlic fermenting strains led to production of 2.5% acid and a decrease in pH to 4.5 in two days. The fermentation was slightly slower with the garlic fermenting strains alone. This is the first report describing the role of garlic as carbohydrate source for LAB in fermented fish products.