Preparation of lactic acid bacteria compound starter cultures based on pasting properties and its improvement of glutinous rice flour and dough

The effects of 5 lactic acid bacteria(LAB)fermentation on the pasting properties of glutinous rice flour were compared,and suitable fermentation strains were selected based on the changes of viscosity,setback value,and breakdown value to prepare LAB compound starter cultures.The results revealed that Latilactobacillus sakei HSD004 and Lacticaseibacillus rhamnosus HSD005 had apparent advantages in increasing the viscosity and reducing the setback and breakdown values of glutinous rice flour.In particular,the compound starter created using the two abovementioned LAB in the ratio of 3:1 had better performance than that using a single LAB in improving the pasting properties and increasing the water and oil absorption capacity of glutinous rice flour.Moreover,the gelatinization enthalpy of the fermented samples increased significantly.For frozen glutinous rice dough stored for 28 days,the viscoelasticity of frozen dough prepared by compound starter was better than that of control dough,and the freezable water content was lower than that of control dough.These results indicate that compound LAB fermentation is a promising technology in the glutinous rice-based food processing industry,which has significance for its application.

通过西门子Starter软件调试G120C变频器

文章介绍了使用西门子变频器调试工具Starter软件对G120C变频器进行调试的过程。其中包括恢复出厂设置、宏应用、软件控制、电机识别、PID压力调节等功能。

Sensory Evaluation of Freeze-Dried Facial Mask and Analysis of User Profile

To thoroughly understand market opportunity of freeze-dried facial mask and deeply get insight of consumers’usage behavior and needs,evaluate sensory feelings of 10 screened commercial freeze-dried facial mask products,group test products according to the differences of sensory attributions via Principal Component Analysis(PCA)and Agglomerative Hierarchical Clustering(AHC),pick up the representative products.Freeze-dried facial mask users evaluate satisfaction degree of picked up products and participate survey of usage behavior/cognition.Analyze consumer data by AHC to get consumer segmentations and their profile.The test results show that,sensory data and consumer data,which is from consumers test of screened representative products by performing PCA and AHC on sensory data,can be verified mutually.It is helpful to understand the needs of consumer segmentations and reason to buy by combining sensory data and consumer test.

Effect of inoculating mixed starter cultures of Lactobacillus and Staphylococcus on bacterial communities and volatile flavor in fermented sausages

The objective of this study was to explore the effects of the inoculation of mixed starter cultures of Lactobacillus and Staphylococcus(labeled L-S)on microbial community and flavor in fermented sausages during the ripening process.Culture-dependent(colony count)and culture-independent(high-throughput sequencing)methods were employed to evaluate bacterial communities.Volatile compounds were identified by gas chromatography-mass spectrometry,and the results were analyzed by principal component analysis(PCA).The identified bacteria with high relative abundance included Lactobacillus and Pediococcus,and the relative abundances of Leuconostoc and Weissella in fermented sausages were remarkably decreased at the end of the ripening process.At the end of ripening,2-nonenal,tetradecanal,ethylstearate and terpinyl acetate played substantial roles in the flavor development of the L-S fermented sausages.Sensory evaluation showed a high score in the L-S fermented sausages.Sausages can be inoculated with L-S starter culture to improve the safety and flavor of meat products.

The protective effect of oleic acid on Lactiplantibacillus plantarum during freeze-drying

Membrane characteristics are determined by the fatty acids composition,which affects survival rates after freeze-drying.However,it is unknown which composition provides the greatest effect.In this study,we found that the addition of Tween 80 and Tween 20 significantly increased survival rates of Lactiplantibacillus plantarum,which reached a maximum of 93.1%.Conversely,Tween 60 caused a significant decrease.We further found that the difference between the effects of adding Tween 80 and Tween 60 was the change in oleic acid contents.To verify the role of oleic acid,we used CRISPR-Cas9 to knock-out the key synthesis gene cla-er.The survival rates of L.plantarum AR113Δcla-er declined to 5.48%.The addition of oleic acid restored the rates to those of wild type strains.Moreover,the membrane integrity and fl uidity of knockout strains markedly decreased.This is the fi rst confi rmation that Tween 80 or Tween 20 increases the survival rate by increasing the content of oleic acid in the cell membrane.These fi ndings also indicated that oleic acid in cell membranes has a substantial protective effect on L.plantarum during freeze-drying.

Effect of thermal processing and fermentation with Chinese traditional starters on characteristics and allergenicity of wheat matrix

Wheat allergy has become a serious health threat worldwide and its prevalence has increased alarmingly in the past few years.Factors such as food matrix and food processing may alter the structure of wheat proteins,and hence affect its allergenic properties.However,few reports have focused on the influence of Chinese traditional starter fermentation on wheat allergy.In this study,5 starters from different regions of China were used for fermentation,and protein characteristics were monitored by sodium dodecyl sulfate polyacrylamide gel electropheresis,and immunoreactivity analyzed by immunoassay with allergenic serum was obtained from New Zealand white rabbits.The allergenicity of steamed and baked matrices was also evaluated.The results showed that the allergenicity of wheat dough was basically increased at the beginning and then decreased during fermentation,but specific trends depend on different starters.With the progress of fermentation,especially as pH value decreased to 3.0-4.0,the allergenicity decreased significantly.Baking and steaming can reduce the allergenicity of wheat matrix,but fermentation is not a key factor affecting the allergenic activity of proteins.Our results can provide a theoretical basis for controlling wheat allergenicity in food proces sing or producing hypoallergenic food.

食品发酵剂研究进展与发展趋势浅析

食品发酵剂能够通过多种代谢途径影响发酵食品的感官特性、营养价值和益生功能,是发酵食品生产制造的核心。优良性能食品发酵剂的挖掘与制造,对发酵食品产业的高质量发展具有重要意义。本文通过综合文献调研和数据可视化分析,系统梳理当前国内外食品发酵剂研究进展及产业现状,总结食品发酵剂产业面临的挑战并展望未来发展趋势,旨在为我国优良性能食品发酵剂的研发及产业发展提供思路和借鉴。

不同发酵剂对发酵牛肉品质、风味特性和安全性的影响

牛肉富含蛋白质、脂肪含量低,深受消费者喜爱,然而其难咀嚼、附加值低。为提高牛肉的口感风味,研究本单位的3株专利菌株——W9-3罗伊氏乳杆菌、M3-16副干酪乳杆菌和MY4马克斯克鲁维酵母制备的单菌和复配发酵剂对牛肉理化、感官品质、生物胺形成和挥发性风味的影响。结果表明,与未发酵和自然发酵的牛肉相比,添加发酵剂可降低牛肉的pH(均小于5.5)、水分活度(降低0.6%~4.1%)、TBA值和羰基值,抑制组胺、色胺、酪胺和丁二胺等生物胺的形成,提升熟化牛肉的亮度和弹性,降低硬度、黏着性、咀嚼性和黏聚性。其中复配组优于单菌组。利用SPME-GC-MS方法从焙烤发酵牛肉中鉴定出86种挥发性化合物,其相对含量和主成分分析结果表明,用发酵剂发酵的烤牛肉的风味物质与未发酵和自然发酵相比形成多种新的醇、醛和酮类。感官评价表明,使用发酵剂能在一定程度上提高牛肉的组织形态、外观色泽、气味和口感。尤其是复配发酵剂可改善发酵牛肉品质,提升风味,抑制生物胺。本文为牛肉发酵工艺优化提供理论依据。

浓香双曲酿造工艺与酒醅微生物群落演替规律的研究

本研究按照浓香型白酒工艺特点,利用不锈钢发酵容器,以混合均匀后的浓香产酒大曲和浓香生香大曲作为糖化发酵剂,粉碎高粱为原料,采用清蒸混入、续糟发酵的生产方式,形成浓香双曲酿造工艺。通过常规理化分析技术和Illumina MiSeq高通量测序技术对双曲酿造工艺酒醅的理化指标和微生物菌群进行测定和分析,以进一步探究其发酵机理。结果表明,整个发酵过程中理化指标的变化具有较明显的规律性,酒精度前期迅速增加,后期趋于平缓,并在第9 d时达到最大值。发酵过程中共检测出317个属,其中真菌225个、细菌92个,酒醅中主要优势真菌属有2种,伊萨酵母属(Issatchenkia)在发酵过程中占绝对优势;主要优势细菌属有3种,发酵前期乳酸菌属(Lactobacillus)占绝对优势,发酵后期unclassified-Lactobacillales占绝对优势。酒醅发酵过程中微生物群落结构的变化与理化因子有显著关系,对真菌而言,还原糖含量与双足囊菌属(Dipodascus)、嗜热子真菌属(Thermomyces)的相对丰度呈极显著正相关;对细菌而言,淀粉和还原糖的含量与葡萄球菌属(Staphylococcus)相对丰度呈显著正相关,水分含量和酒精度与unclassified-Lactobacillales相对丰度呈显著正相关。酒醅发酵过程中温度、酒精度和酸度推动了微生物群落结构的演替。

某液体火箭发动机用起动器峰值压力时间超差故障研究

针对某液体火箭发动机用起动器峰值压力时间超差故障,进行了原因分析,提出了改进措施并对其有效性进行了试验验证。结果表明:造成起动器峰值压力时间超差故障的原因为起动器内膜片与端盖间的焊接强度不足,在高温燃气冲击下膜片过早脱落、烧蚀,从而导致压力提前泄放。提出将1圈焊接改进为2圈焊接、将点焊改进为连续焊接,焊接后增加气密性及承压性能检测,以及加强削弱槽深度检测等改进措施。验证试验表明上述改进措施可有效避免起动器出现峰值压力时间超差故障。

基于高通量测序技术对不同地区米酒曲微生物群落结构的分析

采用高通量测序技术对湖北宜昌当地传统米酒曲与广西玉林传统米酒曲中的微生物群落结构进行解析,获得了酒曲中主要微生物种属和占比。结果表明,广西米酒曲在物种丰富度以及群落多样性上均高于宜昌米酒曲;广西米酒曲中优势真菌属以根霉属(Rhizopus)、毛霉属(Mucor)、毕赤酵母属(Pichia)和假丝酵母属(Candida)为主,宜昌米酒曲中根霉属(Rhizopus)和毛霉属(Mucor)为优势菌属;在细菌属水平上,广西米酒曲以片球菌属(Pediococcus)、假单胞菌属(Pseudomonas)、魏斯氏属(Weissella)、乳杆菌属(Lactobacillus)为主,宜昌米酒曲优势菌属为假单胞菌属(Pseudomonas)和魏斯氏属(Weissella);ASV/OTU韦恩图分析表明宜昌酒曲在物种独特性上要优于广西玉林酒曲。本研究揭示了宜昌传统米酒曲中的真菌与玉林传统米酒曲真菌菌种的差别,为逐步改善传统酒曲质量,以及相关微生物的进一步利用提供了理论指导依据。

肉制品发酵技术对肉品品质的调控及应用研究进展

发酵是现代食品工业中一种重要的加工技术,可用于大规模生产发酵肉制品。本文探讨了发酵技术对肉制品品质的调控作用,从发酵剂的筛选与构建、发酵剂的接种策略、影响发酵的因素及工艺优化三个方面概述了发酵剂和发酵工艺在肉制品加工中的研究与应用现状,并讨论了发酵技术在我国肉制品产业应用中的发展趋势。总的来说,新型发酵技术的应用打破了传统肉类产业的局限性,未来可针对不同发酵肉制品品质需求特点,调整发酵工艺和策略,生产符合现代人们生活需要的营养、美味、安全和多样化的发酵肉制品。

涡轮起动机中斜撑离合器的瞬态冲击与楔合特性研究

将稳态楔合拓展至瞬态冲击是深入研究斜撑离合器正向设计的重要组成部分。本文从机械动力学理论出发,关联输入输出端载荷与响应特征,建立斜撑离合器冲击受载微分方程,揭示出离合器由瞬态楔合至稳态传动过程蕴含的动力学原理和一般规律。在此基础上,推导出斜撑离合器内外传动轴的综合应力分析模型,并提出运用接触应力、综合应力和楔角等指标整体考察离合器传动性能的校核方法。最后以某常见离合器部件为例,从理论计算和仿真分析两方面模拟了涡轮起动机环境下的短时受载工况,验证了本文原理和分析模型的有效性,因而对此类离合器的设计与校核分析具有重要意义。

拨齿式电驱动水稻育秧盘起盘机设计与试验

针对北方水稻棚式育秧移栽生产模式中秧苗移栽前的起盘过程不适宜于铺设大型龙门架起盘机械,创制了一种拨齿式电驱动水稻育秧盘起盘机。阐述了整机结构及工作原理,阐明了机具拨起秧盘的基本原理,采用力学分析法对水稻育秧盘起盘机的拨盘装置进行了设计,确定了影响起盘性能的拨盘装置结构参数及其取值范围。以拨盘装置转速、机具前进速度、拨盘装置离地高度为试验因素,以秧盘完整率和机具起盘效率作为性能指标进行三因素三水平正交试验。试验结果表明:拨齿式电驱动水稻育秧盘起盘机较优的参数组合为拨盘装置转速为40r/min、机器前进速度为0.8km/h、拨盘装置离地高度为0mm,对试验结果进行验证,其秧盘完整率为99%,效率为362盘/h,各项性能指标均满足起盘作业要求。

玉米品种和发酵剂对全株玉米青贮营养品质的影响

本试验旨在探究不同玉米品种和发酵剂对全株玉米青贮营养品质的影响,筛选出最优发酵剂和最适合甘肃中东部地区的青贮玉米品种。以“京科627”(H1)、“金穗1915”(H2)、“铁研53”(H3)、“登海3721”(H4)、“大京九26”(H5)、“陇青贮1号”(H6)6个玉米品种为试验材料,在蜡熟期收获,分别添加以植物乳杆菌、乳酸片球菌等为主的饲草青贮剂1(A1)、以布氏乳杆菌9-2和戊糖片球菌为主的饲草青贮剂2(A2)和以植物乳杆菌A1和植物乳杆菌LP-21为主的饲草青贮剂3(A3)3种发酵剂并设置空白对照组(CK),共24个处理,每个处理3个重复。发酵90 d后测定其品质。结果表明:玉米品种对干物质(DM)、粗蛋白质(CP)、中性洗涤纤维(NDF)、乳酸(LA)、乙酸(AA)、丙酸(PA)、氨态氮(NH 3-N)含量以及中性洗涤纤维消化率有极显著影响(P<0.01);与空白对照组相比,3种发酵剂显著提高了DM、CP、LA、AA含量(P<0.05),极显著降低了NH 3-N含量(P<0.01)。综上所述,3种发酵剂对不同品种全株玉米青贮的品质有不同程度的提升,灰色关联度分析结果表明以“饲草青贮剂3”处理的“登海3721”为最优组合,最适合在临夏地区种植和推广应用。

复配发酵剂对发酵香肠的品质及挥发性风味的影响

为评判植物乳杆菌(L77)和木糖葡萄球菌(S120)复配发酵剂的优良特性,本研究以不接菌为空白对照组,采用顶空固相微萃取/气相色谱-质谱联用(HS-SPME/GC-MS)等技术分析比较了L77-S120组和L77组对发酵香肠的常规理化和微生物指标、主体挥发性风味化合物数量含量及香型、感官品质的影响。结果显示,L77-S120组的TBARS值、亚硝酸盐含量和肠杆菌数量均显著低于空白组和L77组(P<0.05);L77-S120组的主体挥发性风味物质的数量和含量最多,有10种醛类、3种醇类、2种酯类、1种酸类,4种其他类,差异风味化合物包括庚醛、(E)-2-庚烯醛、蘑菇醇、2-戊基呋喃、反-2-辛烯醛、反-2,4-癸二烯醛、反-2-十一烯醛、2-乙基丁酸、癸酸乙酯、戊醛和壬醇,并且主体挥发性风味物质产油脂香、奶油香和花果香的能力最强。结合感官评价,植物乳杆菌L77和木糖葡萄球菌S120复配组合更适合作为发酵香肠的产香型发酵剂。

六堡茶真菌固态发酵优势单菌的筛选

以苍梧群体种六堡毛茶为原料,利用从六堡茶中分离到的20株真菌接种至灭菌六堡毛茶进行固态发酵,通过感官审评、生化成分检测结合主成分分析,探索不同真菌的发酵效果,筛选出可显著提升六堡茶品质或赋予六堡茶新风味的固态发酵优势真菌。结果显示,9株真菌发酵性能优异,分别为塔宾曲霉、黑曲霉、芒果青霉、角膜曲霉、赤曲霉、间型曲霉、团青霉、阿姆斯特丹曲霉、赤酵母。对9株真菌发酵茶样进行理化成分分析,结果显示:接种塔宾曲霉、黑曲霉、团青霉和阿姆斯特丹曲霉发酵能显著改变茶叶中18种化学成分的含量。综合考量确定团青霉和阿姆斯特丹曲霉为发酵优良真菌。本研究可为后期人工控菌发酵六堡茶提供优良菌种资源,并为六堡茶发酵工艺改良、产品研发创新及品质提升提供科学的理论依据。

不同发酵方式对酸豇豆品质的影响

以新鲜豇豆为原料,采用自然发酵(CK组)、接种商业菌种(CS组)、接种自筛直投式菌剂(DVS组)3种方式发酵豇豆,测定发酵过程中发酵液的总酸、pH值及发酵成熟后豇豆的盐度、亚硝酸盐、氨基酸态氮、游离氨基酸、乳酸菌数、色差、感官品质、质构特性,分析发酵方式对酸豇豆品质的影响。结果表明,在发酵过程中,DVS组的总酸增长速度最快,在1~6 d均高于CS组、CK组;CS组、DVS组的pH值下降速率比CK组快,在7 d时CS组p H值最低,DVS组仅次于CS组;在发酵至第7天时,DVS组菌落总数分别比CK组、CS组高33.86%、42.31%。发酵成熟后,DVS组的盐度、亚硝酸盐、b^(*)值最低,氨基酸态氮、游离氨基酸、乳酸菌数、感官评分、硬度、粘力、胶着性、咀嚼性最高,L^(*)值、a^(*)值、弹性与其他发酵方式无显著性差异(P>0.05)。综合可知,DVS组不仅发酵启动快,且酸豇豆成品的综合品质更优。

根霉功能曲制曲工艺条件优化研究

利用中高温大曲中筛选出的高产糖化酶根霉Rhizopus sp.菌株制备功能曲,通过单因素试验及响应面优化设计得出最佳工艺条件为:原料配比小麦粉∶熟糠∶麸皮(36∶10∶5)、接种量2.36%、料水比1∶0.6(g∶mL)、培养温度29.42℃和培养时间54.69 h。在此最佳工艺条件下制备的根霉功能曲糖化力为896 mg/g·h、液化力为1.5 g/g·h、试饭试验还原糖含量为37.5 g/100 g。

不同发酵剂对木薯茎叶青贮品质的影响

试验探究了不同发酵剂对木薯茎叶青贮品质的影响。试验分为对照组(CK组)和3个处理组(A组、B组、C组)。CK组中不添加任何发酵剂,3个处理组在木薯茎叶原料中分别添加0.02%的发酵剂A、发酵剂B、发酵剂C,每组3个重复,发酵90 d后取样分析。结果表明,各处理组的干物质、Ca、P含量与CK组无明显变化;C组粗蛋白、粗脂肪、粗灰分含量均最高,分别较CK组升高8.06%、17.84%、2.01%;A组木质素含量最低,较CK组降低14.43%;C组中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)、可溶性碳水化合物(WSC)含量均最低,分别较CK组降低11.40%、16.62%、14.96%。各处理组的所有饲喂价值指标均高于CK组,C组的所有饲喂价值指标均最高。B组pH值、氨态氮、丁酸和氨态氮/总氮的数值均最低,较CK组分别降低8.88%、20.90%、99.48%和26.82%;C组乳酸含量最高,较CK组升高26.03%;A组乙酸含量最低,较CK组降低5.85%。对发酵品质进行综合评分可知,各处理组得分均高于CK组。利用平均隶属函数值对木薯茎叶青贮品质进行综合比较,B组的青贮品质最佳。研究表明,添加微生物发酵剂在一定程度上能够改善木薯茎叶的青贮品质。