【作者】 李曼；

【导师】 周惠明；

【作者基本信息】 江南大学 ， 粮食、油脂及植物蛋白工程， 2014， 博士

【摘要】 面条是中国及其它一些亚洲国家的传统主食，已有4000多年的历史。为便于保存，目前市场上出售的面条类制品多为干制品，如挂面、油炸方便面等，这些加工工艺均会不同程度的损害面条的风味和口感，营养成分也会受到一定损失，因此已日益不能满足现代人崇尚营养健康的消费时尚。生鲜面制品，因其新鲜、有嚼劲及较好的面香味等特点，作为一种传统食品而长久不衰，实现生鲜面的工业化、规模化生产将具有重大的现实意义，而解决其贮藏运输过程中的品质劣变问题则是实现其批量化生产的前提和关键。首先，对生鲜面贮藏过程中宏观、结构以及分子层面的品质指标变化进行了探索。发现导致生鲜面腐败变质的主要微生物为细菌，其次是霉菌和酵母；贮藏前期生鲜面中菌落总数（TPC）迅速增加，后期趋于平缓；生鲜面的亮度值（L*值）在制作后的24h特别是前4h降低最快；贮藏过程中pH值和总酚含量显著下降（P<0.05）。随品质劣变程度的加深，部分蛋白组分被降解，淀粉的糊化特性和粘度特性也会发生一系列变化。生鲜面变质过程中等温吸湿曲线下移，核磁共振横向弛豫峰右移；MRI图像显示随贮藏时间的延长，生鲜面原有的结构被破坏，水分分布不均且向表面迁移。通过对主要指标变化规律进行相关性分析和因子分析，筛选出TPC和L*值的变化值作为评价生鲜面品质劣变的直观指标；而生鲜面中水分的流动和迁移则对其表面状态及煮后质构参数具有显著的影响，也是维持生鲜面良好品质所需要解决的重要问题。其次，研究确定了生鲜面品质劣变加速的关键转折条件，发现导致其劣变开始加速的关键转折温度为20~25℃，关键水分含量在23%~24%之间，褐变速率最快的pH范围为pH8.0~8.5，而微生物在初始pH6~10整个范围内，都保持着较高的生长速率。在此基础上，以微生物生长速率和褐变速率为评价指标，建立了常温下生鲜面的品质劣变动力学模型，结果表明微生物的生长可以用Gompertz模型和Logistis模型很好的拟合，其中Gompertz模型的拟合精度更高，拟合方程为y=4.364exp[-exp(1.032-0.086t)]，R2=0.98855；而褐变速率则符合二次多项式模型，褐变速率方程为y=76.0629-0.0165x+5.98587x2，R2=0.9814。再次，探讨了生鲜面贮藏过程中水分结合状态对其品质变化的影响，研究了降低水分活度即促进生鲜面中游离水分结构化的关键技术。优化出降低生鲜面水分活度的最佳持水剂组合，使其水分活度从0.979降至0.900；从制面工艺入手，研究了真空和面对生鲜面品质特性及促进游离水分结构化的作用效果，结果表明：真空和面能显著改善生鲜面的色泽、外观、蒸煮及质构等品质指标，但对不同小麦粉所制得的生鲜面改善效果不同，确定-0.06MPa作为实际生产中最适和面真空度；此外，真空和面能促进生鲜面中水与非水组分的相互作用，使其一定含水量下的等温吸湿曲线上移，降低生鲜面中可冻结水含量，使核磁共振弛豫峰左移，弛豫时间变短；进一步研究得出，真空和面能在一定程度上促进生鲜面中各蛋白组分相互作用及面筋网络的充分形成；FR-IT图谱分析得出，真空和面使生鲜面中蛋白质二级结构更加稳定有序，MRI图像显示贮藏过程中真空和面组生鲜面中水分的迁移和内部结构劣变更加缓慢，说明真空和面能显著改善制面特性，促进生鲜面中游离水分结构化，增加生鲜面贮藏稳定性。此外，以将生鲜面水分含量降低到前面得出的相对安全范围为目的，比较了高温短时脱水（HTST,105~135℃,30~200s）和中低温长时间脱水（MTLT,45~75℃,5~20min）对生鲜面蒸煮、质构品质以及内部组分结构和贮藏稳定性的影响。DSC和偏光十字现象分析发现，120℃以下高温短时脱水会导致一少部分淀粉糊化（30%左右）；SEM结果显示，高温短时脱水得到的生鲜面表面更加致密，内部呈现出均匀的孔隙，蛋白和淀粉结合更为紧密；同时高温短时脱水会导致生鲜面中蛋白质通过二硫键（-S-S-）作用发生聚合，其蒸煮损失比中低温脱水生鲜面显著降低，质构参数无显著差异（P>0.05）。同时，高温短时脱水生鲜面具有更高的贮藏稳定性，但由于初始含菌量较高，120℃和135℃适度脱水处理也只能将生鲜面含菌量降至103CFU/g以内，若不经其它处理，室温下的保质期可延长至5天左右。最后，为进一步降低原料及生鲜面中的初始含菌量，增强后续保鲜效果，研究了臭氧处理对小麦粉品质特性及生鲜面货架期的影响。结果表明，臭氧处理能显著降低小麦粉中菌落总数及PPO活性（P<0.05），延长生鲜面货架期。同时，经臭氧处理后小麦粉和生鲜面片的亮度和白度增加，面团稳定性增强，RVA峰值粘度、低谷粘度及最终粘度值增加；SDS-PAGE蛋白电泳条带显示臭氧处理小麦粉中生成了以二硫键作用为主的大分子量蛋白聚合体，说明臭氧可作为小麦粉中化学氧化剂的天然替代。此外，经臭氧处理后的小麦粉在贮藏过程中菌落总数会进一步显著降低；GC-MS结果显示，臭氧处理后小麦粉中主要风味成分变化不大，但风味物质种类增多，相对含量有所改变。更多还原

【Abstract】 Noodle products are the staple food in many Asian countries since ancient time, theyhave been in existence for nearly4000years. For quite a long time, people could only buy drynoodles or instant fried noodles in supermarkets for preservation. However, these dryingprocesses may induce deterioration in the flavor and taste of the products, as well as thenutrients. Thus, as a food product with a long history in China, nowadays, fresh noodle isattracting more and more people for its unique favor and taste. It is of great practicalsignificance to realize the industrialization of fresh noodles.Firstly, changes of the quality parameters of fresh noodles were evaluated at macroscopic,structural and molecular levels. Results showed that the most common spoilagemicroorganisms in fresh noodles are bacteria, followed by molds and yeast; Total plate count(TPC) increased rapidly at the early storage period, and then got slowly; L*value decreasedrapidly during the first24h, especially the first4h; During storage, pH value and totalphenolic content of fresh noodles decreased significantly. Proteins were partly decomposedwith the deterioration of fresh noodles, and changes were also detected in the pasting andviscosity properties of starch. In addition, water sorption isotherm of fresh noodles decreasedduring storage, while the NMR transverse relaxation peak right shifted; MRI images showedthat with the extension of storage time, the original structure in fresh noodles was damaged,water distribution became nonuniform and migrated to the surface. With the correlation andfactor analysis of the changes in quality parameters, TPC and L*value were selected as thevisualized indicators to evaluate the deterioration of fresh noodles; water status and migrationwas shown to significantly affect their apparence and textural properties after cooking, thus itwas also an important problem to be resolved to maintain high quality of fresh noodleproducts.Secondly, critical conditions inducing the acceleration of fresh noodle deterioration weredetermined. Results showed that the critical temperature leading to the initial acceleration was20~25℃, critical water content was between23%~24%; the fastest darkening rate wasdetected at pH8.0~8.5, while microorganisms kept a high growth rate during the whole rangeof initial pH6~10. Based on this, shelf-life model was built at room temperature, showing thatmicrobial growth could be well fitted by both Gompertz and Logistis model, with higherfitting precision for Gompertz model and the fitting equation was y=4.364exp[-exp(1.032-0.086t)], R2=0.98855; Meanwhile, the darkening of fresh noodles could be fitted byquadratic polynomial model, with the fitting equation y=76.0629-0.0165x+5.98587x2,R2=0.9814.Then, the effect of water status on the quality changes of fresh noodles during storagewas discussed, and the key techniques for reducing water activity and promote thecombination between water and other components were studied. The most effective group ofawlowering agents was selected, which reduced the awof fresh noodles to0.900(from0.979);meanwhile, effect of vacuum mixing on noodle quality and the water combination in freshnoodles were determined, results showed that vacuum mixing significantly improved the color, appearance, cooking and textural properties of fresh noodles, the improving effects weredifferent in samples made from different kinds of flour.-0.06MPa was confirmed as the bestvacuum degree for noodle production. In addition, vacuum mixing enhanced the interactionbetween water and other components in noodle dough, with increased water sorption isotherm,decreased freezable water content, as well as the left shifed NMR transverse relaxation peakand reduced relaxation time. Results also showed that vacuum mixing could promote theinteraction of protein components and the development of gluten network; FR-IT spectrumanalysis presented a more stable and ordered secondary structure, MRI images showed thatwater migration and texture deterioration in fresh noodles were retarded. These resultsindicated that vacuum mixing could significantly improve noodle quality, enhance watercombination and increased storage stability of fresh noodlesIn addition, based on the safe range of water content resulted previously, high-temperature-short-time (HTST,105~135℃,30~200s) and medium-temperature-long-time(MTLT,45~75℃,5~20min) dehydration was used for moderate dehydration of freshnoodles. Their effects on the cooking, textural qualities of fresh noodles, as well as thecomponents structure and storage stability were compared. DSC and polarization crossanalysis presented a few part of starch gelatinization (about30%) with HTST dehydration;SEM images showed that the surface of fresh noodles was more compact after HTSTdehydration, with uniform pores detected in the cross section and enhanced protein-starchinteraction; meanwhile, HTST dehydration induced protein polymerization in fresh noodlesby-S-S-, and lead to significantly reduced cooking loss as compared with MTLT dehydration.Textural parameters showed no significant difference for all dehydration temperature. HTSTdehydrated fresh noodles showed higher storage stability, however, due to the high initialbacteria content,120℃and135℃dehydration could only decrease the TPC of freshnoodles to less than103CFU/g and shelf-life of fresh noodles was extended to5days withoutother treatment.Finally, in ordor to further reduce the initial bacteria content in the raw materials andfresh noodles, effect of ozone treatment on the quality characteristics of wheat flour andshelf-life of fresh noodles was evaluated. It was showed that ozone treatment can significantlyreduced TPC in wheat flour and extended the shelf-life of fresh noodles. Meanwhile, wheatflour and noodle sheet whiteness, dough stability, and viscosity properties of wheat starchwere all improved by ozone treatment. Remarkable protein aggregates (mainly by–S-S-interaction) were observed in ozone treated wheat flour in SDS-PAGE patterns,indicating the potential of ozone as a natural alternative for chemical oxidants in wheat flour.In addition, TPC in ozone treated wheat flour was found to be significantly reduced in the firstfew days’ storage. And no obvious changes were detected in the major volatile compounds asshown by the results of GC-MS, with increased types of total compounds and changedrelative content.更多还原