薏米醪糟发酵过程中代谢产物的分析

为弄清薏米醪糟发酵过程中代谢物形成机制及各环节的影响因素,研究薏米醪糟发酵过程中代谢产物的变化。结果表明:薏米醪糟发酵过程中,共检测到49种小分子代谢物,它们的含量存在显著差异(P0.05)。在发酵初始检测到的17种游离氨基酸含量差别不大,仅苏氨酸含量稍高。发酵24 h后游离氨基酸含量明显增加,葡萄糖和半乳糖含量显著增加。除油酸和亚油酸以外,其它非游离脂肪酸变化不明显。游离脂肪酸中油酸、亚油酸、11-十八碳烯酸等不饱和脂肪酸含量明显下降,饱和脂肪酸呈增加、减少、增加的趋势。薏米醪糟发酵过程中微生物的代谢作用是基础代谢变化的主因。     

乳酸菌发酵香肠pH值、水分活度(Aw)及游离氨基酸含量变化研究

本文探索了乳酸菌发酵香肠的ｐＨ值、水分活度（Ａｗ）、乳酸菌数量及游离氨基酸含量的变化,研究结果表明,发酵过程明显影响ｐＨ值变化,试验组与对照组存在显著差异;在发酵和烘烤过程中,两组之间Ａｗ变化无明显差异;肠馅中的乳酸菌在发酵期间均会迅速生长繁殖;游离氨基酸含量试验组比对照组增加２２．８４％,表明发酵有利于蛋白质水解产生氨基酸。     

乳酸菌发酵香肠在加工过程中的变化

探索乳酸菌发酵香肠的pH值、水分活度、乳酸菌数量及游离氨基酸含量的变化。研究结果表明：发酵过程明显影响pH值变化,试验组与对照组存在显著差异;在发酵期间和烘烤过程中,两组之间Aw变化无明显差异;肠馅中的乳酸菌,在发酵期间均会迅速生长繁殖;游离氨基酸含量试验组比对照组增加22．84％,表明发酵有利于蛋白质水解产生氨基酸。     

低盐发酵鳀鱼鱼露过程中品质动态变化分析

实验以低盐发酵鳀鱼鱼露为研究对象,分析其发酵过程中微生物群落结构及理化指标的变化情况。研究结果表明:鱼露发酵过程中微生物菌群主要分布在厚壁菌门、变形菌门、拟杆菌门、酸杆菌门、放线菌门等;微生物菌群结构变化直接影响pH值、AAN值和TVB-N值的变化;挥发性风味物质含量随着发酵时间的延长呈现上升趋势,游离氨基酸总量和必需氨基酸总量与鱼露中微生物菌群结构变化有关,前期含量上升,后期趋于稳定。该研究明确了低盐发酵鳀鱼鱼露过程中微生物菌群与理化指标的联系,分析了其挥发性风味物质与游离氨基酸的变化情况,为低盐鱼露发酵工艺改良及相关研究提供了理论依据及方法借鉴。     

干酪乳杆菌发酵芡实上清液的活性成分及抗氧化活性分析

以芡实为原料,研究干酪乳杆菌发酵过程中上清液中活性成分及抗氧化活性的变化。通过干酪乳杆菌发酵芡实,对其发酵过程中上清液的pH、可滴定酸、多肽产率、多肽分子量分布、游离氨基酸组成、总酚、总黄酮及抗氧化活性的变化进行了研究,并分析各组分与抗氧化活性的相关性。结果表明,在发酵过程中pH呈降低趋势,而可滴定酸含量逐渐升高,在发酵48 h后分别达到3.97±0.02和2.53±0.04 mL/g;多肽产率呈上升趋势,在发酵结束时达到19.09%±0.42%,其中500～180和<180 Da的低分子量多肽比例显著增加（P<0.05）;游离氨基酸总量在发酵过程中增加了5.62倍;总酚和总黄酮的含量持续显著增加（P<0.05）,在发酵结束时分别达到18.00±0.20和10.99±0.14 μg/g;发酵芡实上清液的DPPH自由基清除能力、羟基自由基清除能力和亚铁离子螯合能力在发酵结束时均显著提高（P<0.05）,可滴定酸、多肽产率、总游离氨基酸含量、总黄酮和总酚含量与抗氧化活性具有极显著（P<0.01）正相关关系。综上,干酪乳杆菌发酵可以促进芡实抗氧化活性物质的释放,提高其发酵上清液的抗氧化活性,可以为芡实产品的开发提供参考。     

乳酸菌对豆粕发酵中特定菌群与多肽水平的影响

微生物发酵是改善豆粕营养成分的有效手段,但发酵进程中微生物水平的变化和相关影响尚缺乏足够研究。通过添加外源乳酸菌(屎肠球菌),研究豆粕72h发酵进程内,菌群和蛋白水平的变化情况。结果显示,无论是否添加外源乳酸菌,豆粕中的总菌水平均呈三段式下降。相反,豆粕中的乳酸菌水平成增长趋势,且外源添加对这一趋势具有明显的提速(时间缩短1倍)和增效(1.3倍)作用。在蛋白水平的变化上,上述两组豆粕在粗蛋白和游离氨基酸的时间变化趋势上未有明显差别,但在多肽水平的变化趋势上差别显著。添加乳酸菌组豆粕发酵生成的多肽含量更高,且生成的速度更快(时间缩短1倍),此趋势与豆粕中乳酸菌的增长趋势相对应,表明乳酸菌的添加促进了豆粕中蛋白水解为多肽,但水解不足以产生大量游离氨基酸。     

乳酸菌发酵香肠中风味物质变化的研究

研究了乳酸菌发酵香肠中风味物质的变化,结果表明:发酵香肠中的主要风味物质乳酸、游离氨基酸和游离脂肪酸含量在发酵过程中都有明显增加。添加纯菌种发酵24 h后,乳酸、游离氨基酸和游离脂肪酸含量分别达到0.94%、4.38%(干基)和1.40%(干基),鲜味氨基酸谷氨酸和天冬氨酸分别是发酵前的15.3倍和11.3倍。在成熟期,各种风味物质仍保持平缓增势。     

纳地青霉发酵对鸡肉质构、游离氨基酸及挥发性物质变化的影响

本文运用物性分析仪(TA-XT.plus)、气相色谱质谱(GC-MS)联用仪、高速氨基酸分析仪(Agilent1100)分析了纳地青霉发酵对鸡肉食用品质的变化。将纳地霉菌接入经高压灭菌锅灭菌后的鸡肉糜中,27±1℃下前发酵3 d、4℃下后熟7 d制得发酵鸡肉产品,比较了肉样在发酵过程中、最终发酵产品与未发酵鸡肉样(对照)质构、游离氨基酸及挥发性物质的变化。结果表明:鸡肉在发酵过程中,硬度呈先增大后减小,弹性逐渐减小,黏着性则逐渐升高的趋势;后熟7 d的发酵鸡肉产品中游离氨基酸、游离的必需氨基酸和风味氨基酸含量总和显著增加(P0.05);发酵鸡肉产品的挥发性物质主要包括醇类、醛类、酮类、酯类等,与未发酵鸡肉样相比新产生了愈创木酚、γ-丁内酯等物质。因此,灭菌鸡肉经霉菌发酵后产生了适于食用的品质,这为开发新型发酵肉制品提供了一种新思路。     

四川麸醋发酵过程中有机酸及游离氨基酸含量变化分析

为了解四川麸醋发酵过程中有机酸及游离氨基酸含量的变化规律,采用高效液相色谱和氨基酸自动分析仪对发酵过程中7种有机酸及17种游离氨基酸含量进行测定。结果表明,四川麸醋发酵过程中含量最高的2种有机酸为乙酸和乳酸,随着发酵的进行,其含量显著增加;草酸、柠檬酸、酒石酸、苹果酸、琥珀酸含量较低,在发酵过程中含量略有变化。游离氨基酸含量随着发酵的进行呈增加趋势,从发酵初期668mg/100g增至1 470 mg/100g,其中天门冬氨酸、丝氨酸、谷氨酸、甘氨酸、丙氨酸、缬氨酸、组氨酸、异亮氨酸、酪氨酸、脯氨酸对四川麸醋风味形成具有较大的贡献。     

植物乳杆菌发酵豆薯的营养及挥发性成分变化

该文以鲜榨豆薯汁为植物乳杆菌FZU122 发酵基质,探究发酵时间（0、24、48、72 h）对豆薯汁基本理化指标、游离单糖、游离氨基酸、有机酸和挥发性成分的影响。结果表明：pH 值随发酵时间的延长显著下降。发酵48 h 后,豆薯汁中总还原糖浓度显著变化,葡萄糖和果糖为主要的单糖成分。总游离氨基酸的含量在发酵后出现波动,其中苦味氨基酸含量下降,甜味氨基酸含量上升。气相色谱-质谱联用技术检测发现,醇类物质为发酵豆薯汁的主要香气组分,原有的醛类物质发酵后未被检出。发酵后总有机酸含量升高,苹果酸和乳酸为豆薯中两种主要酸类物质。     

杏鲍菇菌糠制备氨基酸水溶肥

为研究以杏鲍菇菌糠为材料制备氨基酸水溶肥的方法,通过添加复合酶结合微波法提取腐熟菌糠中的游离氨基酸,经旋转蒸发得到水溶肥浓缩液。结果表明,酶反应最佳条件为:添加复合酶(m(风味酶)︰m(木瓜蛋白酶)︰m(纤维素酶)=1︰1︰1),于50℃反应4 h后进行提取,游离氨基酸含量最高;均匀试验得到蒸馏浓缩最优组合为:蒸馏时间30 min、蒸馏温度120℃。此条件下游离氨基酸含量为13.64 g/L。经检测有机质符合肥料标准,杏鲍菇菌糠可用于氨基酸水溶肥生产。     

Effect of Environmental Salinity on Sensory Characteristics of Penaeid Shrimp

White shrimp, Penaeus vannamei, acclimated to 10, 30 and 50 parts per thousand (ppt) salinities were evaluated for flavor by a trained sensory panel. The shrimp were also analyzed for tissue moisture, chloride, free amino acid concentration and free amino acid profile. Results of triangle tests showed a significant flavor difference between shrimp held at 10 and 50 ppt and 30 and 50 ppt but not between 10 and 30 ppt. On a wet weight basis, the free amino acid concentration was 81% higher in shrimp held at 50 ppt than at 10 ppt and 63% higher in shrimp held at 50 as compared to 30 ppt. However, between shrimp held at 30 as compared to 10 ppt the difference was only 11%. The difference in flavor intensity of shrimp held at different salinities appeared to be a direct reflection of the concentration of tissue free amino acids which serve as osmoregulators in shrimp tissue.     

豆豉成熟过程中基本成分及蛋白质体外消化率变化的研究

在实验室模拟工业化生产条件的基础上制作豆豉,并对其在45～48℃成熟42d 的过程中基本成分、蛋白质体外消化率、可滴定酸以及褐变指数的变化进行了研究。结果发现,在豆豉成熟的过程中灰分逐步增长,而膳食纤维于碳水化合物的量明显减少。可滴定酸在成熟前期(0～8d)急剧升高而在后期(32～42d)有缓慢回落的趋势。豆豉成熟的过程中,虽然总氮一直保持恒定,但非蛋白质氮、氨基酸态氮、氮溶解指数、水溶性氮、游离氨基酸以及蛋白质体外消化率都有明显的提升。因此,豆豉的成熟对产品营养价值的提升作用非常明显,同时本研究结果可为建立豆豉产品成熟指标判断体系提供理论依据。     

发芽糙米营养成分及淀粉糊化特性研究

以3个粳稻和2个糯稻为原料,制备发芽糙米,分析了糙米发芽前后游离氨基酸、蛋白质、水溶性糖类、脂肪酸值以及Mixolab淀粉糊化特性的变化。结果表明,与糙米相比,发芽糙米游离氨基酸总量、水溶性总糖、还原糖及果胶酸含量显著增加。Mixolab混合仪测定的发芽糙米米粉团蛋白质结构严重弱化,淀粉糊化能力显著降低。油酸含量和脂肪酸值均增加。发芽糯糙米水溶性总糖、还原糖及果胶酸含量显著高于发芽粳糙米,破损淀粉含量显著低于发芽粳糙米。     

Amino acid profiles of lactic acid bacteria, isolated from kefir grains and kefir starter made from them

The characteristics of cell growth, lactic acid production, amino acid release and consumption by single-strain cultures of lactic acid bacteria (isolated from kefir grains), and by a multiple-strain kefir starter prepared from them, were studied. The change in the levels of free amino acids was followed throughout the kefir process: single-strain kefir bacteria and the kefir starter (Lactococcus lactis C15-1%+Lactobacillus helveticus MP12-3%+(Streptococcus thermophilus T15+Lactobacillus bulgaricus HP1 = 1:1)-3%) were cultivated in pasteurized (92 degrees C for 20 min) cow's milk (3% fat content) at 28 degrees C for 5 h (the kefir starter reached pH 4.7) and subsequently grown at 20 degrees C for 16 h; storage was at 4 degrees C for 168 h. The strain L. helveticus MP12 was unrivaled with respect to free amino acid production (53.38 mg (100 g)(-1)) and cell growth (17.8 x 10(8) CFU ml(-1)); however, it manifested the lowest acidification activity. L. bulgaricus HP1 released approximately 3.7 times less amino acids, nearly 5 times lower cell growth, and produced about 1.2 times more lactic acid. S. thermophilus T15 demonstrated dramatically complex amino acid necessities for growth and metabolism. With L. lactis C15, the highest levels of growth and lactic acid synthesis were recorded (18.3 x 10(8) CFU ml(-1) and 7.8 g l(-1) lactic acid at the 21st hour), and as for free amino acid production, it approximated L. bulgaricus HP1 (17.03 mg (100 g)(-1) maximum concentration). In the L. lactis C15 culture, the amino acids were used more actively throughout the first exponential growth phase (by the 10th hour) than during the second growth phase. The unique properties of the L. helveticus MP12 strain to produce amino acids were employed to create a symbiotic bioconsortium kefir culture, which, under conditions of kefir formation, enhanced lactic acid production and shortened the time required to reach pH 4.7; intensified cell growth activity, resulting in a respective 90- and 60-fold increase in the concentration of lactobacilli and cocci in the mixed culture compared to individual cultures; and accumulated free amino acids in the final kefir with higher total concentrations (56.88 mg (100 g)(-1)) and an individual concentration of essential amino acids (1.5 times) greater than that of yogurt.     

Impact of autolytic, proteolytic, and nisin-producing adjunct cultures on biochemical and textural properties of cheddar cheese

The effect of incorporating a highly autolytic strain (Lactobacillus delbrueckii subsp. bulgaricus UL12) a proteolytic strain (Lactobacillus casei subsp. casei L2A), or a nisin Z-producing strain (Lactococcus lactis, subsp. lactis biovar diacetylactis UL719) into Cheddar cheese starter culture (Lactococcus lactis KB and Lactococcus cremoris KB) on physicochemical and rheological properties of the resultant cheeses was examined. Cheeses were ripened at 7 degrees C and analyzed over a 6-mo period for viable lactococcal and lactobacilli counts, pH, titratable acidity (TA), lipolysis, proteolysis, and textural characteristics. The combination of the nisin-producing strain and autolytic adjuncts significantly increased the production of water-soluble nitrogen, free amino acids, and free fatty acids. The effect of Lc. diacetylactis UL719 alone or of Lb. casei L2A on water-soluble nitrogen and free amino acid contents were also significant, whereas their effect on free fatty acids was not. Viable counts of Lb. bulgaricus UL12 were significantly reduced in the presence of Lc. diacetylactis UL719. Lactobacilli-containing cheeses showed significantly lower values for hardness, fracturability, and springiness. It could be concluded that the addition of Lb. bulgaricus UL12 together with a nisin-producing strain produces a greater increase in cheese proteolysis and an improvement in Cheddar cheese texture.     

Free amino acids and other non-volatile compounds formed during processing of Iberian ham

Fifty-five legs from Iberian pigs were traditionally processed into dry cured hams. Free amino acids and other non-volatile compounds in the water-soluble fraction from the biceps femoris muscle were analyzed by HPLC. At the drying stage and in the last months in the cellar the largest increases in these water-soluble compounds took place. There was a clear influence on free amino acid formation of salt content and on the formation of peptides of the temperature at each processing stage. As the amount of non-volatile compounds in the water-soluble fraction increases with processing time, their determination could provide a maturation index for Iberian ham.     

不同加工方式镇江香醋不同季节理化指标

试验比较不同季节生产的传统手工和现代工艺镇江香醋主要理化指标的差异,以更好指导实际生产。以不同季节生产的传统手工和现代工业镇江香醋为对象,对还原糖、总酸、氨基酸态氮、有机酸、游离氨基酸等含量的差异进行研究,得到冬季生产的镇江香醋中还原糖、氨基酸态氮和游离氨基酸含量均为最高,而夏季生产的食醋还原糖、总酸、氨基酸态氮、有机酸和游离氨基酸含量均为最低,说明冬季生产的镇江香醋口感更柔和;4个季节生产的手工醋中还原糖含量均比工业醋低,而手工醋中总酸、氨基酸态氮、有机酸和游离氨基酸含量均比工业醋高,说明手工醋的口感更柔和、醇厚。     

即食鲜海参生产工艺研究

应用阶段式杀菌技术,在对鲜海参漂烫、调味、包装、杀菌强度等工序研究的基础上,建立了一种生产即食鲜海参的新工艺。本实验通过调味过程中多糖、水溶性蛋白质和游离氨基酸溶出量的变化,确定了低温减压浸味法。研究煮制前后海参质构情况,鲜海参与本产品在口感和营养方面无明显差异。     

Amino acid turnover by elongating cattle blastocysts recovered on days 14-16 after insemination

Blastocyst elongation from day 14 to day 16 after insemination coincides with a major phase of embryo loss in cattle. Protein synthesis, reflected in protein content, increases markedly over this period but little is known about the amino acid requirement of elongating blastocysts at this time. Cattle blastocysts produced in vivo were recovered on days 14-16 after insemination and cultured individually for up to 8 h in synthetic oviduct fluid containing a physiological mixture of amino acids plus 1 mmol glutamine l(-1) and 0.1% (w/v) polyvinyl alcohol (SOFaaPVA). After 1, 4 and 8 h in culture, an aliquot of culture medium was removed and the rate of amino acid depletion or production was calculated per unit of protein and per hour of culture. Amino acids were depleted or produced at different rates. Arginine was depleted from the medium at a significant rate (P < 0.05) during all culture periods. Alanine and glutamate were produced at a significant rate (P < 0.05) during all culture periods. The rate of alanine production was significantly greater (P < 0.05) in blastocysts recovered on day 14 compared with days 15 or 16 after insemination. Alanine production and arginine depletion tended to be greater in smaller embryos recovered on day 14 compared with larger and later stage embryos, indicating that earlier stage embryos may have higher metabolic activity than later stage embryos. Qualitatively, the pattern of amino acid consumption and production during elongation was similar to that shown from the zygote to early blastocyst stage.