无溶剂系统酶促POMF连续化酯交换反应生产类可可脂研究

通过填充床酶反应器中POMF与SME酯交换生产类可可脂(CBE)连续化反应实验,研究空速对产率(R)和连续化特异性酯交换能力(CSIV)影响。当SI为0.54时,R值为121％,比产量(PE)为3.99 g·g～1·h-1。经过差示扫描量热法(DSC)分析,产品热性能符合类可可脂质量要求。     

脱脂麦胚花生酱的研制

研究了脱脂麦胚花生酱的工艺,确定了最佳配方和操作要点。结果表明,脱脂麦胚与花生的配比以１∶３为最好,稳定剂以１．５％的单甘酯为佳,添加适量的调味料和抗氧化剂等,可得到风味、色泽、质地、口感均极佳的产品,其氨基酸含量及平衡得到很大改善     

超临界CO2萃取粉末磷脂的研究

本文以非转基因大豆浓缩磷脂为原料,利用溶剂及吸附剂去除杂质及多环芳烃得到精制大豆浓缩磷脂,经超临界CO2萃取得到大豆粉末磷脂,并通过实际生产到得到超临界CO2萃取大豆粉末磷脂。精制大豆浓缩磷脂的条件为,正己烷添加量为1.5 mL/g,凹凸棒添加量为5%,时间3 h,温度50 ℃,搅拌速度1 500 r/min,精制大豆浓缩磷脂含杂质量为0.05%,多环芳烃量为2.29 μg/kg。经超临界CO2萃取条件为,萃取压力35 MPa,萃取温度50 ℃,萃取时间130 min,得到的粉末磷脂含杂质量为0.03%,多环芳烃量为1.83 μg/kg。通过实际生产,精制大豆浓缩磷脂含杂质量为0.08%,多环芳烃量为2.97 μg/kg。超临界CO2萃取粉末磷脂含杂质量为0.06%,多环芳烃量为2.45 μg/kg,HLB值可以达到8。     

当雄牦牛肉的营养和风味特性

以市售西门塔尔牛肉（下文简称“市售牛肉”）作为对照组,研究当雄牦牛肉的营养和风味特性。采用高效液相色谱、气相色谱-质谱联用、凯氏定氮等方法分别分析当雄牦牛肉和市售牛肉中蛋白质、氨基酸、脂肪酸、挥发性风味物质、矿物质和维生素差异。结果表明：当雄牦牛肉中蛋白质含量（22.89 g/100 g）显著高于市售牛肉（P＜0.05）,剪切力及蒸煮损失率显著低于市售牛肉（P＜0.05）;当雄牦牛肉中VB1、VE含量显著高于市售牛肉（P＜0.05）,2 种牛肉中的VB2、VA含量无显著差异;当雄牦牛肉中总氨基酸、必需氨基酸、总脂肪酸及不饱和脂肪酸含量均显著高于市售牛肉（P＜0.05）;微量元素分析结果发现,当雄牦牛肉中锰、硒、镁、铁、钙元素的含量均显著高于市售牛肉（P＜0.05）;当雄牦牛肉及市售牛肉中分别检测出58、43 种挥发性风味物质,牦牛肉中醇类和酯类的种类及含量均高于市售牛肉,而市售牛肉中酚类、醛类、酮类及含氮化合物的含量均较高。因此,当雄牦牛肉具有较好的食用营养品质。     

Sterol glycosides and cerebrosides accumulate in Pichia pastoris, Rhynchosporium secalis and other fungi under normal conditions or under heat shock and ethanol stress

The occurrence of glycolipids such as sterol glycosides, acylated sterol glycosides, cerebrosides and glycosyldiacylglycerols was examined in the three yeast species Candida albicans, Pichia pastoris and Pichia anomala, as well as in the six fungal species Sordaria macrospora, Pyrenophora teres, Ustilago maydis, Acremonium chrysogenum, Penicillium olsonii and Rhynchosporium secalis. Cerebroside was found in all organisms tested, whereas acylated sterol glycosides and glycosyldiacylglycerols were not found in any organism. Sterol glycosides were detected in P. pastoris strain GS115, U. maydis, S. macrospora and R. secalis. This glycolipid occurred in both yeast and filamentous forms of U. maydis but in neither form of C. albicans. This suggests that sterol glycoside is not correlated with the separately grown dimorphic forms of these organisms. Cerebrosides and sterol glycosides from P. pastoris and R. secalis were purified and characterized by mass spectrometry and nuclear magnetic resonance spectroscopy. The cerebrosides are beta-glucosyl ceramides consisting of a saturated alpha-hydroxy or non-hydroxy fatty acid and a Delta4,8-diunsaturated, C9-methyl-branched sphingobase. Sterol glycoside from P. pastoris was identified as ergosterol-beta-D-glucopyranoside, whereas the sterol glucosides from R. secalis contain two derivatives of ergosterol. The biosynthesis of sterol glucoside in P. pastoris CBS7435 and GS115 depended on the culture conditions. The amount of sterol glucoside in cells grown in complete medium was much lower than in cells from minimal medium and a strong increase in the content of sterol glucoside was observed when cells were subjected to stress conditions such as heat shock or increased ethanol concentrations. From these data we suggest that, in addition to Saccharomyces cerevisiae, new yeast and fungal model organisms should be used to study the physiological functions of glycolipids in eukaryotic cells. This suggestion is based on the ubiquitous and frequent occurrence of cerebrosides and sterol glycosides, both of which are rarely detected in S. cerevisiae. We suggest P. pastoris and two plant pathogenic fungi to be selected for this approach.     

白牦牛乳软质干酪的加工及其质构特性的研究

以甘肃天祝牧区白牦牛乳为原料制作软质干酪。优化了加工白牦牛乳软质干酪的工艺参数,并测定其保藏期前后的理化指标和质构。结果表明,牦牛乳软质干酪在发酵剂添加量2g/100mL,凝乳温度35℃,凝乳pH5.9,CaCl2添加量0.01g/100mL时,品质最佳,出品率为22.5g/100g;保藏30d后的软质干酪与新鲜干酪相比,其非脂物质水分含量(P0.01)、干物质脂肪含量(P0.01)、胶着性(P0.05)、硬度(P0.01)和咀嚼性(P0.01)均有显著变化。     

宰后成熟过程对牦牛肉中挥发性风味化合物的影响

宰后冷却成熟会影响肉类风味,本实验研究冷却成熟对牦牛肉挥发性风味化合物的影响。取甘肃肃南裕固族自治县天然放牧牦牛的背最长肌,用气相色谱-质谱(GC-MS)法检测其成熟前后的挥发性化合物,分析冷却成熟对其种类和相对含量的影响。成熟后的牦牛肉中,含硫化合物(肉香味)比成熟前增加了24%,特别是2-乙酰基噻唑(肉香)、甲硫基丙醛(肉汤味)分别增加了100%和78%;羰基化合物增加了311%,其中3-羟基-2-丁酮(奶香回味)增加了331%,其成熟后的相对含量高达20.54%,是牦牛肉成熟后相对含量最高、增加程度最大的挥发性物质;来自牧草中特殊成分的酚类、萜类及倍半萜类(饲源性化合物)比成熟前减少了34%,其中4-甲基酚(膻味)减少了70%,β-石竹烯减少了40%。以上结果表明,宰后成熟工艺有利于牦牛肉风味的改善,并减少牧草中特殊成分对牦牛肉风味的不良影响。     

基于SDE/GC-MS制备的藏酥油香精及其应用

为开发藏酥油风味香精,采用同时蒸馏萃取方法制备样品,利用GC-MS技术对天然藏酥油中的风味物质进行了分离、鉴定,经NIST谱图库比对,共确定了32个相似度在90以上的化合物,采用面积归一化法确定了各组分的相对含量,其中羧酸类12个,占71.81%;酮类6个,占9.33%;酯类5个,占1.49%;醇类3个,占4.44%;烯类2个,占1.46%;内酯类、醛类、醚类和酚类化合物各1个,分别占0.71%、0.24%、3.53%和13.75%。以GC-MS鉴定结果为依据,结合调香技术制备藏酥油香精,并将其应用于植物性藏酥油的开发。将植物性藏酥油与天然藏酥油在酥油茶中的应用进行感官评定,结果显示:植物性藏酥油在奶香、茶感和协调性方面优于天然藏酥油;滑口度和脂肪感稍逊于天然藏酥油。本文为开发藏酥油风味系列产品提供数据依据。     

精制各阶段牛油风味研究

采用顶空一固相微萃取法提取精制各阶段牛油挥发性成分,用气相色谱—质谱进行分离鉴定。结果显示,毛牛油、脱酸牛油、脱色牛油、精制牛油分别含有54、56、63、26种挥发性成分,主要为烃、醇、醛,及以BHT为代表酚类物质,其次有酮、酸、醚、及少量杂环化合物检出。挥发性组分种类和含量存在较大差异,反映精制过程两方面作用:一方面,使一些产生不良、刺激性及体现脂肪氧化气味物质种类及含量明显减少;另一方面,对油脂原有优良风味物质也具有消减作用。     

磷脂酶A1水解蛋黄卵磷脂的研究

采用磷脂酶A1水解蛋黄卵磷脂,通过单因素实验和正交实验确定该酶水解蛋黄卵磷脂经济合理的工艺条件为：反应温度50℃,反应时间5h,加酶量0．40 IU／g,起始pH6．0,底物质量浓度80g／L;利用电喷雾飞行时间质谱仪分析水解前后蛋黄卵磷脂组分,磷脂酶A1水解Sn-1位脂肪酸,生成含Sn-2位不饱和脂肪酸的溶血磷脂,反应过程中有酰基位移发生。