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31.
为了改善奶酪品质,奶酪生产过程中通常会添加脂肪酶或者产脂肪酶乳酸菌来提升产品品质。该研究以前期筛选的4株高产脂肪酶乳酸菌为发酵剂,分别随机选取3株乳酸菌复配制作酸凝奶酪。试验组:A组T1-5和T1-3属融合魏斯氏菌(Weissella confusa)、H1-6属瑞士乳杆菌(Lactobacillus helveticus),B组H1-6、T1-5、B2-5属植物乳杆菌(Lactobacillus plantarum),C组H1-6、T1-3、B2-5,D组T1-3、T1-5、B2-5,对照组(E组)(添加商业发酵剂),分析发酵剂对传统奶酪pH值、滴定酸度和脂肪氧化情况的影响,并利用气相色谱法(Gas Chromatography,GC)检测奶酪中脂肪酸变化、利用气相色谱-离子迁移谱(Gas Chromatography-Ion Mobility Chromatography,GC-IMS)分析奶酪中风味物质的变化。结果表明:A,B,C,D组4组奶酪的pH值、过氧化值(Peroxide value,POV值)明显低于E组(对照组)(P < 0.05),A,B组奶酪滴定酸度比对照E组高(P < 0.05);A,B,C,D组奶酪中饱和脂肪酸(Saturated Fatty Acids,SFA)含量、单不饱和脂肪酸(Monounsaturated Fatty Acids,MUFA)含量和多不饱和脂肪酸(Polyunsaturated Fatty Acids,PUFA)含量均显著高于E组(P < 0.05);4个试验组样品中亚油酸(C18∶2n6c)含量明显高于对照组(E组)(P < 0.05)。GC-IMS及主成分分析结果显示,A、B组奶酪挥发性风味物质种类多,且相似度较高,其中2-庚酮、丁醛、乙酸丁酯是主要呈味物质;C、E两组奶酪中风味物质比较相似,风味物质主要以乙酸乙酯、乙酸丙酯、己酸乙酯等酯类为主;D组与其他4组有所差异,主要挥发性风味物质为乙酸丁酯、3-辛酮、庚醛等。结合感官评定,A、B两组奶酪整体风味和口感较好,评分较高。筛选得到的产脂肪酶乳酸菌可以作为发酵剂用于提升新疆传统奶酪品质。 相似文献
32.
Pyrophosphate (140 mM, pH 7.1) extracts of two arable soils and one pasture soil were ultrafiltrated separating the extracted material into three fractions: AI with nominal molecular weight (nmw) > 100 kD, AII with nmw between 10 kD and 100 kD and R with nmw < 10 kD. Protease activity was determined in the fractions by using three different substrates: N-benzoyl-l-argininamide (BAA), specific for trypsin; N-benzyloxy-carbonyl-l-phenylalanyl l-leucine (ZPL), specific for carboxypeptidases; and casein, essentially a non-specific substrate. The derivative fractions were also analysed for their amino acid N and humic (HA) and fulvic (FA) acid contents. The organic matter of extracts and derivative fractions obtained from the pasture soil was analysed by isoelectric focusing (IEF) and that of fractions analysed by pyrolysis gas chromatography (Py-GC). Activities of the extract were monitored for their thermal stability and those of the extract and derivative fractions for their optimal pH.Due to the mechanical disintegrating action of sodium pyrophosphate over the humic substances during the fractionation process the amount of total organic C and FA in the fractions was ranked as R > AII > AI. The lowest amino acid N/organic C was found in the R fraction, whereas AII fraction was rich in humic acids, carbohydrates and amino acid N and AI fraction showed the lowest carbohydrate content. At least 70% of the total BAA- and ZPL-hydrolysing activity was associated to particles with nmw higher than 10 kD and at least 30% of these activities were present in particles with nmw higher 100 kD. Casein-hydrolysing activity was quite evenly distributed among the three fractions (AI, AII and R). The extracted protease-organic complexes were resistant to thermal denaturation and some of them showed optimal activity at pH values higher than 10 as a result of the polyanionic characteristics of the humic material surrounding enzyme molecules and of the presence of alkaline protease. Comparison of data obtained in Py-GC analyses and in protease activity suggests that BAA-hydrolysing activity was associated to a highly condensed humic matter and ZPL-hydrolysing activity to less resistant humic substances, while at least some of the extracted casein-hydrolysing activity was present as glyco-proteins not associated to humus. BAA-hydrolysing activity was probably inhibited by fresh organic matter of carbohydrate origin whereas lignin derived organic matter probably inhibited ZPL- and casein-hydrolysing activity. 相似文献
33.
为了解苦参碱在黄瓜和土壤中的残留状况及消解动态,建立了苦参碱在黄瓜和土壤中的气相色谱分析方法,并在天津和安徽两地开展了为期两年的苦参碱在黄瓜和土壤中残留状况和消解动态规律田间试验研究。结果表明,采用无水乙醇超声提取黄瓜和土壤中的苦参碱,使用大孔吸附树脂净化,甲醇定容,气相色谱带氮磷检测器(NPD)进行测定,外标法定量,在0.25-1.0 mg·kg-1添加水平范围内,苦参碱在黄瓜和土壤中的平均回收率为78.32%-98.06%,变异系数为3.72%-7.44%;黄瓜和土壤中苦参碱的最小检出量均为1.36×10-12 g,最低检出浓度为0.004 mg·kg-1(黄瓜)、0.008 mg·kg-1(土壤)。田间试验结果表明,苦参碱在黄瓜和土壤中的残留消解动态符合方程Ct=C0e-kt;苦参碱在黄瓜和土壤中的降解半衰期分别为5.19-7.24 d和6.70-9.18 d。在黄瓜中施用0.3%苦参碱乳油,其制剂施药量为0.18-0.27 g·m-2,施药3-4次,两次施药间隔期为7 d,距收获期为1 d时,苦参碱在黄瓜中的残留量为0.125 6-1.207 1 mg·kg-1,土壤中的残留量为0.045 0-0.183 7 mg·kg-1。目前,国内外尚无苦参碱在黄瓜中最大残留限量标准,该试验研究成果为0.3%苦参碱乳油在黄瓜上的登记、安全使用规则 相似文献
34.
建立了超声破碎酿酒酵母细胞和冷三氯乙酸化学浸提海藻糖的工艺,探索了离子色谱分析技术条件,采用响应曲面法(RSM),研究了液料比R、超声功率W、工作时间T1、超声总时间T2和浸提时间T3等5个试验关键因子对海藻糖提取的影响规律,并构建了动态控制的数学模型,得到了海藻糖提取最优工艺参数依次为:尺为7、W为698W、T1为4.9s、T2为7.3min、T3为9min。结果表明:模型极显著,具有可行性和有效性,超声功率、工作时间和超声总时间对海藻糖提取量的影响最大,为生产中的应用提供了科学依据。 相似文献
35.
36.
富含多糖的转基因石斛基因组DNA提取方法(英文) 总被引:3,自引:0,他引:3
在石斛兰转基因研究中,需通过PCR和Southern杂交等手段检测外源基因是否转入并整合到转化植株基因组.由于转化石斛植株生长缓慢,且含有多糖,因此从转化植株中提取高质量的基因组DNA以尽快对转基因苗进行分子检测存在较大困难.本研究旨在通过改良现有的DNA提取法(CTAB法或SDS法1,克服转化石斛植株基因组DNA提取中碰到的产量低,纯度不高而导致难以进行PCR或酶切等问题.在本研究所用的3种改良法中,方法Ⅱ能从少量的转化石斛苗中提取出高产量和高纯度的基因组DNA.研究结果表明方法Ⅱ提取的基因组DNA完全适用于转基因石斛的外源基因PCR扩增,限制性酶切和Southern杂交分析. 相似文献
37.
Seven wild and ten cultivated blackberries (Arapaho, Bartin, Black Satin, Bursa 1, Bursa 2, Cherokee, Chester, Jumbo, Navaho, and Ness), and six lowbush (Vaccinium arctostaphylos) and four highbush (Vaccinium corymbosum) blueberries fruits (Ivanhoe, Jersey, Northland, and Rekord) were analyzed for total anthocyanins, total phenolics, and antioxidant activity as ferric reducing antioxidant power (FRAP) in this study. The respective ranges of total anthocyanin and total phenolic contents of the tested samples were: blackberries, 0.95–1.97 and 1.73–3.79 mg g−1 and blueberries, 0.18–2.94 and 0.77–5.42 mg g−1. FRAP values varied from 35.05 to 70.41 μmol g−1 for blackberries, 7.41 to 57.92 μmol g−1 for blueberries. Wild blackberries had the highest FRAP values while wild blueberries had the highest total phenolic and total anthocyanin contents. A linear relationship was observed between FRAP values and total phenolics for blueberries (r = 0.981). The anthocyanin pigments in samples were isolated and characterized by high-performance liquid chromatography (HPLC) with UV–visible detection. Cyn-3-glu was the predominant anthocyanin in all blackberry fruits. 相似文献
38.
39.
用气相色谱仪和傅立叶红外光谱仪对燃用DME的ZS195柴油机的排气中的甲醛(HCHO)、甲酸甲酯(CHCOOCH3)、甲酸(HCOOH)非常规排放物进行了检测和分析。结果表明,DME发动机的尾气排放中,均检测到HCHO,HCOOCH3,HCOOH排放物,且甲醛是非常规排放物中的主要成分,甲醛、甲酸甲酯的排放量随转速上升而略有上升,随负荷增加而不同程度的减少,而甲酸排放量变化则不甚明显。 相似文献
40.
JIN Li-qin LU Jian-xin YU Kang YUAN Qian XIE Ke-jian WANG Kai-fa ZHANG Yu-lan 《园艺学报》2000,16(8):726-729
AIM: To study the activation effects of maize pollen polysaccharides(PPM) on human thoracic cavity macrophage (hTMΦ). METHODS: Activities of lactate dehydrogenase(LDH) and acid phosphatase (ACP) in the hTMΦ were detected by automatic biochemical analyzer, and the level of tumor necrosis factor alpha(TNF-α) and interleukin-6(IL-6) in the hTMΦ was analyzed by radioimmunoassay, after hTMΦ were cultured with 0.312, 0.625, 1.250, 2.500, 5.000 mg/mL PPM-RPMI 1640 for 24 and 48 hours in vitro. RESULTS: The activities of LDH and ACP increased in the hTMΦ induced by PPM, and the levels of TNF-α and IL-6 in the hTMΦ induced by PPM increased markedly too. And the induced expression effect of TNF-α and IL-6 is associated with the concentration of PPM, and time for PPM inducing. CONCLUSION: PPM can induce cytokines secretion in hTMΦ, and activate hTMΦ in vitro. 相似文献