脂肪氧合酶在茶叶中的作用

综合叙述了脂肪氧合酶及其在茶叶加工过程中的作用,并据此展望了酶在茶叶加工工艺中的发展前景。     

Impact of genotype and micronutrient applications on nitrate reductase activity of tea leaves

Tea flush shoots comprising three leaves and a bud were collected from various clones (cultivars) from different experimental fields and analysed for nitrate reductase (NR) activity. Most of the cultivars of Assam type had higher NR activity, followed by Cambod and China types. NR activity was maximum in the clone UPASI‐9. It was found that NR activity could be used as a biochemical tool to predict the yield potential of cultivars at the initial stage of selection for a breeding programme. The activity was higher in the youngest part of the tea plant. With the existing methodology it was not possible to measure the NR activity in stem portions of the tea plant. There was a strong positive correlation between NR activity and amino acid contents of tea shoots. Inclusion of molybdenum in the foliar applied micronutrient mixture was found helpful in triggering the NR activity in a few clones and seedlings. Copyright © 2004 Society of Chemical Industry     

荔枝草保健茶的制作工艺研究

以抽茎前期、花前期、结果后期采收的荔枝草为原料,研发出一种新型保健饮料--荔枝草保健茶;对其生产过程中的原料筛选、杀青和干燥工艺参数分别进行了研究。结果表明,以抽茎前期采收的荔枝草为原料,经除杂、整形、微波杀青（480W,150s）、揉捻（15min）、干燥（102℃,140min）、冷却、包装等工序,能生产出色泽、香气、滋味和汤色俱佳的荔枝草保健茶。      

荔枝草保健茶的制作工艺研究

以抽茎前期、花前期、结果后期采收的荔枝草为原料,研发出一种新型保健饮料--荔枝草保健茶;对其生产过程中的原料筛选、杀青和干燥工艺参数分别进行了研究.结果表明,以抽茎前期采收的荔枝草为原料,经除杂、整形、微波杀青(480W,150s)、揉捻(15min)、干燥(102℃,140min)、冷却、包装等工序,能生产出色泽、香气、滋味和汤色俱佳的荔枝草保健茶.     

低档绿茶多糖的酶法辅助提取及抗氧化活性研究

以皖西低档绿茶为原料,通过酶法辅助浸提茶多糖,然后对浸提液进行醇沉、真空干燥得粗多糖,比较三种不同方法对粗多糖脱蛋白效果,并研究茶多糖的体外抗氧化活性。结果表明:酶法辅助浸提的最优条件:料液比1∶30(g/m L)、酶解温度45℃、酶解时间120min、纤维素酶添加量12mg/g,果胶酶添加量12mg/g、浸提1次,茶多糖得率达到5.414%。三氯乙酸法、sevage法、木瓜蛋白酶法对粗多糖中蛋白的最大脱除率分别为84.14%、69.45%、74.34%,多糖损失率分别为18.56%、24.01%、12.34%。相对而言,木瓜蛋白酶法条件温和,更适合茶多糖脱蛋白。另外,茶多糖具有较强的还原能力以及对羟基自由基的清除能力,对亚硝基具有一定的清除作用。      

油脂精炼对茶叶籽油品质变化的影响

对冷榨茶叶籽毛油、脱酸油、脱色油、脱臭油的脂肪酸组成、基本指标、脂肪伴随物、反式脂肪酸和苯并(a)芘的变化进行了系统研究。结果表明:茶叶籽油在精炼过程中,肉豆蔻酸和花生酸大量损失;甾醇和多酚类物质含量逐渐下降,损失率分别为43.30%和58.40%,脱臭工序的生育酚和角鲨烯损失最大;苯并(a)芘含量降低了85.87%;在脱色和脱臭过程中,茶叶籽油的反式脂肪酸大幅上升至1.20%和1.77%,但均未超过欧盟(5%)和美国(2%)的标准。研究为进一步提升茶叶籽油的品质,制定茶叶籽油品质指标和开发新的茶叶籽油产品提供了理论依据。     

黑米总黄酮提取工艺优化 及其对茶叶脂肪氧合酶的抑制

以黑米为原料,采用超声波辅助提取黄酮类化合物,用正交试验对提取工艺进行优化。考察了提取物总黄酮对毛尖茶叶脂肪氧合酶(LOX)的抑制作用。结果表明:超声波辅助提取总黄酮的优化条件为乙醇体积分数50%、料液比1∶40(g/m L)、提取温度30℃、超声时间50 min,优化条件下黑米总黄酮提取率为1.98%。黑米中黄酮类化合物对毛尖茶叶脂氧合酶有一定的抑制作用,IC50为28.14μg/mL。     

Studies on freeze-withering in black tea manufacturing

In order to reduce the withering time during black tea manufacture, freeze-withering was attempted, which resulted in flaccid leaves with increased cell membrane permeability in a shorter period of time. The freeze-withered leaves had similar amounts of quality precursors as that of the conventionally withered leaves. The resultant black tea was better in quality than those manufactured without withering and after normal withering. Manufacturing of fresh leaves resulted in comparable levels of theaflavins, but the tea was not acceptable due to its harshness. Increased cell membrane permeability during freeze-withering showed that the leaf attained a sufficient degree of physical wither. The decreases in the levels of chlorophyll showed that chemical withering had also been achieved during freeze-withering, which is supported by the increased levels of caffeine.     

Impact of high-intensity pulsed electric field variables affecting peroxidase and lipoxygenase activities of watermelon juice

The effects of pulse frequency (50-250 Hz), pulse width (1.0-7.0 μs) and polarity (monopolar or bipolar) of high-intensity pulsed electric field (HIPEF) treatments (35 kV/cm and 1000 μs total treatment time) on peroxidase (POD) and lipoxygenase (LOX) activities were evaluated using a response surface methodology. Second-order expressions were accurate enough to fit experimental results. HIPEF bipolar treatments resulted to be more effective than monopolar treatments in reducing POD and LOX activities. Watermelon juice LOX was more resistant to HIPEF than POD within the range of assayed conditions. HIPEF treatments set at 50 Hz for 1.0 μs pulse width could attain minimum residual POD activity values up to 10%, whereas the highest POD activity reduction was reached by combining high frequencies and pulse widths. Thus, POD could be totally inactivated by applying 7.0-μs bipolar pulses at frequencies higher than 114 Hz. In addition, the effect of frequency on the LOX activity was highly affected by the pulse width of the treatment. Thus, treatments conducted at 220 Hz with bipolar pulses of 1.0 μs led to the lowest residual LOX activity (50%).     

The dynamic change of oolong tea constitutes during enzymatic-catalysed process of manufacturing

To understand leaf enzyme-modulated dynamic changes of character constitutes during withering and turning-over steps of oolong tea manufacturing, complementary proteomic and metabolomic analyses were performed using the processed tea leaves from the two steps. A total of 778 metabolites and 6274 proteins were identified and quantified in this study. A biosynthetic pathway network of flavouring compounds was suggested in combination with the abundance of candidate enzymes. The free amino acids were necessary not only to the umami or sweet tastes of oolong tea, but also to the biosynthesis of secondary metabolites responsible for the environmental stress. As the downstream derivatives of the phenylpropanoid pathway with phenylalanine as one of the upstream metabolites, the glycosides of isoflavonoids and anthocyanins showed decreasing trends during the enzymatic-catalysed process, potentially contributing to flavour of mellow and brisk. The formation of flavouring compounds in oolong tea production is a result of systematic responses to serious stress conditions, during which a series of defensing mechanisms in tea leaves were triggered to induce dynamic changes in various enzymes and metabolites.     

Antioxidant activities of crude tea polyphenols, polysaccharides and proteins of selenium-enriched tea and regular green tea

The crude tea polyphenols, polysaccharides and proteins of regular green tea and Se-enriched green tea were investigated in vitro for antioxidant activities by auto-oxidation test (AAPH) and α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging method. Results showed that crude tea polyphenols of Se-enriched green tea provided the highest antioxidant activity by DPPH assay and the antioxidant activity was decreased in the order: crude tea polyphenols > crude tea proteins > tea polysaccharides. The crude protein of Se-enriched green tea was found to exhibit the highest antioxidant activity by AAPH method and the antioxidant activity was decreased in the order: crude tea proteins > tea polyphenols > tea polysaccharides. Tea polyphenols and tea polysaccharides of Se-enriched green tea presented significantly higher antioxidant activities than that of regular green tea. No significant difference of antioxidant activities was found between crude tea proteins of Se-enriched green tea and regular green tea. The combinations of Se with tea polyphenols and tea polysaccharides were responsible for the higher antioxidant activities of Se-enriched green tea than regular green tea.     

不同季节和茶类的金萱品种茶叶香气成分分析

采用GC-MS法对金萱茶树品种不同季节鲜叶加工而成的绿茶、红茶和乌龙茶的香气组分进行分析。结果表明:金萱绿茶春茶和夏茶的香气组成以醇类物质的相对含量较高,秋茶是吡咯类及其衍生物的相对含量较高。金萱绿茶春茶和夏茶的主导香气成分较多,且组成较相似,秋茶的主导香气组分较少,但都有清香、花香或甜香的特征。金萱红茶春茶、夏茶和秋茶都是醇类物质的相对含量较高,且所占比例较其他茶类高,其次是醛类或酯类。金萱红茶秋茶的FI指数最高,香气品质最好,夏茶次之,春茶最次,与感官审评结果一致。金萱乌龙茶春茶是醇类物质的相对含量较高,夏茶和秋茶是吡咯类及其衍生物的相对含量较高。三个季节的乌龙茶中都是橙花叔醇和吲哚的相对含量最高,占其主导香气成分的54%以上。      

Ultrafiltration isolation,physicochemical characterization,and antidiabetic activities analysis of polysaccharides from green tea,oolong tea,and black tea

Both fermentation degree and preparation method of polysaccharides could influence the bioactivity of tea polysaccharides. The aim of this study was to compare the physicochemical characterization and biological activities of the polysaccharides isolated by ultrafiltration method from three kinds of tea (green tea, oolong tea, and black tea). The bioactivities of tea polysaccharide fractions were compared from four aspects, including antioxidant activities, antiglycation activities, α-glucosidase inhibitory capability, and hypoglycemic effects on L6 myotubes. Results showed that six polysaccharides (GTPS1, GTPS2, OTPS1, OTPS2, BTPS1, and BTPS2) had different contents of neutral sugar and uronic acid, and they showed different morphologies. Six polysaccharides were composed of the seven monosaccharides with different molar ratios. BTPS1 exhibited the highest DPPH scavenging activity and hydroxyl radical scavenging activity (P < 0.05), and BTPS1 also showed the strongest antiglycation inhibitory effects (P < 0.05). BTPS1 and BTPS2 showed strong inhibitory capacity on α-glucosidase and hypoglycemic effects in L6 skeletal muscle cells. The result suggested that the degree of fermentation of tea could improve their bioactivities (BTPS > OTPS >GTPS), and TPS1 with smaller molecular weight distribution showed higher bioactivities than TPS2. This study can provide a scientific foundation for the application of tea polysaccharides and related functional products.     

Growth phase and growth medium effects on the peptidase activities of Lactobacillus helveticus

The effect of growth phase, growth medium and storage conditions on the peptidase activities of Lactobacillus helveticus DPC 4571 were examined. Cell free extracts (CFEs) were prepared from both mid-log and stationary phase cells grown in either 10% (w/v) reconstituted skim milk (RSM) or MRS pH 5.4 broth. In general, Lb. helveticus DPC 4571 was found to possess a broad range of aminopeptidase, dipeptidase, tripeptidase, endopeptidase and proline-specific peptidase activities. The stability of these peptidase activities in a CFE of Lb. helveticus DPC 4571 stored at 4°C was variable. The specific activities of the majority of these peptidases were significantly (P<0.05) influenced by both growth phase and growth medium. Cells grown to mid-log phase in RSM were found to have the highest level of peptidase activity.     

Antioxidant and lipoxygenase inhibitory activities of pumpkin seed extracts

Pumpkin seeds have been implicated in providing health benefits. However their antioxidant or anti-inflammatory activity of their extracts has never been studied. Therefore, four commercially available pumpkin seeds were treated with two different extraction methodologies in order to obtain fractions with different content. The extracts were screened for their antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay and for their inhibitory activity against lipid peroxidation catalyzed by soybean lipoxygenase.Most extracts tested have demonstrated radical scavenging activity, which depends on their total phenolic content, with fractions rich in phenolics showing the strongest activity. On the other hand, the phenolic content of extracts does not determine their activity against lipoxygenase, as acetone and polar lipid fractions are its strongest inhibitors. The presence of molecules being able to scavenge radicals and inhibit lipoxygenase in pumpkin seeds may in part explain the health benefits attributed to them.     

Effects of tea polyphenols on the activities of α-amylase,pepsin, trypsin and lipase

Tea polyphenols (TP) possess many beneficial properties, such as reducing the risk of cancer and heart diseases, and acting as natural antioxidants for the food industry. At the same time, tea polyphenols might inhibit digestive enzymes and reduce food digestibility. To explore this possible antinutritional property, the effects of tea polyphenols on the activity of four typical digestive enzymes were investigated. HPLC analysis of the tea polyphenols extracted from Chinese green tea indicated that their catechin content was 93.6% (w/w), and that the content of ester bond-containing polyphenols was more than 82%. Measurement of the interaction of gelatin with tea polyphenols was first carried out, in order to model enzyme protein–TP interaction. It proved that tea polyphenols were capable of binding and precipitating protein, suggesting a potential ability of TP to denature digestive enzymes. In addition, the inhibitory effects of tea polyphenols on α-amylase, pepsin, trypsin and lipase were studied. In the presence of 0.05 mg/ml tea polyphenols, the inhibition ratios of α-amylase, pepsin, trypsin and lipase were, respectively, 61%, 32%, 38% and 54%, suggesting that TP might possess antinutritional properties.     

In vitro antioxidative and anticancer activities of tea glycoprotein in green tea

In this paper, the antioxidative and anticancer activities of tea glycoprotein (TGP) in green tea were studied. TGP was extracted from coarse old green tea and purified by Sephadex G-100 gel filtration, and its purity was determined by high performance gel permeation chromatography (HPGPC). The antioxidative activity of the TGP was evaluated by determining the change of the values of the heat-induced oxidation in a linoleic acid system with β-carotene, the decoloration of the 1,1-diphenyl-2-picrylhydrazyl (DPPH), and the superoxide generated from autoxidation of pyrogallol. The results show that the TGP possesses distinctive antioxidative activity. Furthermore, the anticancer activity of the TGP at different concentrations was evaluated by the MTT assay using two kinds of colon cancer cell lines (HCT-15, Caco-2). Dose-dependently TGP exhibited good antiproliferation activity to HCT-15, whereas exhibited very weak antiproliferation activity to Caco-2. Only at a very high concentration (409.6 μmol L⁻¹), the TGP obviously inhibited the proliferation of Caco-2. Whether there is a correlation between the antioxidative and the anticancer activity of the TGP, should be studied further.     

超微茶粉面包的研制

介绍了超微茶粉面包的制作工艺,并探讨其添加量对面包质量的影响,结果表明:添加3%的茶粉对面包的质量无不良影响,并具有一定的保健作用。     

Impact of apoE genotype on oxidative stress, inflammation and disease risk

Although in developing countries an apolipoprotein E4 (apoE4) genotype may offer an evolutionary advantage, as it has been shown to offer protection against certain infectious disease, in Westernised societies it is associated with increased morbidity and mortality, and represents a significant risk factor for cardiovascular disease, late-onset Alzheimer's disease and other chronic disorders. ApoE is an important modulator of many stages of lipoprotein metabolism and traditionally the increased risk was attributed to higher lipid levels in E4 carriers. However, more recent evidence demonstrates the multifunctional nature of the apoE protein and the fact that the impact of genotype on disease risk may be in large part due to an impact on oxidative status or the immunomodulatory/anti-inflammatory properties of apoE. An increasing number of studies in cell lines, targeted replacement rodents and human volunteers indicate higher oxidative stress and a more pro-inflammatory state associated with the epsilon4 allele. The impact of genotype on the antioxidant and immunomodulatory/anti-inflammatory properties of apoE is the focus of the current review. Furthermore, current information on the impact of environment (diet, exercise, smoking status, alcohol) on apoE genotype-phenotype associations are discussed with a view to identifying particular lifestyle strategies that could be adapted to counteract the 'at-risk' E4 genotype.