Identification of microbial contaminants present during the curing of honeybush tea (Cyclopia)

Honeybush tea (Cyclopia) is produced over a wide area of the Western and Eastern Provinces of South Africa and exported to several countries worldwide. It is traditionally manufactured by curing honeybush material for several days at relatively high temperatures and moisture contents and this results in extensive mould and bacterial growth. This leads to a product with inferior leaf colour and organoleptic quality as well as health concerns. Unlike during the manufacture of black tea, honeybush curing temperatures do not reach levels where these contaminants are eliminated. The microbial contaminants and the minimum temperatures necessary to eliminate these organisms were thus investigated. Yeast-Glucose (YG), Yeast-Starch (YpSs) and Czapek media were evaluated for the isolation of contaminants that developed during the curing of honeybush tea. YG and YpSs gave good results, while the Czapek medium was found to be unsatisfactory for the detection of microbial contaminants. A low pH (pH 5.0) favoured mould growth, while bacteria proliferated at pH 7.0. Honeybush material fermented in a curing heap and material fermented under controlled conditions at 40 and 50 °C showed microbial contamination, but no contaminants were detected on or in material fermented at higher temperatures (60, 70 and 80 °C). Two thermophilic moulds, Humicola grisea var thermoida and Humicola lanuginosa, a thermotolerant mould, Rhizomucor pusillus, and five endospore-forming species of the genus Bacillus were isolated. The data indicated that R pusillus was the predominant microbial contaminant. © 1999 Society of Chemical Industry     

Effects of osmotic pretreatment and frying conditions on quality and storage stability of vacuum-fried pumpkin chips

The effects of osmotic (OP), ultrasound-assisted osmotic pretreatment (UAOP) and frying conditions on quality and storage stability of vacuum fried pumpkin chips were investigated. The pumpkin samples were pretreated in maltodextrin solution and subsequently fried at different temperatures (90–110 °C) and time periods (10–30 min). The results demonstrated that the moisture content, water activity, lightness, yellowness and carotenoid content of the fried chips decreased, while oil content, hardness and a* (dark brown colour) value increased with increasing frying temperature and time. UAOP reduced about 16.0% of oil absorption and enhanced approximately 70% of carotenoid retention in the fried chips. UAOP samples were also more stable during storage than the untreated ones, indicated by lower degradation kinetics constants of key quality parameters. The proposed pretreatment could be an effective method for food industries to develop vacuum fried pumpkin chips with improved quality and stability.     

复合发酵型黑糖红茶甜米酒发酵工艺研究

以糯米、黑糖和红茶为主要原辅料,以甜酒曲和酿酒曲为发酵剂,研究复合发酵型黑糖红茶甜米酒发酵工艺,并采用单因素试验、正交试验及响应面法优化黑糖红茶汤制备工艺及黑糖红茶甜米酒发酵工艺。结果表明,黑糖红茶汤制备最优工艺条件为：黑糖添加量14%,红茶添加量6.5%,超声波功率180 W,浸提温度85 ℃,浸提时间12 min;黑糖红茶甜米酒最佳发酵工艺条件为：甜酒曲添加量0.4%、酿酒曲添加量0.25%、发酵温度30 ℃、发酵时间3.0 d。经理化与卫生指标检测,发酵型黑糖红茶甜米酒品质符合国家相关标准要求。该产品生产工艺简便,产品质量稳定,酒精度较传统糯米甜酒高,黑糖和红茶风味与香气突出,具有一定特色和创新性。     

负氧化还原电位电解水冷泡绿茶茶汤理化特性、抗氧化性能及香气成分研究

以瓶装饮用天然水冷泡绿茶和常规热泡绿茶作为对比,探讨负氧化还原电位电解水对冷泡绿茶茶汤品质的影响,以期为得到活性成分含量高及抗氧化活性强的冷泡绿茶饮品提供新选择。通过调节电解饮用水时间电解生成不同负氧化还原电位电解水1和2;通过紫外分光光度法、高效液相色谱法以及顶空固相微萃取与气相色谱-质谱联用法测定并比较负氧化还原电位电解水、瓶装饮用天然水冷泡绿茶和常规热泡绿茶茶汤基本理化指标、主要活性成分含量、抗氧化性、感官品质和香气成分。结果表明,负氧化还原电位电解水冷泡绿茶茶汤pH呈弱碱性,氧化还原电位为负值,可溶性固形物含量及茶汤浸提率显著高于瓶装饮用天然水冷泡绿茶（P<0.05）,与常规热泡茶相当;电解水制得茶汤色度黄绿明亮,汤色品质高;电解水茶汤多酚含量显著高于瓶装饮用天然水冷泡,且电解水样2显著高于常规热泡（P<0.05）,游离氨基酸总量显著高于瓶装饮用天然水冷泡以及常规热泡（P<0.05）,咖啡碱含量低于常规热泡,儿茶素类含量均高于瓶装饮用天然水冷泡,除EGCG和EGC外均高于常规热泡;电解水冷泡茶茶汤抗氧化能力显著高于其他两种绿茶茶汤（P<0.05）;电解水冷泡茶汤感官评分最高且茶汤香气成分最为丰富醇和。实验初步验证了负氧化还原电位电解水用作冷泡绿茶加工用水可行性,且筛选出电解水样2制得绿茶茶汤生化成分高、抗氧化活性强且感官评价得分高、香气清香持久。     

Effect of combined treatments of ultrasound and high hydrostatic pressure processing on the physicochemical properties,microbial quality and shelf-life of cold brew tea

Effects of ultrasound combined with high hydrostatic pressure (HHP) on physicochemical properties,microorganisms and storage attributes of cold brew tea were investigated. HHP at 400 MPa/5 min/25 °C inactivated the total aerobic bacteria, yeast and mould in cold brewed tea prepared by static brewing (SB-tea) at 13 h/4 °C, ultrasonic bath (UB-tea) at 150 W/120 min/0 °C and ultrasonic pulveriser (UP-tea) at 600 W/40 min/0 °C, ensuring their microbiological safety. The results showed that there was no significant difference in the concentration of tea polyphenols between hot brewed tea prepared by 7 min/100 °C and cold brewed tea under different preparation conditions, while the caffeine in cold brewed tea was significantly lower (P < 0.05) than that in hot brewed tea. During the storage period of 8 days, compared with the untreated group, the cold brewed tea after HHP treatment had better microbiological safety. In addition, HHP treatment constantly maintained the tea polyphenols, pH, colour, antioxidant capacity and turbidity in cold brewed tea. The untreated and HHP-treated cold brew tea were evaluated by 20 trained volunteers. Results showed that UB-tea was more close to SB-tea than UP-tea in sensory profile, while HHP seem to maintain a good sensory profile as well. Therefore, this particular combined technology of ultrasonic bath and HHP displayed considerable potential for application in the cold brew tea manufacturing industry.     

Evaluation of hot and cold extraction of bioactive compounds in teas

This study evaluated the bioactive compounds of different types of tea by comparing hot and cold infusions. A multivariate data analysis was carried out, where the principal components analysis (PCA) and hierarchical cluster analysis (HCA) were used. Phenolic compounds varied between 267.27–2896.00 mg GAE L^?1 and 215.10–7351.33 mg GAE L^?1 for hot (80 °C) and cold extraction (20–25 °C), respectively. In the case of their antioxidant activity, results with DPPH were 43.10‐73.67% for hot extraction and 46.80‐77.13% for cold extraction. The average values for the ABTS˙⁺ method ranged between 2535.43 and 33 300.17 μmol TE L^?1 and between 1110.34 and 38 300.67 μmol TE L^?1, respectively, for hot and cold extraction. Different compounds were identified by liquid chromatography in the samples evaluated, where caffeine presented the higher concentrations in the teas. Samples of green and black tea (hot extraction) and white tea (cold extraction) showed bacteriostatic activity for S. aureus and E. coli. No extract had any bactericide activity. The current study revealed that cold infusion was more efficient in the extraction of bioactive compounds.     

青砖茶加工过程品质成分变化研究

目的研究青砖茶加工过程中各化学品质成分含量的变化,为青砖茶风味品质形成提供理论依据。方法以青砖茶发酵前、发酵后及成品为材料,比较分析样品水分、水浸出物、游离氨基酸、咖啡碱、茶多酚、儿茶素组分、茶黄素组分、粗纤维、黄酮、可溶性糖、可溶性果胶等含量变化。结果青砖茶加工过程中,水分含量基本不变,控制在9%左右;纤维素含量呈现上升趋势,成品达到(21.29±0.78)%;水浸出物、可溶性总糖、儿茶素、茶黄素-3'-没食子酸酯、茶黄素总量呈现下降趋势;黄酮含量总体较为稳定,为1.40%~1.83%;茶黄素-3,3'-双没食子酸酯基本稳定在1 mg/g左右;咖啡碱含量发酵后显著低于发酵前;氨基酸、茶多酚、表儿茶素、表儿茶素没食子酸酯、表没食子儿茶素、表没食子儿茶素没食子酸酯、儿茶素总量、茶黄素、茶黄素-3'-没食子酸酯、水溶性果胶均呈现下降后上升,但成品含量低于发酵前原料含量的趋势。结论青砖茶加工过程中不同生化成分变化趋势存在差异,成品与原料存在较大差异,具有粗涩味作用的成分含量降低,各成分间含量更加协调,为青砖茶醇和风味品质形成奠定基础。     

Temperature and Time of Steeping Affect the Antioxidant Properties of White,Green, and Black Tea Infusions

Tea (Camellia sinensis) is the most highly consumed beverage in the world next to water. The common way of preparation is steeping in hot water which is varying for different type of tea. We investigated the antioxidant properties of 6 type of tea leaves under different time and temperatures of extraction method used. In general, all samples tested in this study demonstrated high levels of antioxidant capacity and antioxidant activity. The results indicate that the antioxidants activity is significantly affected by time and temperature of steeping and the highest was depending on the variety. White state values, green and black teas showed different levels of antioxidants under different extraction conditions. Overall, the highest activity for white tea was in prolonged hot and in some assays prolonged hot and cold extracts, whereas for green tea the highest activity observed in prolonged cold steeping while, for black tea was in short hot water infusion. The results of this study showed the antioxidant capacity of white and green tea was greater than black tea.     

夏季绿茶发酵产品研制及其品质评价

夏季绿茶滋味苦涩,品质远不及春茶,为提高夏季绿茶滋味品质、拓宽资源利用,文章以夏季绿茶为原料,筛选最佳发酵菌种,研制夏季绿茶发酵产品.通过单因素与响应面优化试验,探究夏季绿茶发酵产品最佳工艺参数,并检测分析夏季绿茶发酵产品的主要生化成分及抗氧化能力.结果 表明,乳酸菌对夏季绿茶浸提液发酵作用效果较佳,优于双歧杆菌和酵母...     

Preparation of an Alcoholic Beverage from Tea Leaves

The preparation of a fermented tea beverage from a Sri Lankan Broken Orange Pekoe (BOP) tea type is reported. The tea beverage was produced using 1–2.5% (w/v) Broken Orange Pekoe and was brewed using boiling sucrose sweetened (5–25°Brix) water (100°C for 3 min), followed by fermentation at 25°C, utilizing an 8.5% (v/v) inoculum of Saccharomyces cerevisiae G. A maximum ethanol of 14.91% (v/v) was obtained from an initial 25°Brix substrate with a 2.67°Brix drop per day. The tea beverage with an initial 15°Brix and 1.5% (w/v) tea yielded the best sensory score and was stable over a test period of 6 weeks at 15°C.     

Suppression of blood glucose level by a new fermented tea obtained by tea‐rolling processing of loquat (Eriobotrya japonica) and green tea leaves in disaccharide‐loaded Sprague‐Dawley rats

BACKGROUND: In the field of food science, much interest has been focused on the development of alternative medicinal foods with the ability to regulate excess blood glucose level (BGL) rise. The authors have successfully developed a new fermented tea product (LG tea) by co‐fermentation of loquat (Eriobotrya japonica) leaf and summer‐harvested green tea leaf. The objective of this study was to examine the acute suppression effect of LG tea on BGL rise in disaccharide‐loaded Sprague‐Dawley (SD) rats and to evaluate its possible usage as an antidiabetic functional food material. RESULTS: As a result of single oral administration of hot water extract of LG tea (50 mg kg^?1) to maltose‐loaded SD rats, BGL at 30 min was significantly decreased by 23.8% (P < 0.01) compared with the control. A corresponding reduction in serum insulin secretion was also observed. The ED₅₀ value of LG tea (50.7 mg kg^?1) was estimated to be about 16‐fold higher than that of the therapeutic drug acarbose (3.1 mg kg^?1). CONCLUSION: No significant change in BGL was observed when sucrose or glucose was administered, suggesting that the suppression effect of LG tea was achieved by maltase inhibition, not by sucrase inhibition or glucose transport inhibition at the intestinal membrane. Copyright © 2010 Society of Chemical Industry     

Quality Characteristics of a Pickled Tea Processed by Submerged Fermentation

There is a traditional pickled tea fermented under anaerobic condition in many Asian countries, but its quality characteristics are still unclear. The dynamic qualities, chemical components, and volatile components of pickled tea processed by submerged fermentation were investigated. The results showed that the sensory qualities of the pickled tea gradually improved with increasing fermentation time. Sensory qualities decreased gradually after 7 d of fermentation, and the change was extremely significant (p < 0.01). Correspondingly, biochemical indicators (except for soluble extract) decreased continuously and significantly (p < 0.01) within 5–7 d of fermentation, but the decrease was much slower in the later stage. The proper control of fermentation time is a key step for obtaining the desired quality of pickled tea. By submerged fermentation for 7 d, the best sensory quality of pickled tea was obtained: the taste of pickled tea was less bitter and astringent, but certainly acidic; the flavor of pickled tea was sour with sweet and floral tastes; the tea had low caffeine content, high gamma-amino butyric acid content, and high contents of special volatile components, such as hotrienol and 2,6-bis (1,1-dimethylethyl)-4-methyl-phenol. Results indicated that submerged fermentation is potentially a new method of processing pickled tea to obtain the desired quality. Our results contribute to the understanding of the microbial transformation of tea components under anaerobic conditions.     

Performance of different fermentation methods and the effect of their duration on the quality of raw cocoa beans

This study aims to compare the effect of three cocoa fermentation methods and their duration on raw cocoa quality. Results showed a decrease in percentage of physical quality defects on fermentation method. Cocoa fermented for 4 days presented higher percentage of purple beans reached 45% and about 10% of slaty beans than cocoa fermented for 6 days whatever the process. Fermentation duration did not influence the mouldy beans that were around 1%. Formation of brown beans increased from 16% to 50% depending on the fermentation duration and process. Using wooden boxes allowed higher percentage of 77%–90% brown beans than others materials. Acidity of cocoa decreased on fermentation duration but beans treated in boxes were significantly (P = 0.05) acidic from 1.40 and 3.07 meq of NaOH g^?1. Fungal population did not vary in number depending both on the duration and the fermentation method with rates that ranged from 3.32 × 10⁷ to 8.63 × 10⁷ CFU g^?1.     

菌菇速溶茶加工关键技术研究与开发

以红茶和香菇为原料,通过微波程序化升温混料直提、二级切向流微滤-反渗透膜组合浓缩和喷雾干燥制备菌菇速溶茶产品,并对加工过程中的相关各工艺参数进行了研究。所制得的菌菇速溶茶产品呈粉末状,无结块,色泽红棕色,有较显著的菌香;冲泡后,汤色橙红,滋味醇厚伴有浓浓的菌菇味;产品中多糖含量高于15%,多酚含量高于16%,兼具菌菇和红茶的功效和风味,市场前景广阔。     

In vitro bioaccessibility of β‐carotene in dried carrots pretreated by different methods

The effects of selected pretreatment methods, i.e. soaking in citric acid, blanching in water and blanching in citric acid, as well as hot‐air drying (at 70, 80 and 90 °C), on the retention and relative in vitro bioaccessibility of β‐carotene in dried carrots were investigated. The results indicated that the selected pretreatments and drying could enhance the relative bioaccessibility of β‐carotene in dried carrots. The relative bioaccessibility of β‐carotene in dried carrots increased to 47–73%, while the values in the fresh (13%) and dried untreated (31–47%) carrots were lower. Although significant losses of β‐carotene occurred during both the pretreatment and drying processes, bioaccessible β‐carotene contents of dried pretreated carrots were in a similar order to those of the fresh carrots, indicating the ability and hence the benefit of appropriate pretreatment and drying processes in maintaining the nutritive quality of a food product.     

速溶保健决明茶的研制

以决明子、中低档绿茶为原料，研制成速溶保健决明茶。产品为棕黄色粉末，冲溶后汤色黄亮，香醇爽口，具有减肥保健效果。文章阐述了其生产工艺、配方和技术关键。     

不同潮水量条件下普洱茶渥堆过程化学成分的变化

通过设置不同潮水量进行实验室模拟普洱茶渥堆过程,系统地研究堆表与堆芯主要理化成分含量的变化规律,找出普洱茶快速模拟发酵的潮水量。结果表明：至渥堆结束,茶坯的茶多酚、儿茶素、茶黄素、茶红素、氨基酸的含量均呈减少趋势,水溶性糖、茶褐素、咖啡碱的含量则呈增加趋势。不同潮水量条件下渥堆茶样的堆温以及参与发酵的微生物的差异,显著地影响普洱茶的品质。结合感官评价得出,潮水量为45%的普洱茶表现出较佳的品质。     

Impact of hot water treatment on sprouting,membrane permeability,sugar content and chip colour of reconditioned potato tubers following long‐term cold storage

BACKGROUND: The efficacy of hot water treatment in facilitating successful reconditioning of processing potato (Solanum tuberosum L.) cultivar Hermes following 6 months cold storage at 4.5 °C was examined. Tubers were subjected to hot water treatments (HWTs) at 52.5, 55.0, 57.5 and 60.0 °C for 0–60, 0–50, 0–40 and 0–20 min, respectively, and then reconditioned for 20 days at 16 °C before evaluated for sprouting, fresh weight loss, membrane permeability, sugar content and processing quality. RESULTS: The study demonstrates that in order to achieve complete inhibition of sprouting during potato reconditioning HWTs must exceed the thermal tolerance threshold of the tubers. Short‐duration HWT was effective in retarding sprout growth and tuber dehydration without significantly affecting storage parenchyma membrane permeability, tuber sugar content or processing quality. On the contrary, prolonged HWT caused extensive heat damage, loss of membrane integrity and induced an increase in tuber sucrose and reducing sugar content resulting in deterioration of chip colour in proportion to treatment duration. CONCLUSION: Although HWT at 52.5–60 °C following long‐term cold storage did not improve the processing quality of potato tubers after 20 days of reconditioning, future work is needed to evaluate the effect of short‐duration HWT on the permissible extent of reconditioning and subsequent processing quality. Copyright © 2008 Society of Chemical Industry     

基于变温发酵技术的黄金茶工夫红茶品质分析

该研究以保靖黄金茶1号1芽2叶鲜叶为原料试制工夫红茶,考察变温发酵(第一阶段40℃&第二阶段30℃)对黄金茶工夫红茶品质的影响.结果表明:变温发酵加工的工夫红茶色泽黑褐尚润,滋味甜醇、鲜爽,甜香尚高长,汤色红亮,叶底尚红匀;与恒温发酵相比,随着发酵程度的加深,茶汤颜色由红亮向红暗转变更明显,滋味由甜醇向纯和尚甜方向发展...     

Internal quality and antioxidants content of cold-stored red sweet peppers as affected by polyethylene bag packaging and hot water treatment

Physical (weight, firmness) and compositional (sugars, organic acids, ascorbic acid, phenolic compounds and carotenoids) changes of red sweet peppers (Capsicum annuum L.) were monitored during 21 days of cold storage (at 7.5 °C); fruits were stored without packaging, packaged in low density polyethylene bags, or after hot water dipping (53 °C for 4 min) and packaging. Packaging prevented water loss, and preserved the firmness of the fresh product. Sugars (fructose and glucose) content was practically constant throughout the whole storage time, for all treatments. A moderate accumulation of citric acid was observed during storage, but no marked effects of packaging and hot water dipping on citric and malic acid content. Ascorbic acid content slightly increased in unpackaged and packaged fruits, but not in treated+packaged peppers. Hydroxycinnamics total content seemed not to be affected by cold storage, packaging or hot water treatment, whereas glycosylated flavonoids showed somewhat lowered levels during storage, particularly in the case of unpackaged and packaged+treated fruits. Regarding carotenoids content, the effect of the considered storage conditions seemed to be much smaller than that due to ripening stage. Provitamin A content showed an increasing trend in unpackaged and packaged fruits; packaged+treated peppers were characterised by a lower retention of provitamin A and a higher level of capsanthin and cucurbitaxanthin A with respect to not treated fruits. On the whole, packaging and hot water treatment did not produce noticeable adverse effects on the majority of the examined compositional quality parameters.