EFFECT OF FAR-INFRARED HEATER ON THE PHYSICOCHEMICAL CHARACTERISTICS OF GREEN TEA DURING PROCESSING

ABSTRACT

The green tea leaves (Camellia sinensis var. sinensis) were irradiated by a far‐infrared (FIR) heater during the roasting and drying step, resulting in three different treatments produced. Green tea was extracted by soaking the leaves in water, and the components were analyzed. FIR irradiation, combined with fryer heating during the roasting step and additionally applied after the drying step, increased total phenolic contents of green tea from 116.30 to 171.77 mg/g, and total flavanol contents from 17.54 to 24.76 mg/g, compared with the non‐irradiated control. Ascorbic acid contents also increased from 3.07 to 4.20 mg/g. The amounts of epicatechin gallate and epigallocatechin gallate were significantly increased from 2.41 to 4.59 mg/mL and 20.61 to 28.54 mg/mL, respectively, compared with the non‐irradiated control. FIR irradiation increased Nitrite Scavenging Ability of green tea at pH 3.0 and pH 4.2, while there was no significant difference at pH 6.0. Sweetness, umami and aroma of green tea were enhanced by FIR irradiation, while bitterness and astringency were decreased compared with those of the control. These results show that FIR heating during the green tea process affected the chemical properties of green tea, and the FIR heater can be applied to increase the physicochemical qualities of green tea.

PRACTICAL APPLICATIONS

Green tea, a widely consumed drink, has received much attention because of the beneficial biological effects attributable to its excellent antioxidant activity. In this article, a far‐infrared (FIR)‐heater for industrial application was used during the processing of green tea leaves, and the chemical characteristics and quality of FIR‐treated green tea were determined. FIR irradiation, combined with fryer heating during the roasting step and additionally applied after the drying step, significantly increased phenolic, flavanol, ascorbic acid, epicatechin gallate, epigallocatechin gallate contents and nitrite‐scavenging activity compared with non‐irradiated control. Sensory evaluation also showed a positive effect of FIR irradiation. The results indicated that FIR heater could be easily applied to increase the quality of green tea in the processing line.     

Effects of different drying methods on the antioxidant properties of leaves and tea of ginger species

Effects of five different drying methods on the antioxidant properties (AOP) of leaves of Alpinia zerumbet, Etlingera elatior, Curcuma longa, and Kaempferia galanga were assessed. All methods of thermal drying (microwave-, oven-, and sun-drying) resulted in drastic declines in total phenolic content (TPC), ascorbic acid equivalent antioxidant capacity (AEAC), and ferric-reducing power (FRP), with minimal effects on ferrous ion-chelating ability and lipid peroxidation inhibition activity. Of the non-thermal drying methods, significant losses were observed in air-dried leaves. Freeze-drying resulted in significant gains in TPC, AEAC, and FRP for A. zerumbet and E. elatior leaves. After one week storage, AOP of freeze-dried E. elatior leaves remained significantly higher than those of fresh control leaves. Freeze-dried tea of A. zerumbet was superior to the commercial tea for all AOP studied.     

Changes produced in the aroma compounds and structural integrity of basil (Ocimum basilicum L) during drying

The influence of drying on the aroma compounds, from a chemical and sensory standpoint, and on the structural integrity of basil (Ocimum basilicum L) was evaluated. The drying methods tested were oven drying at 45 °C, air drying at room temperature and freeze‐drying. The volatile compounds of fresh and dried basil were extracted and concentrated by simultaneous distillation/extraction and analysed by gas chromatography/mass spectrometry. In all, 27 volatile components were identified, linalool being the major component, followed by eugenol. The total quantity of volatiles of fresh basil decreased considerably during oven drying and freeze‐drying, whereas air drying of basil at room temperature brought about only small losses of volatile components. The cell damage produced on basil leaves during drying was evaluated by scanning electron microscopy. From a sensory standpoint, fresh basil was described as having a fresh, herbaceous and floral odour, while the dried samples had a mentholated, spicy, hay‐like and earthy odour. Copyright © 2004 Society of Chemical Industry     

Establishment of a standard reference material (SRM) herbal DNA barcode library of Vitex negundo L. (lagundi) for quality control measures

The majority of the population in the Philippines relies on herbal products as their primary source for their healthcare needs. After the recognition of Vitex negundo L. (lagundi) as an important and effective alternative medicine for cough, sore throat, asthma and fever by the Philippine Department of Health (DOH), there was an increase in the production of lagundi-based herbal products in the form of teas, capsules and syrups. The efficiency of these products is greatly reliant on the use of authentic plant material, and to this day no standard protocol has been established to authenticate plant materials. DNA barcoding offers a quick and reliable species authentication tool, but its application to plant material has been less successful due to (1) lack of a standard DNA barcoding loci in plants and (2) poor DNA yield from powderised plant products. This study reports the successful application of DNA barcoding in the authentication of five V. negundo herbal products sold in the Philippines. Also, the first standard reference material (SRM) herbal library for the recognition of authentic V. negundo samples was established using 42 gene accessions of ITS, psbA-trnH and matK barcoding loci. Authentication of the herbal products utilised the SRM following the BLASTn and maximum-likelihood (ML) tree construction criterion. Barcode sequences were retrieved for ITS and psbA-trnH of all products tested and the results of the study revealed that only one out of five herbal products satisfied both BLASTn and ML criterion and was considered to contain authentic V. negundo. The results prompt the urgent need to utilise DNA barcoding in authenticating herbal products available in the Philippine market. Authentication of these products will secure consumer health by preventing the negative effects of adulteration, substitution and contamination.     

Effects of conventional and nonconventional drying on the stability of Bifidobacterium animalis subsp. lactis INL1

Freeze, spray, vacuum, microwave vacuum‐ and microwave freeze‐drying were applied to Bifidobacterium animalis subsp. lactis INL1. Freeze and microwave freeze‐drying showed the highest survival after drying. When a storage test (25 °C; oxygen) was performed, these cultures were the most sensitive ones at a_w = 0.23, but the addition of lactose improved their stability after 8 weeks. Flow cytometry was useful to assess viability after drying but not during storage. Our results show that dehydration technologies other than freeze‐drying might be suitable alternatives that deserve further investigation for the preservation of sensitive probiotic bacteria. Microwave drying rendered cultures of comparable characteristics to their conventional counterparts, requiring significantly shorter drying times.     

ACCELERATED STORAGE TESTING OF FREEZE-DRIED IMMOBILIZED LACTOBACILLUS ACIDOPHILUS-FERMENTED BANANA MEDIA

ABSTRACT

Freeze‐drying was applied as a drying method for the production of dehydrated immobilized Lactobacillus acidophilus‐fermented banana medium containing high levels of probiotics and appropriate prebiotic (mainly fructooligosaccharides) contents in an attempt to develop dried synbiotic products. Ca‐alginate and κ‐carrageenan were used for the immobilization of L. acidophilus, and the immobilized bacteria were employed directly in the banana media fermentation. The fermented products were then freeze‐dried. Results indicated that cell immobilization could provide effective protection to L. acidophilus, and reduce the damage caused by freezing and freeze‐drying. Meanwhile, accelerated storage testing using temperatures of 50, 60 and 70C was applied to the dehydrated products. Gel‐entrapped L. acidophilus appeared to have lower decimal reduction, and Ca‐alginate immobilized cells had a better survival than κ‐carrageenan. Results of accelerated storage test showed that immobilization could effectively increase the thermal resistance of entrapped microorganisms, and Ca‐alginate showed a better effect than κ‐carrageenan, and the beneficial effects increased with the decrease of the storage temperature. The freeze‐dried products exhibited little hygroscopicity because of the consumption of monosaccharides during fermentation. Results revealed that freeze‐drying could be used as a proper method for the development of dried product of immobilized L. acidophilus‐fermented banana media, and accelerated storage test could be used to evaluate the storage stability of the dried products.

PRACTICAL APPLICATIONS

This research demonstrates the feasibility of the application of accelerated storage testing to the prediction of shelf life and storage stability of freeze‐dried probiotic products manufactured by lactic acid bacteria fermentation. The Arrhenius equation was associated in this study. This will provide an efficient approach for the estimation of shelf life of probiotic products.

     

不同干燥方法对生姜叶活性成分和抗氧化活性的影响

为研究不同干燥方法对生姜叶活性成分和抗氧化能力的影响,以黄酮、多酚、精油含量及精油组分为活性成分指标,以DPPH·、ABTS⁺·及·OH清除率为抗氧化能力指标,对比阴干、晒干、烘干、冷冻干燥及真空干燥5种干燥方法对生姜叶的影响。结果表明,与新鲜生姜叶相比,经过不同干燥处理后生姜叶的活性成分含量及抗氧化能力均有所下降。其中,冷冻干燥处理后的生姜叶黄酮、多酚及精油含量均是最高,分别为21.62 mg/g、1.56 mg/g和1.91%;对DPPH·、ABTS⁺·和·OH的清除化能力最高,分别为70.42%、79.65%和63.41%。其次分别为烘干、真空干燥、阴干及晒干。通过GC-MS分析,新鲜及5种干燥方法得到的生姜叶精油共鉴定出33种组分,其主要组分为α-柏木烯、乙酸异龙脑酯、(Z)-3,7-二甲基-2,6-辛二烯醛及甲基庚烯酮,主要分为7大类,分别为萜烯类、醇类、醛类、酚类、酸类、酮类及酯类。综合比较,冷冻干燥对生姜叶中的活性成分及抗氧化能力保留效果最好。     

加工工艺对茶树花品质及抗氧化活性的影响

以‘黄金桂’品种茶树的鲜花为原料,研究锅式杀青烘干、微波杀青烘干、真空冷冻干燥对茶树花中水浸出物、茶多酚、游离氨基酸、儿茶素组分、生物碱含量及对1,1-二苯基-2-三硝基苯肼自由基清除能力的影响。结果表明,冷冻干燥处理的茶树花茶中茶多酚、游离氨基酸、表没食子儿茶素、表儿茶素、表没食子儿茶素没食子酸酯、表儿茶素没食子酸酯、甲基化表儿茶素没食子酸酯含量以及儿茶素总量显著高于锅式杀青烘干和微波杀青烘干(P<0.05);没食子酸含量最低;水浸出物、茶没食子素和咖啡碱含量与锅式杀青烘干和微波杀青烘干差异不显著(P>0.05)。这3种工艺中,真空冷冻干燥工艺最有利于多酚类化合物的保留,因此成品茶具有最强的抗氧化活性;微波杀青烘干其次,锅式炒青烘干的抗氧化活性最低。感官分析表明,锅式杀青烘干、微波杀青烘干工艺由于经过热脱水处理,所制得的茶树花茶具有玉米香;滋味均有麻涩感,其中冷冻干燥处理的茶树花茶涩味最明显,不同工艺处理下感官风味不同。综上,可将茶树花茶开发为功能性饮品。     

Phenolic composition,antioxidant and cytoprotective effects of aqueous-methanol extract from Anneslea fragrans leaves as affected by drying methods

The present study is aimed to evaluate the effect of three different drying methods, including shade drying (SD), freeze drying (FD) and hot air dying (HAD), on the chemical components, antioxidant and cytoprotective activities of aqueous-methanol extracts from A. fragrans leaves. The total phenolic and flavonoid content were determined by spectroscopic methods, whereas the chemical profile of different extracts was determined by ultra-high-performance liquid chromatography coupled with a tandem mass spectrometry (UHPLC-MS/MS). A total of thirteen compounds were characterised and 9 phenolic compounds have been quantified. Two dihydrochalcone glycosides named confusoside and vacciniifolin were found to be the most abundant phenolic compounds in the SD extract of A. fragrans leaves, which also showed the strongest antioxidant and cytoprotective activities. The results showed that shade drying is an efficient method for preserving the chemical constituents and maintaining the antioxidant and cytoprotective activities of A. fragrans leaves.     

The influence of organ,season and drying method on chemical composition and antioxidant and antimicrobial activities of Juniperus phoenicea L. essential oils

BACKGROUND: Juniperus phoenicea is an important medicinal plant. In the present study, essential oils (18 samples) from leaves and berries of Juniperus phoenicea L. (Cupressaceae), obtained by various drying methods and in different collection months, were analysed by gas chromatography–mass spectrometry and also evaluated for in vitro antimicrobial and antioxidant activities. Correlations were studied between antimicrobial activity and the chemical composition of essential oils. RESULTS: Sixty‐seven compounds were identified in essential oils, representing 97.7–100%. Essential oils were dominated by monoterpenes and sesquiterpenes, which presented 35.0–93.3% and 6.7–62.0%, respectively, depending of organ, season and drying method. Antimicrobial tests showed that essential oils strongly inhibited the growth of Gram‐positive microorganisms and Mucor ramamnianus, but was inactive against Gram‐negative strains. Antioxidant activity was tested using the ABTS radical‐scavenging assay. Most samples showed good activity (the best IC₅₀ = 41.7 ± 1.5 mg L^?1). CONCLUSIONS: It could be concluded that drying of leaves of J. phoenicea in the sun and berries in oven‐drying was more suitable and was recommended for obtaining higher essential oil yield, but for a higher percentage of some special components such as α‐pinene and δ‐3‐carene shade‐drying was more suitable. Copyright © 2009 Society of Chemical Industry     

Processing Techniques to Reduce Toxicity and Antinutrients of Cassava for Use as a Staple Food

ABSTRACT: Cassava is a valuable source of food for developing countries, but it contains highly toxic cyanogen compounds and antinutrients. Cyanogens are found in 3 forms in cassava: cyanogenic glucoside (95% linamarin and 5% lotaustratin), cyanohydrins, and free cyanide. Different processing techniques exist to remove cyanogens and their effectiveness depends on the processing steps and the sequence utilized, and it often is time‐dependent. Pounding or crushing is the most effective for cyanogenic glucoside removal because it ruptures cell compartments, thus allowing direct contact between linamarin and the enzyme linamarase that catalyzes the hydrolytic breakdown. Crushing and sun‐drying cassava roots made into flour removes 96% to 99% of total cyanogens, whereas soaking and sun‐drying into lafun or fufu, or soaking and fermenting and roasting into gari or farina, removes about 98% of cyanogens. For cassava leaves, which have 10 times more cyanogens than roots, pounding and boiling in water is an efficient process to remove about 99% of cyanogens. Other strategies to reduce toxicity include development of low‐cyanogen cassava varieties and cassava transgenic lines with accelerated cyanogenesis during processing. Although phytate and polyphenols have antioxidant properties, they interfere with digestion and uptake of nutrients. Fermentation and oven‐drying are efficient processing methods to remove phytate (85.6%) and polyphenols (52%), respectively, from cassava roots. Sun‐drying the leaves, with or without prior steaming or shredding, removes about 60% phytate. Cassava is a nutritionally strategic famine crop for developing countries and, therefore, reducing its toxicity and improving its nutritional value is crucial.     

Effect of vacuum‐drying,hot air‐drying and freeze‐drying on polyphenols and antioxidant capacity of lemon (Citrus limon) pomace aqueous extracts

The aim of this study was to investigate the effect of freeze‐drying, hot air‐drying and vacuum‐drying at 70, 90 and 110 °C, on dried lemon pomace polyphenols and antioxidant capacity. The total phenolic content and antioxidant capacity were higher in lemon pomace dried by hot air or under vacuum than those dried by freeze‐drying and increased as the temperature increased. The highest total flavonoid content was recorded in the pomace dried under vacuum at 70 and 90 °C. Lemon pomace dried by freeze‐drying had the highest neohesperidin content, whereas pomace dried under vacuum at 70 °C had the highest rutin and p‐coumaric acid content. The highest gallic acid content was recorded in the pomace dried by hot air at 110 °C. The results of this study indicate that drying technique should be carefully selected according to the bioactive compounds aimed to be extracted.     

Sustainable dehydration of onion slices through novel microwave hydro-diffusion gravity technique

Onion is a semi-perishable commodity having prominent nutritional value. The deterioration of onion during storage can lead to huge amount of post-harvest losses. Shelf life can be increased through drying, which also facilitates transportation, storage, and packaging due to reduced weight and volume. In the present study, a novel microwave-assisted drying technique called microwave hydro-diffusion gravity was investigated for process optimization and compared with conventional drying techniques. Results indicated that 400 W and 14 min of process were the best combination for drying that removed 80% moisture present in slices. The overall drying time of onion slices was significantly reduced (about six times) compared to hot air oven and freeze-drying methods. MHG dehydration prevented the burning of onions and maintained their sensorial attributes especially color and texture. Similarly, MHG in combination with hot air oven consumed only 0.5 MJ energy as compared to 3.24 and 3 MJ energy used by hot air oven and freeze drying, respectively. In short, results proved that MHG technique is much better than conventional techniques in terms of end product quality and process efficiency.Industrial relevanceMicrowave hydro-diffusion technology is optimized for onion drying. This technology will help in reducing the use of energy and will avoid the loss of water soluble components. These bioactive components have great importance in the field of pharmaceutical. Thus, this technology simultaneously dries the product and extracts the valuable components. It will increase the process efficiency and reduce the processing cost.     

Antioxidant activity of Camellia sinensis leaves and tea from a lowland plantation in Malaysia

Methanol extracts of fresh tea leaves from a lowland plantation in Malaysia were screened for total phenolic content (TPC) and antioxidant activity (AOA). AOA evaluation included 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging ability, ferric-reducing antioxidant power (FRAP), and ferrous-ion chelating (FIC) ability. Ranking, based on TPC and AOA, was as follows: shoots > young leaves > mature leaves. TPC and AOA of lowland leaves were comparable to those of highland plants. A green tea produced by drying young leaves in a household microwave oven for 4 min showed significantly higher TPC and AOA than did four commercial brands of green and black tea.     

Optimized Aqueous Extraction of Saponins from Bitter Melon for Production of a Saponin‐Enriched Bitter Melon Powder

Bitter melon, Momordica charantia L. (Cucurbitaceae), aqueous extracts are proposed to have health‐promoting properties due to their content of saponins and their antioxidant activity. However, the optimal conditions for the aqueous extraction of saponins from bitter melon and the effects of spray drying have not been established. Therefore, this study aimed to optimize the aqueous extraction of the saponins from bitter melon, using response surface methodology, prepare a powder using spray drying, and compare the powder's physical properties, components, and antioxidant capacity with aqueous and ethanol freeze‐dried bitter melon powders and a commercial powder. The optimal aqueous extraction conditions were determined to be 40 °C for 15 min and the water‐to‐sample ratio was chosen to be 20:1 mL/g. For many of its physical properties, components, and antioxidant capacity, the aqueous spray‐dried powder was comparable to the aqueous and ethanol freeze‐dried bitter melon powders and the commercial powder. The optimal conditions for the aqueous extraction of saponins from bitter melon followed by spray drying gave a high quality powder in terms of saponins and antioxidant activity.     

金银花叶乳酸杆菌发酵凉茶的研制及其抗氧化活性分析

为获得一款具强抗氧化活性的高保健性金银花叶发酵凉茶,以金银花叶为原材料,通过单因素实验和正交试验,研究了发酵时间、发酵温度、保加利亚乳酸杆菌(L. plantarum 758)接种量及糖的添加量(葡萄糖与蔗糖质量比为3:2)对金银花叶凉茶抗氧化活性的影响并对工艺条件进行了优化,还对比了金银花叶凉茶与市场上常见三种凉茶在抗氧化性及挥发性成分上的差异。结果表明,乳酸杆菌发酵金银花叶凉茶的最佳发酵条件为:发酵时间24 h、发酵温度38℃、接种量4%及糖添加量7%,在此发酵条件下所获得的金银花叶凉茶绿原酸含量达到7.11%,总黄酮含量为22.51%,DPPH自由基清除率为84.23%±3.32%,ABTS自由基清除率为85.30%±2.14%,均显著高于市场上的三种凉茶(P<0.05);金银花叶凉茶中共有挥发性物质32种,其种类和含量都较其它对比组高。总体表明,保加利亚乳酸杆菌(L. plantarum 758)发酵的金银花叶凉茶抗氧化能力突出,具有较高的营养价值和实用功能性。     

Comparative effects of sulfur and nitrogen fertilization and post‐harvest processing parameters on the glucotropaeolin content of Tropaeolum majus L.

Under natural conditions, the content of the bioactive compound glucotropaeolin in the vegetative tissue of Tropaeolum majus is too low to be used directly for the preparation of a mono‐drug. In the present study the influence of sulfur and nitrogen fertilization and the post‐harvest drying procedure on the glucotropaeolin content was evaluated in order to minimize losses of the active glucosinolate. In 2001, field experiments with three levels of nitrogen and sulfur fertilization were conducted on two different sites. Nitrogen fertilization had no consistent influence on the glucotropaeolin content while sulfur fertilization with 100 kg S ha^?1 enhanced the glucotropaeolin content in leaves and seeds significantly by factors of 1.4–2.1 and 1.6–1.8, respectively. The results of the post‐harvest treatment showed that a gentle drying procedure at 40°C in a ventilated oven induced an increase in the glucotropaeolin content in leaves of 1.4–3.2‐fold (from 10.7–25.5 to 30.9–44.6 µmol g^?1 dry weight) compared to sampling in liquid nitrogen followed by freeze‐drying of the samples. This paper delivers new insights into glucosinolate metabolism that will contribute significantly not only to warrant a high content of bioactive compounds in medicinal plants, but also to promote glucosinolate concentrations in various crops by appropriate post‐harvest treatments. Copyright © 2007 Society of Chemical Industry     

Evaluation of Drying Methods with Respect to Drying Kinetics,Mineral Content,and Color Characteristics of Savory Leaves

Sun, oven (50 °C), and microwave oven (700 W) drying of savory leaves (Satureja thymbra L.) were carried out to monitor the drying kinetics, changes in mineral content, and color degradation of the product. Oven and microwave oven drying shortened the drying time over than approximately 70% and 99% when compared to the sun and oven drying methods, respectively. Fresh and dried savory leaves had high amounts of K (8875.2–28468.0 mg/kg), Ca (3681.6–9852.03 mg/kg), Mg (1388.0–3102.0 mg/kg), and P (2313.2–5045.8 mg/kg) minerals. K, Ca, P, and Mg were the most abundant elements in savory samples. Mineral content of oven-dried savory were higher than the sun and microwave dried samples. Midilli and Küçük model was shown to give a good fit to the sun and oven drying. The Midilli and Küçük, modified page and page models exhibited high coefficient of determination (R ² ) values ranging between 0.9995 and 0.9997, to the experimental microwave oven drying data of savory. Microwave oven drying revealed optimum color values. Oven drying resulted in a considerable decrease in color quality of savory.     

Nutritional composition and condensed tannin concentration changes as browse leaves become litter

BACKGROUND: The role of condensed tannins (CT) in ruminant nutrition and health makes changes in leaf litter (LL) after abscission of interest. This study compared the effect of different drying methods of green leaves (GL) with that of natural drying of LL on CT, fibre, crude protein (CP) and phosphorus (P) concentrations in nine Texas browse species. Leaves harvested before autumn shedding were oven‐dried (OD) or freeze‐dried (FD). RESULTS: Where different (P < 0.05), extractable CT concentrations were higher while protein‐ and fibre‐bound CT concentrations were lower in GL‐FD than in LL. Drying method changed total CT concentration in three species. Where different, fibre fraction concentrations were greater in LL than in GL, regardless of drying method. In some species, CP and P concentrations were lower in LL than in GL, but in five species they did not change (P > 0.05) from GL to LL, with CP concentrations ranging from 63 to 151 g kg^?1 in the latter. CONCLUSION: Browse LL had high nutritive value and CT concentrations, explaining why browsing ruminants utilise this feed resource. However, changes in nutrient and CT concentrations as leaves become litter in some species mean that information on one is not necessarily applicable to the other. Copyright © 2010 Society of Chemical Industry