Green tea catechins during food processing and storage: A review on stability and detection

Physicochemical and oxidative stability of a soybean oleosome-based emulsion and its in vitro digestive fate as affected by (-)-epigallocatechin-3-gallate

Oleosomes, which are pre-emulsified oil bodies found naturally in plants, have excellent stability, therefore making their use more popular in the food industries. However, the mechanism of EGCG in regulating the physicochemical and oxidative stability, and digestion of oleosome emulsions is not yet clear. In this study, the effect of EGCG on the properties of soybean oleosome emulsions (SOE) was examined at different pH values (5.0, 7.0, and 9.0). EGCG was significantly more effective in maintaining the stability of SOE at pH 5.0 and 7.0 over the 14 days of storage, but less effective at pH 9.0. Furthermore, lipid oxidation of SOE at pH 7.0 was successfully retarded by incorporating EGCG, but not at pH 5.0 and 9.0. The in vitro gastrointestinal results suggested that EGCG retarded the digestion rate of SOE based on a 20% reduction in free fatty acid release. The results of this study will help food technologists to design slow-digestive oleosome-based products that will satisfy health-conscious consumers' demand for healthier food choices.

Effect of tea catechin derivatives on stability of soybean oil/tea seed oil blend and oxidative stability of fried fish crackers during storage

Effect of (-)-epigallocatechin gallate (EGCG) and (-)-epicatechin (EC) at different concentrations (100-300 ppm) on frying stability of soybean oil blended with tea seed oil was studied. Thermal stability of the blended oil increased with the addition of EGCG and EC, especially with increasing concentrations. Frying induced degradation of tocopherols and phenolics of oils, particularly tocopherols. Incorporation of catechin derivatives could retard tocopherol decomposition and formation of polar materials. The highest frying stability was found for the oil added with EC at 300 ppm. When the oil added with EC (300 ppm) was used to prepare fish crackers, lowered lipid oxidation of the resulting crackers than those prepared using the control oil was noted throughout 12 weeks of storage. EC could be effectively used as natural antioxidant in frying oil with carry through effect to enhance oxidation stability of the fried foods during a storage.

Comprehensive NMR analysis of two kinds of post-fermented tea and their anti-glycation activities in vitro

Post-fermented tea (dark tea) is produced from enzyme-inactivated fresh tea leaves by microbial fermentation. Batabata tea and Awaban tea are two major dark teas fermented under aerobic and anaerobic conditions, respectively. However, how their chemical compositions and functionalities change during different post-fermentation processes remains unclear. Nuclear magnetic resonance (NMR)-based analyses showed that (-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC) and (-)-epicatechin (EC) decreased in Batabata tea during post-fermentation with aerobic molds. In contrast, EGC and EC increased, and pyrogallol was produced in Awaban tea during post-fermentation with lactic acid bacteria (LAB). The anti-glycation activities of two dark teas were investigated using an in vitro assay system with human serum albumin (HSA). The anti-glycation activity decreased in Batabata tea, but it was retained in Awaban tea during post-fermentation. Our results showed that post-fermentation with LAB was an efficient way to enhance phenol content and that pyrogallol contributed to anti-glycation activity of Awaban tea.

The application of pomelo peel as a carrier for adsorption of epigallocatechin-3-gallate

BACKGROUND

Pomelo (Citrus grandis) is the largest citrus fruit, the peel of which is a well-known agricultural wastes. Disposal of pomelo peel after consumption is a serious environment problem. As a natural, versatile bio-absorbent, pomelo peel has shown excellent adsorption capacity for several pollutants, attributed to its micro-pores; however, there is no relevant report on its adsorption capacity for natural products or food ingredients. The ability of pomelo peel to adsorb epigallocatechin-3-gallate (EGCG) was examined in this study. The physicochemical characterizations of pomelo peel were determined by Fourier transform infrared spectroscopy, scanning electron microscopy and high-performance liquid chromatography. The adsorption process of EGCG onto pomelo peel from aqueous solution was carried out at a range of concentrations (50-800 mg L^-1 ) and temperatures (25, 40 and 55 °C).

RESULTS

The main components of pomelo peel are composed of dietary fiber, which provide sufficient adsorption sites during the adsorption process. The adsorption of EGCG onto pomelo peel showed excellent fitness with a pseudo-second-order model. Both Langmuir and Freundlich models were able to describe the isothermal adsorption of EGCG onto pomelo peel. The results of thermodynamic analysis suggested that adsorption is spontaneous and endothermic in nature, and that the process is likely to be dominated by a physisorption mechanism.

CONCLUSION

The results of this study indicate that pomelo peel has potential adsorption capacity for EGCG, which can be used as an effective, low-cost carrier for delivery of natural products in functional food and dietary supplement applications. © 2018 Society of Chemical Industry.

A Critical Review of the Characterization of Polyphenol-Protein Interactions and of Their Potential Use for Improving Food Quality

BACKGROUND

Interest in protein-phenol interactions in biological systems has grown substantially in recent decades.

METHODS

The interest has focused largely on food systems in response to reports on the prominent roles of phenolic compounds in nutrition and health.

RESULTS

Phenolic compounds can have both favourable and adverse nutritional effects. Polyphenols are widely known for their antioxidant, anti-inflammatory, anticancer and antiaging properties; however, they have also been ascribed anti-nutritional effects resulting from interactions with some proteins and enzymes. Interactions between proteins and polyphenols can additionally influence food quality by altering some physical-chemical and sensory properties of foods. These effects may be useful to develop new products in food science and technology provided the nature of physical-chemical interactions between proteins and phenols is accurately elucidated. In this paper, we review the different possible modes of interaction between selected food proteins and phenolic compounds.

CONCLUSION

Existing knowledge on the mechanisms behind polyphenol-protein reactions, the structures of the resulting products and their potential uses is reviewed.

Quantification of ascorbyl adducts of epigallocatechin gallate and gallocatechin gallate in bottled tea beverages

Catechins are the major bioactive compounds existing in tea leaves (Camellia sinensis). Dehydroascorbic acid is (DHAA) a reactive dicarbonyl species and previous studies have demonstrated that catechins could effectively trap DHAA to form ascorbyl adducts of catechins, especially epigallocatechin gallate (EGCG). Since catechins in the aqueous solution are unstable due to their structural features, ascorbic acid (AA) is usually added to bottled tea beverages to protect catechins. However, whether ascorbyl adducts of catechins are formed in bottled tea beverages remains unclear. In this study, formation of ascorbyl adducts of EGCG increased along with increased incubation time when EGCG and AA were dissolved in the aqueous solution. Next, 6C-DHAA-EGCG and 8C-DHAA-EGCG were detected in both green tea and oolong tea beverages, and their concentrations ranged from 0.23 to 1.95 µM and 0.28 to 1.97 µM, respectively. Furthermore, an 8C-ascorbyl adduct derived from gallocatechin gallate was also found in some tea beverages.

Antioxidant and Antimicrobial Activities of (-)-Epigallocatechin-3-gallate (EGCG) and its Potential to Preserve the Quality and Safety of Foods

Quality deterioration of fresh or processed foods is a major challenge for the food industry not only due to economic losses but also due to the risks associated with spoiled foods resulting, for example, from toxic compounds. On the other hand, there are increasing limitations on the application of synthetic preservatives such as antioxidants in foods because of their potential links to human health risks. With the new concept of functional ingredients and the development of the functional foods market, and the desire for a "clean" label, recent research has focused on finding safe additives with multifunctional effects to ensure food safety and quality. (-)-Epigallocatechin-3-gallate (EGCG), a biologically active compound in green tea, has received considerable attention in recent years and is considered a potential alternative to synthetic food additives. EGCG has been shown to prevent the growth of different Gram-positive and Gram-negative bacteria responsible for food spoilage while showing antioxidant activity in food systems. This review focuses on recent findings related to EGCG separation techniques, modification of its structure, mechanisms of antioxidant and antimicrobial activities, and applications in preserving the quality and safety of foods.

Enrichment of Biscuits with Matcha Green Tea Powder: Its Impact on Consumer Acceptability and Acute Metabolic Response

Matcha green tea powder (MGTP) is made with finely ground green tea leaves that are rich in phytochemicals, most particularly catechins. Shortbread biscuits were enriched with MGTP and evaluated for consumer acceptability and potential functional health properties. Baking decreased the content of total catechins by 19% compared to dough, although epimerization increased the amount of (+)-gallocatechin gallate at the expense of other catechins such as (−)-epigallocatechin gallate. Consumer acceptability tests using a 9-point hedonic scale showed that consumers preferred enriched biscuits with low content of MGTP (2 g of MGTP 100 g⁻¹ of flour), and an increase of sugar content did not significantly improve the acceptability of MGTP-enriched biscuits. Overall, enrichment of biscuits with MGTP did not significantly affect the postprandial glucose or triglyceride response (area under curve) compared to non-enriched biscuits consumed with water or MGTP drink. Enriching biscuits with Matcha green tea is acceptable to consumers, but may not bring significant postprandial effects.

Detection of Cistanches Herba (Rou Cong Rong) Medicinal Products Using Species-Specific Nucleotide Signatures

Cistanches Herba is a medicinal plant that has tonification properties and is commonly used in Asia. Owing to the imbalance between supply and demand, adulterants are frequently added for profit. However, there is no regulatory oversight because quality control tools are not sufficient for identifying heavily processed products. Thus, a novel molecular tool based on nucleotide signatures and species-specific primers was developed. The ITS2 regions from 251 Cistanches Herba and adulterant samples were sequenced. On the basis of SNP sites, four nucleotide signatures within 30~37 bp and six species-specific primers were developed, and they were validated by artificial experimental mixtures consisting of six different species and different ratios. This method was also applied to detect 66 Cistanches Herba products on the market, including extracts and Chinese patent medicines. The results demonstrated the utility of nucleotide signatures in identifying adulterants in mixtures. The market study revealed 36.4% adulteration: 19.7% involved adulteration with Cynomorium songaricum or Cistanche sinensis, and 16.7% involved substitution with Cy. songaricum, Ci. sinensis, or Boschniakia rossica. The results also revealed that Cy. songaricum was the most common adulterant in the market. Thus, we recommend the use of species-specific nucleotide signatures for regulating adulteration and verifying the quality assurance of medicinal product supply chains, especially for processed products whose DNA is degraded.

Amorphous Solid Dispersion of Epigallocatechin Gallate for Enhanced Physical Stability and Controlled Release

Epigallocatechin gallate (EGCG) has been recognized as the most prominent green tea extract due to its healthy influences. The high instability and low bioavailability, however, strongly limit its utilization in food and drug industries. This work, for the first time, develops amorphous solid dispersion of EGCG to enhance its bioavailability and physical stability. Four commonly used polymeric excipients are found to be compatible with EGCG in water-dioxane mixtures via a stepwise mixing method aided by vigorous mechanical interference. The dispersions are successfully generated by lyophilization. The physical stability of the dispersions is significantly improved compared to pure amorphous EGCG in stress condition (elevated temperature and relative humidity) and simulated gastrointestinal tract environment. From the drug release tests, one of the dispersions, EGCG-Soluplus^® 50:50 (w/w) shows a dissolution profile that only 50% EGCG is released in the first 20 min, and the remains are slowly released in 24 h. This sustained release profile may open up new possibilities to increase EGCG bioavailability via extending its elimination time in plasma.

Influence of brewing conditions on taste components in Fuding white tea infusions

BACKGROUND

White tea has received increasing attention of late as a result of its sweet taste and health benefits. During the brewing of white tea, many factors may affect the nutritional and sensory quality of the resulting infusions. The present study aimed to investigate the effect of various infusion conditions on the taste components of Fuding white tea, including infusion time, ratio of tea and water, number of brewing steps, and temperature.

RESULTS

Brewing conditions had a strong effect on the taste compound profile and sensory characteristics. The catechin, caffeine, theanine and free amino acid contents generally increased with increasing infusion time and temperature. Conditions comprising an infusion time of 7 min, a brewing temperature of 100 °C, a tea and water ratio of 1:30 or 1:40, and a second brewing step, respectively, were shown to obtain the highest contents of most compounds. Regarding tea sensory evaluation, conditions comprising an infusion time of 3 min, a brewing temperature of 100 °C, a tea and water ratio of 1:50, and a first brewing step, resulted in the highest sensory score for comprehensive behavior of color, aroma and taste.

CONCLUSION

The results of the present study reveal differences in the contents of various taste compounds, including catechins, caffeine, theanine and free amino acids, with respect to different brewing conditions, and sensory scores also varied with brewing conditions. © 2016 Society of Chemical Industry.

Formation and Characterization of Green Tea Extract Loaded Liposomes

Green tea extract was encapsulated into liposomes to enhance bioavailability and stability of catechins by protecting their functional properties simultaneously. Encapsulation was achieved by dispersing 1% (w/v) soy lecithin through high pressure homogenization (microfluidization) and ultrasonication. Effects of homogenization type and pH of the dispersing medium on the physical properties and stability of the liposomes during 1-mo storage period were investigated. Mean particle size, total phenolic content by Folin-Ciocalteu method and antioxidant activity by 2-diphenyl-1-picrylhydrazyl radical scavenging and ferric reducing-antioxidant power methods, and transmission electron microscopy (TEM) experiments were conducted for characterization. Green tea extract loaded liposomes prepared by microfluidization in distilled water were determined as the most stable system which demostrated no significant difference (P > 0.05) on mean particle size, total phenolic content, and antioxidant activity between the first and final day of 1-mo storage time. Additionally, uniform size and shape in TEM images supported the results.

Effect of the type of brewing water on the chemical composition, sensory quality and antioxidant capacity of Chinese teas

The physicochemical characteristics, sensory quality, and antioxidant activity of tea infusions prepared with purified water (PW), mineral water (MW), mountain spring water (MSW), and tap water (TW) from Hangzhou were investigated. The results showed that the taste quality, catechin concentration, and antioxidant capacity of green, oolong, and black tea infusions prepared using MW and TW were significantly lower than those prepared using PW. Extraction of catechins and caffeine was reduced with high-conductivity water, while high pH influenced the stability of catechins. PW and MSW were more suitable for brewing green and oolong teas, while MSW, with low pH and moderate ion concentration, was the most suitable water for brewing black tea. Lowering the pH of mineral water partially improved the taste quality and increased the concentration of catechins in the infusions. These results aid selection of the most appropriate water for brewing Chinese teas.

Ultraviolet B (UVB) Photosensitivities of Tea Catechins and the Relevant Chemical Conversions

Ultraviolet B (UVB) photosensitivities of eight catechins were screened. In both water and ethanol, epicatechin (EC, 575 μM) and catechin (C, 575 μM) exhibited low photostabilities under 6 h UVB radiation with the generation of yellow photoproducts, while other catechins (epigallocatechin gallate, epigallocatechin, epicatechin gallate, gallocatechingallate, gallocatechin, catechin gallate) were relatively UVB-insensitive. Photoisomerization and photolysis were two important UVB-induced reactions to EC whereas photolysis was the dominant reaction for C. The influencing factors of time (2–10 h), solvent (water, ethanol) and substrate concentration (71.875–1150 μM) on UVB-induced chemical conversions of EC and C were investigated, and eight photoproducts were identified through ultra performance liquid chromatography-diode array detection-tandem mass spectrometry (UPLC-DAD-MS/MS) and ¹H nuclear magnetic resonance (¹H-NMR analysis). Photolysis reaction involved two pathways, including radical reaction and photo-induced electron transfer reaction. The 2,2-diphenylpicrylhydrazyl (DPPH) scavenging abilities of eight catechins did not change upon 6 h UVB irradiation. EC and C are photosensitive catechins among eight catechins causing deep color.

Statistical Approaches to Assess the Association between Phenolic Compounds and the in vitro Antioxidant Activity of Camellia sinensis and Ilex paraguariensis Teas

Tea presents a diverse phenolic composition which is responsible for its alleged biological activities, including the in vivo and in vitro antioxidant capacity. It is very usual to find researches applying statistical methods, such as analysis of variances (ANOVA) and linear Pearson correlation coefficients to analyze the strength of correlation between phenolic composition and the in vitro antioxidant activity of teas from Camellia sinensis (green, black, white, oolong, red, and yellow teas) and Ilex paraguariensis (Yerba-mate), which are the most produced and consumed types of teas. However, evidence has shown that these approaches are not as suitable as multivariate statistical methods once they do not depict nor show association among all results and variables simultaneously, making it difficult to understand clearly the data structure and patterns. Then, the objective of this work is to review and explain some univariate/bivariate and multivariate statistical techniques used to assess the association between phenolic compounds and the in vitro antioxidant activity of green, white, black, red, yellow, oolong and Yerba-mate teas. Moreover, this paper provides an overview on some assays used to estimate the in vitro antioxidant capacity of teas.

Spectroscopic fingerprint of tea varieties by surface enhanced Raman spectroscopy

The fingerprinting method is generally performed to determine specific molecules or the behavior of specific molecular bonds in the desired sample content. A novel, robust and simple method based on surface enhanced Raman spectroscopy (SERS) was developed to obtain the full spectrum of tea varieties for detection of the purity of the samples based on the type of processing and cultivation. For this purpose, the fingerprint of seven different varieties of tea samples (herbal tea (rose hip, chamomile, linden, green and sage tea), black tea and earl grey tea) combined with silver colloids was obtained by SERS in the range of 200-2000 cm(-1) with an analysis time of 20 s. Each of the thirty-nine tea samples tested showed its own specific SERS spectra. Principal Component Analysis (PCA) was also applied to separate of each tea variety and different models developed for tea samples including three different models for the herbal teas and two different models for black and earl grey tea samples. Herbal tea samples were separated using mean centering, smoothing and median centering pre-processing steps while baselining and derivatisation pre-processing steps were applied to SERS data of black and earl grey tea. The novel spectroscopic fingerprinting technique combined with PCA is an accurate, rapid and simple methodology for the assessment of tea types based on the type of processing and cultivation differences. This method is proposed as an alternative tool in order to determine the characteristics of tea varieties.

Reduction of hexavalent chromium using epigallocatechin gallate in aqueous solutions: kinetics and mechanism

Green tea polyphenol EGCG was utilized as nontoxic reductant for hexavalent chromium reduction in aqueous solution.

Formulation, characteristics and antiatherogenic bioactivities of CD36-targeted epigallocatechin gallate (EGCG)-loaded nanoparticles

Intimal macrophages are determinant cells for atherosclerotic lesion formation by releasing inflammatory factors and taking up oxidized low-density lipoprotein (oxLDL) via scavenger receptors, primarily the CD36 receptor. (-)-Epigallocatechin-3-gallate (EGCG) has a potential to decrease cholesterol accumulation and inflammatory responses in macrophages. We made EGCG-loaded nanoparticles (Enano) using phosphatidylcholine, kolliphor HS15, alpha-tocopherol acetate and EGCG. 1-(Palmitoyl)-2-(5-keto-6-octene-dioyl) phosphatidylcholine (KOdiA-PC), a CD36-targeted ligand found on oxLDL, was incorporated on the surface of Enano to make ligand-Enano (L-Enano). The objectives of this study are to deliver EGCG to macrophages via CD36-targeted L-Enano and to determine its antiatherogenic bioactivities. The optimized nanoparticles obtained in our study were spherical and around 108 nm in diameter, and had about 10% of EGCG loading capacity and 96% of EGCG encapsulation efficiency. Compared to Enano, CD36-targeted L-Enano had significantly higher binding affinity to and uptake by macrophages at the same pattern as oxLDL. CD36-targeted L-Enano dramatically improved EGCG stability, increased macrophage EGCG content, delivered EGCG to macrophage cytosol and avoided lysosomes. L-Enano significantly decreased macrophage mRNA levels and protein secretion of monocyte chemoattractant protein 1, but did not significantly change macrophage cholesterol content. The innovative CD36-targeted nanoparticles may facilitate targeted delivery of diagnostic, preventive and therapeutic compounds to intimal macrophages for the diagnosis, prevention and treatment of atherosclerosis with enhanced efficacy and decreased side effects.

Optimization and prediction of antioxidant properties of a tea-ginger extract

A response surface approach was used to investigate the effects of temperature, concentration, and time on the antioxidant properties (total flavonoid (TF), total phenol (TP), peroxide scavenging activity (PS), iron chelating activity (IC), DPPH radical-scavenging ability (DPPH), ABTS assay (ABTS)) of aqueous extract of tea-ginger (2:1) powder. Color indices, pH, and redox potential of the tea-ginger powder were also measured and used as independent variables for the prediction of antioxidant properties of the extract using ordinary least square (OLSR), principal component (PCR), and partial least square (PLSR) regression. The R (2) values for TP, TF, ABTS, and PS response surface models were 0.8873, 0.9639, 0.6485, and 0.5721, respectively. The OLSR, PCR, and PLSR were able to provide predictive models for DPPH, TP, and TF of the tea-ginger extract (P < 0.05). The PLSR gave the most parsimonious model with an R (2) of 0.851, 0.736, and 0.905 for DPPH, TP, and TF, respectively.