Evaluation of microbial toxins,trace elements and sensory properties of a high-theabrownins instant Pu-erh tea produced using Aspergillus tubingensis via submerged fermentation

Theabrownins (TB) are polymeric phenolic compounds associated with the multiple bioactivities of Pu-erh tea, a post-fermented Chinese dark tea. High-TB instant Pu-erh tea was produced via a novel submerged fermentation (SF) using Aspergillus tubingensis and compared with samples produced commercially via the conventional solid-state fermentation (SSF). Viable microorganisms and microbial toxins, especially aflatoxins B₁, G₁, B₂, G₂, cyclopiazonic acid, fumonisins B₁, B₂, B₃ and ochratoxin A, were below the detection limit in all samples. Fewer microbial metabolites were found in SF instant tea compared with the SSF teas. Based on an adult consuming 1 g of instant Pu-erh tea daily, the dietary intake of investigated elements was below the safe limits recommended by various authorities. Tasters viewed the instant tea infusions as very mild, smooth, mellow and full. This suggested that submerged fermentation using A. tubingensis offers a speedy and safe alternative to commercial production of instant Pu-erh tea.     

Comparative study of commercially available cocoa products in terms of their bioactive composition

Recent trends in food marketing suggest that cocoa products, besides being favourite sweets among consumers, also present multiple-benefit foodstuffs, which are becoming objects of increased scientific research, mainly because of their interesting phytochemical composition. UV/VIS spectrophotometric and high-performance liquid chromatography (HPLC-PDA) methods were applied in order to compare the composition of polyphenols and methylxanthines in commercial cocoa products affected by different extraction solvents. Antioxidant capacity of water and methanol extracts was evaluated using DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) and FRAP (ferric reducing/antioxidant power) assays. The obtained results confirmed that the content of polyphenols and methylxanthines, as well as the antioxidant capacity of cocoa products depend on the content of their cocoa solids. Among the tested cocoa products, the highest content of bioactive compounds (polyphenols and methylxanthines) was determined in extracts of cocoa products with the highest content of cocoa solids (cocoa liquor, cocoa powder and dark chocolate with 88% cocoa solids), while the lowest content was determined in milk chocolate and cocoa bar extracts. The most abundant phenolic compound in cocoa extracts was (?)-epicatechin, while the most abundant methylxanthine was theobromine. In comparison with water, 70% methanol demonstrated higher efficiency for the extraction of the studied bioactive compounds from cocoa products.     

Chemometric evaluation of binary mixtures of alginate and polysaccharide biopolymers as carriers for microencapsulation of green tea polyphenols

In this study principal component analysis and artificial neural networks were used to evaluate the potential of using binary mixtures of sodium alginate and other polysaccharide biopolymers as the carriers for microencapsulation of green tea bioactive compounds. Using binary mixtures of alginate and adjunct biopolymers increased the particle size (from 722 to 1344 µm) and textural parameters of the microbeads. Chemometric techniques revealed the combination of biopolymers and their ratio as the main factors influencing the encapsulation performance. The combination of alginate with hydroxypropyl methylcellulose and locust bean gum enabled to retain the highest (-)-epigallocatechin gallate and caffeine contents, the highest total phenols encapsulation efficiency, and their most retarded release in water, confirming these as the best delivery systems of polyphenol-type active compounds and signifying their potent food applications.     

Encapsulation of thyme (Thymus serpyllum L.) aqueous extract in calcium alginate beads

BACKGROUND: Encapsulation of Thymus serpyllum L. aqueous extract within calcium alginate beads was studied in order to produce dosage formulations containing polyphenolic compounds. Electrostatic extrusion was applied for encapsulation of thyme aqueous extract in alginate gel beads. In addition to hydrogel beads, heat‐dried and freeze‐dried forms of beads were examined. METHODS: Encapsulation systems were examined and compared in order to choose the optimal one with respect to entrapment efficiency, preservation of antioxidant activity and thermal behaviour under heating conditions simulating the usual food processing. RESULTS: The beads obtained with approximately 2 mg g^?1 of gallic acid equivalents encapsulated in 0.015 g mL^?1 of alginate were spheres of a uniform size of about 730 µm. Encapsulation efficiency varied in the range 50‐80% depending on the encapsulation method. Besides, the analysis reveals that the encapsulation process and the material used did not degrade the bioactive compounds, as the total antioxidant content remained unchanged. This was verified by Fourier transform infrared analysis, which proved the absence of chemical interactions between extracted compounds and alginate. Addition of a filler substance, such as sucrose and inulin, in the dried product reduced its collapse and roundness distortion during drying process. CONCLUSION: This study demonstrates the potential of using hydrogel material for encapsulation of plant poplyphenols to improve their functionality and stability in food products. Copyright © 2011 Society of Chemical Industry     

Characterization of odor-active compounds in Croatian Rhine Riesling wine, subregion Zagorje

The aroma of Rhine Riesling must and wine was studied to determine the most intense odor-active compounds. The study was carried out using a special designed method of gas chromatography-olfactometry (GCO) to detect characteristic odorants, which were identified by GC-MS. Generally, the obtained results showed higher odor intensities for the wine than for the must samples. The aroma substances 2-phenylethanol, 3-methyl-1-butanol, 3-(methylthio)-1-propanol, ethyl propanoate, ethyl butanoate, ethyl 3-methylbutanoate, 3-methyl-1-butanol acetate, ethyl hexanoate, ethyl octanoate, ethyl 3-hydroxybutanoate, 2-phenylethyl acetate, hexanoic acid, 3-methylbutanoic acid, butanoic acid, β-damascenone, γ-undecalactone and 4-vinylguaiacol were detected as the most active odorants in the Rhine Riesling wine. The aroma of Rhine Riesling must was characterized by 2-ethyl-1-hexanol, (E)-2-penten-1-ol, 1-terpinen-4-ol, benzyl alcohol, 2-phenylethanol, α-terpineol, d-limonene, β-damascenone, 3-methylbutanoic acid and benzeneacetaldehyde.     

Comparative study of polyphenols and caffeine in different coffee varieties affected by the degree of roasting

The bioactive composition of coffee, as one of the most popular beverages in the world, has attracted interest as a potential source of beneficial bioactive compounds, especially polyphenols and caffeine. Since the content of these compounds is affected by the processing conditions, the objective of this study was to determine the content of polyphenolic compounds and caffeine in four different coffee varieties: Minas and Cioccolatato (Coffea arabica), and Cherry and Vietnam (Coffea canephora syn. Coffea robusta), roasted by three varying degrees (light, medium and dark). The content of the polyphenolic compounds and the antioxidant capacity of coffees were determined using UV/Vis spectrophotometric methods, while the content of chlorogenic acid derivatives was determined using HPLC analysis. The caffeine content was determined by means of two spectrophotometric methods, as well as HPLC analysis. Additionally, raw caffeine was also obtained by an isolation procedure with chloroform. Cherry coffee, a variety of C. canephora exhibited the highest overall content of total phenols (42.37 mg GAE/g), followed by Minas coffee, while Cioccolatato contained the lowest TPC (33.12 mg GAE/g). Cherry coffee also exhibited the highest content of individual classes of polyphenols (flavan-3-ols, procyanidins and tannins), while the highest content of chlorogenic acid (CQA) derivatives was determined in Minas and Cioccolatato coffees (C. arabica). The highest content of total and individual polyphenolic compounds was determined in coffees roasted in both light and medium roasting conditions, which was also observed for the content of CQA derivatives and antioxidant capacity of roasted coffees. The highest caffeine content in the coffee samples was determined by employing the HPLC analysis (0.06–2.55%). Light roasted Cherry coffee contained the highest overall content of caffeine among all coffees, which exhibited a decrease with intensified roasting.     

Phenolic content and antioxidative capacity of green and white tea extracts depending on extraction conditions and the solvent used

The efficiencies of different solvents in the extraction of phenolics from bagged and loose leaves of white and green tea, after different extraction times, as well as the antioxidative capacity of the obtained extracts, were investigated. The developed HPLC method has the potential to separate and determinate 17 phenolics widely distributed in plants, but in investigated tea extracts only four catechins and traces of three flavonols and one flavone were separated and detected based on comparison with authentic standards. The extraction efficiency of phenolics depended strongly on the time of extraction and the solvents used. The extraction of catechins from green tea was significantly affected by the form (bagged or loose) of the tea, whereas this effect was shown not to be statistically significant for white tea. Green tea was a richer source of phenolics than was white tea. The extraction of phenolics from white tea by water could be accelerated by the addition of lemon juice. Aqueous ethanol (40%) was most effective in the prolonged extraction of catechins. The antioxidative capacity of the investigated tea extracts correlated with their phenolic content.     

Comparative study of cytotoxic and cytoprotective activities of cocoa products affected by their cocoa solids content and bioactive composition

Polyphenolic profile and antioxidant properties of water extracts of milk, semisweet and dark chocolates, as well as cocoa liquor, were determined and examined for potential biological activity. Non-fat cocoa solids (NFCS), phenolic compounds content and the antioxidant capacity of cocoa product extracts were determined using UV/Vis spectrophotometric methods and HPLC analysis. The increase in NFCS was consistent with the increase in polyphenol content and antioxidant properties. Methylxanthines, theobromine and caffeine constituted the most abundant bioactive compounds, followed by flavan-3-ols epicatechin and procyanidin B2. Cytotoxic and antioxidative/prooxidative effects of cocoa product extracts were determined on human laryngeal carcinoma cell line (HEp2). Cocoa liquor containing the highest NFCS exhibited the lowest HEp2 cell viability, while milk chocolate characterized by the lowest NFCS exhibited no cytotoxic effect. Experiments revealed a strong relationship between the type of product/concentration/time of exposure and antioxidant/prooxidant character of cocoa products. Lower concentrations of semisweet, dark chocolate and cocoa liquor induced an increase in ROS formation, while the higher concentrations resulted in a decrease in ROS formation when compared with control (growth medium). Principal component analysis of the obtained results revealed specific grouping of samples (milk chocolate and cocoa liquor), while the observed dispersions indicated that the outcome of cytotoxic and cytoprotective activities of cocoa products are greatly affected by their concentration.