No abstract

The variation of different physicochemical parameters related to yerba maté quality (caffeine, water extract, total polyphenol content, color parameters and antioxidant activity) was studied in yerba maté samples obtained by three different aging methods: (1) natural aging (NA); (2) temperature-controlled aging (TCA); and (3) humidity-and temperature-controlled aging (HTCA). Adsorption isotherms at low temperatures (20, 30, 40 and 50C) were also determined. Water extract and color parameters (L and a) increased significantly during aging in the three methods studied (P < 0.05). The results also showed that during NA the polyphenol content of yerba maté diminished (P < 0.05), while caffeine remained constant (P > 0.05). The antioxidant activities of yerba maté obtained by NA and HTCA were significantly higher (P < 0.05) than the antioxidant activity of yerba maté without aging and the yerba maté obtained by TCA. These variations were explained by 0, 1 and 2 kinetic order equations. Kinetic rate constants were higher in the HTCA than in the TCA, and these values were higher than in the NA according to temperature decrease. Experimental data of equilibrium moisture content at different temperatures showed good fitting (P < 0.05) with the three models tested (GAB, Halsey and Henderson). No significant differences were found either with temperature or with the materials obtained using different aging methods. Although the results obtained demonstrate that different aging methods originate similar products, HTCA method is better because it provides a yerba maté with higher total polyphenol content. PRACTICAL APPLICATIONSAging is one stage in yerba maté (Ilex paraguariensis) processing. There are three methods commonly used to age yerba maté in industry, in which different air conditions (temperature and humidity) are employed. Sensorial analysis, usually carried out by expert tasters, is commonly used to control the aging method and the degree of aging of yerba maté. These tests are subjective and suffer from inconsistency and inaccuracy, so it is necessary to develop objective methods to identify the yerba maté quality, chemically or physically. This work evaluates the variation of different physicochemical parameters during the aging stage of yerba maté in order to differentiate the products obtained using the three aging methods. Data were fitted to different kinetic equations in order to predict the degree of aging and the time necessary to reach the end point. Journal of Food Process Engineering

The aim of this study was to determine the drying kinetics and physicochemical properties of yerba maté obtained using three different alternative manufacturing methods and to compare these products with those of the yerba maté produced using the traditional process. Additionally, triangle tests were performed to establish whether there were sensory differences between the products studied. The assayed alternative manufacturing methods included the following: (a) zapecado using boiling water (BWZ) and (b) zapecado using steam water (SWZ), both followed by a final hot air drying step, and (c) an integral manufacturing method (zapecado + drying) using high‐frequency radiation (HFR). The HFR integral method yielded a product with a higher caffeine content (>30%; p < .05) than that of traditional yerba maté. Furthermore, HFR yerba maté showed significantly higher total polyphenol content values than those of BWZ and SWZ yerba maté (>10%; p < .05). Likewise, the HFR integral method resulted in a yerba maté that was much more similar in color and with imperceptible sensory differences (p > .05) when compared to the traditional product. Practical applications During traditional yerba maté manufacturing, freshly harvested branches of Ilex paraguariensis come into direct contact with combustion gases from the burning of forest biomass. This contributes to the formation of polycyclic aromatic hydrocarbons and their subsequent deposition in yerba maté leaves and stems. Polycyclic aromatic hydrocarbons have been proved to be carcinogenic, in addition to having other toxic effects on humans. The elimination of combustion gases as a direct source of heat in the manufacturing process of yerba maté is an emerging need. The development of alternative manufacturing methods that avoid the contact of the raw material with the products of the incomplete combustion of forest biomass burning and the subsequent implementation of these methods in the industry will guarantee a higher quality product from a food safety point of view.

To determine differences in quality parameters between different types of tea elaborated in Argentina, water extract, crude fibre, caffeine, total polyphenol content, antioxidant activity, sorption isotherms and colour parameters (L, a, b) were determined. Fifty-one industrial samples of commercially available teas including green tea, semifermented tea, black tea and black tea sub-product (BTSP) were used for this study. Water extract contents were significantly higher in black tea and green tea (40.3% and 40.7% w/w, respectively), while semifermented tea and BTSP showed higher levels of crude fibre (22.3% and 20.4% w/w, respectively). Caffeine contents of black teas (2.7% w/w) were significantly higher than in the other types of tea. Green teas revealed the highest concentrations of phenolic compounds and the major antioxidant activities (14.9 g GAE/100g dm and 30.0 g AAE/100g dm, respectively). The results also highlighted significant differences (p<0.05) in colour values between the different types of tea.

To determine differences in quality parameters between different types of tea elaborated in Argentina, water extract, crude fibre, caffeine, total polyphenol content, antioxidant activity, sorption isotherms and colour parameters (L, a, b) were determined. Fifty-one industrial samples of commercially available teas including green tea, semifermented tea, black tea and black tea sub-product (BTSP) were used for this study.Water extract contents were significantly higher in black tea and green tea (40.3% and 40.7% w/w, respectively), while semifermented tea and BTSP showed higher levels of crude fibre (22.3% and 20.4% w/w, respectively). Caffeine contents of black teas (2.7% w/w) were significantly higher than in the other types of tea. Green teas revealed the highest concentrations of phenolic compounds and the major antioxidant activities (14.9 g GAE/100g dm and 30.0 g AAE/100g dm, respectively). The results also highlighted significant differences (p<0.05) in colour values between the different types of tea.