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

Yerba mate infusion is widely consumed in Argentina, Brazil and Paraguay. One of the processing steps used in Argentina is aging. The following three methods were used to age yerba mate: 1) air humidity and temperature-controlled aging; 2) temperature-controlled aging and 3) no control. The aim of this research was to determine the physicochemical and sensory attribute differences when yerba mate was aged using these three methods. The concentration of caffeine, glucose, fructose, maltose and phenolic compounds and pH diminished in all three aging methods but by different percentages. The sensory attributes did not exhibit uniform behaviour. Astringency remained constant in the first method and diminished in the other two. Bitterness increased in all three methods but by different percentages. Sweetness  diminished in all three methods. Notably few correlations were determined between physicochemical and sensory attributes.

Yerba mate infusion is widely consumed in Argentina, Brazil and Paraguay. One of the processing steps used in Argentina is aging. The following three methods were used to age yerba mate: 1) air humidity and temperature-controlled aging; 2) temperature-controlled aging and 3) no control. The aim of this research was to determine the physicochemical and sensory attribute differences when yerba mate was aged using these three methods. The concentration of caffeine, glucose, fructose, maltose and phenolic compounds and pH diminished in all three aging methods but by different percentages. The sensory attributes did not exhibit uniform behaviour. Astringency remained constant in the first method and diminished in the other two. Bitterness increased in all three methods but by different percentages. Sweetness diminished in all three methods. Notably few correlations were determined between physicochemical and sensory attributes.