Waste grape skins: evaluation of safety aspects for the production of functional powders and extracts for the food sector

Abstract

Skin powders and aqueous alcohol extracts were obtained from waste marcs from different grape varieties (Barbera, Nebbiolo, Pinot Noir, Chardonnay, Moscato and Müller-Thurgau). Both skins and extracts were analysed for the content of chemical contaminants: ochratoxin A (OTA), biogenic amines (BIAs), pesticides and metals. OTA was detected in low concentrations in Barbera, Moscato and Nebbiolo skins, but only in Barbera and Moscato extracts. Cadaverine, putrescine, ethanolamine and ethylamine were found in extracts at very low levels, while potential allergenic amines, tyramine and histamine, were never detected. Different pesticides were present in both skins and extracts. Pb and Cd were found in trace only in the powders, and K, Ca and Mg were the most abundant elements in both skin powders and extracts. Concentrations of the different contaminants were related to fibre content or total phenolics content of powders and extracts, respectively, in order to evaluate their use in the food sector.

Content and bioavailability of trace elements and nutrients in grape pomace

“…Regarding major elements, K was the most abundant in all samples, with content ranging from 23.7 to 47.9 mg g −1 for skins and from 5.67 to 11.7 mg g −1 for seeds, the significantly higher values corresponding to the skins of red varieties (Sousón and Mencía) ( P < 0.001) compared to the other samples, with the exception of undistilled skins for Treixadura. This elevated K content in winery residues agreed with other values previously published for similar samples, and could be attributed to the use of this macronutrient in viticulture together with the possible utilization of potassium bitartrate in the vinification process . Considering seeds, in the present work Treixadura white and Mencía red varieties were also richer in K ( P < 0.001).…”

“…Mn and Zn were the least abundant micronutrients in all of the samples studied. Low Mn and Zn content with respect to the other micronutrients was also found in other studies on waste grape skins . In the present work, total Mn contents were always lower than 91.3 and 74.3 μg g −1 in skins and seeds, respectively (Tables and ).…”

“…Low Mn and Zn content with respect to the other micronutrients was also found in other studies on waste grape skins. 19 In the present work, total Mn contents were always lower than 91.3 and 74.3 μg g −1 in skins and seeds, respectively (Tables 1 and 2). The highest Mn values were found in all samples of the Mencía red variety.…”

“…The Mg content was always lower than 1.73 mg g −1 for both skins and seeds (Tables and ) and, in contrast to K, the values in skins for red varieties (Sousón and Mencía) were significantly lower than those obtained for white varieties ( P < 0.001). This relative distribution of macronutrients is consistent with that found in other similar residues from the winery and distillery industries …”

“…This relative distribution of macronutrients is consistent with that found in other similar residues from the winery and distillery industries. 8,19 Regarding micronutrients, Cu and Fe were the most abundant elements in skins (Table 1) and Fe was the most abundant element in seeds (Table 2). Higher Fe content was also found than other micronutrients in grape seeds of Turkish grape varieties.…”