Abstract
This study aimed to examine the differences between the antioxidant capacity, and the total polyphenol content of the seed of eight different grape varieties. We also attempt to create a functional loaf enriched with grape seed meal. To achieve this goal, 3, 6, and 9% of the grape seed meal were added to the loaves made of bread flour and gluten-free flour mixture, and then the changes in their antioxidant and polyphenol content were examined. Based on the results, there were significant differences between the polyphenol and antioxidant content of grape seed varieties. The antioxidant content of the grape seeds varied between 228.50 mg AAE/g (94.80 mg TE/g) and 438.33 mg AAE/g (181.86 mg TE/g) in case of fatty samples, and between 176.29 mg AAE/g (41.24 mg TE/g) and 424.91 mg AAE/g (99.40 mg TE/g) in case of defatted samples. The total polyphenol content of the fatty samples changed between 91.16 and 221.81 mg GAE/g; in case of defatted samples, it ranged from 46.01 to 207.68 mg GAE/g. Rhine Riesling contained the greatest amount of these compounds. The functionality of loafs was confirmed by spectrophotometric analysis. Total polyphenol content ranged from 0.91 to 3.16 mg GAE/g in case of wheat loafs, and from 1.39 to 5.92 mg GAE/g in case of gluten-free loafs, while the total antioxidant content changed between 0.70 and 6.44 mg AAE/g in case of wheat loafs, and ranged from 2.55 to 9.75 in case of gluten-free loafs.Graphic abstract
Highlights
Many agricultural by-products contain plant parts that are rich in phytochemicals
Grape seeds account for only 5% of the weight of the fruit; 60–70% of the total polyphenol content is concentrated in the seeds (Ribéreau-Gayon et al 2006)
Vázquez-Calvo et al (2017) investigated the antiviral properties of the natural polyphenols against the flaviviruses. They described that the tested polyphenols reduced the risk of infection because they affected the entry of the tested viruses into the host cell
Summary
Many agricultural by-products contain plant parts that are rich in phytochemicals. A good example of this is the many by-products of grape processing, such as pomace, stalk, sediment (fermentation by-product), and grape seeds. The main phenolic compounds found in by-products of grape processing are ( +)—catechin, (−)—epicatechin, quercetin, myricetin, rutin, kaempferol, gallic acid, ellagic acid, siric acid, caffeic acid, and trans-resveratrol (Rubilar et al 2013; Mattos et al 2017). In addition to these compounds, grape marc contains pigments such as anthocyanidins derived from malvidin, peonidine, and cyanidine (Barba et al 2016). They described that the tested polyphenols reduced the risk of infection because they affected the entry of the tested viruses into the host cell
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