Influence of pH and ionic strength on the color parameters and antioxidant properties of an ethanolic red grape marc extract

Abstract

The aim of present study was to investigate the influences of pH and several salts on the antioxidant activity and color of an ethanolic grape marc extract. Furthermore, the phenolic content of the extract was analyzed using HPLC and spectrophotometric methods while the total antioxidant activity was assessed by the reaction with ABTS radical. Gallic acid, procyanidins B1, B2, polydatin, catechin, epicatechin, hyperoside, ferulic, chlorogenic, and salicylic acids were among the main identified polyphenols. Different pH values had slight influence on the antioxidant activity, the highest value being determined for pH 3.7. The redness, chroma, and hue were significantly enhanced at pH 3.7 and 2.6. The chromaticity decreased at pH = 5.5 and pH = 7.4, so the extract should be used with care in products with such media. The presence of salts did not noticeably affect the antioxidant activity, except the higher concentrations of CaCl2, which decreased the antioxidant activity but enhanced the color intensity. Practical application The data presented in this paper could be used for the development of a new food dye with antioxidant properties of natural origin. The optimal medium conditions (i.e., pH and ionic strength) for the use of an ethanolic red grape marc extract have been identified. The information could be used in product development and product formulation, especially when functional foodstuffs are envisaged. Consequently, this paper would be of significant interest for food chemists, food technologists, food manufacturers, and especially manufacturers of food dyes and all those using natural substances in their production process.

Rose Hips, a Valuable Source of Antioxidants to Improve Gingerbread Characteristics

“…The most drastic decrease was observed in the extract containing CaCl 2 at 0.1 M concentration. Calcium chloride also decreased the antioxidant activities of grape marc, chokeberry and red cabbage extracts in previous studies [21,22,32].…”

“…Driven by the consumer demand, companies in the United States of America are also starting to look at natural colorants. Natural food dyes are required in the production of dairy products, The same relatively high difference between the results obtained by the two methods was observed and reported in the case of other plant materials, specifically grape marc [21], chokeberry (Aronia melanocarpa) [22], and sea buckthorn (Hippophae rhamnoides) [23]. The specific interferences of the Folin-Ciocalteu method, which basically measures the reducing potential in solution, are the main cause of such discrepancies.…”

“…Given that the mechanism of the antioxidant activity of radical elimination of the neutral form of hydroxyflavones is generally considered to be the donation of hydrogen ions, this implies not only the ease of radical elimination, but also changes in the mechanism of the antioxidant action in deprotonation. Respectively, a decrease in the antioxidant activity is observed when the pH shifts to acidic values [21,22] (Table 3). Only the most acidic and the most alkaline tested values of pH, namely pH = 2.5 and pH = 8.7, produced a statistically significant effect on the antioxidant activity by decreasing it by around 10 mmol TE/L and 9 mmol TE/L, respectively.…”

Potential Application of Hippophae Rhamnoides in Wheat Bread Production

“…The content of individual phenolics was analyzed using the Agilent 1100 Series HPLC following the method described by Cristea et al [44].…”

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“…Acrylonitrile butadiene styrene (ABS) resins have attracted considerable attention due to their superior mechanical properties [1], heat resistance [2], chemical resistance [3], recyclability [4][5][6] and ease of processing [7,8], and are widely used in telecommunications, automotive industry, consumer markets and business machines [9,10]. However, ABS is easily excited by the heat [11,12], light [13][14][15], oxygen [16,17] and other conditions during its processing [18,19], leading to aging degradations of the material. Because the presence of unstable carbon-carbon double bonds in the butadiene microstructure generates macromolecular-active radicals during processing, thermal degradation is promoted and results in a rapid yellowing and brittleness of ABS [20,21].…”