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Grape Pomace for Tofu Production
Tofu, soybean curd, or bean curd is one of the most important soya products and is produced by the addition of coagulants (acids, salts or enzymes) to soymilk. It is widely consumed in Asia and has been growing in popularity worldwide because of its high nutritional value, good texture, and unique flavour. It has high contents of highly digestible proteins, dietary fibre, soy saponins, and isoflavones that can prevent the progression of arteriosclerosis by reducing plasma lipids. Furthermore, tofu is cholesterol-free and has a lower amount of saturated fat than animal sources of protein, such as meat or milk. Mixing different types of coagulants can potentially overcome the disadvantages of a single coagulant and improve the quality of tofu although research efforts have also explored new coagulants to replace traditional ones. Grape pomace (GP) can be used as a coagulating agent for tofu production. The GP, composed of a mix of grape seeds and skins, corresponds to approximately 62% of the total waste generated during the winemaking process. GPs are partially distilled for ethanol extraction, although most of this by-product is discarded, with several environmental and economic effects. Nevertheless, GPs are rich sources of high-value compounds, such as acids (tartaric, malic, and citric), fibres, polyphenols, and salts, and have been widely suggested as ingredients in pasta, puree, biscuits, yoghurt, cereal bars, pancakes, and cheese. Moreover, distilled GPs are rich sources of high-value compounds, although in contrast to fresh GPs, no applications have been suggested for distilled GPs; therefore, the problem of the disposal of fresh and distilled GPs still needs to be solved, and their use as ingredients in foods facilitates green production and the minimisation of by-product treatment costs, creating new sources of income for grape producers and increasing consumer interest in healthier foods. Furthermore, the addition of grape by-products to foods may represent a novel strategy to produce functional foods with high contents of polyphenols and high antioxidant activity. Since high concentrations of acids and salts are present in GPs, these by-products could act as coagulants for soy proteins. The possibility of their use in tofu production is very good in regard to reducing winemaking waste and obtaining new and innovative functional foods with high contents of polyphenols that are completely produced from vegetables.
Tofu, one of the most important products made from soymilk, is obtained through a coagulation process performed with various coagulants (acids, salts and, enzymes). Innovative tofu samples were produced using the grape pomace (GP) powders of different varieties (Barbera, Chardonnay, Moscato, and Pinot Noir) with different origins (fermented and distilled) at two concentration levels (2.5% and 5% w/v) as coagulants, and comparisons with traditional tofu were made. Physicochemical characteristics, phenolic contents, radical scavenging activity levels, textural properties, and consumer acceptability were evaluated. The moisture, protein content, and pH levels of GP tofu samples were slightly lower than those of traditional tofu. Regarding textural parameters, except for hardness, all other parameters were significantly lower in GP tofu samples, with differences due to GP concentration. The colours of GP tofu varied from amber-yellow to violet according to the GP origin. The blue-violet colours were observed predominantly in tofu samples obtained with Barbera and Pinot Noir GPs, while the other GP tofu samples showed amber-yellow colours. The concentrations of polyphenols were 2–10 times higher than in traditional tofu, while the radical scavenging activity levels were 9–80 times higher. The GP tofu samples were favoured by consumers, with small differences among the GP varieties.
The entry is from 10.3390/foods10081857
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