Application of Cucumis melo L. peel flour in bakery products

Cucumis melo L. is a very consumed fruit all over the world because it has excellent sensory and nutritional qualities, being a good source of bioactive compounds for humans. However, the peel and seeds are usually discarded 1,2,3. Food waste is considered a major problem with a direct impact on the economy, society and environment. The valorisation of these by-products could be an advantageous approach to face the increase in food waste since it can compromise the implementation of the concept of food sustainability. On the other hand, this valorisation would allow the development of new food products with beneficial properties for the health of the population. The aim of this study was to develop two formulations based on C. melo L. peel flour and to evaluate their nutritional composition, total phenolic content and antioxidant potential. In 2021, the C. melo L. samples were collected from melon production and distribution companies, located in Torres Vedras and Rio Maior (Portugal). The nutritional composition was analytically determined. The energy value and available carbohydrates were calculated. Antioxidant activity was determined using two different methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and ferric reducing antioxidant power (FRAP). Total phenolic content was also assessed by spectrophotometry and the results were expressed as gallic acid equivalents (GAE). According to the results, dietary fibre and available carbohydrates are the main constituents of the C. melo L. peel flour, 50 and 24 g/100 g, respectively. For DPPH•, 26 mg trolox equivalents/100 g were observed, while for FRAP, the value obtained was 863 mg trolox equivalents/100 g. C. melo L. peel flour presented a content of 249 mg GAE/100 g, for total phenolic compounds. The incorporation of C. melo L. peel flour allowed the development of a biscuit and a muffin with 15 and 13 g/100 g of dietary fibre, respectively. According to Regulation (EC) No 1924/2006 on nutrition and health claims, it is possible to say that the products developed can be considered high in fibre (> 6 g/100 g). In the case of the biscuit developed, the use of C. melo L. peel flour, allowed to have a content of total phenolic compounds of 250 mg GAE/100 g. Concerning the developed muffin, a total phenolic compounds content of 254 mg GAE/100 g, and 23 and 892 mg trolox equivalents/100 g for the DPPH• and FRAP method, respectively, were obtained. In conclusion, C. melo L. peel flour can be considered a good source of dietary fibre and total phenolic compounds, allowing the development of two formulations. The dietary fibre and phenolic compounds contents present in the developed food products can contribute to the valorization of C. melo L. peel flour since it is possible to nutritionally enrich different foods, reduce food waste, reduce the environmental impact and contribute to improving public health.

This work was financially supported by Foundation for Science and Technology (FCT) under the projects Food4DIAB (EXPL/BAA-AGR/1382/2021); and UIDB/50006/2020 and by AgriFood XXI I&D&I project (NORTE-01-0145-FEDER-000041) co-financed by European Regional Development Fund (ERDF), through the NORTE 2020 (Programa Operacional Regional do Norte 2014/2020). Rita C. Alves thanks to FCT the CEECIND/01120/2017 contract.

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