Abstract/Summary

Melon seeds (Cucumis melo L.), accounting for 5% - 10% of the total melon weight, are regarded as a low value by-product within the melon supply chain, and are often disposed as a waste. However, this by-product holds potential as a source of nutritionally valuable compounds for food applications. To date, there is still insufficient information about valorisation strategies of melon seeds. Therefore, the aim of this study was to assess melon seed potential value and develop valorisation strategies for food applications. Compositional analysis showed that melon seed contains considerable levels of protein (28.4 - 30.4%, w/w), oil (43.5 - 48.3%, w/w), fibre (15.9 - 16.6%, w/w), as well as minerals, especially potassium (988.3 - 1076.6 mg/100 g DW) and magnesium (514.3 - 541.0 mg/100 g DW). Investigating and developing processing technologies are very important as it can reduce food waste and could result to products of good nutritional quality, suitable for human consumption. Melon seeds were processed via three processing methods namely, soaking, boiling, and roasting, to assess its effect on melon seeds nutritional quality. Soaking and boiling methods showed positive effect on reducing tannins content (13% - 20%, 10% - 26%, respectively), whereas roasting showed adverse effects, including increase in tannins (40% - 114%) and phytic acid content (3% - 5%), and decrease in linoleic acid content (approximately 8%). Melon seed oil extraction was investigated using solvent extraction (SE), cold-pressed extraction (CPE), and aqueous enzymatic extraction (AEE) methods. Melon seed oil was identified as a rich source of linoleic acid (C18:2; 53.6% - 70.8%), β-sitosterol (119.5 – 291.9 mg/100 g), and squalene (101.1 - 164.7 mg/100 g). It was seen that the choice of oil extraction technology influenced melon seed oil quality; oil obtained by aqueous enzymatic extraction (AEE) exhibited higher tocopherol content and better oxidative stability as compared to SE and CPE. After oil extraction, the defatted melon seed, as a major by-product of melon seed oil extraction (often referred to as meal/residue), contained considerable as amounts of protein (34.1% w/w) and fibre (35.1% w/w). Subsequently, defatted melon seed was used as ingredient in bread formulations as partial substitute to wheat flour. The addition of defatted melon seed reduced dough strength, made dough softer and weaker, reduced bread specific volume and increased bread hardness. This could be attributed to gluten dilution and increased fibre content which induces greater disruption of the gluten network. In contrast, from a nutritional point, defatted melon seed addition at 10% (w/w) comprehensively improved the nutritional quality of bread that can be labelled as ‘source of fibre’ and could contribute to an increased dietary intake in fibre.