Utilization of Kinnow peel for candy production: A study on quality attributes and storage stability

Abstract

Kinnow fruit processing generates millions of tonnes of citrus waste yearly. This waste, predominantly of bitter-tasting peels, contributes significantly to environmental pollution when discarded. In this regard, the present study utilized kinnow peel waste for making candy, aiming to track down the straightforward, easy method of preparing the kinnow peel candies with extended shelf life. Additionally, it compared physical and chemical processes for removing bitterness from peels to create valuable food industry products, minimizing waste and enhancing fruit value, thus promoting food security with beneficial ingredients. In this laboratory investigation, the peel was treated with nine different treatments (T₁: Single boiling, T₂: Multiple boiling, T₃: Soaking in baking soda, T₄: Soaking in Vinegar, T₅: Soaking in Alum, T₆: Boiling in Salt solution, T₇: Boiling in bottle gourd juice, T₈: Boiling in cucumber juice, T₉: Control-No boiling). The resulting product was analysed for proximate, physicochemical, and organoleptic attributes at 15-day intervals for up to 45 days. The results showed an increase in crude fibre content (4.54-4.61 g/100g), total soluble solids (TSS) (75.14-75.40 ⁰B), pH (2.92-3.07 %), reducing sugar (20.17-20.77 %), total solids (86.67-87.07 %), and total sugar (62.84-63.58 %). At the same time, the decrease was recorded in ash content (0.75-0.59 g/100g), moisture content (13.37-12.60 %), titratable acidity (0.43-0.38 %), ascorbic acid content (11.23-8.97mg/100g), tannins (55.90-55.27 mg/100g), antioxidant activity (44.50-40.71 %), total phenolic content (25.43-22.62 mg GAE 100 g−1), carotenoid content (1.39-1.32 mg/100g), and pectin content (1.50-1.34 mg/100g). The best treatment was T₂, which involved multiple boiling, cooking in 75 ⁰B sugar syrup solution, and saturating with sugar syrup for 24 hours. It had desirable proximate, physicochemical and organoleptic properties and was stable for up to a minimum of 45 days for storage.