Fruit rind and peel as sources of dietary fibre and fibre -enriched product

Abstract

Waste valorization in the agro-processing industries is a vital strategy for enhancing sustainability and reducing environmental impacts. The agro-processing sector generates significant amounts of by-products and waste, containing beneficial nutrients and bioactive compounds, that can be repurposed into high-value products. One such by-product is fruit rinds and peels, rich in dietary fibre and bioactive compounds with potential health benefits. Dietary fibre, aids in digestion, regulates blood sugar levels and lowers cholesterol. The peels also contain antioxidants, vitamins, and minerals, providing anti-inflammatory and antimicrobial properties that support overall health. Hence, these by-products, commonly discarded can be transformed into functional ingredients to enhance the nutritional quality of food products. In this context, the present study entitled “Fruit rind and peel as sources of dietary fibre and fibre-enriched product” carried out in the Department of Postharvest Management, College of Agriculture, Vellanikkara, evaluated the dietary fibre content of selected fruit rinds and peels (banana, pineapple, jackfruit, and mangosteen) and explored their potential application in product development. Rinds and peels of ripe banana, pineapple, jackfruit, and mangosteen were collected from college orchards and processing units. Yield recovery of collected rinds/peels was estimated and proximate analyses were performed on a dry weight basis to determine moisture, ash, crude fat, crude fibre, crude protein, total carbohydrates, and energy content. The fresh rinds and peels of selected fruits after suitable pretreatments were processed into powder, and a comprehensive analysis was conducted to assess their physical, biochemical, and functional properties. These included parameters such as the colour of the powder, total dietary fibre (TDF), soluble dietary fibre (SDF), insoluble dietary fibre (IDF), lignin, cellulose, hemicellulose, pectin, antioxidant activity, and total phenolic content, as well as functional properties like water holding capacity (WHC), oil holding capacity (OHC), swelling power, solubility, and bulk density. The results showed that jackfruit rind had the highest yield recovery at 59.06%. In proximate composition, jackfruit rind had the highest moisture content (8.85%), while mangosteen rind had the highest levels of ash (9.57%), crude fat (8.48%), and crude fibre content (21.12%). Pineapple peel recorded the highest total carbohydrate (67.70%), crude protein (5.90%), and energy value (315.37 kcal). According to the Royal Horticultural Society (RHS) colour chart, banana peel powder (BPP) exhibited a greyish brown (RHS 166A), while pineapple peel powder (PPP) was characterized by moderate yellow (RHS 162B). Jackfruit rind powder (JRP) displayed a pale greenish yellow (RHS 1D), and mangosteen rind powder (MRP) showed a light orange (RHS 26C) hue. Among the biochemical parameters, JRP exhibited the highest TDF (44.90 g/100g), IDF (37.60 g/100g), and pectin content (11.37%). BPP was notable for having the highest SDF content (11.30 g/100g) and antioxidant activity (3.14 µg/ml) while MRP demonstrated the highest lignin (32.73%) and total phenolic content (65.47 mg/g). Regarding the functional properties, JRP had the highest swelling power (6.17) and OHC (1 ml/g), while BPP exhibited the greatest WHC (5.89 ml/g). MRP showed the highest solubility (19.12%) and bulk density values (0.67 g/cm3). Additionally, the levels of antinutritional factors such as oxalates, phytic acid, and tannic acid were within safe limits, making these peels suitable for consumption in functional food products. Based on its high TDF content, JRP was selected for incorporation into a fibre enriched porridge mix. The porridge was standardized through a trial-and-error approach, with banana flour as the base material, and moong dal powder, peanut powder, milk powder, soy protein, and sugar were added at various proportions. The standardized porridge was then enriched with JRP at concentrations of 2%, 4%, 6%, 8%, and 10%and sensory evaluation was conducted using a 9-point hedonic scale. The porridge incorporated with 4% JRP (T3) was the most acceptable regarding taste, texture, and overall acceptability. Nutritional analysis of the control porridge and the 4% JRP-enriched porridge (T3) revealed that the latter had significantly higher levels of TDF, crude fibre, total minerals, and energy value while the starch and sugar content was reduced. The current study demonstrated the potential of using fruit rinds, particularly jackfruit rind, as a valuable source of dietary fibre for developing nutrient dense food products. Incorporating JRP into the porridge mix enhanced its nutritional profile, and supported industrial waste, this sustainable food consumption practices. By valorizing agro research offered a pathway to reduce food waste, increase resource efficiency, and contribute to a circular economy in the agro-processing sector