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Valorisation of Fruit and Vegetable Waste

Vidisha Tomer1*, Ashwani Kumar2, Navnidhi Chhikara3 and Anil Panghal4

1VIT School of Agricultural Innovations and Advanced Learning, Vellore Institute of Technology, Vellore, Tamil Nadu, India

2Rani Lakshmibai Central Agricultural University, Jhansi, Uttar Pradesh, India

3Department of Food Technology, Guru Jambheshwar University of Science and Technology, Hisar, Haryana, India

4Department of Processing and Food Engineering, AICRP-PHET, Chaudhary Charan Singh Haryana Agricultural University, Hisar, India

Abstract

The ever-increasing global population indicates that food demand will rise for at least another forty years, which will exert immense pressure on our limited natural resources. Hence, wise use of available resources, maximum utilization of available food and minimization of food waste is crucial. Due to their perishable nature, the highest wastage of food occurs in the fruit and vegetable sector, which is approximated to about 30-44%. The fruits contain various unused parts like peel, seed and pomace which sometimes may account for approximately half of the fruit, e.g., pineapple, mango. These components are rich in sugars, pectin, fats, cellulose, hemicelluloses, minerals, and vitamins, which in some cases are richer than the fruit itself. This can be bio-converted into useful products such as acids, alcohols (bioethanol), enzymes, fuels, and value-added products. The seeds and pits can also be used for the extraction of edible grade oils. This chapter introduces and summarises the methods by which fruit and vegetables have been valorised into useful products.

Keywords: Pigments, essential oil, nutraceuticals, bioactive compounds, phytochemicals

1.1 Introduction

With increasing population, the quantity of food required is also increasing, which exerts immense pressure on our natural production mechanisms (Panghal et al., 2021). In addition, it also becomes a source of generation of additional food waste. Trends indicate food demand will rise for at least another forty years. Hence, wise use of available resources, maximum utilization of available food and minimization of food waste is crucial. As per the Food and Agriculture Organization, food loss is "a decrease in quality and quantity of food" (Diaconeasa et al., 2023). Food waste can occur at any step of the supply chain. In the fruit and vegetable processing industries the major waste is generated through the left over and inedible parts of fruits and vegetables. This adds burden on the waste management systems, exacerbates food insecurity and is the biggest source of greenhouse emission. According to the Food Waste Index Report 2021, the food service industry produces 931 million tonnes of waste each year and a large chunk of this (570 million tonnes) is generated at the household level (United Nations Environment Programme, 2021). One-third of the total food produced is wasted and this is estimated to be worth one trillion USD. As per the reports of United Nations Environment Program Publications, the highest wastage of food occurs in the fruit and vegetable sector, which is approximated to about 30-44% (Barrera and Hertel, 2021; Cronjé et al., 2018).

India is the second-largest producer of fruits and vegetables in the world and the food processing sector has been growing at an Average Annual Growth Rate (AAGR) of 10%. However, the postharvest losses are still high and almost 30-40% of fruits and vegetables in the country go to waste (National Herald, 2021). According to the Annual Report 2020-21, published by Ministry of Food Industries, the postharvest losses of major agricultural produce at national level was 92,651 crore Indian Rupees calculated using production data of 2012-13 at 2014 whole sale prices (MOFPI, 2021). The major waste generated from fruit and vegetables is in the form of peels, seeds and pits. For example, apples contain 10.9% as seed, pulp and peel as by-products. Minimal processing treatments like dicing produces only 53% of the fruit as final product and the rest is waste in the form of peel, seed and unusable pulp. Similarly, pineapple processing produces approximately 50% of waste in the form of peel, core, top and pulp (14, 9, 15, 15% respectively). In mango as well, only 58% of the fruit is utilised. Figure 1.1 summarises the waste generated from different fruits and vegetables. The fruit and vegetable juice industry produces around 5 MMT of solid waste and the canning and frozen food industry is responsible for almost an equal amount of waste generation (Sagar et al., 2018). Waste is a big environmental burden.

Currently, fruit and vegetable waste is managed either by incineration or by landfill, owing to its biodegradable nature. The process of incineration results in gradual production and ejection of various primary and secondary compounds which may act as pollutants like gases, acids, etc. Inadequate landfill management leads to release of gases like methane, carbon dioxide, etc., which may impose not just environmental damage but also health risks (Sindhu et al., 2019; Rifna et al., 2021). In addition, this so-called waste is rich in sugars, pectin, fats, cellulose, hemicelluloses, minerals, and vitamins. This can be bio-converted into useful products such as acids, alcohols (bioethanol), enzymes, fuels, and value-added products (Verma and Kumar, 2020). The seeds and pits can also be used for the extraction of edible grade oils. This chapter introduces and summarises the methods by which fruit and vegetables have been valorised to something useful.

Figure 1.1 Waste generated from various fruits and vegetables (Modified from Dalal et al., 2020).

1.2 Valorisation of By-Products from Fruit and Vegetable Processing Industry

Valorisation of waste can be a key not only for better utilization but also for reducing the environmental burden. The by-products obtained from the industry can be transformed into various useful end products like ethanol, enzymes, nutraceuticals, etc. (Figure 1.2). This section deals with the products that fruit and vegetable waste and by-products can be transformed into.

1.2.1 Oil

The seeds of the fruits, especially the stone fruits like mango (Mangifera indica), peach, apricot, and avocado, etc., can be used for the extraction of oil. The yield of the oil varies with the particle size, volume of solvent, temperature and time of extraction. Yadav et al. (2017) reported that the highest yield (15.20%) of oil from the kernels of mango stone (25 g sample extracted with 250 ml n-hexane) can be obtained at a particle size of 1 mm and extraction time of 90 minutes. Karunannithi et al. (2015) optimized soxhlet solvent extraction process for the extraction of mango seed kernel oil using n-hexane. It was found in the study that minimum solvent requirement and time for the extraction of 20 g of mango seed kernel at 40-70 °C was 200 ml, and 3 hours, respectively. The extraction rate of the oil under these conditions was 12%. The composition of mango seed kernel oil is very similar to cocoa butter except the iodine value is higher in mango seed kernel oil than in cocoa butter. The specific gravity of oil is 0.912, refractive index is 1.46, saponification value is 187.7, iodine value is 49.4 and acid value is 1.93 (Moharram and Moustafa, 1982). The stearic acid, oleic acid, linoleic acid and palmitic acid content of mango seed kernel oil is 58.08%, 17.99%, 2.86%, and 1.33%, respectively. The oil is edible and has lower free fatty acids, carotenoid content and peroxidase value and is generally used without any processing. The melting point of oil is 32-36°C and is solid at room temperature. Mango kernel oil is also high in unsaponifiable matter and is extensively used in the cosmetic industry (Yadav et al., 2017). Wu et al. (2011) optimized the extraction process of peach kernel oil using different solvents, i.e., petroleum ether, ethyl ether, chloroform and hexane. The oil extracted with hexane was found to have the highest overall acceptability. The oil is edible and has a high level of unsaturated fatty acids (91.27%). The major fatty acids in peach kernel oil are oleic acid (61.87%), and linoleic acid (29.07%). The acid, peroxide, iodine and saponification values of oil were 0.895 mg KOH/g, 0.916 mg/g, 36.328 mg/g and 101.836 mg KOH/g, respectively. It was also found to have high phenolic compounds (4.1593 mg GAE/g).

Figure 1.2 Valorisation of fruit and vegetable waste.

Savic et al. (2020) optimized the soxhlet extraction process for the extraction of plum seed kernel oil using various solvents, i.e., n-hexane, n-heptane, ethyl acetate, acetone or a mixture of chloroform and ethanol (2:1 v/v). Among the various solvents, the highest oil yield was obtained for n-heptane (30.5%) and n-hexane (30%), while the lowest yield was obtained for ethyl acetate (23.5%). The obtained oil had a density varying from 0.50-1.10 g/mL (varied according to the solvent used), refractive index of 1.47, viscosity of 135.40-183.20 mPas, pH of 3.43-4.63, acid value of 1.41-2.81 mg KOH/g, saponification value of 180-198 mg KOH/g and peroxide value of 1.82-3.75. Plum kernel oil is also rich in unsaturated fatty acids (oleic acid, 52-66%, linoleic acid, 28-35%, a-linoleic acid, 0.2%) and the content of saturated fatty acids is very low (5.8-11.3%). This oil is also rich...