Nutraceutical Potential of Fruit and Vegetable Waste

Nutraceuticals are products derived from foods or food components that are formulated to enhance health and address specific nutritional requirements. The term “nutraceutical” was first coined in 1989 by Dr. Stephen De Felice, integrating the concepts of “nutrition” and “pharmaceutical.”[1]  These products encompass whole foods, fortified foods, dietary supplements, and isolated bioactive compounds that provide benefits extending beyond basic nutritional functions. In addition to supporting general well-being, nutraceuticals have been widely investigated for their potential role in the prevention and management of various chronic diseases. Their increasing acceptance among consumers is largely attributed to the perception that they offer therapeutic advantages while maintaining a favorable safety profile compared to synthetic drugs.[2]

Fruits and vegetables constitute fundamental components of a balanced and health-promoting diet due to their rich supply of essential vitamins, minerals, dietary fiber, and diverse phytochemicals. In response to global population growth, urbanization, and evolving dietary patterns that emphasize plant-based nutrition, the production of fruits and vegetables has expanded considerably. By 2017, global output had reached approximately 0.9 billion tons of fruits and more than 1 billion tons of vegetables.[3]  Despite their nutritional importance and widespread consumption, substantial quantities are lost or wasted during harvesting, post-harvest handling, industrial processing, distribution, and household consumption. Both edible and inedible fractions are frequently discarded, leading to significant environmental burdens and economic losses. It is estimated that the fruit processing sector alone generates over 0.5 billion tons of waste annually.[3,4]

Although vegetable waste is biodegradable in nature, it is often disposed of in open dumping sites and landfills without appropriate treatment. During decomposition, organic waste emits unpleasant odors, attracts disease vectors such as rodents and insects, and produces methane—a potent greenhouse gas that contributes to climate change. Furthermore, leachates generated from decomposing biomass may contaminate soil and groundwater resources, posing risks to ecosystems and public health. These environmental consequences underscore the urgent need for improved waste management strategies [5].

Accordingly, the sustainable management and valorization of fruit and vegetable by-products have emerged as critical areas of research and industrial innovation. Processing residues such as peels, seeds, skins, and pomace are increasingly recognized as valuable sources of bioactive compounds, including polyphenols, flavonoids, carotenoids, and dietary fibers. The recovery and utilization of these compounds offer an opportunity to transform waste streams into functional ingredients with potential health benefits. This review synthesizes current research on the sustainable valorization of fruit and vegetable by-products, with particular emphasis on extraction techniques, nutraceutical applications, and the integration of circular economy principles. By linking waste management strategies with health-oriented product development, it highlights a pathway toward environmental sustainability and improved public health outcomes.[4]

BIOACTIVE COMPOUNDS IN FRUIT AND VEGETABLE WASTE

Banana fruit waste

Banana (Musa spp.) is among the most widely cultivated and consumed fruits worldwide, valued for its high nutritional content and broad consumer acceptance. It is predominantly grown in tropical and subtropical regions, where it serves as both a staple food and a commercially important horticultural crop. Although bananas are primarily consumed fresh, they are also extensively processed into a variety of products, including dried slices, chips, ice cream, smoothies, bakery products, flour, wine, and ingredients incorporated into functional food formulations.[6]

Over the past two decades, global banana production has expanded considerably, reflecting rising demand and improvements in agricultural practices. Average annual production increased from approximately 69 million tons during 2000–2002 to about 116 million tons in 2017–2019, with India emerging as the leading producer at nearly 32 million metric tons annually. This substantial production volume inevitably results in the generation of significant quantities of by-products. The banana peel, which constitutes up to 35% of the total fruit weight, represents the principal waste fraction. Consequently, an estimated 36 million tons of banana peel are produced each year worldwide. Despite its potential value, the majority of this biomass is discarded in landfills or disposed of alongside municipal solid waste.[7]

In recent years, growing scientific interest has focused on the nutritional and phytochemical composition of banana peels. These by-products are rich in micronutrients and possess considerable antioxidant capacity, largely attributed to the presence of phenolic compounds such as catechin and gallocatechin, as well as dopamine. Additionally, banana peels contain diverse classes of bioactive constituents, including terpenoids, alkaloids, flavonoids, tannins, and phlobatannins. Experimental studies have demonstrated that these compounds exhibit a range of biological activities, including antilithic, antiulcerogenic, antidiarrheal, hypoglycemic, and hypolipidemic effects.[8]

Taken together, the compositional richness and biofunctional properties of banana peel highlight its potential as a sustainable raw material for nutraceutical and functional food applications, thereby transforming an underutilized agricultural residue into a value-added health-promoting ingredient.

Citrus fruit waste

Citrus fruits represent one of the most economically and nutritionally significant horticultural crops cultivated globally. Belonging to the family Rutaceae and classified under the genus Citrus L., these fruits are predominantly grown in tropical and subtropical regions, with annual global production exceeding 100 million tons. Citrus fruits are widely appreciated for their characteristic flavor, aroma, and vibrant coloration, and they constitute an integral component of daily diets across many cultures. In addition to their sensory appeal, they are recognized for their rich nutritional profile and associated health-promoting properties. Commonly cultivated varieties include oranges, lemons, grapefruits, mandarins, and limes.[9]

With the steady increase in consumer demand for fresh fruit and processed citrus-based products, global production has continued to expand. A substantial proportion of harvested citrus fruits is industrially processed into juices, concentrates, and flavored beverages. However, this processing generates considerable quantities of by-products, including peels, seeds, pulp residues, and pomace. Notably, citrus peels alone account for nearly 50% of the total fresh weight of the fruit, making them the principal component of citrus processing waste.[10]

Scientific investigations have demonstrated that citrus peels contain significantly higher concentrations of bioactive compounds than the edible pulp. These include phenolic compounds, flavonoids, vitamin C, essential oils, and other antioxidant constituents. The abundance of polyphenols and related phytochemicals in citrus waste contributes to a wide spectrum of biological activities, such as antioxidant, anti-inflammatory, anti-aging, antidiabetic, anticancer, anti-allergic, neuroprotective, and cardioprotective effects.[11]

Given their rich phytochemical composition and documented biofunctional properties, citrus processing by-products represent a highly promising and sustainable source of nutraceutical ingredients. Their valorization not only mitigates environmental concerns associated with agro-industrial waste but also supports the development of functional foods and health-oriented formulations with added economic value.

Apple waste

Apple (Malus domestica) is one of the most widely cultivated and consumed fruits across the globe, appreciated for its appealing taste, texture, and notable nutritional value. It is consumed both as fresh fruit and in processed forms such as juices, cider, purées, and dried or frozen products. The well-documented health benefits associated with apples are largely linked to their diverse range of naturally occurring bioactive compounds, including phenolic constituents, sugar alcohols, vitamins, organic acids, and amino acids.[12]

Apples are particularly rich in antioxidant phytochemicals. These include flavonoids such as quercetin and naringenin derivatives, catechin, epicatechin, and phloridzin, as well as phenolic acids like ferulic, p-coumaric, caffeic, chlorogenic, and gallic acids. Collectively, these compounds contribute to the fruit’s strong antioxidant capacity, helping to counteract oxidative stress and potentially reducing the risk of various chronic disorders. Although a significant portion of global apple production is marketed for fresh consumption, a considerable share is utilized in industrial processing.[12,13]

The processing of apples results in the generation of substantial quantities of by-products, most notably apple pomace—the solid residue remaining after juice extraction. This by-product can account for up to 30% of the original fruit mass and consists mainly of peel and pulp residues (approximately 95%), along with smaller amounts of seeds (2–4%) and stems (around 1%). Despite often being regarded as waste, apple pomace possesses considerable nutritional and functional value. It is especially rich in dietary fiber, which comprises roughly 35–60% of its dry weight. This fiber fraction includes pectin (5–10%), cellulose (7–40%), hemicellulose (4–25%), and lignin (15–25%).[14]

Beyond its fiber content, apple pomace contains appreciable levels of tannins, natural sugars, essential minerals, and a wide array of phenolic compounds. Due to this complex biochemical composition, apple processing residues exhibit notable antioxidant, anti-inflammatory, antidiabetic, cardioprotective, and anticancer properties. Nevertheless, despite its substantial health-promoting potential, apple pomace remains underexploited in many parts of the world. Strategic utilization and valorization of this by-product offer significant opportunities for the development of nutraceutical formulations and functional food ingredients, while also contributing to more sustainable agro-industrial waste management practices.[12]

Mango waste

Mango (Mangifera indica L.), a member of the family Anacardiaceae, is recognized as one of the most economically and nutritionally significant tropical fruits worldwide. It accounts for more than half of the total global production of major tropical fruits, underscoring its agricultural and commercial importance. Although mango is predominantly consumed fresh as a dessert fruit, it is also extensively processed into a diverse range of products, including chutneys, juices, jams, ice cream, dried mango powder, and canned slices preserved in syrup.[15]

Industrial processing of mangoes generates substantial quantities of by-products, primarily consisting of peels, seeds, and kernels. These residues, often regarded as waste, are increasingly being recognized for their rich nutritional and phytochemical composition. Mango kernels are notable sources of essential macronutrients and micronutrients, including lipids, proteins, and minerals. Meanwhile, mango peels contain significant concentrations of bioactive compounds such as protocatechuic acid, mangiferin, and β-carotene, among other phenolic constituents and carotenoids.[16]

These phytochemicals exhibit a wide range of biological activities, including antioxidant, anti-inflammatory, antidiabetic, and anticancer effects, which contribute to their potential role in disease prevention and health promotion. Consequently, mango processing by-products represent a promising and sustainable source of functional ingredients for nutraceutical and food applications. Their effective valorization not only enhances economic returns from mango production but also supports environmental sustainability through the reduction of agro-industrial waste.[4]

Onion waste

Onion (Allium cepa L.) is one of the most extensively cultivated and widely consumed vegetables worldwide, valued for its culinary versatility as well as its nutritional and medicinal properties. Increasing recognition of its health-promoting effects has contributed to sustained growth in global production. However, onion processing—particularly peeling and trimming operations—generates a substantial volume of waste, accounting for approximately 37% of the total fresh weight of the bulb. This waste predominantly consists of dry outer skins and peels, which are commonly discarded and disposed of in landfills, thereby contributing to environmental concerns.[17]Despite being classified as agro-industrial waste, onion skins are a rich reservoir of bioactive compounds. They contain high concentrations of phenolic constituents and flavonoids, notably quercetin and quercetin-4′-O-glucoside, along with various related compounds formed through natural degradation and oxidation processes. Importantly, these phytochemicals are often present in significantly higher amounts in the outer skins than in the edible inner bulb layers.[18]

The biological activities associated with these compounds have been extensively documented and include antioxidant, anti-inflammatory, anticancer, antidiabetic, antimicrobial, cardioprotective, and neuroprotective effects. Such properties highlight the considerable functional potential of onion processing by-products. Nevertheless, despite their demonstrated health benefits, onion skins remain largely underutilized, leading to the loss of a valuable natural resource.[19]

The strategic recovery and application of bioactive constituents from onion waste could contribute to sustainable agricultural practices and more efficient resource utilization. Furthermore, their incorporation into functional foods and nutraceutical formulations offers a promising approach to value addition, while simultaneously addressing environmental challenges associated with agro-industrial waste management.[3]

Tomato waste

Tomato (Solanum lycopersicum L.) is one of the most extensively cultivated vegetable crops worldwide and represents a major component of global horticultural production. In 2021, worldwide tomato output exceeded 189 million tons, with the European Union contributing more than 18 million tons, and Italy emerging as one of the leading producers within the region. Tomatoes play a central role in the Mediterranean dietary pattern and are consumed both fresh and in a wide array of processed forms, including paste, sauces, purees, ketchup, and canned products.[20]

Approximately half of the total tomato harvest undergoes industrial processing, resulting in the generation of substantial quantities of by-products. These residues primarily consist of pomace—a mixture of peels and seeds—as well as separated seeds, vascular tissues, and peel fractions. Although traditionally regarded as waste, these by-products retain considerable amounts of nutrients and bioactive compounds, highlighting their potential for value-added applications. The incorporation of tomato processing residues into food systems aligns with circular economy principles by reducing waste streams while enhancing resource efficiency.[20]

Tomato peels are particularly noteworthy for their high concentration of carotenoids, especially lycopene and β-carotene, which may occur at levels up to five times greater than those found in the pulp, particularly in fully ripened fruits. During the ripening process, carotenoids and flavonoids—including naringenin chalcone, rutin, and kaempferol-3-rutinoside—accumulate predominantly in the peel. These phytochemicals not only contribute to the fruit’s pigmentation and defense against environmental stress but also exhibit significant antioxidant activity with potential health-promoting effects.[21]

A growing body of research has investigated the application of tomato peels and pomace in the development of functional and nutritionally enhanced food products. Their incorporation into formulations has been shown to increase carotenoid content, dietary fiber levels, mineral composition, and overall antioxidant capacity. Consequently, tomato processing by-products represent a promising and sustainable source of functional ingredients for the nutraceutical and food industries, contributing both to improved nutritional quality and to environmentally responsible waste management practices.[20]

Pea waste

Pea (Pisum sativum L.) is the second most extensively cultivated leguminous crop globally and represents an important source of plant-based protein and dietary nutrients. Peas are consumed in both fresh (green) and dried forms and play a significant role in human nutrition and agricultural economies. For instance, in 2020, India produced more than 5.7 million tonnes of peas, underscoring their agronomic and dietary importance. During industrial processing—particularly for frozen, canned, or dried products—the outer pods are typically removed and discarded. These pods constitute approximately 35–40% of the total fresh weight of the pea, thereby generating a considerable volume of agricultural residue. If not appropriately managed, such organic waste may create environmental concerns, including microbial proliferation, unpleasant odors, and potential health risks.[22]

Despite being commonly treated as waste, pea pods possess substantial nutritional and functional value. They are rich in dietary fiber, carbohydrates, and crude protein, while containing relatively low levels of fat and a modest caloric value (approximately 210 kcal per 100 g). In addition, pea pods serve as notable sources of essential minerals, including potassium, magnesium, iron, and zinc. Beyond their macronutrient composition, pea pods are abundant in diverse bioactive compounds. These include phenolic acids such as benzoic and cinnamic acids, as well as a wide spectrum of flavonoids. Identified flavonoid subclasses comprise flavanones (e.g., naringenin and hesperidin), flavanols (catechin and epicatechin), flavonols (quercetin, quercetin-3-galactoside, and rutin), flavones (luteolin, apigenin, and kaempferol-3-glucoside), and isoflavones (genistein and myricetin). Such phytochemicals are associated with antioxidant and anti-inflammatory activities, among other biological effects.[22]

Due to their substantial nutritional composition and diverse phytochemical content, pea pods hold considerable potential as a sustainable source of bioactive ingredients for nutraceutical and functional food applications. Although often treated as processing waste, these by-products can be strategically utilized to develop value-added products with demonstrated health benefits. Their systematic valorization not only enhances the economic value of agro-industrial residues but also supports sustainable resource utilization and aligns with the principles of a circular economy by minimizing waste and promoting environmental stewardship.[3]

Potato waste

Potato (Solanum tuberosum) is one of the most extensively cultivated and economically significant food crops worldwide, serving as a staple dietary component for approximately 1.3 billion people. In 2021, global potato production surpassed 376 million tons, reflecting its major contribution to global food security. Following cereals, potatoes are regarded as one of the most important food crops due to their widespread consumption, affordability, and substantial nutritional value.[4]

A considerable proportion of harvested potatoes is subjected to industrial processing for the production of value-added products such as chips, puree, dehydrated flakes, and French fries. During these operations, the outer peel is removed, resulting in the generation of substantial quantities of by-products. Potato peels account for approximately 15–40% of the fresh weight of the tuber, thereby contributing to significant volumes of agro-industrial waste annually. Consequently, peel residues represent one of the principal by-products of the potato processing sector. Although traditionally considered waste, potato peels possess a rich phytochemical profile and have attracted increasing scientific interest as a potential source of functional ingredients. They are particularly valued for their high concentration of polyphenolic compounds. Among these, chlorogenic acid (trans-5-O-caffeoylquinic acid) is the predominant phenolic constituent. Additional important bioactive compounds include hydroxycinnamic acids such as ferulic acid and caffeic acid, as well as related derivatives like neochlorogenic acid.[23] 

These phenolic constituents are associated with significant antioxidant and anti-inflammatory properties, contributing to a range of potential health benefits. Owing to their biofunctional attributes, potato peels have been widely investigated for applications in nutraceutical development and as natural antioxidants in food systems. The effective valorization of potato processing by-products not only enhances economic returns but also aligns with sustainable waste management practices by transforming agro-industrial residues into valuable health-promoting ingredients.[5]