What Are Prebiotics, and Why Are They Beneficial?

Prebiotic properties of fruit-vegetable peels and their role in probiotic food formulation

Fruits (mango, banana, pomegranate, pineapple, orange, sweet line, papaya, apple, etc.) and vegetables (potato, gourd, onion, tomato, carrot, pumpkin etc.) are rich sources of health-beneficial compounds along with vitamins and minerals. However, from fruit and vegetable processing, handling, and storage, 25-57 million tonnes of waste are generated. 15-60% of this waste is mainly peels that are discarded or used for animal feed.

Due to their higher biodegradable nature and ability to initiate or boost fermentation, these peels can contribute to environmental pollution, green gas emission, and global warming, creating challenges for the balance between the environment and health. Discarded peels are also sometimes burnt to get rid of the wastes and cause air, soil, and water pollution. Thereby, it is necessary to discard these peels properly or reuse them for better purposes such as value-added product formulation, bio-fertilizer, edible food packaging, etc.

What are the benefits of fruit and vegetable peels?

According to ongoing studies, these peels contain higher levels of nutrients, minerals, vitamins, and especially fibers. Eventually, they contain more nutrients than the pulp or the inner part of the fruit or vegetables. They have also shown anti-carcinogenic, anti-diabetic, anti-hypertensive, antioxidant properties, and other medicinal characteristics. Due to the presence of fibers, these peels also showed prebiotic properties and indicated potential use for healthy probiotic food formulation.

Few studies regarding the role of peel-incorporated probiotic food products also revealed controlled metabolic disorders, improved digestion, and better bowel conditions. Besides improving the gut environment, the presence of these peels in the formulated products also enhances the nutrient and food quality of the products.

What are probiotics?

Generally, probiotics are known as ‘live microorganisms’, which play a key role in maintaining our gut environment and our entire health system. Daily intake of probiotics in certain proportions results in health benefits and boosts immunity. Common probiotics used for food formulation include  Lactobacillus casei, Bifidobacterium animalis subsp. lactis, Lactobacillus acidophilus and Lactobacillus paracasei etc.

The use of probiotics in food formulation (Fermented food) is a traditional practice. Yogurt, kefir, kombucha, sauerkraut, tofu, yakult etc. are rich sources of probiotics. Incorporating these fermented foods into a daily diet can help combat nutrient deficiency and contribute to malnutrition mitigation. 

What are the prebiotics?

Prebiotics are generally fibers, and polysaccharides that act as food for live microorganisms. The presence of prebiotics in the colon results in direct contact with good bacteria. Degradation of these prebiotics by the microorganisms boosts or improves the growth and activity of probiotics. However, recent studies have revealed the prebiotic property of certain health-beneficial compounds like polyphenols, proteins, bacterial metabolites, and polyunsaturated fatty acids (PUFAs). Consumption of such food products helps to maintain the population of good bacteria in our gut. 

Probiotic food formulation using prebiotics can be a cost-effective approach to minimize hunger as well as nutrient deficiency. Fibers in fruit and vegetable peels can improve the activity of probiotics in fermented products. Though prebiotics, enriched probiotic yogurt, and capsules are commercially available, understanding the role of prebiotic-probiotic interaction in value-added food product formulation needs more studies. 

According to the available data survey, the market demand for prebiotics will increase by 12.7% by 2025, and there is a probability of having a profit of 10.55 billion dollars. 

What foods are high in prebiotics?

Generally, green leafy vegetables, fruits, fiber-rich foods are the major sources for prebiotics. Some examples of foods containing prebiotic properties are: apples, bananas, pineapple, pomegranate seeds, burdock root, chicory root, seaweed, flaxseeds, oats, barley, chickpeas, lima beans, mung bean, wheat bran, rice bran, fruit peels etc.

How can farmers benefit from fruit-vegetable peels?

The use of fruit-vegetable peels as organic sources of prebiotics in food industries can also benefit fruit and vegetable farmers. Processing of fruit-vegetable peels and formulation of healthy food can be achieved even using conventional culinary techniques and some basic treatments like freezing, drying, heating, blanching (to soak in boiling water for a shorter duration followed by quick cooling), fermentation, etc. These peels need processing as they contain a certain amount of antinutrients (Factors affecting nutrient absorption in the body). Processing of the peels also helps to stop the enzymatic reaction. The presence of certain compounds in fruit peels, like naringin (Orange peel), cause a bitter taste. Proper treatment of these peels can lower the concentration of such compounds resulting acceptable taste. Instead of selling to the middleman, fruit and vegetable farmers can directly provide to markets and collect the post-processing waste (peel) for further use.

What are the uses & benefits in the food industry?

For the aroma, Citrus fruit peel, banana peel, and mango peel are getting attention for food formulation. Other peels from fruit or vegetables like guava, carrot, potato etc., possessing prebiotic properties, are yet to reach that target.

The use of prebiotics (Dietary fibers) in food products contributes as bulking ingredient with low energy and low fat. In some cases, fruit peels can also replace artificial sweeteners, especially in baked products and health drink powder formulations. Food specialists and researchers have formulated peel-incorporated fermented products like yogurt, fermented flavored milk, and ready-to-eat and ready-to-cook products with acceptable sensory qualities. Apart from probiotic foods, attempts also have been made to develop peel-enriched bakery products like cookies, bread, beverages, health drinks, instant health drink powder, etc. Bakery products have been formulated using peels of orange, pear, passion fruit, jackfruit, banana, pomegranate etc. Extruded and snack products have been developed using the peel of watermelon, mango, pumpkin etc. All these formulated products showed improved nutrient composition and product quality. They are keen to accomplish successful formulation to establish the role of these fruit and vegetable-generated peels for better food sustainability as well as economic independence globally. Increased fruit-vegetable waste (peels) generation needs proper valorization techniques with a strategic approach. The presence of beneficial health attributes in these peels can be used for managing food and nutrition security.

Reference

Leong, Y. K., & Chang, J. S. (2022). Valorization of fruit wastes for circular bioeconomy: Current advances, challenges, and opportunities. Bioresource technology, 127459.

Hussain, H., Mamadalieva, N. Z., Hussain, A., Hassan, U., Rabnawaz, A., Ahmed, I., & Green, I. R. (2022). Fruit peels: Food waste as a valuable source of bioactive natural products for drug discovery. Current Issues in Molecular Biology, 44(5), 1960-1994.

Karmali, N., & Le, T. (2020). Equal access to beneficial microbes: A tool for reduced malnutrition. Global Health: Annual Review, 1(5), 3-3.

Kumar, H., Bhardwaj, K., Sharma, R., Nepovimova, E., Kuča, K., Dhanjal, D. S., … & Kumar, D. (2020). Fruit and vegetable peels: Utilization of high value horticultural waste in novel industrial applications. Molecules, 25(12), 2812.