Peanut hulls, an underutilized nutritious culinary ingredient: valorizing food waste for global food, health, and farm economies-a narrative review

Abstract

Peanut hulls (PHs) are an edible food waste that is an underutilized food source for human consumption. While edible and palatable, currently they are mainly diverted to livestock feed or building materials. Here, we describe existing literature supporting human food valorization of PHs, and propose methods to optimize recapturing nutrients (protein, fiber, phenols and other phytonutrients) lost by treating PHs as waste. Incorporated into common foods, PHs could be processed into functional ingredients to improve nutrient-density with anticipated corresponding positive health outcomes associated with increases in plant foods. Valorization of PHs addresses multiple priorities of the UN Sustainable Development Goals using a Food Systems Approach (FSA) including reducing food waste, increasing economic opportunities for farmers, and increasing the availability of healthy shelf-stable foodstuffs to address food security. Recent advances in sustainable food processing technologies can be utilized to safely incorporate PHs into human food streams. We propose future applications that could make meaningful impacts for food availability and the nutritional composition of common foods like bread and plant-based meat alternatives. While the limited literature on this topic spans several decades, no commercial operations currently exist to process PHs for human consumption, and most literature on the topic precedes the technological "green revolution." The approaches outlined in this review may help bolster commercialization of this underutilized and nutritious food potentially improving opportunities for multiple global stakeholders.

Keywords: food manufacturing; food systems approach; food waste; peanuts; plant food; sustainable food systems; sustainable technology; valorization.

Figure 1

Conceptual model of peanut hull valorization for human food. Approximately 46.4 million tons of peanuts are grown annually around the world, of which 22% is waste from the hulls (>10 million tons). Peanut hull waste results in an annual loss of >6.5 million tons of health-promoting dietary fiber and > 595,000 tons of healthful plant protein (1). Recapturing PHs for human foods has applications that could improve the healthfulness of common foods, such as breads and other baked goods by using it to amend traditional baking flour. PHs also provide an abundant source of functional ingredients, that could join or be used in place of popular ingredients like pea protein for use in foods and nutritional supplements. In this figure peanut hull waste in tons is shown being upcycled in order to recapture major nutrients (protein and fiber) along with beneficial polyphenols (luteolin and resveratrol) for use in high-feasibility examples of bread (and baked goods), cellulose commonly used in food production, in nutritional supplements, in alternative proteins such as plant-based and cultivated meat, and as protein powders for direct consumption. Together, these value-added uses increase the market value of peanuts with significant economic benefits for farmers, represent a more efficient use of food system resources, and reduce food waste and the corresponding environmental impacts. These benefits join the benefits of their specific applications which range from improving nutrient profiles of foods to help offset the burden of cardiometabolic disease, and increasing food and nutrition availability as a means to addressing food and nutrition insecurity.