Dietary fibers from fruit and vegetable waste: methods of extraction and processes of value addition

Dietary fiber (DF) is a crucial part of a healthy human diet due to its health benefits in the issues related to cardiovascular, overweight, and digestion. The primary source of DF is fruit and vegetables, but excessive wastage during pre- and post-harvest makes it unaffordable. The globe’s population reach 9.7 billion in next 30 years. To satisfy DF need of increasing population on one side and to valorize fruit and vegetable waste (FVW) on other, DF extraction and purification from FVW is an optimum way. This review highlights various types of FVW reported and even has the potential to explore as a feedstock for DF purification. Paper presents detailed composition of FVW like fat, protein, soluble dietary fiber (SDF), insoluble dietary fiber (IDF), and total dietary fiber (TDF). The merits and demerits of different DF purification methods like dry processing, wet processing, chemical, microbial, gravimetric, and hybrid methods are discussed. Attempts are made to comply with green chemistry principles by substituting inorganic acids with organic acids like lemon juice in hydrolysis and using dry processing as it’s convenient though yielding less. In many FVW-DF, the ratio of SDF to IDF is less than desired (1:2); hence, attempts are made to convert IDF to SDF. Reported methods of increasing SDF are critically examined and found that physical methods like ultrasonication, microwave irradiation, extrusion, homogenization, and micronization are more efficient and environmentally benign. The FVW-DF is used in food industries like bakery, dairy, meat, and processed food industries. The paper deliberate on the research opportunities, challenges, and research gaps.