Öztürk / Eur Food Sci Eng 2023, 4 (1), 15-25 15 A waste material rich in bioactive compounds: Hazelnut waste Göktürk Öztürk Food Technology Programme, Kaman Vocational High School, Kırşehir Ahi Evran University, 40300, Kırşehir, Turkey ARTICLE INFO ABSTRACT Review Article Nowadays, increasing sensitivity to the environment has led to the development of sustainable agricultural policies. In this respect, it has become important to transform agricultural waste products into value-added products. Hazelnut, which has a significant trade volume worldwide, is processed into products, and some waste materials can be emerge. These waste products could transform into high added-value to food, cosmetics, and pharmaceutical industries due to possessing the bioactive compounds such as phenolics, bioactive peptide and, dietary fibre in them. This review represents the research on the bioactive compounds from the hazelnut waste, especially conducted in recently, and concentrates on its tree leaf, husk, and oil meal. Article History: Received: 29 April 2023 Accepted: 6 June 2023 Available Online: 8 June 2023 Keywords: Hazelnut Waste Leaf Husk Oil meal 1. Introduction Today, the energy crisis in the world and the increasing concerns on the environment have accelerated the research on the search for the alternative energy sources to fossil fuels (Havrysh et al., 2021; Tsekos et al., 2021). One of them is waste. According to Directive 2008/98/CE, ‘waste means any substance or object which the holder discards or intends or is required to discard’ (Anonymous, 2008). Based on this definition, waste can be classified as follows; state (solid, liquid, gaseous), source (agricultural, commercial, industrial, municipal), and degradability (biodegradable, non- biodegradable) (Dey et al., 2021; Koul et al., 2022). A considerable amount of waste is generated in the world, for example, only the European Union generated about 2.2 billion tons of waste in 2020 (Anonymous, 2020). On the other hand, in terms of solid waste, 2.02 billion tons of it was produced in the world in 2016, and it is estimated that this number will increase to 2.59 billion tons and, 3.4 billion tons in 2030 and 2050, respectively (Kaza, 2018). If the waste cannot be controlled, that is, if zero waste management is not implemented, the world may inevitably face serious problems. It might affect on both environmental safety by causing air pollution, water pollution, soil contamination and increasing greenhouse gases, and human health (Anonymous, 2016). Due to these adverse effects, the principles of zero waste management have been focused all over the world in recent years, comprising prevention, reduction, recycle, recovery, and disposal (Anonymous, 2008). Therefore, for the implementation of zero waste management, recently, there has been conducted a lot of research on the reusing of the waste from applied as the fertilizer and animal feed (Chew et al., 2018) to manufacturing bio-based films for food packaging (Bastante et al., 2021) and producing biogas (Havrysh et al., 2021), and biodegradable polymers (Maraveas, 2020). Probably, it can seem like that recovering biochemicals, producing energy or value-added products from waste rather than their disposal will be an important philosophy of this century. Agriculture provides an important source of raw materials for the food industry and human need, and eventually a large amount of agricultural waste is occurred as a result of agricultural and agro-industrial activity (Sharma et al., 2022). Agriculture waste is made up field residues (i.e stems, seeds, husk, shell and so on), industrial processing waste (i.e pomace, sugarcane bagasse, hazelnut cake etc.), livestock waste (bedding/litter, wastewater in the slaughterhouse, animal carcasses etc.), and chemical waste (pesticides, insecticides, and herbicides etc.) (Dey et al., 2021). They can comprise a number of bioactive chemicals such as polyphenols, and dietary fiber, especially in field residues and industrial processing waste (Balasundram et al., 2006; Beutinger et al., 2020; Castrica et al., 2019; Dey et al., 2021). The former has antioxidant, antimicrobial, anticancer, and antiproliferative activity (Beutinger et al., 2020; Castrica et al., 2019; Dey et al., 2021). The latter, which is an essential part of the plant cell wall, may be divided into two subgroups; soluble and insoluble in water (Gill et al., 2021). They have a favorable impact on human health, regulating the bile salts, improving the fecal volume by holding the water, influencing the microbial spectrum to beneficial ones, taking part in the production of short-chain fatty acids (propionate, butyrate, and acetate) in the gastrointestinal tract, which have an important role in both energy metabolism, host immunity and inflammation, and in inhibiting colon cancer cell proliferation (Capuano, 2017; European Food Science and Engineering Eur Food Sci Eng 2023, 4 (1), 15-25 doi: 10.55147/efse.1289656 https://dergipark.org.tr/tr/pub/efse *Corresponding author E-mail address: gozturk@ahievran.edu.tr