## 4 Health Benefits and Composition of Kiwi By-Products
### Kiwi Bioactives in Functional Foods Applications  
The shift towards healthier eating habits in developed economies has led to increased demand for high-quality products, with multiple nutritional and functional benefits. This has given rise to the concept of functional foods. The concept of functional foods originated in Japan in 1998. More specifically, a non-alcoholic beverage enriched with fiber was the first functional food to be introduced by Otsuka Pharmaceutical. This initiative aimed to improve dietary habits and promote longevity, while reducing healthcare costs. Subsequently, Japan established a category of foods known as FOSHU (food for specified health use), which is approved by the Ministry of Health and Welfare. In Europe, the definition of functional foods was formalized between 1995 and 1998, emphasizing their beneficial effects on specific bodily functions, beyond basic nutrition [62]. Functional foods, i.e., foods and beverages that have added health benefits beyond their nutritional value, can improve health and well-being indicators [63]. Functional food products have the potential to offer multiple nutrients that are often difficult to obtain, including additional fiber, protein, vitamins, minerals, and antioxidants, and can improve overall well-being [62]. Furthermore, the mechanism of functional foods is capable of improving the availability of several essential fatty and amino acids, probiotics and prebiotics [64]. These products may contribute to achieving optimal nutrition in older individuals, thereby supporting healthy aging. Therefore, functional foods also promote optimal health and reduce the risk of noncommunicable diseases and improve overall well-being. Thus, functional foods are now considered to be an accessible food therapy to eliminate health problems, since many medications have disagreeable side effects, aiming to affect multiple systems in the body, such as the immune, nervous, and skeletal systems [62; 64; 65; 66]. The Actinidia genus holds prominent status globally due to its substantial commercial and nutritional significance, and contains approximately 60 species, with kiwi fruit being the most consumed member, due to its plentiful health advantages. Currently, individuals gravitate toward convenient foods that offer sufficient nutritional value. Kiwi fruit exhibits potent antioxidant properties and immune-boosting effects, both in vitro and in vivo [67; 68; 69]. Kiwi fruits can be stored fresh for weeks, even months, without compromising the quality, in controlled temperatures. On an industrial scale, innovative kiwi products are manufactured and marketed. However, beyond consumption in its natural state, kiwi fruit is commonly incorporated into a variety of functional food products. These kiwi-based functional foods have the potential to fulfill the nutritional and health requirements of consumers, while also encouraging the utilization of natural resources (Table 4) [68; 70]. The development of kiwi-derived products is based on their nutritional and biological properties, attributed to its high content in terms of dietary fiber and bioactive compounds, including vitamins (C, E, and A), phenolic compounds, and minerals [36; 71; 72]. Furthermore, the industrial processing of kiwi fruits results in a large amount of by-products, including peel, seeds, and residual pulp, estimated at approximately one million tons annually. Thus, with the food industry grappling with the disposal of thousands of tons of kiwi by-products annually, there is a pressing need to recognize kiwi by-products as valuable sources of functional ingredients. Nowadays, efforts from both a scientific and practical perspective, are being made to explore the functional potential of these materials as sources of essential chemical compounds with considerable added value for human and animal well-being.