# Utilization of By-Products from the Fruit and Vegetable Processing Industry in Pasta Production
## 3 Incorporation of By-Products
### Nutritional Quality  
As shown in Table 1, most studies on pasta enrichment with fruit and vegetable by-products include the analysis of some of their nutritional components. It is well known that these by-products contain a high amount of fiber and bioactive compounds such as polyphenols or carotenoids [107,108]. In fact, most research has focused on these compounds. The observed results are quite clear, with almost all studies reporting an increase in fiber content, both soluble and insoluble, as well as polyphenic substances and carotenoids. This is expected, as pasta production should not significantly alter the fiber content. The process typically involves mixing and kneading the ingredients, followed by shaping through cold extrusion or lamination, and drying at low temperatures (below 100 \({}^{\circ}\)C). Furthermore, as mentioned previously, when fruit and vegetable by-products are incorporated into pasta, most studies report greater solid loss during cooking. However, the composition of these lost solids is rarely analyzed, even though they may contain bioactive compounds and soluble fiber. Regardless, enriching pasta with nutrient-rich ingredients still results in a higher overall nutrient content in the final product. Even if some components are lost to the cooking water, the majority remain in the pasta. In addition to fiber and phenolic compounds, pasta with by-products also tends to be richer in ash (mineral substances) and fat, as shown in Table 1. This is partly due to the composition of the by-products used and partly due to the low content of these nutrients in the semolina or flours used for pasta production (refined flours, as they have their bran and germ removed, leaving only the endosperm). The results regarding protein content are less consistent, which is due to the varying protein content of the different by-products used. However, in general, by-products with higher protein content than flour or semolina increase the final protein content of the pasta, and vice versa. Obviously, these increases or decreases are less pronounced in fresh pasta than in dried pasta, due to the higher water content in fresh pasta compared to dried pasta, and the diluting effect of the other components unless expressed on a dry basis. A similar phenomenon occurs when comparing dry pasta and cooked pasta. Another nutritionally relevant factor is the antioxidant capacity of the resulting pasta. This capacity can be measured in various ways, as reflected in the different studies incorporating these analyses. In general, pasta enriched with fruit and vegetable by-products exhibits higher antioxidant capacity. This is quite logical, as bioactive compounds such as polyphenols, carotenoids, or flavonoids present in by-products, and which remain in the pasta after processing, have a high antioxidant potential [109; 110]. It has also been shown that the inclusion of by-products generates pasta with a lower predicted glycemic index or reduced starch digestibility [63; 71; 77; 86; 94]. It is important to note that the inclusion of by-products reduces the starch content in the final pasta, leading to lower glucose release since this comes from starch. However, if results are expressed based on total starch, it is also logical, as numerous polyphenols have been shown to reduce the glycemic index by inhibiting digestive enzymes like amylases and through their interaction with starch [111]. Furthermore, the presence of polyphenols in some by-products may help regulate appetite and induce satiety via the gut-brain axis and gut homeostasis [112]. Additionally, the presence of certain hydrocolloids, found in some by-products, such as pectins or beta-glucans, also helps slow starch digestibility. This effect is due both to increased viscosity and to a potential inhibitory action on enzyme activity or reduced enzyme accessibility to starch [113]. Finally, the presence of insoluble fibers, such as cellulose, may also contribute to this effect, as it has been shown to affect postprandial blood sugar regulation [114].