# Utilization of By-Products from the Fruit and Vegetable Processing Industry in Pasta Production
## 3 Incorporation of By-Products
### Culinary Quality
#### 3.2.2 Swelling, Water Absorption, and Weight Loss Index  
In general, pasta containing by-products tends to show greater weight loss during cooking, with only two exceptions [61; 75]. However, the observed differences in swelling index and water absorption are not as clear, and there are significant variations across the studies analyzed. Weight loss during cooking occurs due to the release of soluble components from the pasta (starch and other non-starch polysaccharides) into the cooking water. In traditional pasta, most of this loss corresponds to the release of starch. Starch granules are embedded in the gluten network, and if this network weakens, starch can escape to the outside. In pasta incorporating by-products, two phenomena may contribute to this weight loss. First, the total wheat protein content decreases due to a dilution effect, and second, by-product particles interfere with the gluten network, weakening it. This weakening is well observed when analyzing the microstructure of pasta, as shown in some of the cited studies [58; 63; 71]. In the study by [PERSON] and [PERSON] [75], unlike most studies, weight loss decreased as the content of by-products (watermelon rind powder) increased. However, in this case, the pasta produced was \"wet noodle\", which is not dried, made with wheat flour instead of semolina, and includes kansui (sodium silicate and sodium carbonate), which alters the dough pH and thus the gluten network configuration. The article does not provide a clear explanation for the reduced cooking losses compared to other studies. It is known that using flour instead of semolina results in pasta with different characteristics, where starch granules tend to be less embedded in the gluten matrix [105], which could increase weight loss in the control. However, further investigation into the effect of dough pH on these outcomes is needed. In studies involving grape by-products, a contradiction seems to exist. While [PERSON] and [PERSON] [69] observed increased weight loss due to these by-products, which they attributed to the interactions of the by-product's polymers with the gluten matrix and/or protein competition for water, [PERSON] et al. [61] reported a reduction in weight loss. They attributed this to the ability of antioxidant components in grape pomace extract to form complexes with proteins around the starch granules, encapsulating them during cooking and limiting excessive swelling and amylose diffusion. The studies analyze the solid content of the cooking liquid but not its composition. This could be relevant, as the loss of starch is different from the loss of nutritionally important components, such as polyphenols. To reduce cooking losses, which may result from gluten network weakening, strengthening the gluten network could be attempted. For example, [PERSON] et al. [70] achieved reduced weight loss and increased optimal cooking time by introducing transglutaminase into the formulation. This enzyme is capable of linking lysine and glutamine groups, strengthening the protein network. However, its application also increases the hardness of the pasta, which was already harder due to the by-product incorporation. In other gluten-dependent products, gluten is often added, or oxidative enzymes and additives are used to strengthen the gluten network [7]. However, these aspects have not been extensively studied in pasta production with by-products. Regarding cooking yield, swelling index, and water absorption of cooked pasta (grams of water per gram of dry pasta), as mentioned, the results are less consistent. Both parameters are determined according to the procedure described by [PERSON] et al. [106] and tend to follow the same trend (i.e., if the swelling index increases, water absorption also increases). Water absorption depends on the amount of water absorbed by starch and wheat proteins. Therefore, if some of the starch has passed into the cooking water, it is logical for the water absorption by the pasta to decrease during cooking.