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Introduction to Food By-Products and Their Bioactive Roles
Özlem Tokuşoğlu
Celal Bayar University Manisa, Turkey
By-Products in the food industry are characterized by a high ratio of product-specific waste. Not only is the generation of this waste unavoidable, but also the level and kind of by-products, which consist primarily of the organic residue of processed raw materials, can scarcely be changed if the finished product quality is to remain consistent. Use and disposal of the product-specific waste is difficult, owing to its inadequate biological stability, potential pathogenic structure, high-water content, potential autoxidation tendency, and high degree of enzymatic activity.
In the food industry, the diverse types of by-products can be evaluated by various branches of industry due to the selected desired properties of food by-products. The pulps, dregs, and wastes in food processing depend on the quality of by-product management, while ensuring environmental protection and sustainability in by-production monitoring.
Food by-products or food industry shelf-stable coproducts such as liquid, pomace, or powder forms can be obtained by processing fruits, vegetables, meats, seafoods, milk and dairy, cereals, nuts, and fats and oils (Figure 1.1). These by-products may be evaluated as a source of dietary phytochemicals, including phenolic antioxidants, carotenoids, other bioactive polyphenols, and dietary fiber; as a source of proteins, peptides, and amino acids; as a source of collagen, gelatin, and various food-additive materials; and they may be evaluated as extruded products (Tokuşoğlu 2017). However, some of the by-products can be utilized as compost for plants, animal feed, or industrial material (Figure 1.2).
Figure 1.1 Sources for food by-products.
Figure 1.2 Areas in which food by-products, including liquids, pomaces, and powders, are utilized.
Epidemiological studies have pointed out that fruit and vegetable consumption imparts health benefits on protection of certain types of cancer and on reduced risk of coronary heart diseases. The health benefits of fruits and vegetables are primarily attributed to bioactive nutrients such as phytochemicals, carotenoids, and vitamins (ascorbic acid, tocopherol, etc.), as well as to the dietary fiber they contain.
Dietary supplements and/or food fortification may be an alternative for the above mentioned healthy constituents. The by-products of fruits and vegetables are sources of highly desirable healthy compounds, which are considered highly desirable (Figure 1.3).
Figure 1.3 Fruit and vegetable by-products as powders.
Due to the high consumption and industrial processing of the edible parts of fruit, wastes such as the peels and seeds of fruit (apple, pear, orange, pomegranate, and tomato) residues, citrus fruit skins, mango residues, pineapple residues, residues of other exotic tropical fruits (avocado, banana, guava, jackfruit, and longan fruit), chestnut residues, olive residues, and sugarcane bagasse are generated in large quantities in big cities. Moreover, the peel, leaf, or stem fractions of cabbage, cauliflower, celery, Chinese cabbage, coriander, cucumber, eggplant, endive lettuce, fennel, ginger, green pepper, lotus root, potato, rape, scallion, and spinach can be evaluated as sources of dietary phytochemicals and can be used extruded products, and the dietary fiber is also used in manufactured powder forms. Figure 1.4 shows the powder obtained as a by-product of pear peel.
Figure 1.4 Pear peel powder.
The current methods for further utilization of product-specific waste of fruits and vegetables have been developed along traditional lines and these utilizations are closely bound to the agricultural origins of the raw materials.
The majority of by-products in the meat industry are produced during slaughtering. Slaughterhouse waste consists of the portion of a slaughtered animal that cannot be sold as meat or used in meat products. Such meat by-products include internal organs, fat or lard, skin, feet, abdominal, the contents of the gastrointestinal tract, blood, bones, tendons, and the powders produced from these by-products. Meat by-products are produced by slaughterhouses, meat processors, wholesalers, and rendering plants (Jayathilakan et al. 2012; Valta et al. 2015).
One of the major by-products of meat is slaughterhouse blood (Figure 1.5), which is the foremost part of meat production and represents a rich source of protein. The physicochemical characteristics and utilization of animal blood in various food and industrial applications have been well explored. Angiotensin-converting enzyme inhibitory, antioxidant, antimicrobial, and other bioactive peptides are derived from various slaughterhouse animal blood sources. Furthermore, the choices of enzyme, degree of hydrolysis, and peptide sequence or size has been affected the potency of bioactivity (Bah et al. 2013).
Figure 1.5 Slaughterhouse blood powder.
The by-products of meat containing ash biomass include phosphorous (P). It is known that some high phosphorous ash can be in sludge ash and meat and bone meal, and phosphorous from the biomass ash has very important practical significance for biomass energy, biomass ash disposal, and as a phosphorous source (Tan and Lagerkvist 2011).
Fish by-products are one of the most important raw materials for food, nutraceutical, pharmaceutical, and biotechnological applications. By-Products include fish stomachs, viscera silage, and fish sauce. It has been stated that carnivorous fishes have high stomach pepsin contents, and silage is made from minced viscera or from the separated stomach. By ultrafiltration, concentration, and spray-drying, cod stomach silage can give a pepsin preparation (Baiano 2014).
Fish oil from fish processing waste and marine fish and chicken visceral wastes are rich sources of polyunsaturated fatty acid concentrates and, in particular, of omega-3 essential fatty acids. Not only fish skin (Figure 1.6) but also bones and fins are potential sources of collagen and gelatin (Baiano 2014).
Figure 1.6 Fish meal.
Shrimp processing leads to massive amounts of shrimp biowaste and the major constituents of shrimp by-products are protein, chitin (deacetylated chitosan), lipid, minerals, and also valuable carotenoid astaxanthin (Figure 1.7). Chitosan, a valuable bioactive compound, has widely used in food, agriculture, biotechnology, cosmetics, medicine, and waste treatment (Tokuşoğlu 2017). Shrimp cooking wastewater is also a good source of astaxanthin and bioactive peptides (Amado et al. 2016). Seafood by-products are good sources of antimicrobial compounds (Pezeshk et al. 2015) and seafood-derived peptides are multifunctional ingredients (Nikoo and Benjakul 2015).
Figure 1.7 Shrimp and the shrimp by-product astaxanthin.
The dairy by-product whey is also a very good source of peptides with remarkable biological activities. Whey is an abundant by-product of the dairy industry that corresponds to the liquid fraction remaining after milk clotting and casein removal during cheese manufacturing. Whey includes the lactose and noncasein proteins of milk (Brandelli et al. 2015). It has been reported that ovine and caprine whey proteins including β-lactoglobulin (β-Lg) and α-lactalbumin (α-La) and derived peptides have good biological properties. Moreover, the bioactivity of the other components of cheese whey, including lactose, oligosaccharides, and minerals, is well-known (Hernandez-Ledesma et al. 2011).
Cereal (flaxseed, barley, oat, etc.) by-products are also very important, phenolic compounds can be extracted from cereal brans with the inclusion of antioxidants, and these valuable products provide resistance against free radical damage, cancer, and cardiovascular diseases. Gamma-oryzanol extracted from rice bran is a potent antioxidant, a cholesterol-reducing agent, a tumor-inhibiting agent, and a prevention agent in menopausal syndrome treatment; β-glucans extracted from barley flour improve lipid metabolism, reduce the glycemic index, and lower pl...
