Food industry processing wastes are produced in enormous amounts every year, such wastes are usually disposed with the corresponding economical cost it implies, in the best scenario they can be used for pet food or composting. However new promising technologies and tools have been developed in the last years aimed at recovering valuable compounds from this type of materials. In particular, sub-critical water hydrolysis (SWH) has been revealed as an interesting way for recovering high added-value molecules, and its applications have been broadly referred in the bibliography. Special interest has been focused on recovering protein hydrolysates in form of peptides or amino acids, from both animal and vegetable wastes, by means of SWH. These recovered biomolecules have a capital importance in fields such as biotechnology research, nutraceuticals, and above all in food industry, where such products can be applied with very different objectives.Present work reviews the current state of art of using sub-critical water hydrolysis for protein recovering from food industry wastes. Key parameters as reaction time, temperature, amino acid degradation and kinetic constants have been discussed. Besides, the characteristics of the raw material and the type of products that can be obtained depending on the substrate have been reviewed. Finally, the application of these hydrolysates based on their functional properties and antioxidant activity is described.

Legume waster water has been revealed to contain sufficent nutritional value as an industry by-product. In this study, physicochemical properties and protein profile of pea, chickpea and soybean soaking and cooking water were investigated. Among the three legumes isolates with their wastewater, all of the cooking wastewater exhibited the lowest content of free amino acid. In the yellow pea free amino acid assay, the soaking method contains the highest volume of Ser (6.00mg/g), His (6.01 mg/g), Phe (7.48 mg/g), Ile (4.12mg/g) Thr (4.27 mg/g) and Met (1.68mg/g). Chickpea soaking water has the highest volume of His (12.05mg/g) Phe (16.43mg/g), Ile (9.77mg/g), Thr (10.12mg/g) and Met (11.08mg/g). Pea cooking water Met to Lys is 0.8, which gave it the most elastic properties to form the sponge cake and more nutritional value. To identificate the emulsifying properties, oil-in-water emulsions containing 50% Canola oil were prepared using the legumes wastewater (pea, chickpea and soybeans). These emulsions were then stored at 4°C, and changes in particle size were monitored throughout storage. Chickpea cooking emulsions showed the smallest droplets distribution in the original emulsions. The mean emulsion droplet diameter (nm) evaluated differed significantly(p<0.05) for all centrifugated legume wastewater-based emulsions. Different types of legumes affected emulsifier stability because of different protein content. In conclusion, soybean soaking and cooking water have the best emulsifier stability both at room temperature and the refrigerator temperature, pea cooking water was investigated to form the hardest sponge cake because of its highest protein content.