In recent years, high-energy ultrasound has been used as an alternative to improve the functional properties of various proteins, such as from milk, eggs, soy and poultry. The benefits of implementing this technology depend on the inherent characteristics of the protein source and the intensity and amplitude of the ultrasound, as well as on the pH, temperature, ionic strength, time, and all of the variables that have an effect on the physicochemical properties of proteins. Therefore, it is necessary to establish the optimal conditions for each type of food. The use of ultrasound is a promising technique in food technology with a low impact on the environment, and it has thus become known as a green technology. Therefore, this review focuses on the application of high-energy ultrasound to food; its effects on the functional properties of proteins; and how different conditions such as the frequency, time, amplitude, temperature, and protein concentration affect the functional properties.

Food technologists are always looking to improve the functional properties of proteins. In this sense, in last years ultrasound has been used to improve some functional properties. For this reason, and considering that jumbo squid is an important fishery in northwest Mexico, the purpose of this research was to determine the effect of pulsed ultrasound on the physicochemical characteristics and emulsifying properties of squid (Dosidicus gigas) mantle proteins. Pulsed ultrasound (20kHz, 20, and 40% amplitude) was applied for 30, 60, and 90s to a protein extract prepared from giant squid mantle causing an increase (p<0.05) in surface hydrophobicity (S) from 108.4±1.4 to 239.1±2.4 after application of pulsed ultrasound at 40% of amplitude for 90s. The electrophoretic profile and the total and reactive sulfhydryl contents were not affected (p⩾0.05) by the ultrasound treatment. The emulsifying ability of the protein solution was improved (p<0.05), whereas the Emulsifier Activity Index (EAI) varied from123.67±5.52m/g for the control and increased up to 217.7±3.8m/g after application of the ultrasound. The Stability Emulsifier Index (EEI) was improved at 40% of amplitude by 60 and 90s. The results suggested that pulsed ultrasound used as pretreatment induced conformational changes in giant squid proteins, which improved the interfacial association between protein-oil phases, thus contributing to the improvement of their emulsifient properties.

No abstract

Large volumes of waste are generated in the processing operations of the fishing industry. These effluents contain potentially useful proteins. However, it is necessary to concentrate them for utilization. The stickwater (SW) resulting from this operation was subjected to a protein-fractionation step, pH adjustment (acid + alkaline) and ultrasonic pulsing in order to aid in hydrolysis and evaluate its functional and nutritional properties. The protein fractions, as well as the protein hydrolysates present in the tail water, had a chemical composition of 54.85 ± 4.21 and 74.81 ± 3.89 protein (%), 0.8 ± 0.1 and 0.2 ± 0.015 fat (%), 7.21 ± 0.67% ash (%), respectively. The increase in low-molecular-weight peptides results in an increase in free-radical scavenging activity. However, the increase in ferric-reducing antioxidant power may be due to the HCl treatment performed by the company. An increase in the functional properties of the samples treated with ultrasonic pulses was observed. Therefore, the chemical, nutritional and functional characteristics of stickwater suggest its potential use as a food additive.

Este estudio se enfocó en recuperar proteasas alcalinas de vísceras de Scomberomorus sierra  mediante cromatografía de interacción hidrofóbica. Tres proteasas alcalinas se lograron separar parcialmente usando esta técnica cromatográfica; dos de ellas con pesos moleculares de 19 y 31 kDa fueron identificadas como enzimas tipo tripsina de acuerdo a ensayos de inhibición. La proteasa alcalina con peso molecular de 31 kDa, única enzima aislada, fue purificada bajo las siguientes condiciones cromatográficas: sulfato de amonio l3% (p/v) y etilenglicol al 27% (p/v); esta enzima mostró actividad máxima a pH 9 – 10 y 50 – 60 °C y fue fuertemente inhibida por el inhibidor de tripsina de soya (SBTI) como por el inhibidor de tripsina porcina (TPI). Una tercera proteasa alcalina con peso molecular de 20 kDa fue parcialmente separada e inhibida por tosil fenilalanil clorometil cetona (TPCK), la cual mostró actividad óptima a pH 9 – 11 y 60 °C. Estos resultados muestran que las vísceras de Scomberomorus sierra podrían ser de utilidad como fuente de proteasas.