engleski

Functional properties of ultrasound treated whey and soy proteins

There is an increased interest in and growing demand for novel technologies without the addition of chemicals. The frequently used concept of “minimal processing”, in fact, corresponds to the principle of “as little as possible, but as much as necessary”. These newly developed non-thermal food-processing technologies usually focus on the preservation and modification of the functional properties of food components, while keeping food quality attributes. High pressure and ultrasound are the most advanced in food processing and have found a range of commercial applications. High-intensity ultrasound is used in many food applications, such as emulsifying, sterilizing, extracting, degassing, filtrating, drying, and enhancing oxidation (1, 2). High intensity ultrasound generated by periodic mechanical motions of a probe transfers ultrasonic energy into a fluid medium and triggers extremely high alterations in pressure leading to the formation of small rapidly growing bubbles (cavities) (3), which expand during the negative pressure excursion, and implode violently during the positive excursion generating high temperatures, pressures and shear forces at the probe tip (4). Ultrasound represents mechanical waves, i.e. a variation of pressure or density with frequencies above the human hearing threshold (ca. 18 kHz). When the bubbles attain a volume at which they can no longer absorb enough energy, they implode violently. This phenomenon is known as cavitation. During implosion, very high temperatures (approximately 5 500°C) and pressures (approx. 50 MPa) are reached inside these bubbles (2, 3, 4). Whey and soy proteins, because of their unique functional properties, high nutritional and biological values are widely used as an ingredient in many food products. Their functional properties depend upon various factors like molecular weight, amino acids composition, molecular structure and conformation, surface-active properties as well as water holding capacity. The aim of this work was to examine the effect of high energy low frequencies ultrasound on the some functional properties of several whey and soy protein products.10 % (w/w) water suspensions of whey protein concentrate, whey protein isolate, alpha-lactalbumin, whey protein hydrolysate, soy protein isolate and soy protein concentrate were treated with ultarsound frequencies of 20 kHz with probe and in the bath with 40 kHz frequency. Duration of treatment in both cases were 15 and 30 minutes.

ultrasound; whey proteins; soy proteins; functional properties

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