Abstract
For the high-value utilization of tuna liver, the effects of acid-aided (Acid-pH) and alkali-aided pH-shifting (Alkali-pH) on the physicochemical and functional properties of the protein powder prepared by pH-shifting and freeze-drying were studied. As expected, the protein powder with high purity could be obtained through Acid-pH or Alkali-pH followed by freeze drying, while the Alkali-pH led to a higher protein yield, higher protein ratio, lower lipid ratio and lower heavy metal content than Acid-pH. The amino acid profile of the protein powder prepared by Alkali-pH (Alkali-PP) was similar with that prepared by Acid-pH (Acid-PP). In addition, compared with Acid-PP, the Alkali-PP possessed the greater capacities in emulsion activity, foaming capacity and fat absorption capacity. Furthermore, the foaming capacity, foam stability and fat absorption capacity of Alkali-PP was better than soy protein powder. Therefore, Alkali-pH followed by freeze-drying would be a better alternative to prepare high-quality protein powder from tuna liver in the food industry.
Highlights
Yellowfin tuna (Thunnus albacores) is one of the largest commercially fished seafoods worldwide, with an annual output of 2-3 million tons
The objective of this study was to analyse the effects of acid- pH-shifting (Acid-pH) and Alkali-pH on the physicochemical, nutritional and functional properties of obtained protein powder, in order to identify the better alternative and provide reliable guidance for the deep-processing of tuna liver in industry
The results indicated that Alkalin-pH was more powerful in the remval of heavy metal, and obtained the safer protein powder as a consequence
Summary
Yellowfin tuna (Thunnus albacores) is one of the largest commercially fished seafoods worldwide, with an annual output of 2-3 million tons. Tuna liver is characterized by a high protein level, and can be used as a potential source of protein powder. As a product of economic value, is widely used as additives, such as emulsifiers, adhesives, gelling agents and nutritional supplements, in processed foods for human consumption (Pires et al, 2012). Other scholars (Pires et al, 2012) have reported that the protein obtained from marine species often exhibits better functional or bioactive properties than vegetable protein, which might be due to the special living environment in the ocean. Production of protein powder from low-value tuna liver can contribute to the upgrading of this raw material
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