The comparative sensory, nutritional, and chemical quality properties of protein hydrolysates produced from mackerel and salmon backbones, heads, and viscera were evaluated. All hydrolysates had high essential amino acid and low biogenic amine levels, implying good raw material quality. The mackerel head-based hydrolysate was rich in ash, influencing the salty taste of the product. Hydrolysates based on viscera were significantly more taste intense and bitter compared with hydrolysates based on backbones and heads. There were only small differences in sensory intensity scores of hydrolysates based on either salmon or mackerel, with no significant difference in bitter taste.
Nuclear magnetic resonance (NMR)
metabolomics profiling was evaluated
as a new tool in sensory assessment of protein hydrolysates. Hydrolysates
were produced on the basis of different raw materials (cod, salmon,
and chicken), enzymes (Food Pro PNL and Bromelain), and hydrolysis
time (10 and 50 min). The influence of raw material and hydrolysis
parameters on sensory attributes was determined by traditional descriptive
sensory analysis and 1H NMR spectroscopy. The raw material
had a major influence on the attribute intensity and metabolite variation,
followed by enzyme and hydrolysis time. However, the formation of
bitter taste was not affected by the raw material. Partial least-squares
regression (PLSR) on 1H NMR and sensory data provided good
models (Q
2 = 0.55–0.89) for 11
of the 17 evaluated attributes, including bitterness. Significant
metabolite–attribute associations were identified. The study
confirms the potential prediction of the sensory properties of protein
hydrolysates from cod, salmon, and chicken based on 1H
NMR metabolomics profiling.
The focus on natural foods and “clean” labeled products is increasing and encourages development of new biobased ingredients. Fish solubles derived from downstream processing of side stream materials in the fish filleting industries have potential as emulsifiers based on their surface-active and emulsion stabilizing properties. The aim of this study was to evaluate and compare emulsion properties and critical micelle concentration (CMC) of direct protein extracts and protein hydrolysates based on fish backbones, and to identify associations between molecular weight distribution and process yield with the studied physicochemical properties. Protein extracts and enzymatic protein hydrolysates were produced based on two raw materials (cod and salmon backbones), two enzymes with different proteolytic specificity, and varying hydrolysis time. Emulsion activity index (EAI), emulsion stability index (ESI) and CMC were measured and compared with casein as a reference to protein-based emulsifiers. Protein hydrolysis was found to have negative impact on EAI and CMC, likely due to generation of small peptides disrupting the amphiphilic balance. The direct protein extracts had comparable EAI with casein, but the latter had superior ESI values. Protein hydrolysates with acceptable EAI could only be obtained at the expense of product yield. The study emphasizes the complexity of physicochemical properties of protein hydrolysates and discusses the challenges of achieving both good surface-active properties and high product yield.
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