Hydrolysis of Marine Cod (Gadus Morhua) Head - Utilization of rest raw material from cod for production of ingredients for human consumption
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The main objective of this study was to determine the possibility of utilizingfrozen marine cod head for further processing into high-quality and high-yield fishprotein hydrolysates. The project included determination of the effect of mincingversus whole head, frozen storage and thawing methods on the composition and yieldof FPH.The results show that freezing and thawing of cod head lead to small changes inthe composition of raw material and consequently the resulting fish proteinhydrolysate. The lipid content in freeze dried FPH ranged from 0.37-0.71% dryweightfor all samples, where the lowest belonged to the day one and the highest forthe whole head thawed in air. The protein content in freeze dried FPH was 88.4% forday one and in the other samples, the concentration was more or less similar andslightly lower than the day one sample (67.7-71.6%). While protein recovery was5.7% dry weight for FPH produced from fresh cod head compared to 4.8 to 5.0% dryweight for frozen samples.The degree of hydrolysis showed variations among FPHs produced from differentraw materials and showed higher values for the whole head thawed in water andminced head thawed in air and rather low for the day one sample. There was nocorrelation between DH determined using formol titration and TCA-soluble peptides.For example, there was a very high concentration of TCA-soluble peptides in day onesample.Regarding the yield of the dry matter in 60 min hydrolysed FPH factions; there isa slight difference between the samples (10.6-12.3%), which makes it profitable toproduce FPH from frozen stored cod heads.Economically speaking, it is more beneficial to store and thaw the minced headusing an appropriate thickness of packaging, because of the smaller space that isrequired for the storage of the heads on board. In addition, if the right thickness andsize is used for packaging, the time that is needed to thaw them will be much shorter.Due to small differences between the compositions of minced and whole head, it issuggestible to store the samples in minced state.Some optimizations are required for the hydrolysis process and analyses,including using more appropriate fractionation, adjusting the time of thawingaccording to the raw material to avoid excess changes during thawing and blending ofsediments prior to sampling for analysis.Everything considered, in order to determine the suitability of the used processingmethods, and whether or not cod head can be used as raw material to produce highquality FPH, there should be a clear definition of quality . For instance, it should bedetermined in which section and for what purpose the end product is going to beconsumed. If we are looking for the functional properties of the FPH, there aredifferent characteristics that are required than when it is used for pharmaceuticalpurposes. Therefore, different analysis methods should be used to determine thechanges in those particular required characteristics.