Native proteins from by-products and pelagic fish
PROPEPHEALTH has been successful in developing process lines in the pilot plants of Matis, Ipimar and Ifremer for upgrading by-products/waste and thereby improving the utilisation the fish resources. Alkali solubilisations and isoelectric precipitation can be used for producing proteins from lean fish than can be incorporated into high value fish products. Ifremer is developing promising processes for extraction of both proteins and lipids from fatty fish. In some cases gelation properties need to be improved to be able to apply to ready to eat products like pates, sausages and surimi like products. The use of fish proteins to reduce fat uptake in deep fried fish was tested and the conclusion was that addition of protein isolate in the fish block and having a pre-batter with protein isolate did not change the fat content of the finished product in the set up and conditions used in the tests. Frying time had the most impact. Oxidation is a great problem when it comes to producing dried fish proteins. The drying of pH-shift processed protein could even increase the problem. The sensory quality and storage stability of such products must be improved before they can be used in food applications. Recommended ways of optimising processing parameters include reducing access to pro-oxidants and oxygen, preserving endogenous antioxidants in the raw material by mild processing techniques and using added antioxidants.
Fish protein hydrolysates and bioactive peptides
Enzymatic hydrolysates of fish from various sources from three countries have been successfully screened for various bioactive properties. The reproducibility of fish protein hydrolysate (FPH) on a laboratory scale was good but there were some problems in transferring the conditions to an industrial scale. Saithe protein hydrolysates had CGRP like active molecules (around 3.5 kDa) and all samples showed activity in adenylate cyclase assay and analysis of CCK. CGRP (all samples showing activities, active molecules 2-3 kDa) like activities in differently treated cod backbones of different degrees of hydrolysis was tested. Decreasing activity with increased degree of hydrolysis (DH) in frozen samples was observed. Fermentation of fish protein hydrolysates increased gastrin/CCK activities. There was a linear relationship between DH and antioxidative activity but it depended on enzyme specificity. It was possible to adapt laboratory results to industrial processes on basis of chromatographic patterns. Non enzymatic browning of FPH using reducing sugar improved antioxidative properties. Extended fractionation of FPH will result in a retentate being enriched in peptides > 750 Da while the permeate is enriched in peptides < 250 Da. These « pivot » points depend on the membrane MWCO (4 000 Da), but also of the peptidic profile (the MW distribution) of the crude hydrolysate. A change in ▲P modifies slightly the selectivity and increasing ▲P decreases the real membrane MWCO. The fractionation has a positive effect on antioxidative properties with higher activities in the UF permeate. But activities decrease in all the fractions when the VRF increases.
The SMEs now have processes that have been developed for producing fractionated fish protein hydrolysates with tailor made properties. Some of the active ingredients have been partially identified. Scientific new knowledge has been generated about the influence of the source of the raw material and process parameters on the bioactive properties of fish protein hydrolysates.More knowledge is available about the design of the production processes for tailor make products.
Development of functional foods and intervention studies
The results of the in vivo studies of satiety effects of FPH are quite promising. The findings until now show that fermented saithe protein hydrolysates reduce food intake, body weight, glychemic index and insulin level and increase levels of CCK. But the lack of progress of the