Carla Pires

Impact of ultrafiltration and nanofiltration of an industrial fish protein hydrolysate on its bioactive properties

BACKGROUND Numerous studies have demonstrated that in vitro controlled enzymatic hydrolysis of fish and shellfish proteins leads to bioactive peptides. Ultrafiltration (UF) and/or nanofiltration (NF) can be used to refine hydrolysates and also to fractionate them in order to obtain a peptide population enriched in selected sizes. This study was designed to highlight the impact of controlled UF and NF on the stability of biological activities of an industrial fish protein hydrolysate (FPH) and to understand whether fractionation could improve its content in bioactive peptides. RESULTS The starting fish protein hydrolysate exhibited a balanced amino acid composition, a reproducible molecular weight (MW) profile, and a low sodium chloride content, allowing the study of its biological activity. Successive fractionation on UF and NF membranes allowed concentration of peptides of selected sizes, without, however, carrying out sharp separations, some MW classes being found in several fractions. Peptides containing Pro, Hyp, Asp and Glu were concentrated in the UF and NF retentates compared to the unfractionated hydrolysate and UF permeate, respectively. Gastrin/cholecystokinin-like peptides were present in the starting FPH, UF and NF fractions, but fractionation did not increase their concentration. In contrast, quantification of calcitonin gene-related peptide (CGRP)-like peptides demonstrated an increase in CGRP-like activities in the UF permeate, relative to the starting FPH. The starting hydrolysate also showed a potent antioxidant and radical scavenging activity, and a moderate angiotensin-converting enzyme (ACE)-1 inhibitory activity, which were not increased by UF and NF fractionation. CONCLUSION Fractionation of an FPH using membrane separation, with a molecular weight cut-off adapted to the peptide composition, may provide an effective means to concentrate CGRP-like peptides and peptides enriched in selected amino acids. The peptide size distribution observed after UF and NF fractionation demonstrates that it is misleading to characterize the fractions obtained by membrane filtration according to the MW cut-off of the membrane only, as is currently done in the literature.

Extraction of Sardine Proteins by Acidic and Alkaline Solubilisation

Muscle sardine (Sardina pilchardus) proteins were extracted using acidic or alkaline-aided solubilisation followed by isoelectric protein precipitation and compared to the traditional surimi process. This work reports the results obtained with unwashed and washed sardine mince. The highest solubilisation of sardine miofibrillar proteins was recorded at pH 2.5 (85%) and 11.5—12 (80%) and the isoelectric point was around pH 5—5.5. The global yields achieved were 77% and 73% for the alkaline and acidic processes respectively, which are considerably higher than that of the traditional surimi process (ca. 28%). The fat content reduction was 65.3% and 51.0% for the proteins recovered after alkaline and acidic solubilisation respectively. A reduction of 91.1% was obtained in the surimi process. However, higher fat elimination was achieved when washed mince was used (95.3% and 99.0% for acidic and alkaline processes, respectively). The protein recovered after both solubilisation processes showed poor gelling properties than surimi but the acidic recovered proteins had the lowest gel strength. The washing of mince did not influence the whiteness of acidic protein recovered but the proteins recovered in the alkaline-aided solubilisation process from the washed mince were whiter.

Functional and antioxidative properties of protein hydrolysates from Cape hake by-products prepared by three different methodologies.

BACKGROUND The production of fish protein hydrolysates (FPH) is a convenient technology for upgrading fish by-products. The aim of this work was to study three different methods of FPH preparation from Cape hake by-products to improve yield and quality. Functional and antioxidative properties of all FPHs were determined. RESULTS The protein content of hake FPH was in the range 807-860 g kg(-1) and the degree of hydrolysis was between 19% and 22%. The maximum yield (71.9%) was achieved by methodology B but the hydrolysate was darker. The peptide profile of all FPHs was very similar. FPH prepared by methodology C had significantly higher emulsifying activity index and hydrolysate prepared by methodology B had the highest foaming capacity. The solubility of FPH was in the range 71-76% and increased the water-holding capacity of minced fish by about 9%. The fractionation of FPH obtained by methodologies A and B allowed concentrating peptides with higher radical scavenging activity and reducing power. CONCLUSION The properties of the FPH prepared indicated that they can be used in food systems as natural additives, particularly to improve their water-holding capacity.

Utilization of Alkaline-Recovered Proteins from Cape Hake By-Products in the Preparation of Frankfurter-Type Fish Sausages

The objective of this study was to prepare a Frankfurter-type fish sausage with different levels of recovered proteins from Cape hake by-products and choose the optimum formulation using the response surface methodology. The simultaneous analysis of added-recovered protein (0–40%), pork fat (5–30%), and water (20–35%) on texture, color, and sensory evaluation was done. Two optimum formulations were determined: R1: 20% recovered protein, 5% pork fat, and 27.5% water; and R2: 20% recovered protein, 17.5% pork fat, and 20% water. Fish sausages prepared with these formulations showed lighter color and softer texture than pork sausages. The sausages prepared following the formulation R1 with two levels of carrageenan (0.5 and 1%) were significantly harder (p  <  .05) than those obtained with the formulation R1. However, no significant differences (p ≥ .05) were observed for work of penetration, elasticity, and cohesiveness. Sausages prepared with the formulation R1 and 3.5% of cod liver oil had 6.4% of fat and 658 mg EPA + DHA/100 g sausage, which was 3.7 times higher than in R1 product. The flavor and overall acceptability of these sausages with cod liver oil added were not affected.

Functional and Biochemical Characterization of Proteins Remaining in Solution After Isoelectric Precipitation

ABSTRACT The resulting supernatant from the isoelectric precipitation of “sawdust” from Cape hake portioning and blue whiting muscle was concentrated by ultrafiltration and the retentate spray-dried. Two main peaks corresponding to molecular weights of 15 kDa and 65 kDa were detected in the supernatant from both raw materials; in the retentate the main proteins had approximately 18 kDa and 73 kDa, and some proteins with 59 kDa were detected in the permeate. The protein content was 74.0% and 70.0% for hake by-products and blue whiting, respectively. Dried proteins had relatively low emulsifying and foaming capacity but high foaming stability and were whitish in color. Hydrophobicity and sulphydryl content were similar to those from other protein sources.