COAGULATION OF FISH PROTEINS FROM FROZEN FISH MINCE WASH WATER BY OHMIC HEATING

A batch-type ohmic heating device was developed to investigate the possibility of coagulating fish proteins from frozen fish mince wash water. At constant voltage (90 VAC), the temperature of wash water samples was raised to different set points (40, 50, 60, 70, and 80C, respectively). Effect of heating on coagulation of proteins and removal of COD, TS, and TSS was investigated. When the temperature reached 70C, 33.0%, 59.3%, 33.3%, and 92.1% protein, COD, TS, and TSS, respectively, were removed from the wash water. Holding samples at constant temperatures for longer time periods did not improve solids removal, except at 40C. The highest heating temperature for effective coagulation of proteins and removal of solids is 70C. The relationship between heating temperature and heating time followed a second order polynomial model. Apparent electrical conductivity and energy consumption increased linearly with the heating temperature. At the early stage of heating, almost all electric energy was converted to heat energy. As the temperatures rose, energy efficiency began to decrease linearly with the temperature. Overall energy efficiency was above 86%.     

CONTRACTIBILITY OF MUSCLE FIBRES AS A POSSIBLE AID TO JUDGING TEXTURAL CHANGES IN FROZEN MEATS AND FISH

Abstract Following addition of ATP, the contractibility of muscle fibres in suspension (obtained by muscle homogenization) changes during frozen storage of the muscle. These changes were detected by turbidity measurements. In beef, there were no significant changes up to 6 months storage at— 8°C or lower. Considerable loss in contractibility occurred in chicken white muscle. Losses were rapid in cod and carp muscle, contractibility being completely lost in one month at— 3°C. The method is proposed as one criterion for judging textural changes in lean fish during frozen storage.     

PREDICTION OF SENSORY TEXTURE OF FETA CHEESE MADE FROM ULTRAFILTERED MILK BY UNIAXIAL COMPRESSION AND SHEAR TESTING

The ability to predict sensory texture properties of Feta cheese made from ultrafiltered milk (UF-Feta) from uniaxial compression, small shear deformation measurements (frequency sweep, strain sweep, relaxation) and indices of proteolysis was studied. In principal component analysis (PCA) some of the instrumental variables were highly correlated, e.g. the moduli from uniaxial compression and shear measurements; and strain at fracture from uniaxial compression and indices of proteolysis. PCA of the six sensory attributes determined by a trained panel showed that mainly one type of information was present in the sensory results. Partial Least Squares regression (PLS) of all results revealed that stress at fracture from uniaxial compression was the individual instrumental parameter having the highest correlation with the sensory texture attributes. Of these, the three firmness attributes were best predicted by the instrumental parameters. As the shear measurements were not very useful for prediction of sensory texture properties by themselves, and as the increase in prediction precision by inclusion of these measurements was marginal, it is suggested that either stress at fracture alone, or together with three other parameters from uniaxial compression should be used to describe texture properties of UF-Feta cheese.     

CHARACTERIZATION OF LINEAR AND NONLINEAR DEFORMATION BEHAVIOR OF A WEAK STANDARD GEL MADE FROM HIGH-METHOXYL CITRUS PECTIN

A physical characterization of the deformation behavior up to the gel fracture is given for a weak pectin-saccharose-water standard gel from high-methoxyl citrus pectin. The results refer to citrus pectin from different commercial sources and also to high-methoxyl apple pectin.     

UNIAXIAL COMPRESSION OF GELS MADE FROM PROTEIN AND K-CARRAGEENAN

Investigations of gels (18% total solids) made from pea protein isolates (PPI) or soy protein isolate (SPI) with differing amounts of _K-carrageenan added showed that the gel strength increased with the concentration of _K-carrageenan. When the concentration of_K-carrageenan exceeded 0.4%, gels made with PPI were stronger and more stiff than equivalent gels made with SPI. Addition of _K-carrageenan stabilized gels made with PPI towards variations in brittleness (indicated by strain at fracture) with pH. This was not the case when SPI was used. Preheating (75C, 2 min) suspensions containing protein isolates and _K-carrageenan before gel formation increased the strength and stiffness of the final gels, most pronounced when SPI was used. Addition of NaCl (0.5–2%) reduced strength and stiffness of gels, whereas CaCl₂ had no influence on gel properties. Mixtures of PPI and SPI proved to be weaker and more brittle than gels made from only SPI of PPI. Results indicate that using proteins of different origin can cause differences in gel structure.     

AN ENERGY USE ANALYSIS of A FRESH and FROZEN FISH PROCESSING COMPANY

An energy use analysis was performed on a fresh and frozen fish processing company to identify current levels of energy consumption and establish an energy conservation program. Electrical energy constituted 79% and 87% of the fish and ice plants’energy consumption, respectively. Baseload electricity in the fish plant was 88% and 30% in the ice plant. the fish plant's intensity index was 1,882.3 BTU/Ib (4,371.9 KJ/Kg) of product while the ice plant's 172.5 BTU/lb (399.6 KJ/Kg) of ice. the trucking fleet had a fuel intensity index of 29,910.6 BTU/mile (19,630.6 KJ/Km) and was the largest energy consumer accounting for 60% of the company's total energy usage. Proposed energy conservation measures can lead to significant reductions in the current levels of energy consumption.     

RETENTION OF VITAMINS IN FRESH AND FROZEN BROCCOLI PREPARED BY DIFFERENT COOKING METHODS

Fresh and frozen broccoli were analyzed for retention of ascorbic acid, riboflavin and thiamine by semi-automated fluorometry before and after steaming, boiling or microwave cooking for 5 min. Retention of vitamins in general was higher for fresh than for frozen broccoli. Steamed fresh broccoli retained most ascorbic acid, riboflavin, and thiamine. Boiled fresh samples retained least riboflavin and ascorbic acid and microwaved samples, the least thiamine. In frozen broccoli, microwaved samples retained most ascorbic acid and riboflavin, and steamed samples retained most thiamine.     

CHANGES IN FREE AMINO ACIDS AND BIOGENIC AMINES DURING RIPENING OF FRESH AND FROZEN SARDINE

A study was carried out on the evolution of free amino acids and biogenic amines throughout the ripening process of fresh and frozen sardine. The effect of the level of fish gutting was also followed. During ripening a general increase of free amino acids content was observed in all samples. Histidine was the exception to this trend and decreased throughout the processing period. On the basis of the ratio of basic/acidic amino acids, as an indicative of the ripened state, the fresh nobbed sardine ripened faster than the gutted fish. During the course of ripening a considerable increase in biogenic amines and particularly histamine occurred until the 20th day in products from fresh fish. The maximum histamine content allowed in ripened fish products in the European Union (400 mg/Kg) was never attained in this period. A general decrease in most amines was observed by the 240th day of ripening. Tyramine behaves differently and increased in the same period. The samples prepared with frozen fish consistently showed the lowest amine values throughout the ripening period. It seems that freezing has a good effect on the final quality of ripened products as it could decrease the bacterial activity responsible for biogenic amine formation.     

DEVELOPMENT OF FISH MINCE PAKORA FROM A CULTURED CARP SPECIES, LABEO ROHITA (HAM.)

A convenience ready-to-cook product Fish Mince Pakora (FMP) has been developed at the Fisheries Research Complex of the Punjab Agricultural University from the deboned meat of Labeo rohita (Ham.). The sensory evaluation of the product (on a 9-point hedonic scale) scored between 7.7 and 8.5 for different sensory attributes. The overall acceptability score was 8.0. The cooking yield of FMP was 98.43% with fat retention capacity of 359.51%. The crude protein content of the fried FMP was 22.79%, total lipids 3.36%, total soluble sugars 2.60% and gross energy 188.31 kcal/g.

PRACTICAL APPLICATIONS

Processing of carps such as Labeo rohita into value-added ready-to cook/ready-to-eat products such as fish mince pakora (FMP) has a great potential in the present scenario of the increasing number of nuclear families and more and more women getting jobs. The development of FMP from L. rohita has a special significance in making carp culture sustainable. Carps can be cultured in semi-intensive fish farming systems, which are based on low-input technology and are most widely adopted in south and Southeast Asian countries. But as such, carps have limited consumer acceptability because of the presence of intramuscular bones. Processing of carps into value-added products such as FMP can enhance their acceptability and market value as revealed by the sensory evaluation of the product (FMP).     

VITAMIN C AND β-CAROTENE IN FRESH AND FROZEN GREEN BEANS AND BROCCOLI IN A SIMULATED SYSTEM

The reduced ascorbic acid and β-carotene contents of “retail market-fresh” (RMF) and “fresh-frozen” (FF) green beans and broccoli in a simulated handling system were determined. Changes in ascorbic acid content in the two vegetables during a retail market period and frozen storage followed different patterns. In green beans, ascorbic acid content decreased during refrigerated storage for up to 7 days, but in broccoli there was a significant increase. Blanching resulted in a loss of approximately 40% of the ascorbic acid in broccoli. Ascorbic acid content of FF green beans stored at-20C for 16 weeks was approximately twice that in RMF green beans, but in FF broccoli stored under the same conditions it was only about half that of RMF broccoli. β-carotene content of green beans and broccoli did not change during either the retail market simulation of frozen storage and did not differ from that of fresh.