EXAMINATION OF SOME FUNCTIONAL PROPERTIES OF SILVER CARP ( HYPOPHTHALMICHTHYS MOLITRIX VAL . ) AND CARP ( CYPRINUS CARPIO LIN . ) MEAT

Waterbinding ability (WBA), held water (HW) and gel-forming properties of silver carp (Hypophthalmichthys molitrix Val.) and carp (Cyprinus carpio Lin.) meat were examined in this paper. Two variants of fish meat gels: A with 50% of meat and B with 60% of meat were examined at temperatures: 70, 75, 80, 85 and 90 C. The variant A of silver carp meat gels has shown the maximum of WBA and HW at 80 C, and the variant B at 75 C. In both variants of carp meat gels slow increase of WBA and HW with rise of temperature to 80C was established. Silver carp meat gels have had better WBA than control gels (beef and poultry meat), and carp meat gels have better HW, but somewhat worse WBA than control gels. In gels of variant A of silver carp meat the highest module of elasticity (6.862 N/cm) was found at thermal treatment at 85 C, but statistically significant differences in relation to other temperatures were not established. In variant B, with the rise of temperature, the module of elasticity increases; statistically significant differences were established among gels treated at 70 C and others. Differences between variants A and B were statistically significant at all examined temperatures. Meat gels of silver carp have significantly lower module of elasticity compared to control gels. Under conditions of our experiment the module of elasticity of carp meat was below measuring limit.


I n t r o d u c t i o n
Non-conventional technological processes in fish processing are becoming increasingly present thanks to the possibilities they offer, in respect of assortment and rational (economical) usage of raw material, and they are based on minced fish meat or surimi as a raw material (S c h u b r i n g et al., 1993).
The texture of final product is obtained by heat denaturation and formation of three-dimensional protein gel net.
Rheological characteristic and quality of final product are determined by functional characteristics of raw material, (K i m et al., 1986), and it is possible to improve them with additives, and/or by conditions of heat treatment, (H a m a n n et al ., 1990).
Waterbinding ability, as meat basic functional property and rheological properties of protein gels (strength and elasticity) are closely related , and they are in the function of type and concentration of protein, temperature and time of heating, concentration of NaCl, pH, and ionic strength of the system (Anne-Marie H e r m a n s s o n ,1982; H i c k s o n et al., 1982).
Fish meat functional properties are determined by quantity and state of myosine and they can significantly differ among each fish species (F r e n c h et al.,1988 Instability of myosin, in vivo and post mortem, influences functional characteristics of fish meat and final product quality too.(C r u p k i n et al., 1988; B e c h t e l and P a r i s h , 1983).
A serious problem related to fish meat gels texture is caused by a group of heat-activated muscle proteinases which bring about texture degradation called the "modori" phenomenon.K i n o s h i t a et al., (1990), and T o y o h a r a et al., (1990) quoted four, for the time being, known proteinases at temperatures of 50 o and 60 o C, respectively.

Materials and Methods
Silver carp (Hypophthalmichthys molitrix Val.) and carp (Cyprinus carpio Lin.) meat was used for this investigation.Average fish mass was between 2 and 4 kg.Fishes were kept in a refrigerator (+4 o C) till slaughtering.
Slaughtering and preliminary processing were done 6 to 8 hours after catch, in a usual way (scales were removed and carcass was gutted, washed and drained).After filleting and skinning meat was ground through a Ø 4 mm end plate.Beef and poultry meat, used as control variants, were also ground through a Ø 4 mm end plate.Samples were homogenized, packed in polyethylene bags and frozen at -18 o C.
Homogenates were prepared in a laboratory blender from frozen meat (around -4 0 C), cooled water (4 o C), common salt and polyphosphate preparation Tari K2 (Giulini Chemie, GMBH).Samples homogenization was done at the speed of 3000 rpm, until the temperature of 11 0 C was attained.
Prepared homogenates were carried in glass tubes Ø 30 mm and thermally treated during 30 min at the following temperatures : 70, 75, 80, 85 i 90 o C.After heat treatment the obtained gels were kept in a refrigerator (4 o C) over night.
Variant A of homogenates (gels) in the ratio of meat: water + additives -50:50 was prepared of 160 g meat, 150g water, 9.6g common salt and 0.96g polyphosphate preparation.Variant B of homogenates (gels) in the ratio of meat: water + additives -60:40 was prepared of 160g meat, 98.2g water, 9.6g common salt and 0.96g polyphosphate preparation.
Elasticity of cylinders (base diameter 11 mm and height 10 mm), cut out from cooled gels was measured with Hőepler consistometar at load axle of 250g.
Elasticity (module of elasticity ) -E was calculated by using the following formula: Waterbinding ability was determined as held water according to the method of F o e g e d i n g and R a m s e y (1986): g held water per g dry matter = (total water in a sample) -(free water in a sample) (dry matter in a sample) The analyses of basic chemical composition as well as the analyses of water content and dry matter content in gels were carried out by the following methods: -water content JUS ISO 1442 -protein content JUS ISO 937 -total fat content JUS ISO 1443 -total ash content JUS ISO 936 The obtained results were analyzed statistically using Student t-test, in program ANOVA-MANOVA, Stat.Soft.Inc 1995., Microsoft.

Results and Discussion
The results of chemical composition examination of silver carp and carp meat presented in figs. 1 and 2 showed very significant differences, especially in protein and lipid content.Protein content in silver carp meat was 28% higher than in carp meat, and lipid content was 380% higher in carp meat than in silver carp meat.These differences in chemical composition are consequences of a marked influence of species (S i d v e l l at al., 1974; I w a s a k i et H a r a d a , 1985).Waterbinding ability of silver carp meat gels, expressed as % of separated water, is presented in graph 1.With an increase of temperature from 70 o to 75 o C, % of separated water decreases.Gels of variant B had the lowest % of separated water just at the temperature of 75 o C, and then with the increase of temperature opposite reaction was noticed.In variant A % of separated water decreased to the temperature of 80 o C and then had a similar tendency as variant B. Almost the same trend was ascertained by Anne-Marie H e r m a n s s o n and Mara L u s i c a n o (1982) for beef plasma gels.In relation to control gels produced of beef meat (both variants) and variant A of poultry meat, both variants of silver carp meat gels had significantly lower % of separated water, namely higher WBA.Waterbinding ability of variant B of poultry meat gels was the best concerning that % of separated water was the lowest (10.49%).Silver carp meat gels held water better then control gels, especially compared to beef meat gels (graph 2).In variant A of silver carp meat, HW slightly increases in the interval of 70 -75 o C, and then more intensively at 80 o C. At cited temperature, 1 g of dry mater binds 5.31 g of water, which is the highest value established for silver carp meat.With further increase of temperature HW decreases.In variant B of silver carp meat gels, HW increases 41% with the rise of temperature from 70 to 75 o C, but it is somewhat lower than in variant A at the same temperature.With further increase of temperature during heat treatment, HW slightly and steadily decreases.This occurrence of inferior functionality related to WBA in gels with higher protein content (variant B) at temperatures higher than temperatures of gelation, Anne-Marie H e r m a n s s o n and Mara L u c i s a n o (1982) explained by very strong protein-protein interaction which caused ruptures and pressing out of water from gel.Regarding the results presented in graph.3, it can be seen that carp meat gels had the best water binding ability at temperature interval between 80 and 85 o C, which is for about ten degrees higher than temperatures at which the best WBA was obtained for silver carp meat.This trend could be explained by somewhat shorter period of exposition of mentioned gels (treated at 80 and 85 o C) to temperatures between 50 and 60 o C, at which modori inducing proteinases (MIP) are activated.H a m m a n et al. (1990) cited this possibility and accented the activity of MIP, especially in carp meat.Carp meat gels of variant A show lower water binding ability than control gels.However, it can be concluded that variant A of carp meat gels generally had very good water binding ability.Only variant B of poultry meat was superior over variant B of carp meat.
The results for held water ability presented in graph.4 also point out that optimal temperature of heat treatment of fish meat gels was 80 o C. It was noticed that significantly lower held water ability of carp meat (2.03 to 3.02 g held water/g dry mater) in relation to silver carp meat (3.07 to 5.31 g held water/g dry mater).This difference was probably not only the consequence of negative protein/water ratio in carp meat, but also the consequence of decrease of protein functionality.The results of gel elasticity examination pointed to this assumption.The elasticity of all carp meat gels variants were low and below the measuring border of the instrument.The results of silver carp meat gels elasticity examination are presented in table 1.Both variants of gels (A and B) had a low module of elasticity at the temperature of 70 o C, (gels A were not measurable), which pointed out that temperature of gelation of this type of meat protein is somewhat higher (about 75 o C).At temperature interval, from 75 to 90 o C, in variant A similar values of E were established, and the existing differences were not get statistically confirmation of significance.Comparison of the results for elasticity of silver carp meat gels and control gels, presented in table 2, shows significantly better rheological characteristics of control gels than silver carp meat gels and similar data reported by H a m a n n at al. (1990).However, if we compare variant B of fish meat gels and variant A of control gels, we can state very similar or even better characteristic of fish meat gels.These results lead to the conclusion that silver carp meat, with little increase of protein concentration, can be successfully used for obtaining a meat system or meat emulsion.

C o n c l u s i o n
Silver carp meat is characterized by exceptional waterbinding ability, even better than that of beef and poultry meat.The best water binding ability was established at temperature interval from 75 o to 85 o C.
Silver carp meat gel-forming ability and gel elasticity were also very good, but somewhat inferior to gel-forming ability and gel elasticity of control gels.
Silver carp meat, with little increase of protein concentration, can be successfully used for obtaining a meat system or meat emulsion.
Carp meat had good waterbinding ability, but somewhat worse than water binding ability of beef and poultry meat.
Carp meat gels elasticity was very low, which makes this meat inferior to silver carp meat.

Graph. 2 .
treatment o C Graph. 1. -Water binding ability of silver carp meat (by Foegeding and Ramsey) -Held water ability of silver carp meat (by Foegeding and Ramsey)

Graph. 3 .
-Water binding ability of carp meat (by Foegeding and Ramsey)

Graph. 4 .
-Held water ability of carp meat (by Foegeding and Ramsey) It variant B statistically significant difference was established (P<0.01) between gel elasticity treated at 70 o C, and others.Gel elasticity of variant B is significantly higher (P<0.05 and P<0.01) than gel elasticity of variant A treated at the same temperature.T a b.1.-Influence of temperature of heat treatment and composition on elasticity of silver carp meat gels (module of elasticity E -N/cm 2 ) Means in the same row with different superscript are significantly different (P<0.01,d.f.= 8) c Means in the same column with the same superscript are significantly different (P<0.05,d.f.= 8) d Means in the same column with the same superscript are significantly different (P<0.01,d.f.= 8).
R E F E R E N C E S ISPITIVANJE NEKIH FUNKCIONALNIH SVOJSTAVA MESA TOLSTOLOBIKA (Hypophthalmichthys molitrix Val.)I ŠARANA (Cyprinus carpio Lin.) D. Živković 1 , V. Perić 1 i Marija Perunović 1 Means in the same row with different superscript are significantly different (P<0.01,d.f.= 8) c d Means in the same row with different superscript are significantly different (P<0.05,d.f.= 8 * temperature of heat treatment, t = 75 o C