SUMMARY— A method was developed to objectively measure the emulsifying capacity (ECJ of meat and fish protein extracts by electrical resistance. The method of Swift et al. (1967) was modified to deliver oil at a constinuous rate at the point of blender agitation, thus forming an emulsion for testing the validity of the electrical resistance method. This modification reduced the variance of the end‐point determination within samples. The precision of end‐point determinations by electrical resistance was equivalent to the modified visual method, and had the advantages of being objective, having a finite end‐point and providing a continuous record of the emulsion during formation and collapse. The EC of fresh muscle slurry extracts from fish were higher than those from beef and pork. However, the EC of fresh muscle supernatant extracts ranked from highest to lowest are beef, fish and pork, respectively. In all cases, the EC of supernatant and fresh muscle extracts was higher than the slurry and frozen muscle extracts, respectively.

Effects of rate of heating and final internal temperatures on the texture of fish gels were studied using mechanically deboned fish tissues of 2 species and 2 harvest locations. Generally, rapid heating to 85°C internal temperature (using 100°C steam) produced a firmer, more springy texture in fish gels in comparison with those heated slowly to 70°C internal temperature. However, these thermal effects on gel textures were species and harvest location dependent. Degradations of tropomyosin and myosin observed in cooked fish gels were highly related to gel textural properties. Results further suggested that changes in muscle proteins during heating were caused by proteolytic factor(s) in the sarcoplasmic fraction. The proteolytic crude fraction was isolated and partially characterized. Optimal temperature for proteolytic activity was 60°C; optimal pH was between pH 8.0 and pH 8.5; calcium ion activated the proteolytic activity and the optimal calcium ion concentration for activation was 1 mM; metal chelators, EDTA and EGTA, inhibited the proteolytic activity. A thorough understanding of these proteolytic factors and their subsequent control is important for the utilization of mechanically deboned fish tissues.

Protein functionalities were studied in cornminuted fish gels from mechanically deboned fish tissues of four species after storage .at -29°C up to 12 months. Differences in gel textures, which were evaluated instrumentally and by a texture profile sensory panel, were evident among fish species and time in frozen storage. Fish gel texture was not significantly related to, protein solubility of raw tissues, but was closely related to water-holding capacity and protein solubility of cooked gels. Degradation of tropomyosin and myosin probably occurred in some of the fish gels during therfnal processing.Protein extraction of raw and cooked fish gel Two grams of raw or cooked fish g&l (in duplicate) was homogenized with 20 ml of solution (either 3% NaCl or.5 mhJ Tris) in a Sorvall OmniIMixer for three -15-set periods and centrifuged at 15,000 x G for 20 min to obtain the soluble fraction. The protejn Volume 44 (7979)--JOURNAL OF FOOD SCIENCE-1087 '* .: :

A collaborative study was conducted to compare automated methods for rapid determination of fat and moisture in meat and poultry products with the official AOAC solvent extraction and forced-air oven methods, respectively. Fourteen products were tested, with fat and moisture contents ranging from 2 to 43% and 44 to 74%, respectively. Eight of the collaborating laboratories analyzed the products by using a moisture/fat analyzer; 4 laboratories used the AOAC methods. Standard deviations for within-laboratory repeatability, between-laboratory reproducibility, and bias for each product indicated that the rapid methods were acceptable. The moisture/fat analyzer methods have been adopted official first action for fat and moisture analyses in meat and poultry products.

A laboratory technique for the preparation of small batches of sausage emulsion was developed for a comparative study of the effectiveness of fresh and frozen beef in achieving emulsion stability.The technique consisted of three basic steps: (I) low speed chopping and blending of ingredients at -2" to +20c; (2) low speed blending with the gradual addition of soybean oil at 2" -8°C; and (3) high speed chopping to a temperature of 15"16°C.The preparation and evaluation of emulsions with widely varying compositions revealed that the lean and fat percentages could be varied over wide ranges without significantly affecting emulsion stability, but the range for percentage of water was narrow and critical to stability.The relative stability for fresh and frozen lean was influenced by the amount of added water. For example, at 30% fat level, there was a sharp drop in stability as the added water was reduced below 16% for fresh beef; whereas, an equivalent drop in stability was found as the added water was reduced below 21% for frozen beef. The theory is proposed that emulsion instability is highly dependent upon the level of added water based on results of this investigation.