Factors affecting the texture of gels prepared from minced American shad (Alosa sapidissima) flesh

Graduation date: 1989Machine separated flesh from American shad (Alosa\ud sapidissima) was evaluated for preparing heat set gel products.\ud Round fish frozen for 15) to 10 months at -18°C served as raw\ud material for processing investigations. The effectiveness of\ud various additives and processing procedures for improving gel\ud strength and sensory characteristics were determined.\ud Addition of 0.5% polyphosphate to sols enhanced the\ud hardness (P [greater than or equal to] .005), cohesiveness (P [greater than or equal to] .01) and springiness (P [greater than or equal to] .001)\ud of heat set gels. Small amounts (0.5 and 1.0%) of dried egg\ud white also improved hardness, cohesiveness and springiness\ud (P [greater than or equal to] .001). Employing a two stage heat setting regime (40°C for\ud 30 min followed by 90°C for 20 min) strengthened (hardness,\ud cohesiveness and springiness) (P [greater than or equal to] .001) gels over a one stage\ud (90°C for 30 min) heat set. Two stage heating improved gel strength when sol fonnulations contained additives that\ud improved, lowered or exerted no effect on gel strength.\ud Concentrations of dried egg white (1.0, 2.0, 3.0 and 4.0%)\ud and potato starch (1.0, 2.0 and 5.0%) did not improve gel\ud strength. Dried egg white (>1%) did not alter (P > .05) any\ud physical parameters of gel texture. Potato starch (>1%) reduced\ud gel hardness (P [greater than or equal to] .001). More basic pH conditions produced by the\ud addition of 0.1 and 0.2% sodium carbonate to sols did not alter\ud gel hardness or springiness (P < .05) and only caused a slight\ud inprovement in cohesiveness (P [greater than or equal to] .001).\ud Ihe cryoprotectants sorbitol, (0.0, 2.0, 4.0, 6.0 and 8.0%)\ud and sucrose (0.0, 2.0, 4.0 and 6.0%), reduced gel strength in a\ud concentration dependent manner. Gel hardness was reduced in a\ud linear manner as fish protein was replaced with sorbitol\ud (r =.976) or sucrose (r =.965) in sols formulated to contain\ud 74 + 1.5% moisture. Cohesiveness was reduced in a similar\ud manner (r = .942) by sorbitol, but not by sucrose. Gel\ud springiness was not altered by additions of sorbitol or sucrose.\ud Incorporation of sucrose into formulations reduced sensory\ud preference for the texture, flavor, appearance and overall\ud desirability of heat set gels. Analysis of covariance of\ud texture preference scores and physical measurements of texture\ud reveal a strong linear correlation with hardness (P =.0004), but\ud not with cohesiveness (P =.6675). Within the range of sucrose\ud levels evaluated, harder gels were preferred.\ud Washing was evaluated for improving the strength and\ud sensory preference for heat set gels containing 0.5% polyphosphate and 0.5% dried egg white. Sols were set by\ud heating for 30 min at 40°C followed by 90°C for 20 min and\ud exposed to wood smoke. Gel hardness and springiness were\ud reduced by washing (P [greater than or equal to] .05), but not cohesiveness (P > .05). This\ud was surprising, since the gel strength enhancing effect of\ud washing is well documented. Sensory preference for the flavor,\ud color, texture or overall desirability of heat set gels was not\ud affected (P > .05) by washing. Mean overall desirability scores\ud for gels prepared from unwashed minced flesh of 5.25 and 5.27\ud for washed minced flesh were only slightly above a neutral\ud preference (5.0 = neither like nor dislike).\ud Round shad yielded 65.06% planks, 41.20% minced flesh and\ud 40.10% refined flesh. A single exchange wash followed by\ud dewatering yielded 23.02% pressed flesh based upon round weight\ud which was reduced to 20.68% by refining. Processing minced\ud flesh into washed and refined flesh recovered 51.37% of total\ud solids. The yield through refining was 97.33 and 89.83%\ud respectively for unwashed and washed flesh. The protein and\ud lipid content of flesh was not altered (P > .05) by washing, but\ud ash content was reduced (P [less than or equal to] .001)