WAXY CORN STARCH AFFECTING TEXTURE AND ULTRASTRUCTURE OF SARDINE SURIMI GELS

The effect of waxy corn starch (WCS) on the texture, water-holding cap acity and microstructure of sardine (Sardina pilchardus) surimi gels i n two different systems was studied. In the type A system, increasing amounts of WCS (2, 4, 6 or 8 g/100 g surimi) were added to surimi whil e maintaining the gel moisture constant at 78%; in the type B system, WCS was added without correcting the gel moisture. Gels were made usin g two different heat treatments [heat-induced setting (HS) and direct cooking (DC)]. When starch was replaced by surimi (type A) and a heat treatment was applied that favoured formation of a preliminary actomyo sin (AM) network (i.e. HS), gel strength (GS) was lower than in the co ntrol and decreased as more starch was added, despite an increase in t he amount of water held by the gel. Scanning electron microscopy (SEM) showed that the matrix network was fibrillar with a globular surface. Starch appeared to be totally gelatinized and surrounded by a continu ous matrix. When the amount of dry matter in gels was increased (type B), in no case did starch have a reinforcing effect, despite an increa sing water-holding capacity; SEM showed a denser continuous matrix sur rounding the gelatinized starch. Both types of gel made using the heat treatment that allows simultaneous gelling of surimi and gelatinizati on of starch (i.e. DC) exhibited much poorer GS than did HS gels, whil e addition of starch made practically no difference to gel texture. Th e findings suggest that the effect of starch is related to the type of gel matrix that forms upon addition of ingredients. Although such gel s contained more water or dry matter, their texture parameters were lo wer, possibly because of the type of network formed by sardine surimi. Nonetheless, gels of acceptable quality were successfully made with a dded starch by incorporating less surimi.