Measurements obtained with a simple rigorometer (muscle tension measuring device) were found to correlate well with measurements of the relative ATP/IMP content ratio (258/250 nm absorbance ratio of perchloric extracts), muscle pH, and visual measurements of stiffness in wholt fish (tilapia, Areochromis aureus) during rigor development. These simple tests yielded measurements which clearly differentiated the effects of ante-mortem stress on the rate of onset of rigor mortis and associated biochemical changes in the fish muscle.

MATERIALS & METHODSQuality of surimi and unwashed fish (tilapia, Areochrumb aureus) mince was investigated as affected by development of rigor mortis in fish prior to processing. Significantly higher protein content and yield, reduced cook loss, and enhanced gel-forming ability and protein extractability were associated with surimi produced from pre-rigor fish. Gels prepared from unwashed minced muscle exhibited less cook-loss pre-rigor, but stage of rigor had little effect on gel rheological properties and protein extractability. Thermal rigidity scanning and differential scanning calorimetry showed substantially higher rigidity values and enthalpies of denaturation, respectively, for surimi prepared from pre-rigor fish, but no effect on transition temperatures due to stage of rigor. Sample preparationThe fish used for this study were blue tilapia (Areochromis aureus), obtained from AB Limited (Raleigh NC) and held as described by Korhonen et al. (1990). Fish were gently removed from tanks and immediately sacrificed by insertion of a knife blade into the brain.

ABSTRACT

Subjective ratings for muscle color and firmness were utilized to segment 299 fresh hams into four different quality groups (low, average, high, dark and soft). Individual hams were pumped to 115% of their green weights with a 62" brine (8-2-2 mixture) by either an artery (188 hams) or stitch (111 hams) brine injection system and then held at 3" C for a 21-day brine equalization period. The hams were then washed, placed in stockinettes and smoked. Prior to smoking, individual hams were assigned to one of six smoking schedules which were based upon three different levels of relative humidity (40, 60 and 80%) and two heating schedules (60, 71,82"C and 49,60, 71"C, dry bulb). Center-cut slices (1.25 cm thick) were removed from five or six average quality hams in each smoking schedule. Three 0.3 cm thick slices were removed from the top (medial side) and two 0.3 cm thick slices from the bottom (lateral side) of each center-cut slice for smoke deposition determinations (phenolic compounds). Artery-pumped hams produced significantly higher processing yields than the stitch-pumped hams. Smoke deposition was not affected by method of brine injection. Processing yields were significantly lower for the lowquality group of hams.Smoking schedules employing the lower smokehouse temperatures and relative humidities (40 and 60%) produced higher overall processing yields At the higher temperature schedule, 60% relative humidity decidedly reduced overall processing yields. Processors desiring to use higher smokehouse temperatures should use a relative humidity greater than or less than, but not equal to, 60% to optimize processing yields. The concentrations of phenols observed in all six treatments would result in acceptable smoke flavor ratings.