The effect of internal and external roasting temperatures on pork sensory properties, physical measurements and consumer liking : a thesis presented in fulfillment of the requirements for the degree of Master of Technology (Food Technology) at Massey University, Palmerston North, New Zealand

Abstract

The objectives of this research were twofold. Initially it was to quantify the effects of external (roasting) temperature and meat internal (end-point) temperature on the sensory and physical characteristics of selected cuts of pork. Secondly, to investigate Australian consumer preferences to selected cut and cooking condition combinations, and determine the sensory attributes that are most important for preference formation. A two factor central composite rotatable design with independent variables external temperature (120°C-200°C) and internal temperature (65°C-100°C) was used in this trial. A trained sensory panel evaluated the sensory differences of selected cuts (C-loin chop; F-fillet; LE-leg; LO-loin, SH-shoulder, SC-scotch) of cooked pork. Using response surface analysis the effects of these cooking conditions on pork sensory properties (initial and sustained juiciness, pork flavour, hardness, cohesiveness, chewiness) and physical measurements (evaporation loss (%), drip loss (%), cooking time (min/kg), Instron shear force (N), Hunter colour L*, a*, b*) were studied. Sensory attributes initial juiciness (C, F, SC), sustained juiciness (C, F, LE, SC), pork flavour (C, F), hardness (LE, LO, SH), cohesiveness (LE, LO, SH, SC), and chewiness (LO) showed a significant linear relationship with internal temperature. Except for hardness (C) and pork flavour (C, F) all the other sensory attributes showed no significant linear relationships with external temperature. Relationships were also observed between physical measurements and relevant temperatures depending on the cut used. The second stage of consumer evaluation (degree of liking) of selected pork samples was done in Brisbane, Australia and internal preference mapping was used to correlate the trained panel data with consumer data. The results from preference mapping indicated tenderness (hardness) to be the most important sensory attribute driving consumer liking. This segment of Australian consumers primarily liked tender meat that was also flavourful and juicy. Tenderness of pork is achieved at lower internal temperatures for smaller cuts and at higher internal temperatures for larger cuts. Increasing internal temperature also significantly increases cooking time. Therefore, the recommended internal temperatures for smaller cuts should be within the range 68-70°C and for larger cuts within the range of 80-85°C to optimise the sensory properties in accordance with the liking of this segment of Australian consumers. The recommended external (ET) and internal (IT) temperatures from this research are: Chop Roast- ET 160°C-170°C, IT 68°C-70°C; Fillet Roast- ET 160°C-170°C, IT 68°C-70°C; Leg Roast- ET 180°C-190*C, IT 80°C-85°C; Loin Roast- ET 180°C-190°C, IT 80°C-85°C; Shoulder Roast- ET 180°C-190°C, IT 80°C-85°C; Scotch Roast- ET160°C-170°C, IT 68°C-70°C