PubMed · 16567274
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Duane Sunwold. 2006. Desserts first.. https://doi.org/10.1053/j.jrn.2006.01.014
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This study investigated the evolution of eating quality (colour, texture and volatile flavour compounds), water status, microstructure and protein structure of pork meat under different cooking methods. The methods analysed included traditional cooking (TC: 10, 20, 30 and 40 min, 100 °C), sous-vide cooking (SV: 1, 2, 3 and 4 h, 60 °C) and micro-pressure cooking (MC: 10, 20, 30 and 40 min, 120 °C). Across the three cooking processes, as cooking time increased, cooking loss, lightness, yellowness, P23, β-sheet, random coil and surface hydrophobicity of the meat samples increased. By contrast, redness, P22, hydrogen proton density, esters content, α-helix, β-turn and sulfhydryl group content decreased. Moreover, the Warner-Bratzler shear force (WBSF), adhesiveness, hardness, springiness, gumminess, chewiness, alcohols, aldehydes, ketones and fluorescence intensity of the meat samples, initially increased and then decreased as cooking progressed. SV resulted in higher water-holding capacity (WHC), improved redness and increased alcohol and ester levels, whereas MC produced softer meat and greater water mobility. Furthermore, MC enhanced the degree of microstructural damage and protein structural unfolding in the meat. MC requires less time to achieve textures and flavours similar to those obtained using the TC and SV methods. Thus, MC is an efficient cooking method for the catering industry to obtain desired meat quality rapidly.
Three mechanisms have been previously proposed to explain the complex process of oil uptake during deep-fat frying. The mechanisms reviewed are water replacement, cooling-phase effect and surface-active agents. The former mechanism describes mainly oil uptake of relatively large voids in the fried food created due to water evaporation. The second mechanism furnishes an explanation for the significant amount of oil absorbed when the food is removed from the fryer. At this point, product surface characteristics and oil viscosity play paramount roles. Surface-active agents' formation provides only a limited explanation for the increased oil uptake during prolonged frying. Reviewed literature, theory and new data show contradicting values and do not support the myth that during extended frying time the surfactants generated reduce the contact angle and/or the interfacial tension, and consequently, influence oil uptake significantly. Higher oil uptake after extended frying time is probably related to higher oil viscosity caused by polymerization reactions and oil adherence to the product surface. Further research is needed for establishing the interrelationships between surface-active agents' formation and their effect on fried product oil uptake and quality to resolve this myth.
In situ changes in pectin fractions for thermally processed carrots were related to textural changes. The texture of pretreated and subsequently thermally processed carrot disks was determined. Alcohol insoluble residue (AIR) was extracted from the pretreated and thermally processed tissues. The AIR was characterized in terms of the degree of methylation (DM) and changes in pectin fractions. Distinct differences in texture and DM were observed during thermal processing. Pretreatment conditions that induced a significant decrease in DM showed better textures. Demethoxylation caused interconversion of pectin fractions, water soluble pectin (WSP) changing into water insoluble pectin [chelator (CSP) and alkali (NSP) soluble pectin]. This process was reversed during cooking accompanied by remarkable alterations in molecular weight (MW) distribution patterns. The WSP depicted polydisperse MW distribution patterns, strongly dependent on the pretreatment condition. Confirmatory results of interconversions of pectin fractions (WSP, NSP) were demonstrated by the MW distribution patterns and neutral sugar profiles. All thermal related transformations of pectin structural parameters were decelerated by lowering the DM.