The influence of gel structure type and amount of lipid on texture of whey protein isolate (WPI) gels was evaluated by descriptive sensory analysis and determination of fracture and water-holding properties. A series of 16 gels of varying structure (particulate or stranded) and lipid composition (0% to 20%) were developed at a constant protein concentration (12% w/v). Stranded gels had higher values for fracture strain, strain hardening, and held-water. Particulate and stranded gels were similar in fracture stress. Eighteen sensory texture attributes were used to evaluate gels throughout the mastication process that was separated by the following phases: prefracture, 1st bite, chew-down, and preswallowing. The 1st bite property of firmness and preswallowing properties of number of chews and time to swallow were the only sensory properties associated with lipid content. Fracture stress was correlated with these properties. The remaining 15 texture terms were primarily determined by gel structure type. It appears that gel structure type determines the primary texture properties of WPI emulsion gels. An increase in lipid content increases gel firmness and amount of chews required; however, it did not change the primary texture sensation.

The effect of fat reduction on sensory texture and physical properties of commercially available natural and processed cheeses was investigated. The texture of 5 cheeses in full-and reduced-fat versions was characterized by modified descriptive analysis and torsional fracture methods. Reduced-fat cheeses were perceived to be more waxy, fracturable, chewy, hard, and springy and less sticky, cohesive, meltable, and smooth than full-fat cheese. Fullfat cheese had lower fracture stress values than the equivalent reduced-fat products. Fracture strain values did not distinguish cheeses based on fat content. These results demonstrate general textural differences between the full-fat and reduced fat versions of select cheeses.

Although menthol is a common ingredient in pharmaceutical and food products, its sensory properties have not been studied extensively. The objective of this study was to describe and compare the temporal properties of l‐ and d‐menthol. The cooling, burning, and bitterness of two menthol isomers (l‐, d‐) each at 0.01, 0.02, 0.04, 0.08% (w/v) in aqueous solution were evaluated by 11 trained panelists using time‐intensity methodology. The intensity of all three attributes were evaluated continuously from introduction of the sample into the mouth, through expectoration at 10 s, until the termination of the sensation. The l‐menthol samples had a greater maximum intensity and longer total duration of cooling and burning sensations than the d‐menthol samples. In addition, maximum intensity and total duration of cooling and burn increased with concentration. In contrast, the total duration of the burning sensation was only dependent upon concentration of the l‐isomer. Increasing menthol concentration significantly increased maximum intensity and total duration of bitterness for both isomers.

Hyperthermia has been used to treat cancer in the liver. However, significant hepatotoxicity occurs at a therapeutic temperature of 42-43 degrees C. We have proposed that heat toxicity is the result of oxidative stress from superoxide generation with resultant lipid peroxidation. Further, iron release from liver iron stores (ferritin) appears to play a central role in hyperthermic toxicity. In this study, rat livers were perfused in situ at 37 or 42.5 degrees C with and without deferoxamine for 1 h with an asanguinous perfusate. Oxidative stress was assessed by the efflux of glutathione (GSH) into the perfusage. Prior studies by Skibba et al. (1989a, 1991) showed that perfusage equivalents of GSH were primarily present as oxidized glutathione (GSSG). Lipid peroxidation was assessed by the measurement of aldehydes appearing in the perfusate and formation of hydrocarbon gases (ethane and pentane) in the perfusion chamber head space. Liver injury was assessed by the leakage of cytosolic enzymes, AST and LDH, into the perfusate. Livers perfused at 42.5 degrees C showed significant rises (p < 0.05) in AST and LDH after 60 min of perfusion but perfusion at 42.5 degrees C with deferoxamine added, was not significantly different from perfusion at 37 degrees C. Perfusion at 42.5 degrees C caused an increase in GSH into the perfusate at a level significantly (p < 0.05) greater than at 37 degrees C. GSH levels in the liver after 60 min of perfusion decreased from 4.82 +/- 0.76 microM/gm at 37 degrees C to 1.48 +/- 0.54 microM/gm at 42.5 degrees C (p < 0.05) but only fell to 3.42 +/- 1.23 microM/gm at 42.5 degrees C with deferoxamine added. Efflux of iron into the perfusate increase significantly with time and temperature. Low molecular weight chelated iron within the liver after perfusion increased from 5.88 +/- 1.46 nM/gm at 37 degrees C to 25.8 nM/gm at 42.5 degrees C (p < 0.05). Perfusate total aldehyde levels increased from 0.085 +/- 0.056 to 0.32 +/- 0.09 microM/ml after 60 min at 37 degrees C and 0.87 +/- 0.45 to 2.01 +/- 0.90 microM/ml at 42.5 degrees C (n = 8). There was a significant decrease in total aldehyde levels at 42.5 degrees C with the addition of deferoxamine to the perfusate, 0.36 +/- 0.14 to 0.86 +/- 0.27 microM/ml, when compared to 42.5 degrees C levels (p < 0.05). Levels of ethane and pentane in the perfusion chamber head space showed no significant changes with time or temperature of perfusion. The data suggest that lipid peroxidation may play a causal role in hyperthermia induced liver toxicity and that iron plays a major role in this injury. Failure of hydrocarbon analysis to support this conclusion appears related to the use of membrane oxygenators.

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