Impact of dietary dairy polar lipids on lipid metabolism of mice fed a high-fat diet.

The effect of milk polar lipids on lipid metabolism of liver, adipose tissue, and brain and on composition of intestinal microbiota was investigated. C57BL/6J mice were fed a high-fat diet (HFD) for 5 weeks, followed by 5 weeks with HFD without (control) or supplemented with total polar lipids (TPL), phospholipids (PL), or sphingolipids (SPL). Animals fed SPL showed a tendency for lower triglyceride synthesis (P = 0.058) in the liver, but not in adipose tissue. PL and TPL reduced de novo hepatic fatty acid biosynthesis. The ratio of palmitoleic to palmitic acid in the liver was lower for animals fed SPL or TPL compared to control. There was little effect of the supplementation on the cecal microbiota composition. In the brain, DHA (C22:6) content correlated negatively with tetracosanoic acid (C24:0) after TPL supplementation (-0.71, P = 0.02) but not in control (0.26, P = 0.44). Arachidonic acid (C20:4) was negatively correlated with C24:0 in both groups (TPL, -0.77, P = 0.008; control, -0.81, P = 0.003).

Temporal, biochemical and structural factors that influence beef quality measurement using near infrared spectroscopy.

This study included simultaneously measured pre and post-rigor meat quality indicators and attributes, using near infrared (NIR) spectroscopy and reference methods, to understand the temporal, biochemical and structural factors that influence beef quality and use this knowledge to build calibrations for measurement of meat quality using NIR. Eighty beef M. longissimus lumborum (LL) were measured from early pre-rigor (pH, glycogen concentration, and temperature) through to completion of post-rigor ageing (pH, shear force, and water holding capacity (WHC)). To create a range in the attributes, the LLs were subjected to various pre-rigor treatments, including electrical stimulation, restraint wrapping and cooling temperature (5°C, 15°C, or 35°C). Alongside the reference quality measurements and throughout the pre and post-rigor period, the LLs were measured with a diode array NIR spectroscopy system. NIR reflectance measurements were shown to be correlated to reference measurements of pre and post-rigor pH (R(validation)(2)=0.84), pre-rigor glycogen content (R(validation)(2)=0.70), post-rigor shear force (R(validation)(2)=0.58) and post-rigor WHC (R(validation)(2)=0.68). The shape of the NIR and reference plots over time and the ability of NIR to correctly measure differences in treatments indicated that NIR was not merely measuring changes that occur over time, but was measuring specific biochemical and physical changes, most likely changes in glycolytic metabolites, muscle shortening and/or proteolysis. Accounting for the reference method variance showed NIR measurement accuracy to be as good as or slightly better than that of the reference method.

The protective effect of electrical stimulation and wrapping on beef tenderness at high pre rigor temperatures.

A three factorial experimental design involving electrical stimulation (ES/NES), wrapping (wrapped/unwrapped) and pre rigor temperature (15°C or 35°C) was applied to 70 beef M. longissimus lumborum muscles to obtain a wide variation in shear force and drip loss. The shear force of all treatment groups decreased during ageing. As anticipated, wrapping and electrical stimulation had positive effects on shear force. However, high pre rigor temperature (35°C) did not result in higher shear force values if the muscles were electrically stimulated, wrapped or both. The results suggested that electrical stimulation protects against the negative effects of high pre rigor temperatures. The drip loss of all treatment groups increased during ageing in a manner that was unrelated to treatment but was correlated to tenderness (r(2)=0.70; p<0.0001). It was concluded that the application of electrical stimulation, whatever the pre rigor temperature, protects beef from toughening through the prevention of rigor shortening and the avoidance of inhibition of ageing enzymes.