Depth profiling of porcine adipose tissue by Raman spectroscopy

Abstract

Raman spectroscopy was applied on a depth profile of porcine adipose tissue (from skin to meat) with the purpose of (1) discriminating between fat layers and (2) estimating the variation in fatty acid composition as a function of fat depth and fat layer: total degree of unsaturation (iodine value), fractions of saturated, and monounsaturated and polyunsaturated fatty acids. The thickness and composition of the outer layer of porcine adipose tissue influences the final quality of backfat. A too‐thick outer layer is associated with problems such as oily appearance, rancidity development, and difficulties in separating muscle and adipose tissue when cutting. From principal component analysis on standard normal variate preprocessed Raman spectra (1800–800 cm–1), it was possible to discriminate between the outer and the inner backfat layer. Principal component analysis loadings showed that the separation of layer was mainly explained by variation in the bands originating from vibration of double bond C = C stretching plus = C–H twisting and rocking. In the prediction of iodine value a three‐component partial least squares regression model based on full range Raman spectra showed a root mean square error of cross validation of 2.00 and R2 = 0.69. Applying Cauchy–Lorentz band fitting proved that information regarding fat unsaturation was found not only in band intensity, but also in band parameters such as location and width. The results suggest Raman spectroscopy as a potential measurement technique for rapid grading of pork carcasses. Copyright © 2011 John Wiley & Sons, Ltd.

Prediction of intramuscular fat content and major fatty acid groups of lamb M. longissimus lumborum using Raman spectroscopy

“…This is evident in the increase of the C-C out of phase vibration at 1059 cm − 1 , the CH 2 twist vibration at 1290 cm −1 and the CH 2 scissor vibration at 1438 cm −1 (Fig. 4), which previous RS studies on adipose tissue have related to increasing levels of saturation Beattie et al, 2004;Lyndgaard et al, 2011). FAs in IMF are different to FAs in adipose tissue investigated in previous RS lipid studies, as they consist of triglycerides in adipocytes as well as phospholipids in the membranes of the myofibril (te Pas, Everts, & Haagsman, 2004).…”

“…4) C_C bonds and at 1260 cm −1 , which characterises the C-H deformation is evident compared with this band measured from loins with lower PUFA concentrations. This is to be expected as these vibrations reflect the higher degree of unsaturation of PUFA (Lyndgaard et al, 2011;Olsen et al, 2007Olsen et al, , 2010.…”

“…However, a tentative interpretation is plausible based on FA composition studies using data from RS research on animal adipose tissues (Beattie et al, 2007;Lyndgaard et al, 2011) and other FA mixtures (Afseth, Segtnan, Marquardt, & Wold, 2005;Beattie, Bell, & Moss, 2004).…”

“…Other studies using Raman spectroscopy to predict the FA composition of porcine adipose tissue (Lyndgaard et al, 2011;Olsen et al, 2007Olsen et al, , 2010 have indicated that FA composition could be predicted with high coefficients of determination (cross validated coefficients cited range from 0.95-0.98). However, measuring adipose tissue in previous studies avoided the need to discriminate between meat and fat spectra to remove contributions from overlapping protein vibrations on the lipid signals which can arise when IMF is measured in-situ.…”

“…Subsequently, RS is able to detect small amounts of substances in a variety of sample types with no preparation (Das & Agrawal, 2011). The advantages of RS technologies in meat science have not been overlooked and recent studies have utilised it to determine the species of origin of subcutaneous adipose tissue (Beattie, Bell, Borggaard, Fearon, & Moss, 2007) and predict the composition of subcutaneous adipose tissue of pork carcases (Lyndgaard, Sorensen, van den Berg, & Engelsen, 2011;Olsen, Baustad, Egelandsdal, Rukke, & Isaksson, 2010;Olsen, Rukke, Flåtten, & Isaksson, 2007) and salmon .…”