Quantitative study of the α- and γ-tocopherols accumulation in muscle and backfat from Iberian pigs kept free-range as affected by time of free-range feeding or weight gain

The experiment was undertaken to quantify the a and gamma-tocopherols accumulation in muscle and backfat from Iberian pigs given food free-range as affected by the time of free-range feeding or the weight gained during the fattening in free-range. Pigs were given their food in a free-range production system with pasture and acorns (Quercus rotundifolia) for different periods of time: 46 days (free-range 3), 83 days (free-range 2) and 111 days (free-range 1). A control was given food free-range for 0 days. In addition another experiment was developed to determinate the effect of the the weight gained on the tocopherols accumulation at a similar period of time (111 days) given food free-range: one group gained 68.7 kg of weight (free-range A) and the other 43.6 kg (free-range B). The concentration of gamma-tocopherol significantly (P < 0.0001) increased after 83 days of feeding in the longissimus dorsi (LD) and biceps femoris (BF) muscles, and after 111 days in the inner and outer backfat layers. The concentration of a-tocopherol was not statistically affected by the days of free-range feeding in any case. Iberian pigs that put on more weight had significantly (P < 0.0001) higher concentration of alpha and gamma-tocopherols in the inner and outer backfat layers, and a-tocopherol in the BF muscle than those given food free-range B. However, no differences were detected in the proportion of a-tocopherol in the LD and y-tocopherol in the LD and BF The y-tocopherol content of LD and BF muscles depending on the days of feeding were adjusted to linear and quadratic regressions (R-2 = 0.8705 and 0.8697, respectively), while the outer and inner backfat layers were linear equations (R-2 = 0.8480 and 0.8119, respectively). However, the gamma-tocopherol concentration as affected by the weight gained in free-range showed in all tissues a linear and a quadratic trend that were adjusted to exponential responses. The a-tocopherol content was affected by the y-tocopherol concentration in muscle and outer backfat layer. The tocopherol concentration (alpha and gamma-tocopherols) in the backfat layers may discriminate better between the pigs of high quality that were given food free-range for a long period of time and those that stayed an intermediate period. However, to discriminate between the pigs on formulated food and those given food free-range, the quantification of the gamma-tocopherol concentration in muscle could be a better indicator.