Abstract
Tan sheep are greatly preferred by consumers in China because of their nutritional value and unique flavor. However, the meat quality of Tan sheep has decreased due to the change in feeding systems from grazing to indoor. Studies investigating the mechanisms for the decrease in meat quality are limited. A total of 28 Tan sheep were randomly allocated to two treatments, receiving a concentrated diet, or pasture. Flavor precursors and volatile compounds were analyzed with foodomics. E-nose and E-tongue analyses suggested that the aroma and taste profiles differed between the feeding systems. The grazing lambs had higher levels of linoleic acid and n-3 polyunsaturated fatty acids (p < 0.01). Metabolomics indicated that 25 hydrophilic metabolites active in glycolipid and amino acid metabolisms were changed by the feeding system. Among the 57 volatile compounds identified, methional, γ-butyrolactone, benzaldehyde, and ethyl acetate were at concentrations significantly higher in the grazing lambs than the indoor-fed lambs (p < 0.01). These results reveal key changes in flavor precursors and flavor profiles affected by the feeding system, which may provide an initial view of the reason for consumer preference for the grazing Tan sheep.
Highlights
Tan sheep, one of the domestic ovine breeds, are famous for their nutritional value and delicious flavor, and are highly preferred by consumers in China [1]
Intramuscular Fat (IMF) content significantly decreased in the PF group against the CF group (p < 0.01)
Through a targeted metabolomics approach, we identified a total of 163 different hydrophilic metabolites in longissimus thoracis from Tan sheep (Table S3)
Summary
One of the domestic ovine breeds, are famous for their nutritional value and delicious flavor, and are highly preferred by consumers in China [1]. After decades of grazing restrictions, Tan sheep have been fed mainly a concentrated diet rather than fed with natural pasture. This results in a decrease in meat quality, reducing consumer satisfaction. Understanding the underlying reason for the unique flavor of the grazing Tan sheep is necessary to improve indoor-fed lamb quality, and meet consumer demand. Meat flavor is decided largely by some volatile compounds, which are mainly generated from lipids and water-soluble compounds by means of the Maillard reaction and lipid oxidation upon processing [3,4]. Many carbonyl compounds with low thresholds originate from the degradation of unsaturated fatty acids and greatly contribute to flavor formation [6,7]. Determining the flavor precursors in detail is beneficial to understanding the flavor of grazing lambs
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