Comparison of Physicochemical Properties and Characteristic Flavor Compounds of Rendered Lard from Different Pig Breeds

To investigate the differences in the quality characteristics of various lard types, the study selected Chinese indigenous pig breeds Rongchang Pig (RCP) and Laiwu Black Pig (LWBP), as well as the hybrid pig breed Lu Lai Black Pig (LLBP), the foreign pig breed Spanish-Iberian Black Pig (SIBP), and the commercial pig breed White Pig (WP) as research subjects. The study analyzed the differences in the physicochemical properties and volatile flavor compounds of lard from each pig breed after rendering. The results showed that LWBP lard had the highest moisture content, acid value, and peroxide value, at 0.077%, 1.03 mg KOH/g, and 0.068 g/100 g, respectively, which were significantly higher than other lards (P<0.05). The ratio of unsaturated fatty acids (UFAs) to saturated fatty acids (SFAs) in RCP lard was the highest at 1.33. Gas chromatography-mass spectrometry (GC-MS) identified 78 volatile compounds in five types of lard, with RCP lard containing the most diverse range of volatile flavor compounds (64 types) and the highest concentration (2194.21 μg/kg). Odor activity value (OAV) analysis results indicated that hexanal, (E)-2-nonenal, (E,E)-2,4-decadienal, 2-pentylfuran, and 17 other flavor compounds were widely present in the five types of lard, with OAV values all exceeding 1, making them key flavor compounds in lard. Based on variable importance for the projection (VIP), OAV values, and P-values, four characteristic flavor compounds associated with RCP lard quality were identified: nonenal, (E)-2-hexenal, (E)-2-heptenal, and δ-decalactone. At the same time, four and three characteristic flavor compounds were screened out from LWBP and LLBP lard, respectively, while most flavor compounds in WP and SIBP lard showed no significant differences in their odor activity values. Correlation analysis showed that the formation of the four characteristic flavor compounds in RCP lard was not significantly correlated with the degree of fat hydrolysis and oxidation, suggesting that the formation of these characteristic flavors may be related to the flavor precursor compounds in the raw material itself.