Dry Fractionation Combined with Solvent-Assisted Fractionation for Process Optimization and Saturated Fatty Acid Enrichment in High-Melting- Point Mutton Tallow Fractions

To develop high value-added mutton tallow products, high-melting-point fractions were prepared from Altay sheep rump fat using a dry fractionation process combined with solvent-assisted fractionation. Solid fat yield, melting point, peroxide value, and acid value were selected as evaluation indices. Single-factor experiments were conducted to investigate the effects of various parameters on the fractionation efficiency, followed by Box–Behnken response surface design. The Analytic Hierarchy Process–Criteria Importance Through Intercriteria Correlation (AHP–CRITIC) method was applied to assign subjective and objective weights to each evaluation index, with the comprehensive score used as the response value. Physicochemical properties and fatty acid composition of the fractionated products were analyzed. The optimal conditions were determined as an oil-to-solvent ratio of 1:2, crystallization temperature of 20  °C, cooling rate of 8  °C/h, and crystallization time of 12  h. Under these conditions, the solid fat yield reached 33.23%, melting point was 50.1  °C, peroxide value was 0.02 mg/g, acid value was 0.42  mg/g, and the comprehensive score was 93.88. The high-melting-point mutton tallow fraction exhibited peroxide value, acid value, saponification value, malondialdehyde content, and iodine value of 0.025  mg/g, 0.44  mg/g, 195.38  mg/g, 1.94  nmol/mL, and 42.42  g/100 g, respectively, which were significantly lower than those of the raw tallow and the solid fat obtained by dry fractionation at 28  °C (28S) (P<0.05). The saturated fatty acid content increased from 43.94% in raw tallow to 47.8% in 28S, and further to 63.21% in the solid fat obtained by the combined fractionation method at 20  °C (20S). These results indicate that the high-melting-point fraction exhibits markedly enhanced oxidative stability and melting point, thereby improving its potential as a specialty fat. Compared with raw tallow, the saturated fatty acid content increased by 19.27% (P<0.05), providing a reference for the rational development of high-melting-point mutton tallow fractions and the enrichment process of saturated fatty acids.