Ten FFAs were quantified, the most abundant being oleic acid (C18:1), followed by linoleic acid (C18:2), then palmitoleic acid (C16:1) (Figure 2b). Very small amounts of myristic acid (C14:0) and tetracosanoic acid (C24:0) were also detected. The contents of most FFAs increased after roasting and the contents of palmitoleic acid (C16:1), oleic acid (C18:1), and linoleic acid (C18:2) increased significantly, for example, the C16:1 in Guire 1 from 280.95 to 577.95 ug/g, the C18:1 in O.C from 819.14 to 1,308.87 ug/g, the C18:1 in O.C from 819.14 to 1,308.87 ug/g, the C18:1 in Guire 1 from 838.36 to 1,220.25 ug/g, the C18:2 in O.C from 210.79 to 601.67 ug/g, resulting from hydrolysis of TAGs into FFAs by lipase, or nonenzymic hydrolysis. FFAs liberated from TAGs were related to the fatty acid composition and positional distribution (Liu et al., 2018). Fatty acids in the 2-position of TAG molecules are more easily hydrolyzed to form FFAs (Lu et al., 2019; Xie et al., 2019). Generally, saturated FAs, especially C18:0, mostly occupied the 1 and 3 positions, whereas unsaturated FAs, particularly C18:1 and C18:2, were primarily concentrated in 2-position of TAGs (Xie et al., 2019). This explains the larger increases in the FFAs C18:1, C18:2, and C16:1. Since the total TAG content is more than 95.5% and the total FFA content is less than 0.15%. Therefore, even a small amount of TAG hydrolysis can cause a significant increase in FFA content during roasting (Sinanoglou et al., 2014). Lipid oxidation was used to evaluate postharvest quality of nuts during processing and storage, FFAs are more susceptible to oxidation than triglycerides (TAGs), and an FFA concentration exceeding 1% decreased the shelf life of hazelnuts with previous reports (Moscetti et al., 2012). Therefore, the FFA levels are a more reliable quality indicator of macadamia kernels (Toth, 2017). From Figure 2, Our results suggest that the production of the total FFAs from Guire 1 and O.C kernels was not accelerated significantly by high temperature, although the content of several unsaturated free fatty acids has increased. The low production of free fatty acids, despite the exposure of kernels to high temperature, was possibly because there was insufficient moisture in the kernels for lipid hydrolysis (Walton & Wallace, 2011). The Australian Macadamia Society (AMS) considers 0.5% FFA acceptable of kernel quality standard for processors. Combined with the results of Table 1, the quality and shelf life of macadamia nuts did not decrease after roasting.🏁

Submitted by lego - 06/14/2025

Ten FFAs were quantified, the most abundant being oleic acid (C18:1), followed by linoleic acid (C18:2), then palmitoleic acid (C16:1) (Figure 2b). Very small amounts of myristic acid (C14:0) and tetracosanoic acid (C24:0) were also detected. The contents of most FFAs increased after roasting and the contents of palmitoleic acid (C16:1), oleic acid (C18:1), and linoleic acid (C18:2) increased significantly, for example, the C16:1 in Guire 1 from 280.95 to 577.95 ug/g, the C18:1 in O.C from 819.14 to 1,308.87 ug/g, the C18:1 in O.C from 819.14 to 1,308.87 ug/g, the C18:1 in Guire 1 from 838.36 to 1,220.25 ug/g, the C18:2 in O.C from 210.79 to 601.67 ug/g, resulting from hydrolysis of TAGs into FFAs by lipase, or nonenzymic hydrolysis. FFAs liberated from TAGs were related to the fatty acid composition and positional distribution (Liu et al., 2018). Fatty acids in the 2-position of TAG molecules are more easily hydrolyzed to form FFAs (Lu et al., 2019; Xie et al., 2019). Generally, saturated FAs, especially C18:0, mostly occupied the 1 and 3 positions, whereas unsaturated FAs, particularly C18:1 and C18:2, were primarily concentrated in 2-position of TAGs (Xie et al., 2019). This explains the larger increases in the FFAs C18:1, C18:2, and C16:1. Since the total TAG content is more than 95.5% and the total FFA content is less than 0.15%. Therefore, even a small amount of TAG hydrolysis can cause a significant increase in FFA content during roasting (Sinanoglou et al., 2014). Lipid oxidation was used to evaluate postharvest quality of nuts during processing and storage, FFAs are more susceptible to oxidation than triglycerides (TAGs), and an FFA concentration exceeding 1% decreased the shelf life of hazelnuts with previous reports (Moscetti et al., 2012). Therefore, the FFA levels are a more reliable quality indicator of macadamia kernels (Toth, 2017). From Figure 2, Our results suggest that the production of the total FFAs from Guire 1 and O.C kernels was not accelerated significantly by high temperature, although the content of several unsaturated free fatty acids has increased. The low production of free fatty acids, despite the exposure of kernels to high temperature, was possibly because there was insufficient moisture in the kernels for lipid hydrolysis (Walton & Wallace, 2011). The Australian Macadamia Society (AMS) considers 0.5% FFA acceptable of kernel quality standard for processors. Combined with the results of Table 1, the quality and shelf life of macadamia nuts did not decrease after roasting.🏁

Submitted by lego - 06/14/2025