Investigating the effects of variety and harvest year on taste and mouthfeel of pecan kernels

Limited work has investigated the pecan kernel flavor as affected by variety and harvest year. This study aimed to quantify 21 free amino acids with GC-MS, five 5-nucleotides with HPLC, °Brix with a refractometer, three sugar with HPLC, five organic acids with HPLC, and total polyphenols content (TPC) with Folin–Ciocâlteu for 21 pecan varieties, which were eight native, six cross, four improved, and three seedling across two harvest years. The total free amino acids (FAA) ranged 57.9 – 167.4 mg/100 g in 29 tested kernels, while individual FAA ranged from 0.012 – 4.43 mg/100 g of kernel. Glu, Asp, and Arg were the most dominant FAA in all samples. Most varieties, especially native and selected cross, showed high amounts of umami contributing FAA (Asp and Glu), ranging 5.35 – 44.43 mg/100g kernels. The sweetness (Ala, Gly, Pro, and Glu) and bitterness (Arg) contributing FAA ranged 0.83 – 17.57 and 7.32 – 14.93 mg/100 g of kernel, respectively, both showed a wide variation among the varieties. Only Glu is above the threshold level in some varieties to contribute an umami flavor. The total 5-nucleotides ranged 16.49 – 49.68 mg/100 g of whole kernel for all varieties across both harvest years. IMP was the most abundant across most varieties tested. The °Brix ranged 4.17 – 7.39% for all varieties. The total sugars ranged 1.57 – 5.44 g/100 g, with primary content of sucrose, and only a few varieties contained fructose and glucose. Among the quantified organic acids, the most abundant was citric acid with a range of 37.86 – 245.83 mg/100 g. All four acids were present in concentrations above their threshold values in water to indicate their contribution to sour taste. The TPC ranged 12.67 – 67.29 mg GAE/100 g for both harvest years and there was a significant difference in variety and harvest year. This study can potentially lead to better tasting pecan varieties in pecan breeding program that can benefit consumers and producers.