Submitted to: American Peanut Research and Education Society Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 10, 1998
Publication Date: N/A
Technical Abstract: Roasting of peanuts to achieve and maintain optimum roasted flavor is critical to the peanut industry. A study was conducted to evaluate the effect of peanut pre-roast moisture content on after-roast shelf life quality. Samples were cured to moisture contents ranging from 5.7-9.4 percent and stored for approximately one year in plastic containers. Moisture content was evaluated immediately before five 0.9 kg samples of each moisture content were roasted in a flame-heated, bi-directional oven. The temperature of roast was 163 C with an air flow of 175 CFM. All peanuts were roasted to Hunter L values of 49-51. Roasted samples were held in cold storage for two weeks then stored at 30 C and samples were taken at weekly intervals for peroxide value (PV) and oxidative stability index (OSI) analyses. Descriptive sensory analysis was conducted on the 0, 4, and 8 week samples. After-roast moisture content of samples ranged from m1.13-1.43. PV's for samples with high pre-roast moisture were higher immediately after roasting and the differences increased with storage time. Similarly, oxidative stability index values were lower for high moisture samples. PV's increased and OSI's decreased approximately two-fold after one week of storage. Initial roasted peanutty intensity of ca. 5.5 for all samples decreased to ca. 4.3 and 2.6 in low and high moisture samples, respectively, after 4 weeks. Initial painty intensity of 1.1 for low moisture samples increased to ca. 5.1 while the highest moisture sample changed from 1.6 to 11.6. These data suggest that the moisture content of peanuts going into the roaster directly influences the post-roast shelf life of peanuts. Data from another study in which peanuts of different moisture were roasted within two weeks of curing produced similar results.