Submitted to: American Peanut Research and Education Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/14/2009
Publication Date: N/A
Technical Abstract: Physical characteristics of peanuts may interact with processing conditions to impact quality. This study examined the effects of peanut pre-roast moisture content (MC) on chemical, physical and sensory characteristics developed in oil roasting. A large lot of Virginia type peanuts were dried in-shell to obtain 4.2%, 4.5%, 5.8% and 6.6% MC. Shelled, sized (ELK) peanuts were oil roasted, stored in glass jars at 30C and sampled at eight time points over one year. With roasting, Oxidative Stability Index (OSI) increased more in the low MC samples 11.1 H (raw) to 16.2 H (roasted) compared to high MC (10.3 to 10.7 H), but OSI decreased with time in all samples. Lower pre-roast MC resulted in lower peroxide values (PV) after 12 month’s storage (3.37 meq/kg) compared to higher MC (4.83 meg/kg). Descriptive sensory analysis indicated that cardboard and painty notes appeared in all samples at 4 months, with higher intensities in the higher pre-roast MC samples which both increased with time. The cardboardy off note was slightly higher in the lower MC than in the higher MC. The roast peanutty flavor decreased in all samples over time. Physically, the higher MC peanuts had less of an oily appearance throughout the storage time than the lower MC samples. The relationship between MC and oil uptake during roasting was examined by roasting the samples in a peanut/coconut oil blend (90/10 v/v). The lauric acid (C12:0) from the coconut oil served as a marker of the movement of the roasting oil into the peanuts and was found to have been incorporated into the peanuts after roasting indicating a MC dependent uptake of the roaster oil. Scanning electron microscopy (SEM) was used to examine changes at the cellular level in the samples. Greater physical damage was seen on the surfaces of the higher MC samples compared to the lower MC peanuts and was attributed to the release of larger amounts of steam from the high MC samples during the roasting operation.