Influence of Moisture Content on Quality and Shelf-life of Oil Roasted Virginia-type Peanuts

Abstract

ABSTRACT DEBRUCE, MINIAYAH. Influence of Moisture Content on Quality and Shelf-life of Oil Roasted Virginia-type Peanuts (Under the direction of Dr. Timothy H. Sanders and Dr. Lisa Dean).

Consumer studies have shown that oil roasted peanuts are by many consumers the preferred; however, oil roasting of food products may increase oil content. There are numerous factors that can affect roasting oil uptake and one notable factor is moisture content. Moisture content is measured and monitored throughout processing in the peanut industry and it is a important factor in overrall peanut quality during processing. The moisture content of shelled peanuts used for processing, may range from 5.5% – 8.5%. The purpose of this experiment was to determine if pre-roast moisture content has an effect on the amount of oil uptake or exchange that occurs during oil roasting of virginia market type peanuts and also to determine the effect of pre-roast moisture content on the physical characteristics, sensory attributes and storage quality of oil roasted peanuts. Peanuts of final dry weight moisture of 4.2%, 4.5%, 5.8% and 6.6%. Peanuts used to further examine oil uptake were roasted in a peanut oil/coconut oil mixture in which the coconut oil served as a marker compound. Peanuts used to study the relationship of moisture content and oxidation were roasted in peanut oil and placed in storage for 48 weeks. Increasing moisture content resulted in decreased oil content and oil uptake The presence of C12 fatty acids found in coconut oil in the roasted peanuts indicated uptake did take place. More oil was present at the surface; however, fatty acid profiles indicated less C12 at the surface than inside the peanut. Scanning electron microscopy images revealed that more structural damage was prevalent on peanuts with high moisture content than those with low moisutre content. Results indicated that pre-roast moisture content did not have a significant effect on of free fatty acids and peroxide values; however, increases in these compounds did indicate that some lipid cxidation occurred. Low moisture content had high roast peanutty flavor throughout storage; however, storage did have a significant affects to flavor causing a slight decrease in flavor and a slight increase in off flavors related to lipid oxidation.