Vitamin E content and stability in peanuts and peanut products during processing and storage
Abstract (Summary)Vitamin E content and changes in moisture, color, microstructure and oxidative stability of raw and roasted peanuts were investigated during processing and storage. The mean ?-tocopherol levels (mg/100g) were 8.2 for raw peanuts, 4.1 for roasted peanuts, 9.4 for peanut butter, 5.5 for reduced-fat peanut butter and 12.3 for peanut oils. Contribution of the oil and stabilizer added to the roasted peanuts during peanut butter processing was 4% of ?-T and 5% of ?-T in peanut butter. Tocopherol loss by peanut butter manufacture was below 6%. Oven roasting at 140 to 160 ºC rapidly decreased moisture content. About 5, 12, 20, and 10% of initial levels of ?-, ?-, ?- and ?-T in peanuts were lost during roasting at 160 ºC, respectively. Tocopherol levels of peanuts slightly increased at 140 ºC and were remained constant at 150 ºC. Tocopherol levels of peanut oils prepared by pressing the roasted peanuts significantly decreased at all roasting temperatures (p < 0.05). After roasting at 160 ºC for 20 min, a 16% loss of ?-T occurred in the peanut oils. Swollen epidermal cells and rupture of parenchyma tissue of peanuts were observed in roasted peanuts by SEM. During storage at 21 ºC, lipid oxidation rapidly progressed in roasted peanuts. Under vacuum, lipid oxidation was significantly retarded for both raw and roasted peanuts (p < 0.05). Tocopherol levels of raw and roasted peanuts exponentially decreased with increasing peroxide value during storage (?- T=8.8956e-0.0468PV, R2 = 0.9246). Under air, ?- and ?-T of roasted peanuts dramatically decreased during the initial four weeks of storage, resulting in about 84 and 68% losses for ?- and ?-T, respectively. ?-T showed the least stability during storage and the most stability to roasting. After 12 weeks of storage, more than 50% of ?-T remained for roasted peanuts stored under vacuum compared to about 10% stored under air.
School:The University of Georgia
School Location:USA - Georgia
Source Type:Master's Thesis
Date of Publication: