Abstract SCHIRACK, ANDRIANA VAIS. The Effect of Microwave ...

headspace concentrations of hexanal, heptanal, octanal, and nonanal increased
during storage, with hexanal being the major aldehyde at concentrations of 187-865
ng/mL headspace gas/10g peanuts after 26 days. In combination with this, higher
TBA values and oxidative rancid flavor scores were seen, indicating that off-flavor
production was in part due to production of low-molecular weight aldehydes from
lipid oxidation.
Peanuts naturally contain antioxidants which can slow or prevent lipid
oxidation reactions. For example, it has been noted that peanuts contain alpha-
tocopherol and carotenoids (Sanders et al., 1995). In addition, some products of
reducing sugar reactions and Maillard browning such as reductones are free radical
scavengers, which protect peanuts from oxidative damage to proteins,
phospholipids, nucleic acids, and polysaccharides (Sanders et al., 1993).
Off-flavors Due to Anaerobic Respiration
When peanuts are subjected to cold or heat stress, the respiration process
changes from aerobic to anaerobic (Singleton and Pattee, 1992, Osborn et al.,
1996). Anaerobic respiration is initiated by an insufficient supply of oxygen diffusing
into the seed for the increased respiratory need at higher temperatures.
Temperature stress in peanut seeds can occur at any temperature greater than
35 °C or less than 4 °C, for example during an abusive curing process. In addition,
when cells are exposed to heat or cold stress, membrane damage occurs and
cellular components can leak, disrupting metabolic processes (Singleton and Pattee,
1997).
52