The role of moisture and common ingredients in quality changes in stored model peanut confections
Abegaz, Eyassu Getachew
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Model roasted peanut confections were formulated with addition of 3 levels (0, 2, and 5%) water, two levels (0 and 4%) sucrose and two levels (0 and 180 ppm) the antioxidant, tertiary butylhydroquinone (TBHQ) to a peanut paste. Color, texture, microstructure, sensory flavor and volatile aroma compounds were evaluated over 52 weeks of storage. A modified Spectrum . technique was used to evaluate six established roasted peanut flavor attributes: 'sweet', 'bitter', 'roasted peanutty', 'rancid', 'painty' and 'cardboard'. 'Sweet' and 'roasted peanutty' attributes were scored low in high moisture samples while 'rancid', 'painty' and 'cardboard' attributes were rated high. Roasted peanutty attribute decreased over storage time and oxidation related attributes, 'rancid', 'painty' and 'cardboard' scores intensified during storage time. Treatments with added antioxidants had higher 'roasted peanutty' scores and lower 'rancid' scores. Headspace solid-phase microextraction (SPME) method was used to extract aroma components. Critical volatile compounds, hexanal, heptanal, 1-methylpyrrole, 2- methylpyrazine, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, 2,3-dimethylpyrazine, and 2,3,5-trimethylpyrazine were tentatively identified by means of gas chromatography retention times employing authentic standards. Peanut pastes, treated with antioxidant had higher concentrations of pyrazine compounds and lower hexanal and heptanal. In general, samples with no added water had higher levels of specific pyrazines, hexanal and heptanal compounds. Pyrazines concentrations decreased during storage while hexanal and heptanal increased. Color values, lightness (L*), hue angle (h °) and Chroma (C) of peanut paste decreased with added water. L*, h ° and C increased during storage for all treatments. Texture profile analysis (TPA) of hardness, cohesiveness, adhesiveness, springiness, gumminess and chewiness revealed peanut pastes with added water had significantly higher hardness, gumminess, chewiness and adhesiveness and lower cohesiveness and springiness (p<0.05). Light and scanning electron micrographs of peanut paste with high moisture had aggregated protein bodies.