Application of Sensory and Instrumental Analyses for the Characterization of Flavor in Roasted Peanuts and Farmstead Cheddar Cheese.

摘要

The driving force for the consumption of peanuts is the unique flavor that is developed during roasting. The peanut plant has an indeterminate flowering pattern, which means that peanuts of different maturity classes exist in lots of a seed-sized commercial grade. Due to compositional variations, the seed maturity distribution within a lot may affect flavor development during roasting. The main objectives of this study were to characterize the flavor of roasted peanuts from five maturity classes, and to reconstitute the aroma of roasted peanuts in model systems. A secondary objective was to correlate the chemical and sensory characteristics of roasted peanuts from five maturity classes. Different statistical techniques including Pearson's correlations, principal component analysis (PCA), and partial least square regression (PLSR) were used to establish relationships where appropriate. An additional study characterized the earthy/bell pepper (EBP) flavor in Farmstead Cheddar cheeses.;In the first study, HS-SPME (headspace solid-phase microextraction) sampling conditions were optimized for the analysis of roasted peanuts. Eight compounds were used to assess the extraction efficiency of various testing conditions. For gas chromatography-mass spectrometry (GC/MS) analysis, the use of DVB/CAR/PDMS fiber led to greater peak areas than the PDMS fiber. For a given extraction time and temperature, addition of salt increased extraction efficiency. Peak areas also increased with increasing extraction time and temperature. Optimized conditions increased response of target compounds by 40% to 1760% when compared to undiluted paste extracted at 40ºC/30 min with a DVB/CAR/PDMS fiber. Optimized conditions also resulted in higher number of detected compounds by gas chromatography-olfactometry (GC/O) analysis.;In the second study, the flavor of roasted peanuts from five maturity classes was characterized, and the aroma of roasted peanuts was reconstituted in model systems. Twenty-five compounds were selected by aroma extract dilution analysis (AEDA) as being potential contributors to roasted peanut flavor. Five additional compounds detected by headspace solid-phase microextraction (HS-SPME) were selected based on their high intensity scores on the GC-O analysis. Similarity score against the aroma of roasted peanuts for the optimized model system was 8 a 10-point scale. Omission experiments indicated that methional, 1-octen-3-one, nonanal, hexanal, octanal, 2-acetyl-1-pyrroline, carbon disulfide, and phenylacetaldehyde were the main contributors to roasted peanut aroma.;In the third study, the compositional variations in peanuts of five maturity classes were determined, and correlations among their chemical and sensory characteristics were established. Roasted peanutty was positively correlated with sweet aromatic and sweet taste, and negatively correlated with bitter. Free amino acids decreased with increasing maturity (P0.05), possibly due to protein synthesis during maturation. Free amino acids also decreased during roasting in all maturity classes, due to involvement of these compounds in Maillard reactions. Oleic/linoleic ratio significantly increased with seed maturity, which suggests that more mature peanuts may be less susceptible to lipid oxidation.;In the final study, the earthy/bell pepper (EBP) flavor that has been previously recognized in some Farmstead Cheddar cheeses with natural bandage wrappings was characterized. EBP flavor was detected in four out of eight Farmstead Cheddar cheeses by a trained sensory panel. 2-secbutyl-3-methoxypyrazine and 2-isopropyl-3-methoxypyrazine were identified as the main sources of EBP flavor in these cheeses by GC/O and GC/MS analysis. In general, those pyrazines were prevalent towards the exterior of the cheeses, which suggests they are formed near the surface and migrate into the cheese during ripening. Sensory analysis of mild Cheddar cheese model systems confirmed that direct addition of those individual pyrazines resulted in EBP flavor.