Relationship Between Consumer Acceptability and Pungency-Related Flavor Compounds of Vidalia Onions.

A consumer study was conducted to evaluate preferences in Vidalia onions, and define consumer acceptability thresholds for commonly analyzed flavor compounds associated with pungency. Two varieties of Vidalia onions (Plethora and Sapelo Sweet) were grown at 3 fertilizer application rates (37.5 and 0; 134.5 and 59.4; and 190 and 118.8 kg/ha of nitrogen and sulfur, respectively), creating 6 treatments with various flavor attributes to use in the study. Bulb soluble solids, sugars, pyruvic acid, lachrymatory factor (LF; propanethial S-oxide), and methyl thiosulfinate (MT) content were determined and compared to sensory responses for overall liking, intensity of the sharp/pungent/burning sensation (SPB), and intent to buy provided by 142 consumers. Onion pyruvate, LF, MT, and sugar content increased as fertilization rate increased, regardless of onion variety. Consumer responses showed participants preferred onions with low SPB, which correlated positively to lower pyruvate, LF and MT concentrations, but showed no relationship to total sugars in the onion bulb. Regression analyses revealed that the majority of consumers (≥55%) found the flavor of Vidalia onions acceptable when the concentrations of LF, pyruvic acid, and MT within the bulbs were below 2.21, 4.83, and 0.43 nmol/mL, respectively. These values will support future studies aimed at identifying the optimal cultivation practices for production of sweet Vidalia onions, and can serve as an industry benchmark for quality control, thus ensuring the flavor of Vidalia onions will be acceptable to the majority of consumers. PRACTICAL APPLICATION: This study identified the relationship between consumer preferences and commonly analyzed flavor compounds in Vidalia onions, and established thresholds for these compounds at concentrations which the majority of consumers will find desirable. These relationships and thresholds will support future research investigating how cultural practices impact onion quality, and can be used to assist growers in variety selection decisions. In addition, this information will provide a benchmark to Vidalia onion producers for quality control of the sweet onions produced, ensuring that the onions are consistently of a desired quality, thereby increasing consumer's reliability in the Vidalia onion brand.

Effect of staining reagent on peptide mass fingerprinting from in-gel trypsin digestions: a comparison of SyproRuby and DeepPurple.

As the new fluorescent stains such as SyproRuby and DeepPurple are getting widespread recognition for proteome analyses by the traditional 2-D gel method, it becomes important to test the feasibility of these stains with respect to staining reproducibility, protein quantitation, and compatibility of the stain with downstream MS. The binding of epicocconone, active ingredient of DeepPurple, to one of the primary cleavage sites of trypsin (lysine residue) raises the possibility of incomplete cleavage and interference with PMF. However, the current study tests and concludes that the DeepPurple stain can result in increased peptide recovery compared to SyproRuby stain and can improve MS-based identification of lower intensity proteins spots.