Effect of Enzyme Activity and Frozen Storage on Jalapeño Pepper Volatiles by Selected Ion Flow Tube—Mass Spectrometry

Abstract:  Samples of unblanched (fresh), stannous chloride‐treated, or blanched jalapeño peppers were measured for real‐time generation of lipoxygenase‐derived volatiles during 10 min after tissue disruption. Volatiles were also measured before and after 1.5, 2.5, 3, 6, and 9 mo of frozen storage at −15 °C. The concentration of all lipoxygenase‐derived compounds was significantly higher in unblanched jalapeño peppers compared to enzyme inhibited peppers. The maximum concentration of  (Z)‐ 3‐hexenal,  (E)‐ 2‐hexenal, and hexanal was detected at about 1.2, 1.5, and 1.5 min after tissue disruption, respectively. A decrease in  (Z)‐ 3‐hexenal and an increase in dimethyl sulfide and methylbutanal occurred in blanched compared to stannous chloride‐treated peppers due to heat. Frozen storage resulted in no major changes in the lipoxygenase‐derived volatiles of whole and pureed blanched peppers after 9 mo. However, in whole unblanched peppers a gradual decrease of  (Z)‐ 3‐hexenal,  (E)‐ 2‐hexenal, hexanal, hexenol, and hexanol was observed over time; whereas in pureed unblanched peppers these compounds increased, reached maximum concentration, and then decreased. Similarly, the minor volatiles 2‐pentenal, 1‐penten‐3‐one,  (E)‐ 2‐heptenal,  (E)‐ 2‐octenal, and  (E)‐ 2‐nonenal showed an initial increase followed by a decline in both whole and pureed unblanched peppers. Tissue disruption increased generation and degradation rates during frozen storage. The compounds ( E,Z) ‐2,6‐nonadienal, n‐propyl aldehyde, 2‐isobutyl‐3‐methoxypyrazine, and a mixture of terpenes decreased in unblanched and blanched frozen samples, while nonanal and methylbutanal increased only in unblanched samples. Practical Application:  Data obtained in this study contribute to the understanding of the dynamics of lipoxygenase‐derived volatile formation upon tissue disruption of jalapeño pepper. In addition, it contributes to generate knowledge on the effect of processing techniques, namely blanching and frozen storage, on the volatile profile of these peppers. This knowledge has applications in the manufacturing, product development, and quality control areas of the food industry as useful information to help in the designing and monitoring of processes aimed to obtain products with specific aroma characteristics. For instance, maximum levels of “fresh” and “green” aroma compounds are achieved rapidly during the first few minutes after pepper tissue is disrupted. The inhibition of enzyme activity shortly after this may help to maximize concentration of these aroma notes in the product. Frozen storage produces enzymatic and chemical changes in the volatile profile of unblanched peppers. The aroma profile of blanched peppers is more stable under frozen conditions, with a lower total volatile concentration.