Hydrophilic interaction liquid chromatography-mass spectrometry for cinnamic acid determination and its use to evaluate components of dried hot peppers (Capsicum annum ) associated with growth inhibition of Salmonella enterica serovars

Abstract

A rapid and selective hydrophilic interaction chromatography‐mass spectrometry (HILIC‐MS) method was developed to measure cinnamic acids in dried chili peppers (Capsicum annum) for the purpose of investigating the association between cinnamic acid levels and inhibition of Salmonella growth in the peppers. Trans‐cinnamic and hydroxy‐cinnamic acids were quantified in 15 varieties of chili peppers by the HILIC‐MS method, using electrospray ionization in negative mode with multiple reaction monitoring for detection. Trans‐cinnamic acid and 4‐OH‐cinnamic acid were found in all samples; highest concentrations were 0.81 and 7.15 ppm, respectively. The compound, 2‐OH‐cinnamic acid was not detected. Mean recoveries of the target compounds from spiked samples were greater than 79%. The pepper samples were evaluated for Salmonella growth inhibition after addition of moisture to the dried samples. No correlation was found between Salmonella growth inhibition and cinnamic acid content, suggesting that these cinnamic acids are not major inhibitory compounds in these peppers. Practical applications The HILIC‐MS method developed for the analysis of dried chili peppers is a simple, sensitive method for organic acids and is applicable to any food matrix. Only extraction and automated filtration are employed to produce extracts for analysis. Ammonium formate buffer in the mobile phase, pH 6, enhances ionization of acids for negative ESI‐MS detection relative to the degree of ionization from use of acidic mobile phases containing formic or acetic acid modifiers. The use of 4‐Cl‐benzoic acid as internal standard and evaluation of matrix effects from the dried pepper extracts are important for future research in similar applications. The HILIC chromatographic separation may separate critical peak pairs in pepper extracts that are not resolvable by reversed‐phase HPLC.