SPME−MS−MVA as an Electronic Nose for the Study of Off-Flavors in Milk

Abstract

A new technique using solid-phase microextraction, mass spectrometry, and multivariate analysis (SPME−MS−MVA) was developed for the study of off-flavors in milk. The analytical column of a GC/MS system was replaced with a 1-m deactivated fused-silica column, which served as a transfer line to deliver volatiles extracted from milk samples with a Carboxen-SPME fiber to the mass spectrometer. Mass fragmentation data resulting from the unresolved milk volatile components were subjected to MVA. Principal component analysis based on SPME−MS−MVA provided rapid differentiation of control reduced-fat milk (2% butterfat content) samples from reduced-fat milk samples abused by light, heat, copper, and microbial contamination. The three psychrotrophic bacteria studied included Pseudomonas fluorescens, Pseudomonas aureofaciens, and Pseudomonas putrefaciens. SPME−MS−MVA is rapid and offers significant advantages over commercial electronic nose instruments currently being used as quality assurance tools to differentiate normal-tasting food and beverage samples from those containing off-flavors and malodors. Keywords: SPME−MS−MVA; electronic nose; solid-phase microextraction; off-flavors, multivariate analysis; milk