Changes in Volatile Sulfur Compounds in Strawberry Puree during Heating

Abstract

Solid-phase microextraction coupled with gas chromatography/pulsed flame photometric detection was used to monitor methane thiol, hydrogen sulfide, sulfur dioxide, dimethyl sulfide, carbon disulfide, methyl thioacetate, dimethyl sulfide, methyl thiobutyrate, and dimethyl trisulfide after heating strawberry puree at 95 °C for 0, 0.5, 1.0, 1.5, 2.5, 4, and 10 min. After heating 10 min, dimethyl trisulfide increased from 0.11 to 0.41 ng/mL, and dimethyl disulfide decreased from 1.3 to 0.3 ng/mL. Concentrations of methyl thiobutyrate and methyl thioacetate were approximately 6 and 60 ng/mL, respectively, and essentially unaffected by heating. Dimethyl sulfide (cabbage aroma) was not detected in fresh puree but increased exponentially during heating, reaching a value of 500 ng/mL (100ϫ ϫ ϫ ϫ ϫ its odor threshold) at 10 min. Dimethyl sulfide was the major sulfur aroma impact compound in heated strawberry puree and a major contributor to the flavor change associated with heated strawberry puree.

The Significance of Volatile Sulfur Compounds in Food Flavors

“…Volatile sufur compounds (e.g., methane thiol, dimethyl sulfide) can undergo thermal oxidation to form dimethyl disulfide and dimethyl sulfoxide, respectively, unless suitable analytical conditions are employed. Changes in dimethyl sulfide/disulfide/trisufide were reported in strawberry puree as a result of heating (29). Thermal reactions were reported to influence formation of sulfur compounds in Welsh onions and scallions during their identification; branched polysulfides were found in volatile distillates (32), but were absent in solvent extracts (32).…”

“…Methyl thioacetate ("cheesy, garlic") and methyl thiobutanoate ("cheesy, garlic, cabbage") were reported in strawberry as aroma-active sulfur volatiles with very low thresholds at relatively high concentrations (29). Recently, a series of novel thioesters were reported in fresh strawberry, including methyl (methylthio)acetate, ethyl (methylthio)acetate, methyl 2-(methylthio)butyrate (fruity, floral, garlic), methyl 3-(methylthio)propionate, ethyl 3-(methylthio) propionate, methyl thiopropanoate, methyl thiohexanoate, and methyl thiooctanoate (fruity, pineapple) (28).…”

“…The PFPD detector provides enhanced sensitivity relative to flame photometric detectors, and lower cost than atomic emission detection. PFPD has been recently utilized to measure sulfur compounds in cheese (26,27), wine (21), and strawberry (28,29) flavors.…”

Recent analyses using solid phase microextraction in industries related to food made into or from liquids

“…Usually, sulfur containing organic compounds in fruit and vegetables were minority volatile components when identified by SPME detected at ng/g concentrations (Schulbach, Rouseff, & Sims, 2004). Despite the low concentration of sulfur containing organic compounds, some studies monitored these compounds to assess food quality.…”

Analysis of volatile compounds from Malaysian durians (Durio zibethinus) using headspace SPME coupled to fast GC-MS

“…SPME provides advantages such as eliminating the need for solvent; it is inexpensive, rapid and easy to use; it is compatible with a wide range of analytical instruments; and the detection limits are improved (Zhang and Pawliszyn, 1993;Workhoff et al, 2002). To date, SPME has been successfully applied in the qualitative and quantitative analysis of volatiles in fruits such as kiwi, strawberry, blackcurrant, cantaloupe and banana (Wan et al, 1999;Schulbach et al, 2004;Ruiz del Castillo and Dobson, 2002;Beaulieu and Grimm, 2001;Liu and Yang, 2002). However, a calibration or optimization of SPME conditions is always required for increasing the sensitivity and accuracy of the analysis (Penton, 1999).…”