The analysis of volatile compounds in beer is important for quality control in the brewing industry. In this study, stir-bar sorptive extraction (SBSE) and solid-phase microextraction (SPME), two solvent-less enrichment techniques, were applied in combination with gas chromatography flame ionization detection (GC/FID) for the determination of four flavour compounds (isoamyl acetate, ethyl hexanoate, benzaldehyde, myrcene) in beer. Limits of detection, linearity and repeatability of both methods were determined using standard ethanol solutions, while accuracy was determined by conducting recovery tests on commercial beer samples. Both methods were characterized by high linearity (r > 0.996) and repeatability (RSD = 1.76-10.66%). When both methods were compared, higher recoveries were obtained by SBSE, with limits of detection 1.8-2.8 times lower compared with SPME. In the analysis of commercial beer samples using both methods, SBSE analysis resulted in higher recoveries, therefore demonstrating promise for the analysis of beer volatiles.
Aims: To investigate the effect of lactic acid (LA), copper (II), and monolaurin as natural antimicrobials against Cronobacter in infant formula.
Methods and Results: The effect of LA (0·1, 0·2 and 0·3% v/v), copper (II) (10, 50 and 100 μg ml−1) and monolaurin (1000, 2000, and 3000 μg ml−1) suspended into tween‐80™ or dissolved in ethanol against Cronobacter in infant formula was investigated. Reconstituted infant formula and powdered infant formula were inoculated with five strains of Cronobacter spp. at the levels of c. 1 × 106 CFU ml−1 and 1 × 103 CFU g−1, respectively. LA at 0·2% v/v had a bacteriostatic effect on Cronobacter growth, whereas 0·3% v/v LA resulted in c. 3 log10 reduction. Copper (II) at the levels of 50 μg ml−1 and 100 μg ml−1 elicited c. 1 and 2 log10 reductions, respectively. The combination of 0·2% LA and 50 μg ml−1 copper (II) resulted in a complete elimination of the organism. Monolaurin exhibited a slight inhibitory activity against Cronobacter (c. 1·5 log10 difference) compared to the control when ethanol was used to deliver monolaurin.
Conclusions: A complete elimination of Cronobacter was obtained when a combination of sublethal concentrations of LA (0·2%) and copper (II) (50 μg ml−1) was used.
Significance and Impact of the Study: The use of the synergistic interactive combination of LA and copper (II) could be beneficial to control Cronobacter in the infant formula industry.
Specialty malts are commonly used in brewing to provide flavor, aroma, and color to wort and beer. The use of specialty malts contributes to the variety of beer products; therefore, it is important to understand their effect on the characteristics of wort and beer. This study investigates the impact of various specialty malts on wort and beer properties. A control beer was prepared with 100% base malt, and four beer treatments were prepared with the addition of kilned, roasted, and caramel specialty malts. For each treatment, 20% of the base malt was substituted with the various specialty malts when preparing the wort. The fermentable sugars and free amino nitrogen (FAN) content for each wort were analyzed. Alcohol by volume (ABV), international bitterness units (IBU), diacetyl, and polyphenol content of each prepared beers were subsequently analyzed. Results showed that wort prepared with the addition of roasted and caramel malts contained a lower concentration of fermentable sugars and FAN than wort prepared with the base and kilned malts. Beers prepared with the addition of roasted and caramel malts exhibited the lowest levels of ABV, as well as the lowest levels of diacetyl. These beers also exhibited higher levels of total phenolic compounds compared to the other beer samples. No change was observed in IBU levels as a result of brewing with the different specialty malts. This study illustrates how the use of specialty malts impacts wort and beer properties, providing useful information to aid in the production of quality beer products.
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