With the growing demand for high-quality coffee, it is becoming increasingly important to establish quantitative measures of the freshness of coffee, or the loss thereof, over time. Indeed, freshness has become a critical quality criterion in the specialty coffee scene, where the aim is to deliver the most pleasant flavor in the cup, from highest quality beans. A series of intensity ratios of selected volatile organic compounds (VOC) in the headspace of coffee (by gas chromatography-mass spectrometry) were revisited, with the aim to establish robust indicators of freshness of coffee - called freshness indices. Roasted whole beans in four different packaging materials and four commercial capsule systems from the Swiss market were investigated over a period of up to one year of storage time. These measurements revealed three types of insight. First, a clear link between barrier properties of the packaging material and the evolution of selected freshness indices was observed. Packaging materials that contain an aluminum layer offer better protection. Second, processing steps prior to packaging are reflected in the absolute values of freshness indices. Third, differences in the standard deviations of freshness-indices for single serve coffee capsule systems are indicative of differences in the consistency among systems, consistency being an important quality attribute of capsules.
An oxygen scavenger based on a catalytic system with palladium (CSP) was recently developed to remove oxygen in food packagings. Although the CSP worked with various types of food, with some foods, an inhibition of the CSP was observed. Because such catalytic systems are susceptible to poisoning by sulfurcontaining compounds, the aim of this study was to understand the inactivation of palladium-based catalysts in presence of foods containing volatile sulfur compounds (VSCs). To achieve this, the oxygen scavenging activity (OSA) of the CSP was evaluated in presence of selected food products. Afterwards, VSCs mainly present in these foods were exposed to the CSP, and the influence on the OSA was evaluated. Finally, headspace analysis was performed with the diluted VSCs and with the packaged food products using proton transfer reaction time-of-flight mass spectrometry. It was found that the catalytic activity of the CSP was inhibited when VSCs were present in the headspace in concentrations ranging between 10.8-36.0 ppbv (dimethyl sulfide, DMS), 1.2-7.2 ppbv (dimethyl disulfide), 0.7-0.9 ppbv (dimethyl trisulfide), 2.1-5.8 ppbv (methional) and 4.6-24.5 ppbv (furfuryl thiol). It was concluded that in packaged roast beef and cheese, DMS may be the compound mainly responsible for the inactivation of the CSP. In packagings containing ham, the key compounds were hydrogen sulfide and methanethiol; in peanuts, it was methanethiol; and in par-baked buns, an accumulation of methional, DMS, butanethiol and methionol. When potato chips were packaged, it was demonstrated that when VSCs are present in low concentrations, oxygen can still be scavenged at a reduced OSA.Such technologies aim to remove residual oxygen present in food packagings 3,10-15 and thereby prevent negative effects, such as growth of aerobic microorganisms 10 or oxidation of the product, 16 and hence contribute to the overall preservation of quality during storage.Recently, an oxygen scavenger based on a catalytic system with palladium (CSP) has been developed [17][18][19] showing the potential to extend shelf life and improve the overall quality of oxygen-sensitive foods packaged in modified atmosphere. 20 The oxidative mode of action of this CSP is based on the catalytic oxidation of hydrogen into water 21 so that headspace oxygen can be removed when hydrogen is included in the modified atmosphere of a packaging. Although the CSP works with several types of food, for some foods, such as peanuts or cheese, an inhibition of the oxygen scavenging activity (OSA) of the CSP was observed after the food was packaged. As described in the literature, such catalytic systems are susceptible to catalyst poisoning, which is defined as the strong chemisorption of reactants, products or impurities on sites otherwise available for catalysis. [22][23][24] Common catalyst poisons are sulfurous compounds, and the adsorption of volatile sulfur compounds (VSCs) on palladium surfaces has been well studied. [25][26][27][28][29][30] Volatile sulfur compounds are also present in se...
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