No abstract

The foul odour of cheese-production wastewater is a common problem in areas surrounding dairy wastewater treatment plants. For successful odour management, a better understanding of the key odorants and how to handle them during wastewater treatment is needed. This paper documents the results of using gas chromatography-mass spectrometry coupled with olfactometry (GC-MS/O) to analyze odours emanating from a possibly overloaded treatment plant in Czechia. Using a DB5 capillary column, 20 compounds were detected and identified, nonanal (FDgeomean 152) and octen-3-ol (FDgeomean 2048) having the most pungent odours.

Liquid whey is a nutritious product with high water activity and neutral pH. Therefore, it is very susceptible to microbiological spoilage that results in undesirable off-odors. Additionally, minimally processed foods are the recent trend so setting an appropriate shelf life is essential. The commonly used microbiological methods are lengthy and time-demanding, so a quick and early identification of microbial degradation would be a significant benefit. Here we tested a solid-phase microextraction, gas chromatography with mass spectrometry coupled with olfactometry analysis (SPME-GC-MS/O) on samples of sweet unpasteurized liquid whey stored at 6 °C, 12 °C and 25 °C for a week. We compared the common methods – plate methods, measurement of pH, and dry matter determination with our proposed SPME-GC-MS/O. We have identified seven sensory active compounds while octanoic acid and a compound not reliably identified by the MS detector (with main m/z observed 133 (100), 151 (65), and 135 (26)) being the most prominent. Microbiological methods proved irreplaceable for proper setting of storage conditions (with the growth of coliforms being significant (p <0.001) at 25 °C). However, SPME-GC-MS/O was able to identify volatile substances responsible for off-odors and can be used as a powerful tool to detect the cause of undesirable chemical and microbial changes in whey beverages.

After a general introduction and introduction to acetic acid bacteria, this work focuses on the genus Asaia, which causes sensory defects in non-alcoholic beverages. Asaia representatives have strong adhesive properties for materials used in the food industry, where they subsequently form biofilms and are highly resistant to chemical preservatives. After the basic characteristics of the genus Asaia and its influence on humans, the main part of the paper deals with microbial contamination of beverages by these bacteria. The paper summarizes the knowledge of the influence of packaging materials on the development of defects in beverages and the use of natural bioactive substances and plant extracts as an alternative to maintaining the microbiological stability of beverages.

The aim of this work is to devise a methodology and identify the cause of off-odour in bottled water. For initial screening, sensory analysis and gas chromatography with mass spectrometry and olfactometric detector were used. Selected compounds were then analyzed and quantified by selective ion monitoring. 2,4-decadienal, a fatty acid oxidation product, was identified as the source of off-odour. It is produced during frying and it can diffuse through the packaging material into the product. Its concentration in three analyzed samples ranged from <0.15 µg/l to 3.1 µg/l. Since its detection threshold is 1 µg/l, improper storage conditions can decrease the sensory quality of bottled water.