| 1. |
- Ferrentino, Giovanna, et al.
(author)
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Application of culture-independent methods for monitoring Listeria monocytogenes inactivation on food products
- 2015
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In: Process Biochemistry. - : Elsevier BV. - 1359-5113 .- 1873-3298. ; 50:2, s. 188-193
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Journal article (peer-reviewed)abstract
- When new food processing technologies are investigated as alternative to traditional thermal pasteurization processes, conventional cultivation-based methods are usually applied to evaluate microbial concentration before and after the treatment to determine the process efficiency. However, these standard methods lead to a typical underestimation of the microbes present in the sample, which may represent an issue when pathogenic strains have to be detected. Here, the efficiency of SC-CO2 pasteurization treatment in the inactivation of Listeria monocytogenes spiked on cured ham skin surface was evaluated using plate counts, flow cytometry (FCM) coupled with SYBR-Green I (SYBR-I) and propidium iodide (PI), and propidium monoazide quantitative PCR (PMA-qPCR), at different process conditions. SC-CO2 best performed at 12 MPa, 45 and 50 °C, resulting in a 7.5 log reduction of cultivable cells quantified by plate counts after 15 min of treatment, while FCM and PMA-qPCR revealed a 4 log and 2 log reduction of intact cells, respectively. This striking difference between culture-based and culture-independent quantification methods was independent from treatment time and indicated that a large fraction of the cells lost cultivability after treatment but maintained an intact membrane, likely entering in a so-called Viable But Not Culturable (VBNC) state. Our study highlights the usefulness of FCM and PMA-qPCR to assess the viability status of microbial populations and support their application in microbiological quality control in the food industry, in particular when mild pasteurization technologies are used.
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| 2. |
- Tomic, Nikola, et al.
(author)
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Challenging chemical and quality changes of supercritical Co 2 dried apple during long-term storage
- 2019
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In: Lebensmittel-Wissenschaft + Technologie. - : Academic Press. - 0023-6438 .- 1096-1127. ; 110, s. 132-141
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Journal article (peer-reviewed)abstract
- The aim of this study was to analyze the stability of sensory properties and secondary metabolites in supercritical-CO 2 (scCO 2 ) dried ‘Elstar’ apple cuts/snacks during twelve months of storage at ‘room’ temperature. Air-drying and freeze-drying were used as reference methods. ScCO 2 -dried apple packed in aluminum-polyethylene bags under nitrogen gas retained a high sensory and nutritional quality, and acceptance level until the end of the observed period. The overall acceptance scores of these apples after 6 and 12 months of storage remained in the range of neutral consumer attitude “neither like nor dislike”. Packaging under nitrogen gas preserved the content of flavonols (≥0.14 g/kg), dihydrochalcones (≥0.10 g/kg), hydroxycinnamic acids (≥0.18 g/kg), triterpenes (≥5.72 g/kg), and proanthocyanidins (≥0.08 g/kg) in dried apple irrespective of the drying method applied. The comparison with the conventional drying processes demonstrated that scCO 2 -drying represents a promising alternative technology for the production of dried apple snacks. The study was assisted by the evaluation of consumer attitudes towards dried fruit and drying technologies. Freeze-drying, air-drying and scCO 2 -drying were recognized by the tested consumers as trustful drying-processes, with expressed interests in buying scCO 2 -dried products if the technology was scientifically proven as excellent in preserving nutrients, color and taste of food products.
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