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Use of near infrared spectroscopy and chemometrics to evaluate the shelf-life of cloudy sonicated apple juice
摘要： Fresh products, such as cloudy apple juice, could be preserved from early spoilage through the application of non-thermal processes such as sonication. However, shelf-life analyses based on microbiological and sensory evaluations are expensive and time consuming. Few studies have applied near infrared spectroscopy to evaluate the quality and decay of apple juices. Here, a feasibility trial was conducted to study the spectral behaviour at 1300–2500 nm combined with chemometric approaches. The shelf-life was monitored during two experiments, a challenge test with juices inoculated with spoilage yeasts (inoculated non-sonicated (INS)) and then submitted to sonication treatments (inoculated sonicated (IS)), and a storage test to evaluate the spoilage on non-inoculated juices (non-inoculated non-sonicated (NINS)) and sonicated non-inoculated juices (non-inoculated sonicated (NIS)). These experiments were investigated at six different refrigeration times 7, 14, 21, 28 and 60 days. Two functions were modelled to describe the behaviours of the first principal component according to the storage time. In agreement with a previous chemical and sensory evaluation, this approach allowed us to highlight shelf-life end points of 7 and 14 days for non-sonicated and sonicated samples, respectively. Three different models were evaluated for classification purposes: (1) sonicated versus non-treated samples, (2) end-point shelf-life evaluation at seven days for the NINS and INS juices and (3) end-point shelf-life discrimination at 14 days for IS and NIS samples. A partial least square-discriminant analysis enabled a group classification with accuracy values ranging from 0.63 to 1.00. The application of a variable importance in projection index to interpret the wavelengths of the spectral features suggests a contribution of organic acids and lipids to the prediction of decay. A canonical discriminant analysis provided a clearer separation of samples according to the storage time, especially in relation to the two time thresholds of 7 and 14 days.
关键词： Apple juice,spoilage,near infrared spectroscopy,shelf-life,sonication
更新于2025-09-23 15:23:52
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Increased resistance of <i>Salmonella</i> Typhimurium and <i>Escherichia coli</i> O157:H7 to 222-nm krypton-chlorine excilamp treatment by acid adaptation
摘要： In this study, we examined the change in resistance of Salmonella Typhimurium and Escherichia coli O157:H7 to 222-nm krypton-chlorine (KrCl) excilamp treatment as influenced by acid adaptation, and identified a mechanism of resistance change. In addition, changes in apple juice quality indicators such as color, total phenols and DPPH free radical scavenging activity during treatment were measured. Acid adapted- and non-acid adapted pathogens were induced by growing the cells in TSB without dextrose (TSB w/o D) at pH 7.3 and TSB w/o D at pH 5.0 adjusted with HCl, respectively. For the KrCl excilamp treatment, acid-adapted pathogens exhibited significantly (P < 0.05) higher D5d values, which indicate dosages required for achieving 5-log reduction, than non-acid adapted pathogens in both commercially clarified apple juice and PBS, and the pathogens in the juice showed significantly (P < 0.05) higher D5d values than those in PBS because of the UV-absorbing characteristics of apple juice. Through mechanism identification, it was found that the generation of lipid peroxidation in cell membrane, inducing cell membrane destruction, of acid adapted cells was significantly (P < 0.05) less than that of non-acid adapted cells for the same amount of reactive oxygen species (ROS) generated at the same dose because the ratio of unsaturated to saturated fatty acids (USFA/SFA) in the cell membrane was significantly (P < 0.05) decreased as a result of acid adaptation. Treated apple juice showed no significant (P > 0.05) differences in quality indicators compared to untreated controls during the treatment of 1773 mJ/cm2.
关键词： acid adaptation,ROS,E. coli O157:H7,apple juice,cell membrane fatty acid,ultraviolet irradiation,S. Typhimurium,222-nm KrCl excilamp
更新于2025-09-23 15:22:29
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Inactivation of ascospores of Talaromyces macrosporus and Neosartorya spinosa by UV-C, UHPH and their combination in clarified apple juice
摘要： This work addresses the use of a thin-film short wave ultraviolet radiation (UV-C) reactor and its combination with ultra-high pressure homogenization (UHPH) for the inactivation of Talaromyces macrosporus (CBS 130.89) and Neosartorya spinosa (CBS 586.90), fungal species that can cause food spoilage in products made of fruits. Ascospores of these microorganisms were inoculated in phosphate buffer solution (PBS) and clarified apple juice at a concentration between 5 and 6 Log10 spores/mL before treatments. Ascospores of both microorganisms were not detected in PBS after UV-C treatments even at the lowest assayed dose (1.8 J/mL), but in apple juice T. macrosporus showed to be significantly more UV-C resistant than N. spinosa. A UV-C dose of 21.5 J/mL in a single pass achieved decimal reductions of 2.15 Log10 and 5.4 Log10 respectively. Decimal reductions of both strains significantly increased in many cases when the same UV-C dose was applied in 2 or 3 passes throughout the UV-C reactor achieving T. macrosporus a maximum reduction of 3.88 Log10 after a UV-C dose of 21.5 J/mL applied in 3 passes. UHPH treatments at 100 and 200 MPa were ineffective in inactivating ascospores of both microorganisms, However, UHPH left ascospores more vulnerable to UV-C resulting in a synergistic effect achieving a maximum reduction of 3.6 Log10 on T. macrosporus after a combined treatment of UHPH at 200 MPa and a single pass of UV-C at 21.5 J/mL. The use of scanning electron microscopy revealed that only UHPH caused small changes in the cell wall structure of ascospores, but that might have left cells better exposed to UV-C.
关键词： Talaromyces macrosporus,Apple juice,Heat-resistant ascospores,Neosartorya spinosa,UHPH,UV-C
更新于2025-09-23 15:21:01