Doukaki Angeliki, Papadopoulou Olga S, Baraki Antonia, Siapka Marina, Ntalakas Ioannis, Tzoumkas Ioannis, Papadimitriou Konstantinos, Tassou Chrysoula, Skandamis Panagiotis, Nychas George-John, Chorianopoulos Nikos
Laboratory of Microbiology and Biotechnology of Foods, Department of Food Science and Human Nutrition, School of Food and Nutritional Sciences, Agricultural University of Athens, Iera Odos 75, 11855 Athens, Greece.
Institute of Technology of Agricultural Products, Hellenic Agricultural Organization-DIMITRA, S. Venizelou 1, 14123 Lycovrissi, Greece.
Microorganisms. 2024 Sep 10;12(9):1870. doi: 10.3390/microorganisms12091870.
Lately, the inclusion of additional lactic acid bacteria (LAB) strains to cheeses is becoming more popular since they can affect cheese's nutritional, technological, and sensory properties, as well as increase the product's safety. This work studied the effect of L33 and L125 free cells and supernatants on feta cheese quality and fate. In addition, rapid and non-invasive techniques such as Fourier transform infrared (FTIR) and multispectral imaging (MSI) analysis were used to classify the cheese samples based on their sensory attributes. Slices of feta cheese were contaminated with 3 log CFU/g of , and then the cheese slices were sprayed with (i) free cells of the two strains of the lactic acid bacteria (LAB) in co-culture (F, ~5 log CFU/g), (ii) supernatant of the LAB co-culture (S) and control (C, UHT milk) or wrapped with Na-alginate edible films containing the pellet (cells, FF) or the supernatant (SF) of the LAB strains. Subsequently, samples were stored in air, in brine, or in vacuum at 4 and 10 °C. During storage, microbiological counts, pH, and water activity (a) were monitored while sensory assessment was conducted. Also, in every sampling point, spectral data were acquired by means of FTIR and MSI techniques. Results showed that the initial microbial population of Feta was ca. 7.6 log CFU/g and consisted of LAB (>7 log CFU/g) and yeast molds in lower levels, while no were detected. During aerobic, brine, and vacuum storage for both temperatures, pathogen population was slightly postponed for S and F samples and reached lower levels compared to the C ones. The yeast mold population was slightly delayed in brine and vacuum packaging. For aerobic storage at 4 °C, an elongation in the shelf life of F samples by 4 days was observed compared to C and S samples. At 10 °C, the shelf life of both F and S samples was extended by 13 days compared to C samples. FTIR and MSI analyses provided reliable estimations of feta quality using the PLS-DA method, with total accuracy (%) ranging from 65.26 to 84.31 and 60.43 to 89.12, respectively. In conclusion, the application of bioprotective LAB strains can result in the extension of feta's shelf life and provide a mild antimicrobial action against and spoilage microbiota. Furthermore, the findings of this study validate the effectiveness of FTIR and MSI techniques, in tandem with data analytics, for the rapid assessment of the quality of feta samples.
最近，在奶酪中添加更多乳酸菌（LAB）菌株变得越来越普遍，因为它们会影响奶酪的营养、工艺和感官特性，还能提高产品安全性。本研究探讨了L33和L125的游离细胞及上清液对费塔奶酪品质和保存期限的影响。此外，还运用了傅里叶变换红外光谱（FTIR）和多光谱成像（MSI）分析等快速、非侵入性技术，根据感官属性对奶酪样品进行分类。将费塔奶酪切片用3 log CFU/g的[具体菌种未给出]污染，然后对奶酪切片喷洒（i）两种乳酸菌（LAB）菌株共培养的游离细胞（F，约5 log CFU/g）、（ii）LAB共培养的上清液（S）以及对照（C，超高温灭菌牛奶），或者用含有LAB菌株菌珠（细胞，FF）或上清液（SF）的海藻酸钠可食用膜包裹。随后，将样品分别在4℃和10℃的空气中、盐水中或真空中储存。在储存期间，监测微生物计数、pH值和水分活度（aw），并进行感官评估。此外，在每个采样点，通过FTIR和MSI技术获取光谱数据。结果表明，费塔奶酪的初始微生物数量约为7.6 log CFU/g，由LAB（>7 log CFU/g）和较低水平的酵母霉菌组成，未检测到[具体菌种未给出]。在两个温度下的有氧、盐水和真空储存过程中，S和F样品中的病原菌数量增长稍有延迟，与C样品相比达到较低水平。酵母霉菌数量在盐水和真空包装中稍有延迟。在4℃有氧储存时，与C和S样品相比，F样品的货架期延长了4天。在10℃时，与C样品相比，F和S样品的货架期均延长了13天。FTIR和MSI分析使用偏最小二乘判别分析（PLS-DA）方法对费塔奶酪品质提供了可靠估计，总准确率（%）分别为65.26至84.31和60.43至89.12。总之，应用具有生物保护作用的LAB菌株可延长费塔奶酪的货架期，并对[具体菌种未给出]和腐败微生物群提供温和的抗菌作用。此外，本研究结果验证了FTIR和MSI技术与数据分析相结合用于快速评估费塔奶酪样品质量的有效性。
