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An examination on the role of artificial neural networks (ANN) for milk shelf-life revealed that that were useful for predicting milk shelf-life when applied to gas chromatographic profiles with sensory-based shelf-life. The predictive ability were better than the principal components regression. It is a more amenable for quality control situations. The principle components in this network are calculated before regression analysis is applied. more...

It has been recognized that lactic acid bacteria exhibit antioxidant properties, which have been mainly endorsed to the intact viable bacteria. However, recent studies have shown that intracellular content (IC) may also be good sources of antioxidative metabolites, which may potentially contribute to oxidative homeostasis in vivo. Hence, the modulatory effect of the intracellular content of Lactobacillus casei CRL 431 (IC431) on aflatoxin B1 (AFB1)-induced oxidative stress in rats was evaluated on the basis of its influence on hepatic lipid peroxidation (LPO), antioxidant status-antioxidant capacity (TAC), catalase (CAT), and glutathione peroxidase (GPx) activities; and on the oxidative stress index (OSi). Results demonstrated that CAT and GPx activities, and TAC, determined in plasma samples, were significantly (P < 0.05) higher in rats treated with AFB1 plus IC431 (3.98 μM/min/mg protein, 1.88 μM/min/mg protein, and 238.7 μM Trolox equivalent, respectively) than AFB1-treated rats (3.47 μM/min/mg protein, 1.46 μM/min/mg protein, and 179.7 μM Trolox equivalent, respectively). Furthermore, plasma and liver tissue samples from rats treated with AFB1 plus IC431 showed significantly (P < 0.05) lower LPO values (52 and 51%, respectively) and OSi (59 and 51%, respectively) than AFB1-treated rats. Hence, our results proved that the intracellular content of Lact. casei CRL 431 contains metabolites that are capable to modulate the antioxidant defense systems in living organism, which may help to ameliorate the damage associated to AFB1-induced oxidative stress. [ABSTRACT FROM AUTHOR] more...

Previous studies have demonstrated that milk fermented by specific Lactococcus lactis strains significantly inhibits the activity of angiotensin I-converting enzyme (ACE). However, the relationship between the ACE inhibitor and its in vivo action has revealed discrepancies. Therefore, the aim of the present study was to investigate the antihypertensive and heart rate (HR)-lowering effect of milk fermented by specific L. lactis in a murine model. Spontaneously hypertensive male rats (271 (SD14) g) were randomised into four treatment groups that were orally administered with milk fermented by L. lactis NRRL B-50 571 or L. lactis NRRL B-50 572 at 35 or 50 mg protein/kg body weight (BW), respectively. Further, two more groups were fed with different solutions as controls: a saline solution as the negative control and Captopril™ (40 mg/kg BW), a proven ACE inhibitor, as the positive control. Blood pressure and HR were monitored by the tail-cuff method before the treatments and at 2, 4, 6 and 24 h post-oral administration. The results demonstrated that milk fermented by L. lactis NRRL B-50 571 as well as by L. lactis NRRL B-50 572 presented an important systolic and diastolic blood pressure- and HR-lowering effect. Thus, milk fermented by specific L. lactis strains may present potential benefits in the prevention and treatment of CVD associated with hypertension in humans. [ABSTRACT FROM PUBLISHER] more...

Queso Fresco is a fresh, high moisture, white, rennet-set cheese that is the most popular Hispanic-style cheese in the US and Mexico. Traditionally, Mexican Queso Fresco is made with raw milk although the use of pasteurized milk is slowly replacing this practice. In the US, the FDA mandates that cheeses, such as Queso Fresco, sold less than 60 d after manufacture must be made with pasteurized milk. Queso Fresco has not been studied extensively and it is not known if the pasteurized milk cheeses are different from the raw milk originals. In this study, the compositional (moisture, fat, protein, and salt) and physical properties (whiteness value, water activity, and pH) of Queso Fresco from 6 commercial cheese plants in Sonora, Mexico (4 using raw milk and 2 using pasteurized milk) were characterized and compared to 8 commercial US-made cheeses. In composition, raw milk cheeses were higher in moisture (58-60%), and lower in fat (20-24%) and protein (15-17%) than the pasteurized milk cheeses from Mexico and the US (47-52% moisture, 23-36% fat, and 18-24% protein); the US-made cheeses contained more salt than the Mexicanmade cheeses (1.2-1.9% and 0.7-1.2%, respectively). In physical properties, all cheeses were bright white (whiteness L* values of 92-93) whereas raw milk cheeses had higher water activities (0.980 to 0.998) than the pasteurized cheeses (clustered near 0.975). The pH values of Mexican-made cheeses ranged from 4.8 to 6.0 whereas the pH values of US-made cheeses were above 6. The differences in manufacturing techniques, the unique microflora presence in the raw milk, and the excessive acid production in some of the cheeses contributed to the differences noted in composition and physical properties of the Queso Frescos. Establishing the basic chemical and physical properties of Queso Fresco is the first step in understanding the unique quality traits of this cheese and identifies traits that need to be maintained in pasteurized versions. [ABSTRACT FROM AUTHOR] more...

Queso Fresco is the most popular variety of Hispanic-style cheese consumed in the United States and Mexico. It is traditionally made from raw milk without specific starter cultures and the functional and flavor properties of the cheese are determined by the native microflora present in the raw milk. In the U.S., Queso Fresco is made from pasteurized milk with non-specific starter cultures resulting in a product with different organoleptic qualities from the traditional cheese. In this ARS-CIAD study, the indigenous microflora from six commercial Queso Fresco cheeses, obtained from Sonora, Mexico, were analyzed to identify bacterial species which may function as specific starter cultures. Four of the cheeses analyzed were made from raw milk and two from pasteurized milk. Classification of bacterial species was based on growth on selective media and 16S rDNA sequencing. The highest colony counts were obtained on M17 and MRS agar used for the selection of streptococci and lactobacilli respectively. Growth on MRS agar supplemented with vancomycin suggested that Leuconostoc species were present in all six samples. A high number of coliforms, enterococci and coagulase-positive staphylococci were identified in all raw milk samples. The number of enterococci remained high in cheese samples made from pasteurized milk but a 2 log10 reduction of coliforms was observed. Coagulase-positive staphylococci were reduced by 3 log10 in one pasteurized milk sample but remained high in the other (log 6.26 CFU/g). 16S rDNA sequence analysis revealed that lactobacilli were not present in any sample. Lactococcus lactis ssp. lactis was identified in four samples and Leuconostoc mesenteriodes and Entercoccus faecium were identified in all six samples. The results suggest that these species need further study to explore their potential as starter cultures for the production of cheese made from pasteurized milk while preserving the organoleptic qualities of traditional Queso Fresco. [ABSTRACT FROM AUTHOR] more...

This review aims to provide an overview of artisanal Mexican cheeses microbiota focused on microbiological quality and safety, as well as native Lactic acid Bacteria (LAB) diversity. For the search, key words of artisanal Mexican cheeses varieties was carried out through several online databases and original articles were screened and data about populations of indicator microorganisms, presence of pathogens, and native LAB identified were extracted. Several artisanal Mexican cheeses exceeded the permissible limit established in Mexican regulation (NOM-243-SSA1-2010) for indicator microorganisms, as well as in some types of cheese, the presence of pathogens was confirmed. However, other varieties of artisanal Mexican cheeses possess unique physicochemical characteristics, and during their manufacturing particular steps are used that contribute to ensuring their quality and safety. Additionally, strains able to control the growth of pathogenic and spoilage bacteria are part of the microbiota of some artisanal Mexican cheeses. About native LAB diversity, it is composed by species of Lactobacillus, Enterococcus, Streptococcus, Leuconostoc, Weisella, Lactococcus, Pediococus, Aerococus, Carnobacterium, Tetragenococus, among others genera. Otherwise, artisanal Mexican cheeses represent an important source of specific LAB with several approaches within human health because they showed potential for the development of functional foods, nutraceutical, and bioprotective cultures., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.) more...

Safety assessment of probiotics is difficult but essential. In this work, the Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae), was used as in vivo model to assess the biosafety of Limosilactobacillus fermentum J23. In the first set of experiments, the strain was orally administered to adult flies through direct feeding, whereas in the second set of experiments, it was supplemented through the larval rearing medium. Data showed that L. fermentum J23 did not lead to increased mortality or treatment-related toxicity signs in adult female and male flies. Ingestion of L. fermentum J23 by adult female flies led to a statistically significant improvement in locomotor activity compared to the control groups (ca. 59% decrease in climbing time, p < 0.0001). A positive trend in lifespan extension under stress (maximum lifespan = 144 h) was also observed. When L. fermentum J23 was administered to the larvae, the adult emergence (p = 0.0099), sex ratio (p = 0.0043), and flight ability (p = 0.0009) increased significantly by 7%, 31%, and 8%, respectively, compared to the control diet. No statistical effect between the control diet and the L. fermentum J23-based diet for the number of pupae recovered, pupal weight, duration of the pupal stage, lifespan under stress, and morphological development was observed. We conclude that feeding L. fermentum J23 to the novel experimental model A. ludens had no toxic effects and could be safely considered a potential probiotic for food supplements; however, further studies are still needed to establish its biosafety in humans., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.) more...

The survival of probiotic microorganisms during their exposure to harsh environments plays a critical role in the fulfillment of their functional properties. In particular, transit through the human gastrointestinal tract (GIT) is considered one of the most challenging habitats that probiotics must endure, because of the particularly stressful conditions (e.g., oxygen level, pH variations, nutrient limitations, high osmolarity, oxidation, peristalsis) prevailing in the different sections of the GIT, which in turn can affect the growth, viability, physiological status, and functionality of microbial cells. Consequently, probiotics have developed a series of strategies, called "mechanisms of stress response," to protect themselves from these adverse conditions. Such mechanisms may include but are not limited to the induction of new metabolic pathways, formation/production of particular metabolites, and changes of transcription rates. It should be highlighted that some of such mechanisms can be conserved across several different strains or can be unique for specific genera. Hence, this review attempts to review the state-of-the-art knowledge of mechanisms of stress response displayed by potential probiotic strains during their transit through the GIT. In addition, evidence whether stress responses can compromise the biosafety of such strains is also discussed., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.) more...