Stability of a lyophilized milk enriched with microbial CLA/CLNA

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In situ CLA and CLNA production: a potential strategy to elaborate food products enriched in bioactive fatty acids

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Stability of a fermented milk enriched with microbial CLA/CLNA

There is an increasing interest towards the development of innovative value-added food products with a potential to prevent or counteract disease conditions, many times impelled by unbalanced diets, such as cardiovascular diseases and cancer. Several promising food-derived lipids with potential bioactive properties have been identified over the last decade, and these include conjugated linoleic (CLA) and conjugated linolenic (CLNA) acids [1], [2]. Due to concentration and availability limitations in their natural sources (e.g. ruminants’ milk and meat or vegetable oils) [3], [4], the in situ microbial production may reveal itself to be a good strategy to increment CLA/CLNA daily intake. Several probiotic strains have demonstrated the ability to produce CLA/CLNA isomers using linoleic (LA) and alpha-linolenic (α -LNA) acids as precursor substrates, respectively [5], [6]. This research team has previously assayed a combination of screening tools from a wide collection of probiotic strains and selecting the best producer of CLA and CLNA isomers – Bifidobacterium breve DSM 20091 – to proceed afterwards with studies on CLA/CLNA-enriched milk. Seeking to explore industrial viability, commercial edible vegetables oils were applied as precursor substrate sources instead, being previously hydrolysed with lipases to enhance the amounts of free LA/α- LNA. After a series of optimization assays, the flaxseed oil (FSO), which is rich in α-LNA, provided the highest yield of microbial conjugated FA (~1 mg/g) at 2 mg/mL α-LNA. After elaborating the new functional milk, the next required step is evaluating its compositional stability throughout storage. Therefore, the aim of the present work was to investigate i f a microbial CLA/CLNA-enriched fermented milk is stable, in terms of probiotic viable counts, pH and fatty acid (FA) profile, at conditions mimicking shelf-life. Pasteurized cow milk was inoculated with B. breve DSM 20091 and 2 mg/mL of α-LNA (from hydrolysed FSO) or not (control) and distributed by 100 mL containers for each sampling point and in triplicate. The containers were fermented for 22 h at 37 ºC under anaerobic conditions. After fermentation, three containers from each substrate condition were separated for further analysis (T0d) and the rest was stored at 4 ºC, being well sealed with parafilm and protected from light with aluminium foil. Samples were taken from storage each 7 days until the end of the assay (T28d). At each sampling point, it was performed viable cell counting in cys-MRS agar plates and total microbial count in PCA plates, measure of pH and FA analysis content through GC-FID. According to the obtained results, after 7 days of storage, viable cell counts of B. breve DSM 20091 decreased significantly, especially in the enriched milk (from 8.09 to 4.51 log10), and kept decreasing, reaching insignificant counts by the end of the assay. Concerning to total microbial count in PCA, insignificant numbers were detected throughout all storage period at both conditions. In terms of pH, it maintained constant overall (Control: 5.05-5.14; Enriched milk: 4.86-4.99). As for FA profile, in the non-esterified fraction, it was detected higher levels of CLA and CLNA isomers in the enriched milk, and consequently of total polyunsaturated FA (PUFA) as well, at T28d, comparing to all other sampling points, with values of 0.17 mg/g CLA, 1.11 mg/g CLNA and 2.04 mg/g PUFA. In the esterified fraction, was observed variations throughout storage in total saturated FA of control (7.85-9.18 mg/g), and in total monounsaturated FA of both conditions (Control: 2.23- 2.81 mg/g; Enriched milk: 2.19-2.66 mg/g). In conclusion, a microbial CLA/CLNA-enriched fermented milk is not entirely stable during storage, including its CLA/CLNA content, which was in fact increased.info:eu-repo/semantics/publishedVersio

Quantitative and qualitative determination of CLA produced by bifidobacterium and lactic acid bacteria by combining spectrophotometric and Ag+-HPLC techniques

Bifidobacterium and lactic acid bacteria (LAB), especially from the genera Lactobacillus and Lactococcus, are commonly used in the production of fermented dairy products due to their potential probiotic characteristics. Moreover, some strains of these microorganisms also have the ability to produce conjugated linoleic acid (CLA) from linoleic acid (LA), which has attracted much attention as a novel type of beneficial functional fermented milk. In the present work 22 probiotic bacteria were tested for the production of CLA, using a UV screening method and HPLC techniques. Five microorganisms, two strains of the genera Bifidobacterium, two Lactobacillus and one Lactococcus were selected for their ability to produce CLA after incubation in skim milk with free LA as a substrate. It was possible to quantify the production of CLA (in the range of 40–50 lg CLA/ml) and identify the CLA isomers produced as C18:2 cis 9, trans 11 (60–65%), C18:2 trans 10, cis 12 (30–32%), C18:2 trans 9, trans 11 and C18:2 trans 10, trans 12 (2–5%)

In situ milk enrichment with microbial CLA/CLNA using vegetable oils as substrate source

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Impact of sterilization on phytosterols in canned tuna-based products

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Impact of exposure to cold and cold-osmotic stresses on virulence-associated characteristics of Listeria monocytogenes strains

The objective of this work was to investigate the effect of stress conditions frequently encountered in food-associated environments on virulence-associated characteristics of eight strains of Listeria monocytogenes. Strains were grown at low (11 ºC, cold stress) and optimal (37 ºC) temperatures and in high NaCl concentrations (6% NaCl, 11 ºC; cold-osmotic stress) and tested for their ability to invade the human intestinal epithelial Caco-2 cells. Results demonstrate that the correlation between exposure to cold stress and increased invasion phenotype is strain-dependent as strains investigated exhibited different behaviours, i.e. exposure to cold stress conditions resulted in a significant increase of invasion levels in five out of the eight strains tested, when compared to growth under optimal conditions. On the other hand, when these cold-adapted cells were subsequently submitted to high salt concentrations and low temperature, their enhanced ability to invade Caco-2 was lost. Surprisingly, saturated fatty acids (SFA) and branched chain fatty acids (BCFA) decreased when L. monocytogenes were exposed to stress conditions as opposed to what has been observed in other studies, therefore highlighting that further studies will need to deepen in the understanding of the lipid metabolism of these strains. The effect of stress conditions on the survival of three selected L. monocytogenes strains through an in vitro gastrointestinal (GI) tract digestion model was further investigated. The exposure to cold-osmotic stress increased the survival of one strain through the GI tract.info:eu-repo/semantics/acceptedVersio

Study of the viability of using lipase-hydrolyzed commercial vegetable oils to produce microbially conjugated linolenic acid-enriched milk

This work studied the viability of using vegetable oils as precursor substrates to develop a dairy product enriched in microbial conjugated linoleic (CLA) and conjugated linolenic (CLNA) acids. Hydrolysis of hempseed, flaxseed (FSO) and soybean (SBO) oils was tested with Candida rugosa (CRL), Pseudomonas fluorescens, or Pancreatic porcine lipases. FSO and SBO, previously hydrolyzed with CRL, were further selected for cow’s milk CLA/CLNA-enrichment with Bifidobacterium breve DSM 20091. Thereafter, higher substrate concentrations with hydrolyzed FSO were tested. For all tested oils, CRL revealed the best degrees of hydrolysis (>90%). Highest microbial CLA/CLNA yield in milk was achieved with hydrolyzed FSO, which led to the appearance of mainly CLNA isomers (0.34 mg/g). At higher substrate concentrations, maximum yield was 0.88 mg/g CLNA. Therefore, it was possible to enrich milk with microbial CLNA using vegetable oil, but not with CLA, nor develop a functional product that can deliver a reliable effective dose.info:eu-repo/semantics/publishedVersio

Short-communication: study of fatty acid metabolites in microbial conjugated fatty acids-enrichment of milk and discovery of additional undescribed conjugated linolenic acid isomers

Microbially enriched food in conjugated linoleic (CLA) and conjugated linolenic (CLNA) acids is intensively studied nowadays. The conversion of linoleic (LA) and α-linolenic acids (α-LNA) into these compounds may involve different fatty acid (FA) intermediates. This research aimed to investigate potential FA byproducts in milk during microbial CLA/CLNA-enrichment using Bifidobacterium breve DSM 20091. Milk fermented with pure α-LNA showed a decrease in free myristic acid, while pure LA led to an increase in free stearic acid. No additional FA compounds were found alongside CLA/CLNA isomers. The strain produced several CLA isomers from LA, but only when administered alone. Nonetheless, when α-LNA was assayed, additional CLNA isomers, never reported before for bifidobacteria, were observed. In conclusion, except for stearic acid in the presence of LA, no side-FA metabolites were released during milk microbial CLA/CLNA-enrichment. Results suggest either CLA/CLNA production occurs in one single-step or intermediates biotransformation is very fast.N/

Antioxidant activity evaluation of fermentation distillation residues

Nature offers an unlimited variety of molecules with incredible biological activities, such as antioxidants among others, that are valuable for the maintenance of a good health by reducing the damage caused by oxidation [1,2]. This purpose allied to the richness of some wastes and by-products make distillation residues from industrial fermentation (FDRs) potential sources to obtain bioactive compounds. Accordingly the study for both its valorization and integration into a circular economy context was the aim of this work [3,4]. FDRs are known to be rich in several compounds such as phytosterols, triterpenes or fatty alcohols with potential biological activities [3,4]. Thus, two FDRs, from fermentation using sugarcane juice (FDR_SC) or very high polarity sugar (FDR_VHP) and respective extracts obtained by winterization with different solvents (ethanol (EtOH), acetone (AcO) and dichloromethane (DCM)) were used and the evaluation of its antioxidant activity were performed by DPPH, ABTS and ORAC assays. Inhibition percentage, IC 50, TEAC and ORAC Value parameters were determined. The results revealed great antioxidant potential for the studied FDRs, in particular for FDR_SC that had the best performance in most of the measured parameters. Also, the differences on solvents polarity used for the FDRs winterization had an important role in the antioxidant capacity results, which could be related to the selectivity to isolate different compounds.info:eu-repo/semantics/publishedVersio