Technological activities of Staphylococcus carnosus and Staphylococcus simulans strains isolated from fermented sausages

The aim of this study was to determine the technological properties of 2 strains of Staphylococcus simulans (Ssm12, Ssm21) and 4 strains of S. carnosus (SC28, SC31, SC54 and SC55) for the selection of a potential starter cultures to employ in the processing of dry fermented sausages. The strains were studied to evaluate nitrate reductase, proteolytic, lipolytic, decarboxylase and antioxidant activities as well as growth ability at different temperatures, pH and NaCl concentrations. Nitrate reductase activity was determined at 15, 20 and 30 degrees C. By spectrophotometric method all the strains were able to reduce nitrate to nitrite at the different temperatures but these results were not confirmed by the agar plate method. Antioxidant and lipolytic activities were evaluated by spectrophotometric assay. All the strains showed antioxidative enzymes superoxide dismutase (SOD) and catalase whereas all appeared unable to hydrolyse pork fat. Proteolytic activity was determined by agar plate method, spectrophotometric assay (OPA) and sodium dodecyl sulphate gel-electrophoresis (SDS-PAGE) and all strains appeared to be able to hydrolyse sarcoplasmic proteins but not myofibrillar proteins. Finally, all the strains grew at 15 and 20 degrees C, in presence of 10%, 15% and 20% of NaCl and at pH 5.0 and 5.5 and were unable to produce histamine, cadaverine and putrescine. The results showed that all strains studied possess useful technological activities that would make them eligible as a good starter cultures for fermented sausages

Short communication: Identification and technological characterization of yeast strains isolated from samples of water buffalo Mozzarella cheese

Abstract Sixty yeast cultures were isolated from samples of water buffalo Mozzarella, a popular "pasta filata" cheese, originating on 16 farms located in the provinces of Salerno, Caserta, and Frosinone (Italy). Strains were identified by means of 5.8S internal transcribed spacer rDNA PCR-RFLP combined with 26S rRNA gene partial sequencing and characterized for their ability to exert biochemical properties of technological interest. The recorded dominance of fermenting yeasts such as the lactose-fermenting Kluyveromyces marxianus (38.3% of the total isolates) and the galactose-fermenting Saccharomyces cerevisiae (21.6% of the total isolates) suggests that these yeasts contribute to the organoleptic definition of the water buffalo Mozzarella. The speciographic analysis revealed the presence of 7 other species rarely or never reported in a dairy environment belonging to the genera Pichia and Candida , whose role in Mozzarella cheese organoleptic properties need to be further investigated

Selection of Lactobacillus strains from fermented sausages for their potential use as probiotics.

A rapid screening method was used to isolate potentially probiotic Lactobacillus strains from fermented sausages after enrichment in MRS broth at pH 2.5 followed by bile salt stressing (1% bile salts w/v). One hundred and fifty acid- and bile-resistant strains were selected, avoiding preliminary and time-consuming isolation steps. Strains were further characterized for survival at pH 2.5 for 3 h in phosphate-buffered saline and for growth in the presence of 0.3% bile salts with and without pre-exposure at low pH. Twentyeight strains showed a survival >80% at pH 2.5 for 3 h; moreover, most of the strains were able to grow in the presence of 0.3% bile salts. Low pH and bile resistance was shown to be dependent on both the species, identified by phenotypic and molecular methods, and the strain tested. This is the first report on the direct selection of potentially probiotic lactobacilli from dry fermented sausages. Technologically interesting strains may be used in the future as probiotic starter cultures for novel fermented sausage manufacture

Development of a Wet-Granulated Sourdough Multiple Starter for Direct Use

The search for sourdough starters for the direct production of baked goods with all the advantages of biological sourdough fermentation is still a crucial issue. In this study, 43 Lactic Acid Bacteria strains isolated from mature sourdoughs were evaluated for features of technological interest and tested for fermentation ability. Three microbial combinations were selected and used to produce bread. Based on GC-MS and sensory analysis, bread made by using the three combinations of strains was characterized by a more complex aroma profile with the prevalence of VOCs typical of sourdough bread. To set up the best way to keep microbial viability upon drying, the three combinations were subject to freeze-drying and wet granulation, with the latter being used for the first time for food starters’ stabilization. Wet granulation ensured optimal strains’ viability. Surprisingly, the height attained by mature sourdoughs when inoculated with wet granulated starters was constantly higher than the height reached by sourdoughs made with the same starters as fresh cells. The microbial combination E75-B72 exhibited the best performances and may represent a starter able to ensure sourdough bread production in 16 h of fermentation at 28 °C

Microbial characterization of sourdough for sweet baked products in the Campania region (southern Italy) by a polyphasic approach

The microflora of nine sourdoughs used for sweet bakery products underwent preliminary microbiological characterization using lactic acid bacteria (LAB) and yeast enumeration. Five sourdough samples were submitted for microbial identification by culture-dependent techniques employing 16S and 26S rRNA genes sequencing, as well as a culture-independent technique using PCR-DGGE analysis. The LAB species isolated belonged principally to facultative heterofermentative Lactobacillus spp., Leuconostoc spp., and Lactococcus spp. Yeast strains were identified as Saccharomyces cerevisiae, with one exception represented by a strain belonging to Metschnikowia pulcherrima. PCR-DGGE analysis allowed the identification of Streptococcus thermophilus, Lactobacillus sakei, Weissella groceries and Lactobacillus sanfranciscensis among lactic acid bacteria and Saccharomyces cerevisiae and Metschnikowia pulcherrima among yeasts. This polyphasic approach highlighted different levels of biodiversity, from two to eight different typical LAB species, always associated to Saccharomyces cerevisiae, that could be selected to be specifically used in naturally fermented brioche and cornetto preparation

The effects of probiotics and prebiotics on the fatty acid profile and conjugated linoleic acid content of fermented cow milk

The ability of probiotic bacteria (Lactobacillus acidophilus La5 and Bifidobacterium animalis Bb12), to produce conjugated linoleic acid (CLA) in association with Streptococcus thermophilus and Lb. bulgaricus during milk fermentation has been evaluated in this study. Pasteurized cow milk and infant formula were used. Infant formula was selected for its high linoleic acid content, for being a source of CLA and for its prebiotic compounds, e.g. galacto-oligosaccharides. The microorganisms were not able to increase the CLA content of the fermented products under the given experimental conditions. No statistically significant differences (p>0.05) occurred between the CLA content in milk and the fermented samples. The CLA contents of 10 commercial fermented milk products were determined. The highest CLA content was observed in fermented milk containing only Str. thermophilus and Lb. bulgaricus. © 2015 Informa UK Ltd. All rights reserved

Volatile Organic Compounds in Breads Prepared with Different Sourdoughs

Sourdough is an old example of a natural starter composed of a mixture of flour, water, and metabolites and is produced by naturally occurring lactic acid bacteria and yeasts that influence bread aroma. In this work, four types of sourdough were used to prepare bread: one sourdough with yeast beer and three with bacteria and yeasts. The physicochemical parameters (pH, moisture, water activity, and organic acids) of the bread and sourdoughs were assessed. Lactic, acetic, and succinic acids were found in considerable amounts in sourdoughs and the corresponding breads. The fermentation quotient (molar ratio between lactic and acetic acid) ranged from 0.39 to 3.4 in sourdoughs. Lactic acid was prevalent in all types of bread and showed the highest value in bread made from sourdough with a 1.5 bacteria/yeast ratio (8722.24 mg/kg). Moreover, volatile organic compounds were identified in bread samples. Alcohols, aldehydes, and acetic acid were mainly found. The alcohol concentration ranged from 140.88 to 401.20 ng/g. Aldehydes ranged from 185.01 to 454.95 ng/g, and acetic acid ranged from 91.40 to 173.81 ng/g. Bread prepared from sourdough with a 1.5 bacteria/yeast ratio showed a considerable amount of alcohols and acetic acid

Selection of Wine Saccharomyces cerevisiae Strains and Their Screening for the Adsorption Activity of Pigments, Phenolics and Ochratoxin A

Ochratoxin A is a dangerous mycotoxin present in wines and is considered the principal safety hazard in the winemaking process. Several authors have investigated the ochratoxin A adsorption ability of Saccharomyces cerevisiae yeasts, and specifically selected strains for this desired trait. In the present work, a huge selection of wine yeasts was done starting from Portuguese, Spanish and Italian fermenting musts of dierent cultivars. Firstly, 150 isolates were collected, and 99 non-redundant S. cerevisiae strains were identified. Then, the strains were screened following a multi-step approach in order to select those having primary oenological traits, mainly (a) good fermentation performance, (b) low production of H2S and (c) low production of acetic acid. The preselected strains were further investigated for their adsorption activity of pigments, phenolic compounds and ochratoxin A. Finally, 10 strains showed the desired features. The goal of this work was to select the strains capable of absorbing ochratoxin A but not pigments and phenolic compounds in order to improve and valorise both the quality and safety of red wines. The selected strains are considered good candidates for wine starters, moreover, they can be exploited to obtain a further enhancement of the specific adsorption/non-adsorption activity by applying a yeast breeding approach

Production of butyric acid by different strains of Lactobacillus plantarum (Lactiplantibacillus plantarum)

The butyric acid content produced by three Lactobacillus plantarum (Lactiplantibacillus plantarum) strains (FP37, FP38 and FP48) deposited as probiotic strains was determined. The experimentation was carried out to evaluate whether the production of butyric acid was due to lipolytic activity for the presence of specific lipases or was related to the fermentation of saccharides. Therefore, the three strains were inoculated in different substrates with and without the addition of fat (tributyrin). The free butyric acid contents were determined by gas chromatography after distilling each culture medium. The results showed that butyric acid production occurred mainly in the substrates supplemented with fat and therefore it was linked to the activity of specific L. plantarum lipase. The L. plantarum FP48 strain produced the highest amount of butyric acid in fat substrates and could be a useful strain in the development of dairy products with functional properties