Modelling Bacillus cereus adhesion on stainless steel surface as affected by temperature,pH and time

The adhesion of Bacillus cereus to stainless steel was modelled as a function of pH (4.0–8.0), time (2–24 h) and temperature (4.0–36.0 °C) using response surface methodology. Based on the initial inoculum (3 or 6 log cfu mL⁻¹), two equations describing B. cereus adhesion to stainless steel were obtained. The results indicated that B. cereus was able to reach up to 5.5 cfu cm⁻² and 6.4 cfu cm⁻² when the initial inocula were 3 log cfu mL⁻¹ and 6 log cfu mL⁻¹, respectively. The significance of the factors varied with the model; i.e., inoculum of 3 or 6 log cfu mL⁻¹. Bias and accuracy factors showed that the models are adequate to predict B. cereus adhesion to stainless steel surface under conditions assessed and to assess the adhesion of B. cereus under a range of conditions to which this microorganism can be exposed during either milk processing or cleaning procedures.     

Chemical composition,protein fraction and fatty acid profile of donkey milk during lactation

The chemical composition, fatty acid and protein fraction of donkey milk samples from domestic (Arcadian) breed were assessed from the 30th day to the 210th day of lactation. Total fat, proteins and minerals (Ca, Mg, K and P) were affected by the stage of lactation. Fatty acids were significantly influenced, with a decrease of 31.4% in saturated fatty acids, an increase of 53.8% in unsaturated fatty acids, a concomitant elevation of polyunsaturated fatty acids and a low n-6/n-3 ratio (2:1). Analysis by sodium dodecylsulphate-polyacrylamide gel electrophoresis found, on average, 42.8% casein and 57.2% whey protein. The concentration of lysozyme was between 1.20 and 2.54 mg mL⁻¹, while the highest values were detected by the lysoplate method. Finally, low microbial content and somatic cells were also found in donkey milk with overall average log 4.4 cfu mL⁻¹ and log 4.8 cells mL⁻¹, respectively.     

Determination of menaquinone production by Lactococcus spp. and propionibacteria in cheese

Two genera of lactic acid bacteria are principally known to produce menaquinones in cheese: Lactococcus spp. in semi-hard cheese such as Vacherin Fribourgeois and Raclette, and propionibacteria in Swiss-type cheese such as Emmental. Menaquinone (MK) content of several cheese loaves was analysed to determine the impact of sampling site, ripening time and cultures used during cheese making. With Lactococcus spp., in Vacherin and in Raclette, the principal menaquinone was MK-9 (median = 149 μg kg⁻¹ and median = 167 μg kg⁻¹) followed by MK-8 (median = 70 μg kg⁻¹ and median = 66 μg kg⁻¹). In Emmental cheese, the principal menaquinone was MK-4 (median = 48 μg kg⁻¹) in young cheese and MK-9(4H) (median = 468 μg kg⁻¹) in cheese older than 90 days. The only difference in sampling site was found in Raclette for MK-9. In Vacherin, MK-8, MK-9 and total contents of menaquinones were significantly different according to the strain of Lactococcus lactis ssp. cremoris used.     

Development of an immunomagnetic separation–propidium monoazide–polymerase chain reaction assay with internal amplification control for rapid and sensitive detection of viable Escherichia coli O157:H7 in milk

A rapid, reproducible, sensitive and specific combination assay was developed for Escherichia coli O157:H7 comprising sequential immunomagnetic separation (IMS), followed by propidium monoazide (PMA), exclusion by viable cells, internal amplification control (IAC) and polymerase chain reaction (PCR). IMS was used to improve sensitivity, reduce detection time and eliminate false positives. PMA was used to detect viable cells, and IAC was incorporated into the system to eliminate the inhibitors of PCR from the food matrix. In the presence of inhibitors, IAC produced no signal, thereby eliminating false negative results. The results indicated that the IMS cell capture efficiency was about 90% at a concentration of 1 × 10⁶ cfu mL⁻¹ with a detection limit of 2.1 × 10² cfu mL⁻¹ for pure culture. In an unoptimised system, IMS–PMA–PCR with IAC showed a detection limit of 5 × 10³ cfu mL⁻¹ in spiked milk over a 240 min assay, faster than conventional methods of detection.     

Effect of gums on viability and β‐galactosidase activity of Lactobacillus spp. in milk drink during refrigerated storage

The viability and β‐galactosidase activity of four Lactobacillus strains in milk drink containing gums during 28 days of refrigerated storage at 4 °C were assessed. The population of Lactobacillus rhamnosus GGB101 and Lactobacillus rhamnosus GGB103 were maintained, whereas the population of Lactobacillus reuteri DSM20016 and Lactobacillus reuteri SD2112 significantly decreased. The recommended level of 6 log CFU g^?1 was exceeded for all tested trains throughout storage. The highest viable number of Lactobacillus rhamnosus GGB103 (8.76 ± 0.03 log CFU mL^?1) was obtained in the product containing carrageenan–maltodextrin. The addition of guar–locust bean–carrageenan led to 20‐fold increase in the level of β‐galactosidase activity for L. rhamnosus GGB101 (1208 ± 2.12 Miller units mL^?1) compared to the control (61 ± 2.83 Miller units mL^?1). Our results suggested that gums could be added to milk to improve viability and enhance β‐galactosidase activity of Lactobacillus.     

Development of rapid and highly specific TaqMan probe-based real-time PCR assay for the identification and enumeration of Lactobacillus kefiri in kefir milk

Lactobacillus kefiri is one of the key functional lactic acid bacteria in kefir milk. We designed a novel real-time PCR primer/probe set, LK_508 targeting the recA gene, for the rapid identification and enumeration of L. kefiri. In inclusivity and exclusivity test using standard strains and kefir isolates, only the 9 tested L. kefiri strains were positive, with the remaining 38 closely related microorganisms testing negative, thus indicating 100% sensitivity and specificity of the assay. The population of L. kefiri was 3.77, 4.30, 4.79, and 5.63 log cfu mL⁻¹ of kefir milk fermented at 25 °C with 5% grain-milk ratio for 12, 24, 36, and 48 h, respectively. The newly developed qPCR assay could be applied to investigate the quantitative relationship of kefir microbiota in fermentation process.     

Effective valorisation of distillery stillage by integrated production of lactic acid and high quality feed

Utilization of distillery stillage from bioethanol production for lactic acid and feed production was studied. The lactic acid fermentation of the stillage was performed by Lactobacillus rhamnosus ATCC 7469 and maximal lactic acid concentration of 50.18 g L^− 1, yield of 0.90 g g^− 1, productivity of 1.48 g L^− 1 h^− 1 and viable cell number of 5 × 10⁹ CFU mL^− 1 were achieved. Solid residues with biomass remains after lactic acid fermentation were assessed for animal consumption. The content of proteins and ash decreased in the residues after the fermentation, whilst the content of oil and nitrogen free extract was higher when compared to unfermented samples. The digestible (17480.64 kJ kg^− 1) and metabolisable (17389.08 kJ kg^− 1) energies as well as digestibility (966.95 g kg^− 1) of the fermentation residue were very high. The in vitro assessment of L. rhamnosus ATCC 7469 survival in simulated gastric conditions has shown high survival rate (87%). In addition, this bacterium has shown good antimicrobial activity against the most important pathogens and capability to produce exopolysaccharide on different sugars present in animal diet. After effective lactic acid fermentation, the residues could be recommended as a high quality feed for monogastric animals.     

Hazelnut milk fermentation using probiotic Lactobacillus rhamnosus GG and inulin

Following the consumer demand of healthy vegetable products due to their interesting nutritional profiles and potential functionalities, the fermentation process of hazelnut milk with Lactobacillus rhamnosus GG and S. thermophilus was studied. The effect of different factors (glucose, inulin and inoculum contents) was analysed to ensure sufficient probiotic survivals in a minimum time. The shelf life of the optimised product was characterised in terms of its main physicochemical and quality parameters (probiotic survivals and sensory analysis). Results showed that the defined formulation allowed high probiotic survivals (≈10⁸ cfu mL^?1) throughout cold storage and >60% survived to the in vitro digestion process (≈10⁵ cfu mL^?1). Lactobacillus rhamnosus GG was no able to degrade inulin, which remained to exert health benefits in the host. The product was highly appreciated by the sensory panel during its shelf life despite the formation of a weak gel, which presented syneresis at the last storage time.     

Effect of fructooligosaccharides and galactooligosaccharides on the folate production of some folate-producing bacteria in media cultures or milk

The present work investigated the ability of Bifidobacterium catenulatum, Bifidobacterium adolescentis, Lactobacillus plantarum, Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus to produce folate in milk and complex media. Moreover, the effect of two prebiotics, fructooligosaccharides and galactooligosaccharides, on folate biosynthesis was also evaluated. Levels of the predominant folate forms, i.e., tetrahydrofolate and 5-methyltetrahydrofolate, were determined using high performance liquid chromatography after 0, 6, 10 and 24 h incubation. B. catenulatum (28.82 ± 2.02 μg 100 mL⁻¹) and S. thermophilus (19.03 ± 1.95 μg 100 mL⁻¹) produced the highest level of folate in complex media and milk, respectively. In most cases, the bacteria tested reached the maximum folate levels within 6 h and 10 h of incubation. The inclusion of prebiotics in the culture medium did not stimulate the synthesis of folate by any of the five bacteria studied, although it increased the rate of bacterial growth.     

Selenium supplementation of diets of dairy cows to produce Se-enriched cheese

Selenium (Se) deficiency in people and animals is a nutritional problem in many regions of the world. Ten mid-lactation Estonian Red dairy cows were supplemented for 64 days with inorganic Se [0.39 mg kg⁻¹ in total mixed ration (TMR)] followed by a 57-day period of supplementation with organic and inorganic Se (0.44 mg kg⁻¹ in TMR), according to EU directives on maximum allowed amounts. Feeding organic Se increased Se content in blood (from 186.5 to 287.9 μg kg⁻¹), milk (from 17.1 to 51.8 μg kg⁻¹) and Edam-type cheese made there from (from 146 to 361 μg kg⁻¹). Se content in milk after supplementation was high enough to produce a cheese enabling the nutrition claim “high in Se” and related health claims. The concentration of the main primary oxidation products of linoleic acid (oxylipins) was low and leukotoxin diols were found in trace amounts; the oxidative stability of cheeses was high.     

Antihypertensive activity of milk fermented by Enterococcus faecalis strains isolated from raw milk

A total of 231 microorganisms were isolated from raw cow milk samples and the angiotensin-converting enzyme-inhibitory (ACEI) activity of the resultant fermented milk produced with the isolated microorganisms was assayed. Forty-six of these microorganisms were selected on the basis of high ACEI activity. Four Enterococcus faecalis strains stood out as producers of fermented milk with potent ACEI activity (IC₅₀ (the protein concentration that inhibits 50% of ACE activity): 34–59 μg mL⁻¹). Single doses (5 mL kg⁻¹) of the whey fraction obtained from these fermented milk samples were administered to spontaneously hypertensive rats (SHR) and to normotensive Wistar-Kyoto (WKY) rats in order to investigate their possible antihypertensive activity. Highly significant decreases in the systolic blood pressure (SBP) and in the diastolic blood pressure (DBP) were observed when the fermented milk was administered to SHR. Nevertheless, the fermented milk did not modify the SBP and the DBP of the WKY rats. Raw cow milk is an excellent source of wild lactic acid bacteria able to produce fermented milk with antihypertensive activity and antihypertensive activity of milk fermented by Enterococcus faecalis strains was associated with peptides different from Ile-Pro-Pro and Val-Pro-Pro.     

Evaluation of antibacterial protein with antioxidant activity from Rahnella aquatilis L103 and its effect on beef during refrigerated storage

A strain, Rahnella aquatilis L103, which was isolated from the soil around the roots of mushrooms, produced antibacterial protein though fermentation. This protein has broad antibacterial spectrum towards gram-positive and gram-negative bacteria. The protein has a significant antioxidant capacity on scavenging ABTS^+· (82.5%, 120 μg mL⁻¹), DPPH^· (64.1%, 600 μg mL⁻¹) and OH^· (60.1%, 750 μg mL⁻¹) as well. The protein was considered to be safe within concentration of 150 μg mL⁻¹ as shown by MTT results and was applied to beef refrigerated preservation. The treatment group presented lower total viable counts (TVC), total volatile basic nitrogen (TVB-N), 2-thiobarbituric acid (TBA), meanwhile, higher sensory score and longer shelf life (2 days) compared with the control group (P < 0.05). The results indicated that the protein under safe concentration was beneficial to beef preservation.     

Effect of debittering and solid-state fermentation processes on the nutritional content of lupine (Lupinus mutabilis Sweet)

There is a growing interest in vegetable-based sources of proteins. Despite its high nutrient content, lupine has been rarely exploited as a protein source due to the presence of high levels of non-nutritive compounds such as alkaloids, which impart a bitter taste. Here, we evaluated the effect of debittering and solid-state fermentation on the nutritional contents of three lupine varieties (Lupinus mutabilis Sweet). These processes induced significant changes (P < 0.05) in the nutritional composition of the three lupine varieties (INIAP-450, INIAP-451 and Criollo) and increased the protein levels to 644.55 g kg⁻¹ (Criollo variety) and the levels of several constituent amino acids such as valine (54.62 g kg⁻¹), methionine (42.47 g kg⁻¹), isoleucine (59.27 g kg⁻¹) and leucine (76.32 g kg⁻¹). The ether extract of INIAP-450 showed increased levels (up to 244.03 g kg⁻¹); especially, monounsaturated fatty acids (559.78 g kg⁻¹) and polyunsaturated fatty acids (293.17 g kg⁻¹) were observed. The omega-6/omega-3 ratio in the debittered grain oil reached the minimum requirement established for good-quality oils (5/1). However, the levels of other components decreased, showing levels up to 13.04 g kg⁻¹ (total starch) in the Criollo variety, 22.62 g kg⁻¹ (resistant starch) in INIAP-450, 6.53 g kg⁻¹ (potassium) in INIAP-451, 46 g kg⁻¹ (iron) in INIAP-451 and 29.75 g kg⁻¹ (zinc) in INIAP-450.     

Preconditioning of the stainless steel surface affects the adhesion of Bacillus cereus spores

The adhesion of Bacillus cereus on stainless steel, with and without prior conditioning of the surface (water, skimmed milk, and whole milk) was evaluated. Inocula consisting of a pool of spores of four different B. cereus strains isolated from the dairy industry, and spores of B. cereus ATCC 14579 were used. The pool of B. cereus spores adhered in all conditions evaluated. Higher adhesion of B. cereus spores (4.93 log cfu cm⁻²) was observed when using whole milk as conditioning matrix. However, without prior conditioning, lower adhesion was observed (3.01 log cfu cm⁻²) when the pool of B. cereus spores was inoculated on whole milk, suggesting the interaction between milk fat and microorganism on the stainless steel. The pool of B. cereus spores showed higher adhesion to the surface, possibly due to its greater hydrophobicity (66%) when compared with the B. cereus ATCC 14579 spores (47%).     

Yoghurt added with Lactobacillus casei and sweetened with natural sweeteners and/or prebiotics: Implications on quality parameters and probiotic survival

The effect of addition of natural sugar substitutes (stevia, erythritol or xylitol) and prebiotics (oligofructose or polydextrose) on physicochemical characteristics, probiotic survival (Lactobacillus casei) and sensory acceptance of yoghurts during storage (7 °C, 28 days) was evaluated. Yoghurts with sucrose or sucralose were also prepared. Xylitol and sucralose added yoghurts had physicochemical characteristics and sensory acceptance similar to those of the product with sucrose. Xylitol was more efficient in maintenance of textural characteristics and probiotic survival in simulated gastrointestinal conditions (SGIC) than sucralose. Addition of erythritol and stevia changed the textural parameters, reduced acceptance and decreased probiotic survival in SGIC. Addition of oligofructose or polydextrose improved texture and increased probiotic survival but decreased flavour acceptance. All formulations could be considered probiotic products during shelf life (7 °C, 28 days) with counts higher than 10⁷ cfu mL⁻¹ in the product and 10⁴ cfu mL⁻¹ after SGIC.     

Effect of nutrient supplements on growth and viability of Lactobacillus johnsonii NRRL B-2178 in whey

The main objectives of the paper were to study the effects of nutrient supplementation of cows' whey on the growth and viability of the probiotic microorganism Lactobacillus johnsonii NRRL B-2178. Because of the short lifespan of probiotics, this study was aimed at the evaluation of the contribution of nutrients in the improvement of growth and viability of the microorganism for the purpose of its further application in the formulation of whey-based beverages. A maximal cell growth of 8.70 log₁₀ cfu mL⁻¹ and viability of less than 5 days were achieved during the fermentation of whey supplemented with yeast extract (3.0%) and inulin (1.0%), including the synergistic effect of temperature 39 °C. Elimination of inulin from the fermentation process reduced the viable cell count by 0.2 log₁₀ cfu mL⁻¹, but the addition of 1.0% inulin after fermentation extended the viability of Lb. johnsonii NRRL B-2178 by 10 days.     

Behaviour of Listeria monocytogenes and Staphylococcus aureus in sliced,vacuum-packaged raw milk cheese stored at two different temperatures and time periods

The behaviour of Listeria monocytogenes and Staphylococcus aureus in raw milk cheese slices packaged under vacuum was evaluated. Artificially contaminated 80-day ripened cheese was portioned, vacuum packaged, and then stored for 28 days at 4 °C and for 56 days at 10 °C. Bacterial counts were obtained before vacuum packaging and then weekly during storage. At the end of ripening, the initial L. monocytogenes count was 4.46 ± 0.89 log cfu g⁻¹; weekly bacterial counts remained substantially unchanged in the samples stored at 4 °C but decreased to 3.54 ± 1.54 log cfu g⁻¹ in those stored at 10 °C. The initial S. aureus count before vacuum packaging was 3.60 ± 0.78 log cfu g⁻¹; it then gradually decreased to 2.60 ± 1.32 log cfu g⁻¹ in the samples stored at 4 °C and to about 1.9 log cfu g⁻¹ in those stored at 10 °C.     

Characterisation of the anti-microbial activity of bovine milk ribonuclease4 and ribonuclease5 (angiogenin)

Two members of the ribonucleaseA (RNaseA) family were identified in cows' milk. RNase5, already known to be present, was found at concentrations between 3 and 19 μg mL^?1. RNase4, which was not previously known to be in milk, was found at concentrations between 1 and 4 μg mL^?1. These proteins were purified from milk. Purified RNase5 suppressed the growth of Candida albicans, particularly its hyphal form, but not any other microbes tested. The concentrations required to suppress growth were higher than those found in milk. RNase4 had no growth suppression activity. Both RNases reduced the number of viable C. albicans cells, with RNase5 being the more potent. This activity was abrogated by physiological concentrations of NaCl. Although both RNases bound to C. albicans cell membrane, their mode of action was not through membrane lysis or permeabilization. Together, these results suggest that the bovine milk RNases do not have intrinsic anti-microbial activity in milk.     

Effect of incubation conditions and possible intestinal nutrients on cis-9, trans-11 conjugated linoleic acid production by Lactobacillus acidophilus F0221

The purpose of this study was to optimise the incubation conditions for cis-9, trans-11 conjugated linoleic acid (c9, t11 CLA) production by Lactobacillus acidophilus F0221 and evaluate the effect of possible intestinal nutrients on c9, t11 CLA production. Growth in Mann Rogosa Sharp broth supplemented with cysteine and containing 0.5 g L⁻¹ linoleic acid at pH 6.5 with anaerobic incubation at 37 °C for 40 h were found to be the optimal conditions for CLA production. Galactosaccharide, arabinogalactan, galactose and glucose had a higher promoting effect on CLA production (96.19–123.89 μg mL⁻¹) than other carbohydrates. Acetic acid had a higher promoting effect on CLA production (130.98 μg mL⁻¹) than other short chain fatty acids. These results provide detailed parameters for the production of c9, t11 CLA by L. acidophilus F0221 and are valuable for further understanding of c9, t11 CLA formation in the human intestine by this strain.     

In vitro inhibitory effects of cranberry bean (Phaseolus vulgaris L.) extracts on aldose reductase, α‐glucosidase and α‐amylase

The in vitro inhibitory activities of different seed extracts prepared from cranberry bean mutant SA‐05 and its wild‐type variety Hwachia against aldose reductase, α‐glucosidase and α‐amylase were examined. The results indicated that the polyphenolics‐rich extracts obtained using 800 g kg^?1 methanol and 500 g kg^?1 ethanol demonstrated inhibitory activities against aldose reductase (IC₅₀ of 0.36–0.46 mg mL^?1) and α‐glucosidase (IC₅₀ of 1.32–1.94 mg mL^?1). The 500 g kg^?1 ethanol extracts also showed α‐amylase inhibitory activities (IC₅₀ of 70.11–80.22 μg mL^?1). Subsequent extracts, prepared further with NaCl and H₂O from precipitates of 800 g kg^?1 methanol or 500 g kg^?1 ethanol extracts, exhibited potent α‐amylase inhibitory activities (IC₅₀ of 17.68–38.68 μg mL^?1). A combination of 500 g kg^?1 ethanol extraction plus a subsequent H₂O extraction produced highest polyphenolics and α‐amylase inhibitors. The SA‐05 α‐amylase inhibitor extracts showed greater inhibitory activities than that of Hwachia. Thus, cranberry bean mutant SA‐05 is an advantageous choice for producing anti‐hyperglycaemic compounds.