Decontamination of Salmonella enterica Typhimurium on green onions using a new formula of sanitizer washing and pulsed UV light (PL)

Pathogenic bacteria such as Salmonella and Shigella flexneri have been linked to green onion contamination. This study was conducted to evaluate decontamination of Salmonella Typhimurium using a new formula of sanitizer washing (0.4 mg/mL thymol and five new formula sanitizers including 300 ppm H₂O₂ + 4% SDS, 2 mg/mL citric acid + 4% SDS, 0.2 mg/mL thymol + 4% SDS, 0.2 mg/mL thymol + 2 mg/mL citric acid and 0.2 mg/mL thymol + 2 mg/mL acetic acid), pulsed UV light (PL) as well as synergy between the sanitizer wash and PL. New formula sanitizers based on decontamination efficacy of single washing solutions (organic acids, hydrogen peroxide (H₂O₂), essential oil or surfactant) were applied to decontaminate spot inoculated green onions. PL, the novel technique, alone has been applied to inactivate Salmonella on both dip and spot inoculated green onions. Salmonella inactivation of PL–new formula sanitizer combinations on dip inoculated green onions was investigated for their potential synergy. As a result, for spot inoculated green onions, 0.4 mg/mL thymol individually and the five new formula sanitizers all achieved higher log reduction of Salmonella (4.5–5.3 log 10 CFU/g reduction) than the 200 ppm chlorine washing. These new formulas of sanitizer would be potential alternatives to chlorine. The 5 s dry PL (4.6 log 10 CFU/g) or 60 s wet PL treatment (3.6 log 10 CFU/g) was better or comparable as chlorine washing. The sanitizer combinations did not provide significantly higher log reduction than PL, and PL has the potential of being used in the green onion industry for decontamination purpose. For dip inoculated green onions, none of our treatment provided > 0.8 log 10 CFU/g (0.6–0.8 log 10 CFU/g) reduction of Salmonella. As a result, the PL–new formula sanitizer combinations had no or minimal synergy to inactivate Salmonella dip inoculated on green onions.     

Optimization of d-lactic acid production by Lactobacillus coryniformis using response surface methodology

New low-cost media for lactic acid fermentation are desired to enhance the economics of the d-lactic acid production by Lactobacillus coryniformis. The aim of this work was to optimize the production of d-lactic acid from glucose by L. coryniformis in a reduced nutritional medium composed of corn steep liquors (CSL), yeast extract (YE) and peptone (P). Response surface methodology has been successfully used to modelling and optimizes the d-lactic acid production at variable fermentation times (20, 31, 44, 53, 72 and 96 h). The models predicted a maximum d-lactic acid concentration (58.9 g/l) at 96 h using 5 g CSL/l, 3.6 g YE/l and 10 g P/l. However, the maximum economic yield (10.14 $/$) was obtained at 96 h using 5 g CSL/l as a sole nutrient and the maximum economic productivity (0.22 $/h$) was obtained by reducing the fermentation time at 44 h.     

Effect of cider maturation on the chemical and sensory characteristics of fresh cider spirits

The influence of cider maturation on the chemical and sensory characteristics of fresh cider spirits was evaluated in the present study. To this end, a single-factor experiment with three maturation levels and five replicates (ciders) per level was developed. Level 1 corresponded to spirits obtained when alcoholic and malolactic fermentation of the ciders ceased, Level 2 corresponded to spirits obtained from ciders with a volatile acidity of 1.0 g/L acetic acid, while Level 3 corresponded to spirits made from ciders with a volatile acidity of 1.5 g/L acetic acid. Cider maturation significantly influenced the composition of the spirit as regards the ethyl esters of the major organic acids of cider (lactic, acetic and succinic). It also significantly influenced the content of aromas produced by bacterial activity (2-butanol, 2-propen-1-ol, 4-ethylguaiacol and eugenol), the concentration of which was found to increase with higher levels of maturation. The attributes “spicy” and “sweetness” were likewise influenced by the level of cider maturation. The distillates made from the most matured cider (volatile acidity 1.5 g acetic acid/L) scored better for “odour quality”.     

Effect of Adding Formaldehyde,Glutaraldehyde, or Dimethylolurea to Alfalfa before Ensiling

Formaldehyde, glutaraldehyde, or dimethylolurea were sprayed on alfalfa wilted to approximately 35 and 62% dry matter at rates of 1, 3, and 4 g of formaldehyde; 1.7, 5.0, and 6.7 g of glutaraldehyde; and 2.5, 5.0 and 10 g of dimethylolurea/100 g of crude protein. Treatment of alfalfa with formaldehyde resulted in marked inhibition of silage fermentation as characterized by large amounts of residual water-soluble carbohydrates and low amounts of lactic acid, free NH₃-N, and amino acids. The effects with glutaraldehyde and dimethylolurea were similar but to a lesser extent. Addition of formaldehyde and glutaraldehyde resulted in similar reductions of rumen degradable nitrogen as estimated by in situ techniques. However, fiber digestion tended to be less for glutaraldehyde than formaldehyde silage. Addition of these additives to alfalfa containing 62% dry matter resulted in almost complete inhibition of silage fermentation. Presence of surface mold on the 62% dry matter-treated silages suggest that the silage was unstable.     

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.     

Effect of ozone on microbial,chemical and sensory attributes of shucked mussels

The effect of ozonation in aqueous solution (O₃ concentration=1 mg/l, time of ozonation: 60 and 90 min) on the shelf-life of shucked, vacuum-packaged mussels, stored under refrigeration was studied by monitoring the microbiological, chemical and sensory changes occurring in mussel samples, for a period of 12 days. Non-ozonated vacuum-packaged mussels served as the control sample. Ozonation affected populations of bacteria namely, aerobic plate count (APC) (0.7–2.1 log cycle reduction), Pseudomonas spp. (0.5–1.1 log cycle reduction) and H₂S-producing bacteria (1.1–2.5 log cycle reduction), Brochothrix thermosphacta (0.3–1.4 log cycle reduction), lactic acid bacteria (0.3–0.8 log cycle reduction) and Enterobacteriaceae (0.5–1.5 log cycle reduction). The effect of ozonation was more pronounced at the longer time of ozonation. Of the chemical indicators of spoilage monitored, trimethylamine values of all mussel samples remained relatively low throughout the entire storage period, attaining values of 7.5, 6.0 and 6.4 mg N/100 g for the control and ozonated for 60 and 90 min samples, respectively, on day 12 of storage. Total volatile basic nitrogen (TVB-N) values similarly remained relatively low (⩽20 mg N/100 g) until day 6 of storage, and increased to 31.9, 24.2 and 26.9 mg N/100 g mussel meat for the control and ozonated for 60 and 90 min samples, respectively, on day 12 of storage. Initial TBA values were surprisingly high (30–35 mg MA/kg) and decreased to 23.0, 21.7 and 13.3 mg MA/kg mussel meat on day 12 of storage for the control and the ozonated for 60 and 90 min samples, respectively. Sensory evaluation (odor, taste and texture) of cooked mussels showed a good correlation with bacterial populations. On the basis of sensory analyses, a shelf-life of 12 days was obtained for vacuum-packaged mussels ozonated for 90 min as compared to a shelf-life of 9 days for the control sample.     

Electrostatic spraying of organic acids on biofilms formed by E. coli O157:H7 and Salmonella Typhimurium on fresh produce

Electrostatic spraying which has an even and retained surface coverage could be an effective novel technique to completely cover the surface of fresh produce to disrupt biofilm formation by pathogenic bacteria. Spinach leaves and cantaloupe rind were spot-inoculated with a bacterial culture and stored at 8 °C for 72 h to allow biofilm formation. Among various green fluorescent protein-labeled strains, ED 14 strain of E. coli O157:H7 and SD 10 strain of Salmonella Typhimurium had the best attachment based on colony counts. The produce samples were electrostatically sprayed with malic (MA) and lactic (LA) acid solutions alone (1.0/2.0/3.0/4.0% w/v) or in combination (0.5 + 0.5/1.0 + 1.0/1.5 + 1.5/2.0 + 2.0% w/v) to test for a reduction in the attached bacteria. A combined treatment of LA 2.0% w/v + MA 2.0% w/v had the highest log reduction (CFU/disk) of 4.14 and 3.6 on the attached E. coli strain ED 14 (spinach) and Salmonella strain SD 10 (cantaloupe), respectively. Crystal violet assay demonstrated the disruptive effect of organic acids on biofilms formed by the pathogenic bacteria. Application of electrostatic spray with a combination of malic and lactic acids resulting in a log reduction (CFU/disk) of 3.6 or higher can improve the microbial safety of spinach and cantaloupe by preventing the pathogenic biofilm formation and bacterial growth.     

Combinations of nisin with organic acids or salts to control Listeria monocytogenes on sliced pork bologna stored at 4°C in vacuum packages

This study evaluated dipping solutions of nisin with or without organic acids or salts, as inhibitors of Listeria monocytogenes introduced on sliced cooked pork bologna before vacuum packaging and storage at 4°C for 120 days. Inoculated (10²–10³ cfu/cm²) slices were immersed in nisin (5000 IU/ml), or in lactic or acetic acid (1, 3, 5 g/100 ml), sodium acetate or diacetate (3, 5 g/100 ml), and potassium benzoate or sorbate (3 g/100 ml), each combined with nisin. Additional slices were immersed in nisin, inoculated and then immersed in acid or salt solutions without nisin. Nisin reduced L. monocytogenes by 1.0–1.5 log cfu/cm² at treatment (day-0) followed by a listeriostatic effect for 10 days. Thereafter, however, the pathogen multiplied in treatments without acid or salts, with growth being faster on slices immersed in nisin after as compared to before inoculation. Nisin in combination with 3 or 5 g/100 ml acetic acid or sodium diacetate or 3 g/100 ml potassium benzoate, applied individually or as mixtures, did not permit growth before day-90. Other treatments were of variable and lesser effectiveness (20–70 days), whereas in untreated or water-treated (control) bologna L. monocytogenes increased at 6–7 log cfu/cm² at day-20. Based on the antilisterial efficacy and effects of treatments on product pH, nisin with 3 g/100 ml sodium diacetate may be the most promising combination in dipping solutions to control L. monocytogenes on sliced cured pork bologna.     

Influence of preprocessing methods and fermentation of adzuki beans on γ-aminobutyric acid (GABA) accumulation by lactic acid bacteria

The effects of pre-processes (immersing, germinating, and cold shock) and fermentation conditions of adzuki beans on γ-aminobutyric acid (GABA) accumulation using mixed cultures of Lactococcus lactis and Lactobacillus rhamnosus were investigated in this study. Among the preprocessing methods, cold shock treatment resulted in the highest observed GABA content (201.2 mg/100 g); a 150-fold increase compared to the non-treated adzuki beans. The LAB strains grew rapidly in cold-treated adzuki bean substrates and reached 10⁸ cfu/ml after 24 h of fermentation at 30 °C. After optimization, the GABA yield reached 68.2 mg/100 ml; a 20-fold increase compared to the non-fermentation yield. The viable cell counts of LAB remained above 10⁸ cfu/ml after 28 days of storage at 4 °C. Our results suggest that the combination of cold shock pretreatment and fermentation by LAB may be used for the preparation of adzuki beans with high GABA content, which can then be used as a natural resource of functional foods.     

Continuous Production of Lactic Acid from Whey Perméate by Free and Calcium Alginate Entrapped Lactobacillus helveticus

Lactobacillus helveticus strain milano was used for the continuous fermentation of lactic acid in cheese whey-yeast extract permeate medium. The best productivity of lactic acid was with the free cell system, which was 9.7 g/L per h at a dilution rate of .352 h⁻¹. Under such conditions, lactose conversion was 87.5%, based on the lactose concentration of 37.4 g/L in feed. Under high dilution rates, the cells were elongated to several times their normal size, resulting in wall growth. The cell growth on the fermentor wall caused system instability; however, it prevented cell wash-out under high dilution rates. The packed bed column system using Ca alginate entrapped cells is not suitable for practical application. Nonuniform pH control, plugging of the column by leaked cells, and decalcification of Ca alginate beads were major drawbacks of the packed bed system.     

Effect of Lactobacillus brevis-based bioingredient and bran on microbiological,physico-chemical and textural quality of yeast-leavened bread during storage

The effects of wheat bran and of a Lactobacillus brevis-based bioingredient (LbBio), obtained after growth in flour-based medium, on quality of yeast-leavened wheat bread (WWB) were investigated. Bran was used in bread formulation by substituting a part (20 g/100 g) of white wheat flour (WBB), while LbBio was used instead of the water content (WWB + LbBio and WBB + LbBio). The use of LbBio in WWB resulted in the biological acidification of the dough due to lactic, phenyllactic and OH-phenyllactic acid contents determining a high fermentation quotient value and an improved bread texture and microbiological quality. Conversely, wheat bran reduced the specific volume and crumb hardness during storage at 25 °C, and affected the antibacterial ability of LbBio during 30 °C storage. Our findings demonstrated that LbBio counteracted the negative effects of bran and allowed to obtain an enriched fibre bread with specific volume and soft crumb comparable to bread without bran.Industrial relevanceBread is a perishable food with a short microbiological and physico-chemical shelf-life. The main microbiological alteration occurring into few days after baking is the “rope spoilage” caused by spore-forming bacteria originating from raw materials. This phenomenon, often misinterpreted as a sign of unsuccessful dough leavening and not visible from outside, is more common under industrial production conditions during the hot season causing large economic losses in the warm climates of Mediterranean countries, Africa and Australia. The use of sourdough often controls this alteration even if the industrial application of this traditional process is limited by the long leavening times. In this study, an innovative procedure for the preparation of yeast-leavened bread comprising the addition of a fermentation product from Lactobacillus brevis grown in a flour-based medium has been applied. The resulting fermentation product (LbBio bioingredient) acts as a sourdough acidifying the dough and improving the textural, physico-chemical and microbiological properties of the resulting bread. The application of bioingredient LbBio could represent an innovative strategy in industrial bread production to obtain acidified yeast-leavened products, thus, preventing the ropy spoilage and reducing the negative effects of bran addition.     

Evaluation of stored lamb bio-preserved using a three-strain cocktail of Lactobacillus sakei

Commercially prepared lamb was stored at −1.5 °C after inoculation with a combination of three Lactobacillus sakei strains previously shown to inhibit spoilage and pathogenic bacteria of importance to the meat industry. Between 6 and 14 weeks storage samples were evaluated for growth of inoculated strains, production of fermentation end-products and sensory acceptance of the cooked product. All three L. sakei strains flourished during storage, formed consistently dominant populations and were associated with lower surface pH and increased levels of lactic and acetic acids. Inoculated samples were determined to be as equally acceptable for smell, acidity, rancidity and overall liking as un-inoculated controls.     

Evolution of potential and free furfural compounds in milk-based infant formula during storage

HPLC-DAD was used to monitor the evolution of potential and free furfural compounds (5-hydroxymethyl-2-furaldehyde, HMF; 2-furaldehyde, F; 2-furyl methyl ketone, FMC; and 5-methyl-2-furaldehyde, MF) over the shelf life of two types of infant powder formula: one supplemented with long-chain polyunsaturated fatty acids (LC-PUFA) in the form of microencapsulated fish oil (MFO), the other not supplemented with LC-PUFA. Following production, the formulae were stored at 25 and 37 °C. The initial furfural content in the supplemented formula was as follows: potential HMF (485.88 μg/100 g), potential F (167.13 μg/100 g), and free HMF (58.23 μg/100 g), while free F was not detected. In the unsupplemented formula, the following values were recorded: potential HMF (515.85 μg/100 g), potential F (170.29 μg/100 g), free HMF (84.92 μg/100 g), and free F (1.19 μg/100 g). In general, increased furfural content was observed during storage, an increase more pronounced in formula stored at 37 °C. Hardly any differences in furfural evolution during storage were observed between supplemented and unsupplemented infant formulae. The results suggest that the uses of MFO material for supplement formula not affected furfural formation. Neither FMC nor MF was formed in the formulae studied.     

Fermentation of beet juice by beneficial lactic acid bacteria

Red beets were evaluated as a potential substrate for the production of probiotic beet juice by four species of lactic acid bacteria (Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus delbrueckii, Lactobacillus plantarum). All the lactic cultures were found capable of rapidly utilizing beet juice for cell synthesis and lactic acid production. However, L. acidophilus and L. plantarum produced a greater amount of lactic acid than other cultures and reduced the pH of fermented beet juice from an initial value of 6.3 to below 4.5 after 48 h of fermentation at 30°C. Although the lactic cultures in fermented beet juice gradually lost their viability during cold storage, the viable cell counts of these lactic acid bacteria except for L. acidophilus in the fermented beet juice still remained at 10⁶–10⁸ CFU/ml after 4 weeks of cold storage at 4°C.     

Pectin quantity,composition and physicochemical behaviour as influenced by the purification process

To examine the purification procedure effect on the pectin amount, purity, macromolecular characteristics, and gelling ability, three pectin isolates, namely, alcohol (APP)-, dialysis (DPP)-, and metal ion (MPP)-purified pectins are obtained from acid extracts of yellow passion fruit rind using alcohol-precipitation, dialysis, or ion-binding precipitation. The results show that the amount of MPP (4.1 g/100 g) is significantly (p < 0.05) lower than the amount of the two other pectins (6.8–7.5 g/100 g). In contrast, MPP has a higher galacturonic acid (78.9 g/100 g) and lower neutral sugar (9.7 g/100 g), ash (0.9 g/100 g), and protein (1.4 g/100 g) contents than the remainder (62.4–70.1, 16.0–17.8, 2.7–5.8, 3.1–3.2 g/100 g, respectively). Molecular-weight distribution patterns suggest that MPP is free of neutral sugar oligosaccharide contaminants unlike the others, especially APP. Therefore, the term of ‘the galacturonic acid yield’ is introduced to complement the conventional term of ‘the pectin yield’. Furthermore, MPP gel preparation is likely to set more rapidly, with the gel formed achieving a much higher strength. It is concluded that the pectin amount, composition, and physicochemical properties can be considerably affected by the purification mode.     

Extending shelf-life of minimally processed apples with edible coatings and antibrowning agents

Effect of edible coatings in combination with antibrowning agents on minimally processed apple slices was studied during storage at 3°C for 2 week. To control initial respiration rate of apple slices, edible coatings were applied to cut apples as semipermeable barriers against air. Initial respiration rate showed a decrease by 5% and 20% in carrageenan (0.5 g/100 mL)-coated and whey protein concentrate (5 g/100 mL)-coated apples, respectively, at 25°C. Edible coatings in combination with antibrowning agents effectively prolonged the shelf-life of minimally processed apple slices by 2 week when stored in packed trays at 3°C. Addition of various antibrowning agents to these coating solutions was advantageous in maintaining color during storage. Addition of CaCl₂ (1 g/100 mL) significantly inhibited the loss of firmness. These edible coatings in combination with antibrowning agents also showed positive sensory analysis results and beneficial reduction of microbial levels. WPC (5 g/100 mL) containing ascorbic acid (1 g/100 mL) plus CaCl₂ (1 g/100 mL) was the most effective preservation treatment in terms of sensory quality after 2 week.     

Incorporation of bovine dry blood plasma into biscuit flour for the production of pasta

Spray-dried blood plasma (DBP) (10.9 g/100 g [w/w] nitrogen) was added to medium-protein biscuit flour (1.4 g/100 g N) during pasta manufacture. High-protein durum semolina (2.0 g/100 g N) was used to produce the control pasta. Sensory data indicated that the addition of DBP produced pasta with significantly better colour intensity and acceptability, aroma intensity, flavour intensity, textural strength, texture acceptability, aftertaste intensity, aftertaste acceptability, and overall acceptability. The DBP/biscuit flour formulation that gave the optimum balance between pasta protein content and organoleptic acceptability contained 2.2 g/100 g DBP. A higher content of DBP resulted in increased protein levels, but these pasta formulations were less acceptable organoleptically.     

Microbiological and chemical changes during the manufacture of Kefir made from cows’ milk,using a commercial starter culture

The counts of total aerobic mesophilic bacteria, lactic acid bacteria (in three different culture media, M17 agar, MSE agar, and Rogosa agar) and yeasts, and some biochemical parameters (levels of lactose, glucose, galactose, L(+)- and D(−)-lactic acids, ethanol, titratable acidity and pH) were determined during 196 h of fermentation in five batches of Kefir made from cows’ milk using a commercial starter culture. Lactococcus spp. predominated during the first 48 h of fermentation (∼8 log₁₀ cfu g⁻¹); Lactobacillus spp. became the predominant species after 48 h (∼8.5 log₁₀ cfu g⁻¹). During the first 24 h of fermentation, the lactose content decreased from a mean value of 4.92% (w/w) to 4.02% (w/w); the concentration of L(+)-lactic acid increased from 0.01% to 0.76% (w/w) and the pH decreased to 4.24 over the same period. After 24 h of fermentation, the changes in the levels of lactose and L(+)-lactic acid, and in pH, occurred more slowly. Neither glucose nor galactose were detected during fermentation. The production of ethanol was limited, reaching a mean final value of 0.018% (w/w).