Lactic Acid Treatment Research Articles

Effects of Citric and Lactic Acid on the Reduction of Deoxynivalenol and Its Derivatives in Feeds

Exposure to mycotoxin-contaminated feeds represents a serious health risk. This has necessitated the need for the establishment of practical methods for mycotoxin decontamination. This study investigated the effects of citric acid (CA) and lactic acid (LA) on common trichothecene mycotoxins in feeds contaminated with Fusarium mycotoxins. Contaminated feed samples were processed either with 5% CA or 5% LA solutions in a ratio of 1:1.2 (w/v) for 5, 24, or 48 h, and analyzed for multiple mycotoxin metabolites using a liquid chromatography–tandem mass spectrometric method. The analyses showed that treating the feed with CA and LA lowered the concentration of deoxynivalenol (DON), whereby 5% LA lowered the original DON concentration in the contaminated feed samples by half, irrespective of the processing time. Similar lowering effects were observed for the concentrations of 15Ac-DON, 5-hydroxyculmorin, and sambucinol. The concentration of nivalenol was only lowered by the LA treatment. In contrast, CA and LA treatments showed no or only small effects on the concentration of several mycotoxins and their derivatives, including zearalenone, fumonisins, and culmorin. In conclusion, the present results indicate that the use of 5% solutions of LA and CA might reduce the concentration of common trichothecene mycotoxins, especially DON and its derivate 15Ac-DON. However, further research is required to determine the effect on overall toxicity and to identify the underlying mechanisms.

In vitro efficacy of teat antiseptics against Staphylococcus aureus strains isolated from bovine mastitis

The process of teat disinfection is a widely accepted component of successful mastitis control programs by reducing the number of bacteria on the teat skin and healing teat lesions. For contagious pathogens such as Staphylococcus aureus, post-milking teat disinfection remains a simple, effective and economical practice for prevention of new intramammary infections (IMIs) of lactating dairy cows. Despite the universal acceptance of teat dipping as a method of mastitis control, variations in the susceptibility and resistance profile of mastitis pathogens among antiseptics have been described. Thus, here we sought to explore the in vitro efficacy of the followings antiseptics against S. aureus isolated from IMIs: chlorhexidine (2.0%), chlorine (2.5%), quarternary ammonium (4.0%), lactic acid (2.0%) and iodine (0.6%). We used 50 S. aureus strains isolated from bovine IMIs from 50 dairy herds located at Minas Gerais, São Paulo, Paraná and Rio Grande do Sul States (Brazil). The antiseptics were evaluated at four different specific intervals (15, 30, 60 and 300 s). We found a higher activity for quarternary ammonium and chlorhexidine against S. aureus at all time-points, followed by iodine and then chlorine. Lactic acid treatment produced the worst results for all time-points and strains. Due to variations in the sensitivity and resistance profile of antiseptics against S. aureus isolated from IMIs, the effectiveness of the antiseptics against the major mastitis pathogens should be periodically evaluated in dairy farms in an attempt to reduce the rate of new IMIs in the herd.

Does antibiotic resistance influence shiga-toxigenic Escherichia coli O26 and O103 survival to stress environments?

The presence of antibiotic-resistant bacteria in the food supply chain is a major concern. There is a great need to revalidate the effectiveness of the intervention strategies commonly used in food processing environments for multidrug-resistant strains. The purpose of this study was to determine the survival of antibiotic-resistant O26 and O103 Shiga-toxin producing Escherichia coli (STEC) strains to lactic acid (2.5, 3.5, 5%), sodium hypochlorite (0.2, 0.5, 1 ppm free chlorine), and heat (60, 61, 62.5 °C) treatments. Six strains from STEC serotypes O26 and O103 with three distinctive antibiotic-resistant profiles (susceptible, low and high resistance) were selected for the study. As expected, the rates of inactivation were faster at increasing biocide concentrations or temperature level. The Weibull model provided a better fit than the traditional log-linear model due to the appearance of nonlinear patterns. A 5% lactic acid treatment for 10 min reduced the population of all STEC strains by 5 log CFU/ml. Sodium hypochlorite treatment (1 ppm for 5 min) achieved a similar reduction. Thermal D values for O26 and O103 serotypes ranged from 0.37 to 2.09 and 0.37–1.71 min, respectively. No statistical differences (P > 0.05) in tolerance were found between the two STEC serotypes to the different treatments. The antibiotic profile was not related to the ability to tolerate any of the treatments. Only the susceptible strain showed a relative higher resistance to the lactic acid and lower resistance to sodium hypochlorite treatment. These results would contribute to assess the risk for the presence of STEC strains in food processing environments.

Preparation of Y zeolite composites with adjustable, highly dispersed intra-crystal mesoporosity: Effect of lactic acid treatment in CTAB-assisted two-step approach

Series of meso/microporous zeolite Y composites with adjustable hierarchy factors (HF) from 0.04 to 0.16, are prepared from commercial NaY zeolite (Si/Al = 2.5) by the two-step method with first lactic acid leaching and then CTAB-assisted ammonia treatment. The essential effect of lactic acid on the formation of diverse mesoporous domains in microporous crystals are systematically investigated. A possible scheme is proposed. The lactic acid leaching process is found to be very crucial to controllably remove the framework aluminum and regulate the amount/size of intra-crystal amorphous silicon-rich domains, which then evolve to mesostructures within the microporous crystals via structural re-arrangement/dissolution-reassembly process during the CTAB-assisted ammonia treatment. Varying the lactic acid concentrations would result in different crystallinity preservations and diverse proportions/dispersity of mesoporous regions, and thus well tune the HF values of the final composites. The zeolite Y composites with moderate mesoporosities allow much better performances in the acetalization reactions of cyclohexanone with pentaerythritol due to the improved diffusion ability of large sized guest molecules, whereas accompanying loss of acidity would depress reactivities of the treated samples for dehydration of small isopropanol.

Efficacy of Neutral Electrolyzed Water, Quaternary Ammonium and Lactic Acid-Based Solutions in Controlling Microbial Contamination of Food Cutting Boards Using a Manual Spraying Technique.

Bactericidal activity of neutral electrolyzed water (NEW), quaternary ammonium (QUAT), and lactic acid-based solutions was investigated using a manual spraying technique against Salmonella Typhimurium, Escherichia coli O157:H7, Campylobacter jejuni, Listeria monocytogenes and Staphylococcus aureus that were inoculated onto the surface of scarred polypropylene and wooden food cutting boards. Antimicrobial activity was also examined when using cutting boards in preparation of raw chopped beef, chicken tenders or salmon fillets. Viable counts of survivors were determined as log10 CFU/100 cm(2) within 0 (untreated control), 1, 3, and 5 min of treatment at ambient temperature. Within the first minute of treatment, NEW and QUAT solutions caused more than 3 log10 bacterial reductions on polypropylene surfaces whereas less than 3 log10 reductions were achieved on wooden surfaces. After 5 min of treatment, more than 5 log10 reductions were achieved for all bacterial strains inoculated onto polypropylene surfaces. Using NEW and QUAT solutions within 5 min reduced Gram-negative bacteria by 4.58 to 4.85 log10 compared to more than 5 log10 reductions in Gram-positive bacteria inoculated onto wooden surfaces. Lactic acid treatment was significantly less effective (P < 0.05) compared to NEW and QUAT treatments. A decline in antimicrobial effectiveness was observed (0.5 to <2 log10 reductions were achieved within the first minute) when both cutting board types were used to prepare raw chopped beef, chicken tenders or salmon fillets.

Pyruvate Dehydrogenase Kinase-mediated Glycolytic Metabolic Shift in the Dorsal Root Ganglion Drives Painful Diabetic Neuropathy

The dorsal root ganglion (DRG) is a highly vulnerable site in diabetic neuropathy. Under diabetic conditions, the DRG is subjected to tissue ischemia or lower ambient oxygen tension that leads to aberrant metabolic functions. Metabolic dysfunctions have been documented to play a crucial role in the pathogenesis of diverse pain hypersensitivities. However, the contribution of diabetes-induced metabolic dysfunctions in the DRG to the pathogenesis of painful diabetic neuropathy remains ill-explored. In this study, we report that pyruvate dehydrogenase kinases (PDK2 and PDK4), key regulatory enzymes in glucose metabolism, mediate glycolytic metabolic shift in the DRG leading to painful diabetic neuropathy. Streptozotocin-induced diabetes substantially enhanced the expression and activity of the PDKs in the DRG, and the genetic ablation of Pdk2 and Pdk4 attenuated the hyperglycemia-induced pain hypersensitivity. Mechanistically, Pdk2/4 deficiency inhibited the diabetes-induced lactate surge, expression of pain-related ion channels, activation of satellite glial cells, and infiltration of macrophages in the DRG, in addition to reducing central sensitization and neuroinflammation hallmarks in the spinal cord, which probably accounts for the attenuated pain hypersensitivity. Pdk2/4-deficient mice were partly resistant to the diabetes-induced loss of peripheral nerve structure and function. Furthermore, in the experiments using DRG neuron cultures, lactic acid treatment enhanced the expression of the ion channels and compromised cell viability. Finally, the pharmacological inhibition of DRG PDKs or lactic acid production substantially attenuated diabetes-induced pain hypersensitivity. Taken together, PDK2/4 induction and the subsequent lactate surge induce the metabolic shift in the diabetic DRG, thereby contributing to the pathogenesis of painful diabetic neuropathy.

Evaluating the Effectiveness of Essential Oils and Combination of Copper and Lactic Acid on the Growth of E. coli O157:H7 in Laboratory Medium.

In this study, we compared the effectiveness of armoise and clove bud essential oils (EOs) and the combination of low concentrations of copper (Cu) and lactic acid (LA) against E. coli O157:H7 in a laboratory medium. Three strains of Escherichia coli O157:H7 (ATCC700599, ATCC51659, and ATCC43895) were used in this study. Antibacterial activity was determined by measuring the turbidity of a broth medium and by determination of bacterial populations. Our results showed that armoise (0.15% v/v), clove bud (0.1% v/v) EOs, or Cu (50 ppm) in combination with LA (0.2% v/v) caused a minimum 5.0 log reduction of E. coli O157:H7 in the laboratory medium. Cu in combination with LA may thus be preferable to EOs in food in order to control the growth of foodborne pathogens. In addition, the combination treatment of Cu and LA could provide the food industry with a practical approach to reducing the risk of foodborne pathogens.

Arginine- and Polyamine-Induced Lactic Acid Resistance in Neisseria gonorrhoeae.

Microbe-derived lactic acid protects women from pathogens in their genital tract. The purpose of this study was to determine lactic acid susceptibility of Neisseria gonorrhoeae, and identify potential acid resistance mechanisms present in this pathogen. Tested in vitro, lactic acid killed all 10 gonococcal strains analyzed in a low pH-dependent manner. Full inactivation occurred at pH 4.5. At low pH, lactic acid treatment resulted in the entry of the DNA-binding fluorochrome propidium iodide into the microbial cells, suggesting that hydrogen ions from lactic acid compromise the integrity of the bacterial cell wall/membrane. Most likely, hydrogen ions also inactivate intracellular proteins since arginine rendered significant protection against lactic acid presumably through action of the gonococcal arginine decarboxylase, an enzyme located in the bacterial cytoplasm. Surprisingly, arginine also lessened lactic acid-mediated cell wall/membrane disruption. This effect is probably mediated by agmatine, a triamine product of arginine decarboxylase, since agmatine demonstrated a stronger protective effect on GC than arginine at equal molar concentration. In addition to agmatine, diamines cadaverine and putrescine, which are generated by bacterial vaginosis-associated microbes, also induced significant resistance to lactic acid-mediated GC killing and cell wall/membrane disruption. These findings suggest that the arginine-rich semen protects gonococci through both neutralization-dependent and independent mechanisms, whereas polyamine-induced acid resistance contributes to the increased risk of gonorrhea in women with bacterial vaginosis.

Microbial load reduction of sweet basil using acidic electrolyzed water and lactic acid in combination with mild heat

Sweet basil has been used worldwide as an ingredient for several cuisines. However, it can be contaminated with pathogens; especially Escherichia coli and Salmonella spp. are mainly introduced by poor hygiene during harvesting, cleaning, packaging and distribution. This study aimed to study the efficacy of lactic acid (LA) and acidic electrolyzed water (AEW) against mesophilic bacteria on sweet basil. In addition, a combination treatment was also investigated, using mild heat with the selected sanitizer to disinfect sweet basil inoculated with S. Typhimurium and E. coli. The 2% LA treatment showed high efficiency in microbial decontamination, and mesophilic bacteria were reduced by about 3 log CFU/g. Additionally, the decontamination efficacy of LA increased when combined with mild heat. The use of 2% LA at 50 °C showed the highest microbial reduction in sweet basil, in which mesophilic bacteria, S. Typhimurium, and E. coli were reduced by 4.62, 3.80 and 3.61 log CFU/g, respectively. These findings indicate that LA can be more effective than AEW in disinfection and provides greater efficiency when combined with mild 50 °C heat.

Inhibitory effects of lactic and malic organic acids on autoinducer type 2 (AI-2) quorum sensing of Escherichia coli O157:H7 and Salmonella Typhimurium

Several organic acid based antimicrobials are reported to reduce bacterial populations but studies showing inhibition of autoinducer-2 (AI-2) activity or quorum sensing are limited. The effect of lactic and malic acids on autoinducer activity of selected strains of Escherichia coli O157:H7 and Salmonella Typhimurium is tested in this study. The strains were screened for AI-2 like activity on spinach and cantaloupe homogenates using autoinducer sensing Vibrio harveyi biosensor strains. The ED 14 strain of E. coli O157:H7 and the SD 10 strain of Salmonella showed highest AI-2 like activity of 55 and 53 Relative Light Units respectively. These two strains were used to evaluate the AI-2 inhibitory activities of lactic and malic acids at 1–4% concentrations (alone or in combinations). Lactic acid at 4.0% had the highest inhibition of 80% on ED 14 E. coli strain while the combination treatment of lactic acid + malic acid at 4.0% each had the highest inhibition of 80% on SD 10 Salmonella strain. Results from the study indicate that the quorum sensing ability of the E. coli O157:H7 and Salmonella Typhimurium strains can be effectively inhibited by antimicrobial organic acids.

Microbial populations and fermentation profiles in rumen liquid and solids of Holstein cows respond differently to dietary barley processing.

To evaluate the effects of treating barley grain with lactic acid (LA) and heat on postprandial dynamics of 19 microbial taxa and fermentation in the rumen of dairy cows. This study was designed as a double 3×3 Latin square with six rumen-cannulated cows and three diets either containing untreated control barley or barley treated with 1% LA and 1% LA and heat (LAH, 55°C). Microbial populations, pH and volatile fatty acids were assessed in rumen liquid and solids during the postprandial period. Propionate increased and butyrate decreased in rumen solids of cows fed LA and LAH treated barley compared to the control barley. The LA but not LAH treatment depressed Fibrobacter succinogenes in rumen liquid and solids, whereas the opposite effect was observed for Ruminococcus albus in both fractions and Ruminococcus flavefaciens in rumen solids. LA promoted Ruminobacter amylophilus with the effect being more pronounced with LAH. The Lactobacillus group and Megasphaera elsdenii increased in both fractions with LA but not with LAH. LA and LAH treatment of barley differently altered ruminal abundance of certain bacterial taxa and fungi and increased propionate fermentation in rumen solids, whereby LA and LAH effects were consistent and mostly independent of the rumen fraction and time after barley feeding. Results provided evidence that LA and LAH treatment of barley can enhance rumen propionate fermentation without adversely affecting rumen pH. As propionate is the major contributor to gluconeogenesis in ruminants, the present barley treatment may have practical application to enhance energy supply in dairy cows.

Treatment of grain with organic acids at 2 different dietary phosphorus levels modulates ruminal microbial community structure and fermentation patterns in vitro

Recent data indicate positive effects of treating grain with citric (CAc) or lactic acid (LAc) on the hydrolysis of phytate phosphorus (P) and fermentation products of the grain. This study used a semicontinuous rumen simulation technique to evaluate the effects of processing of barley with 50.25g/L (wt/vol) CAc or 76.25g/L LAc on microbial composition, metabolic fermentation profile, and nutrient degradation at low or high dietary P supply. The low P diet [3.1g of P per kg of dry matter (DM) of dietary P sources only] was not supplemented with inorganic P, whereas the high P diet was supplemented with 0.5g of inorganic P per kg of DM through mineral premix and 870mg of inorganic P/d per incubation fermenter via artificial saliva. Target microbes were determined using quantitative PCR. Data showed depression of total bacteria but not of total protozoa or short-chain fatty acid (SCFA) concentration with the low P diet. In addition, the low P diet lowered the relative abundance of Ruminococcus albus and decreased neutral detergent fiber (NDF) degradation and acetate proportion, but increased the abundance of several predominantly noncellulolytic bacterial species and anaerobic fungi. Treatment of grain with LAc increased the abundance of total bacteria in the low P diet only, and this effect was associated with a greater concentration of SCFA in the ruminal fluid. Interestingly, in the low P diet, CAc treatment of barley increased the most prevalent bacterial group, the genus Prevotella, in ruminal fluid and increased NDF degradation to the same extent as did inorganic P supplementation in the high P diet. Treatment with either CAc or LAc lowered the abundance of Megasphaera elsdenii but only in the low P diet. On the other hand, CAc treatment increased the proportion of acetate in the low P diet, whereas LAc treatment decreased this variable at both dietary P levels. The propionate proportion was significantly increased by LAc at both P levels, whereas butyrate increased only with the low P diet. Treatments with CAc or LAc reduced the degradation of CP and ammonia concentration compared with the control diet at both P levels. In conclusion, the beneficial effects of CAc and LAc treatment on specific ruminal microbes, fermentation profile, and fiber degradation in the low P diet suggest the potential for the treatment to compensate for the lack of inorganic P supplementation in vitro. Further research is warranted to determine the extent to which the treatment can alleviate the shortage of inorganic P supplementation under in vivo conditions.

Effects of lactic acid and lemongrass oil treatment on the pre-existing microorganisms and foodborne pathogens in Tatsoi (Brassica rapa var. rosularis) baby leaves

The effects of lactic acid and lemongrass oil treatments on microbial growth in Tatsoi baby leaves were investigated to ensure microbial safety. To determine the optimal concentrations of lactic acid and lemongrass oil as a sanitizer, the effects of several concentrations of lactic acid (0.25, 0.5, 1, and 2 %) and lemongrass oil (0.1, 0.3, 0.5, and 1 %) on aerobic mesophilic bacteria, Salmonella Typhimurium, and Listeria monocytogenes in Tatsoi baby leaves were evaluated. The results showed that the 1 % lactic acid and 1 % lemongrass oil treatment reduced the populations of the microorganisms to the greatest extent. In particular, after the combined treatment with 1 % lactic acid and 1 % lemongrass oil, the count of aerobic mesophilic bacteria was reduced from 7.63 to 2.45 log colony forming unit (CFU) · g−1, and L. monocytogenes was reduced from 6.71 to 1.96 log CFU · g . In addition, S. Typhimurium was not detected in the Tatsoi baby leaves during 7 days of storage. These results suggest that a combined treatment using 1 % lactic acid and l % lemongrass oil could be an effective method for the inactivation of bacteria on the surfaces of Tatsoi baby leaves.

Treatments with organic acids and pullulanase differently affect resistant starch and fiber composition in flour of various barley genotypes (Hordeum vulgare L.)

An enrichment of foodstuffs with RS and dietary fiber is meaningful for a healthier diet. Main goal of this research was to evaluate the effects of treating barley with citric acid (CA), lactic acid (LA), separately or together, and with the enzyme pullulanase (PUL) on RS and the contents of main nutrients of four barley genotypes. Treatment with PUL increased the RS content from 0.26 (control) to 1.29%. Enhancement of RS was also observed with 5% LA as well as with 5% CA, but these effects were barley genotype‐dependent. Treatment with CA increased the organic residue, a fraction that includes (1 → 3,1 → 4)‐β‐glucan, from 10.2 to 14.0%. Ash contents decreased from 2.42 to 1.98% by LA treatment and neutral detergent fiber decreased from 14.1 to 8.4% by CA treatment, depending on the used barley genotype. In conclusion, data indicated that treating barley with organic acids or PUL may have the potential to enhance the RS and beneficially modulate nutrient composition of barley. Further research is warranted to understand the mechanisms behind the effects observed herein and their nutritional implications in the diet.

Antimicrobial Interventions for O157:H7 and Non-O157 Shiga Toxin-Producing Escherichia coli on Beef Subprimal and Mechanically Tenderized Steaks

Non-O157 Shiga toxin-producing Escherichia coli (STEC) is an emerging risk for food safety. Although numerous postharvest antimicrobial interventions have been effectively used to control E. coli O157:H7 during beef harvesting, research regarding their effectiveness against non-O157 STEC is scarce. The objectives of this study were (i) to evaluate effects of the spray treatments-ambient water, 5% lactic acid (LA), 200 ppm of hypobromous acid (HA), and 200 ppm of peroxyacetic acid (PA)-on the reduction of O157:H7 or non-O157 STEC (O26, O103, O111, and O145) with high (10(6) log CFU/50 cm(2)) or low (10(2) log CFU/50 cm(2)) levels on beef subprimals after vacuum storage for 14 days and (ii) to evaluate the association of the antimicrobial treatments and cooking (50 or 70°C) on the reduction of the pathogens in blade-tenderized steaks. The treatment effects were only observed (P = 0.012) on samples taken immediately after spray intervention treatment following inoculation with a high level of O157:H7. The LA and PA treatments significantly reduced low-inoculated non-O157 STEC after spray intervention; further, the LA and HA treatments resulted in significant reductions of non-O157 STEC on the low-inoculated samples after storage. Although cooking effectively reduced the detection of pathogens in internal steak samples, internalized E. coli O157:H7 and non-O157 STEC were able to survive in steaks cooked to a medium degree of doneness (70°C). This study indicated that the reduction on surface populations was not sufficient enough to eliminate the pathogen's detection following vacuum storage, mechanical tenderization, and cooking. Nevertheless, the findings of this study emphasize the necessity for a multihurdle approach and further investigations of factors that may influence thermal tolerance of internalized pathogenic STEC.

Processing barley grain with lactic acid and tannic acid ameliorates rumen microbial fermentation and degradation of dietary fibre in vitro.

Cereal grains are important ingredients of ruminant diets, but their rapid degradation seriously impairs rumen fermentation and the host's health. The goal of this study was to evaluate whether processing of barley grain with 1 or 5% lactic acid (LA) and 1 or 5% tannic acid (TA), without or with an additional heat treatment (1% LAH or 1% TAH), may affect microbial ruminal abundance, fermentation profile, and nutrient degradation in vitro. Processing with LA lowered (P < 0.05) the concentration of short-chain fatty acids (SCFAs), proportions of branched-chain SCFA, and the acetate-to-propionate ratio. Treatment with 1% TAH and 1% LAH lowered (P < 0.05) gene copy numbers of total protozoa, rumen lipopolysaccharide, and degradation of crude protein, and tended (P = 0.08) to lower the proportion of the genus Prevotella. Treatment of barley grain with 1% LA or 1% LAH stimulated Clostridium cluster XIV. Degradation of fibre was enhanced (P < 0.05) by all LA and TA treatments. Chemical and heat treatment of barley grain modulated the ruminal fermentation profile and enhanced fibre degradation; however, processing of grain with LA seems to be superior because this effect was not associated with a concomitant depression in ruminal degradation of organic matter.

Antibacterial mechanism of lactic acid on physiological and morphological properties of Salmonella Enteritidis, Escherichia coli and Listeria monocytogenes

Lactic acid is widely used to inhibit the growth of important microbial pathogens, but its antibacterial mechanism is not yet fully understood. The objective of this study was to investigate the antibacterial mechanism of lactic acid on Salmonella Enteritidis, Escherichia coli and Listeria monocytogenes by size measurement, TEM, and SDS-PAGE analysis. The results indicated that 0.5% lactic acid could completely inhibit the growth of Salmonella Enteritidis, E. coli and L. monocytogenes cells. Meanwhile, lactic acid resulted in leakage of proteins of Salmonella , E. coli and Listeria cells, and the amount of leakage after 6 h exposure were up to 11.36, 11.76 and 16.29 μg/mL, respectively. Measurements of the release of proteins and SDS-PAGE confirmed the disruptive action of lactic acid on cytoplasmic membrane, as well as the content and activity of bacterial proteins. The Z-Average sizes of three pathogens were changed to smaller after lactic acid treatment. The damaged membrane structure and intracellular structure induced by lactic acid could be observed from TEM images. The results suggested that the antimicrobial effect was probably caused by physiological and morphological changes in bacterial cells. • Pathogens could be completely inactivated after exposure to lactic acid. • Lactic acid resulted in great leakage of protein of three pathogens. • Bacterial protein bands of lactic acid-treated cells got fainter or disappeared. • Z-Average sizes of pathogens were changed to smaller after lactic acid treatment. • Lactic acid caused collapsed or even broken cells with obvious pits and gaps.

Shelf-life extension of vacuum-packaged meat from pheasant (Phasianus colchicus) by lactic acid treatment

We investigated the influence of lactic acid treatment of pheasant meat before vacuum-packaged storage of 3, 7, and 10 d at +6°C on microbiota and pH. Breast muscle samples were collected from carcasses of slaughtered as well as from hunted (shot) wild pheasants. Immersion of meat samples in 3% (wt/wt) lactic acid for 60 s effectuated a significant drop in pH of approximately 0.5 to 0.7 units, which remained during the entire storage period. In parallel, total aerobic counts of such treated and stored samples were on an average 1.5 to 1.7 log units lower than in non-acid-treated samples. Similar results were found for Enterobacteriaceae. A significant decrease in pH was measured at d 7 and 10 in the acid-treated samples in comparison with the untreated ones. In summary, the immersion of pheasant breast meat cuts in dilute lactic acid significantly reduced microbiota during vacuum-packed storage, even at slight temperature abuse conditions.

Lactic acid and thermal treatments trigger the hydrolysis of myo-inositol hexakisphosphate and modify the abundance of lower myo-inositol phosphates in barley (Hordeum vulgare L.).

Barley is an important source of dietary minerals, but it also contains myo-inositol hexakisphosphate (InsP6) that lowers their absorption. This study evaluated the effects of increasing concentrations (0.5, 1, and 5%, vol/vol) of lactic acid (LA), without or with an additional thermal treatment at 55°C (LA-H), on InsP6 hydrolysis, formation of lower phosphorylated myo-inositol phosphates, and changes in chemical composition of barley grain. Increasing LA concentrations and thermal treatment linearly reduced (P<0.001) InsP6-phosphate (InsP6-P) by 0.5 to 1 g compared to the native barley. In particular, treating barley with 5% LA-H was the most efficient treatment to reduce the concentrations of InsP6-P, and stimulate the formation of lower phosphorylated myo-inositol phosphates such as myo-inositol tetraphosphate (InsP4) and myo-inositol pentaphosphates (InsP5). Also, LA and thermal treatment changed the abundance of InsP4 and InsP5 isomers with Ins(1,2,5,6)P4 and Ins(1,2,3,4,5)P5 as the dominating isomers with 5% LA, 1% LA-H and 5% LA-H treatment of barley, resembling to profiles found when microbial 6-phytase is applied. Treating barley with LA at room temperature (22°C) increased the concentration of resistant starch and dietary fiber but lowered those of total starch and crude ash. Interestingly, total phosphorus (P) was only reduced (P<0.05) in barley treated with LA-H but not after processing of barley with LA at room temperature. In conclusion, LA and LA-H treatment may be effective processing techniques to reduce InsP6 in cereals used in animal feeding with the highest degradation of InsP6 at 5% LA-H. Further in vivo studies are warranted to determine the actual intestinal P availability and to assess the impact of changes in nutrient composition of LA treated barley on animal performance.

Surface physiological changes induced by lactic acid on pathogens in consideration of pKa and pH

Antimicrobials affected the surface characteristics and membrane integrity of bacterial cells. The objective of this study was to investigate the physiological changes on the surface of Salmonella Enteritidis (ATCC 14028), Escherichia coli (CGMCC 1.2385), and Listeria monocytogenes (ATCC 19115) induced by lactic acid. Lactic acid was more effective than hydrochloric acid (HCl) at the same pH in inhibiting the growth of these pathogens. The results of zeta potential indicated that surface charges of three pathogens were significantly disturbed by lactic acid treatment. After exposure to 0.5% lactic acid, a rough cell surface with discrete ridges and concave collapses were observed by scanning electron microscopy (SEM). Meanwhile, the release of intracellular potassium (K+) also suggested the damage of cytoplasmic membrane. As an effective antimicrobial, lactic acid led to leakage of intracellular K+, damage of membrane permeability and integrity, and changes of surface charge in the pathogens.