Lactic Acid Treatment Research Articles

Lactic Acid Treatment of Cereals and Dietary Phytase Modified Fecal Microbiome Composition Without Affecting Expression of Virulence Factor Genes in Growing Pigs.

Besides the major nutrients, phosphorus (P) is an essential mineral for both the host animal and the porcine gut microbiota. Different strategies including phytase supplementation and more recently lactic acid (LA) are used to enhance the P availability from cereals in pig diets; however, their impact on the gut microbiota has been rarely related to fecal shedding of opportunistic pathogens. The present study investigated the effect of phytase supplementation and the treatment of dietary cereals with 2.5% LA on the fecal microbiome composition of metabolic active bacteria and expression of virulence factor genes of enterotoxigenic Escherichia coli and Clostridium perfringens in growing pigs. Phytase supplementation reduced the fecal abundance of the most abundant Lactobacillaceae family, whereas the LA-treatment of cereals had a stronger impact on the bacterial community, reducing amylolytic, pullulanolytic and hemicellulolytic Lactobacillaceae, Lachnospiraceae and Ruminococcaceae as well as the fecal bacterial species richness (Chao1) and diversity (Shannon index). Mainly the family Clostridiaceae benefited from the decline in the aforementioned families, being enriched by both dietary treatments. Multigroup data integration using sparse partial least squares-discriminant analysis showed that among the most discriminative operational taxonomic units (OTU) especially two unclassified Clostridiaceae-OTUs, one Prevotella copri-like OTU and one OTU within the vadinCA11 group were associated with calcium and P levels but were negatively linked with complex carbohydrates in feces. Heat-stable toxin A (Sta) of enterotoxigenic E. coli and Stx2e of Shiga-toxin producing E. coli were expressed in feces but were similar among feeding groups. Without modifying the total bacterial gene copies and virulence factor expression of E. coli, both dietary phytase supplementation and LA-treatment of cereals drastically altered the bacterial community composition in pig feces. Results thereby allowed for the characterization of bacterial nutrient dependencies, indicating a link between fecal P availability, complex carbohydrate composition and alterations in the predominant genera.

Zinc mediates resuscitation of lactic acid-injured Escherichia coli by relieving oxidative stress.

Lactic acid is a natural antimicrobial in food industry, and also exists in fermented food. It was reported that sublethally injured Escherichia coli could survive in acidic conditions. When conditions become advantageous, injured E. coli can restore physiological function, which is a potential threat in food industry. Recovery is a necessary step for discriminating injured bacteria, but the resuscitation mechanism of injured bacteria is still unknown. In our study, sublethal lactic acid treatment (pH 4·2, 60min) posed oxidative stress on E. coli by decrease of superoxide dismutase (SOD) activity and overproduction of reactive oxygen species (ROS). Zinc with low concentration (1·0mmoll-1 ) significantly increased the recovery ratio of injured E.coli induced by lactic acid. The recovery ratios of injured cell in minimal A medium (minA) with 1·0mmoll-1 zinc reached to that with 3·0mmoll-1 catalase (CAT). Conversely, the addition of zinc chelator N, N, N', N'-tetrakis (2-pyridylmethyl) decreased the recovery ratio. Zinc accelerated resuscitation of injured E. coli by improving SOD activity, and decreasing ROS production. Deletion of sodC encoding Cu/ZnSOD, katE/katG encoding CAT or regulating gene rpoS significantly decreased the recovery ratio. Among all of the mutants in this study, ΔrpoS and ΔsodC showed the lowest recovery ratio, which means they played significant roles in the process of resuscitation. We provided direct evidence that zinc mediated resuscitation of lactic acid-injured E. coli by relieving oxidative stress. Zinc can be used as a low-cost and effective agent to improve recovery ratio and detection efficiency of injured bacteria. Antibacterial agents are a challenge for bacteria, but bacteria can survive as a sublethally injured state under stresses. Using injured E. coli induced by lactic acid as a model organism, we validated the significant role of zinc on resuscitation of injured cells.

Production and antimicrobial activity of sophorolipid against Clostridium perfringens and Campylobacter jejuni and their additive interaction with lactic acid

Abstract The poultry industry experiences enormous economic losses due to microbial contamination, leading to searches for natural antimicrobials. Sophorolipid is a glycolipid produced by Starmerella bombicola, that acts as an emulsifier and antimicrobial agent. The aim of this research was to produce, characterize and apply sophorolipid from S. bombicola against the chicken pathogens Clostridium perfringens and Campylobacter jejuni, which are responsible for diseases that cause great damage to the poultry industry. The application of sophorolipid against these microorganisms has not yet been reported and to aggregate value to the product, sophorolipid was associated with lactic acid, a nontoxic molecule already utilized in the food industry. Sophorolipid production reached 69.83 g.L−1 with a productivity of 0.24 g.L−1.h−1 and a yield of 46.41% at 288 h in a bioreactor. The structural characterization analyses confirmed the predominance of the lactonic form. Sophorolipid demonstrated antimicrobial activity against the tested bacteria and the combined treatment of sophorolipid and lactic acid represented an additive interaction. Therefore, this combination could be an alternative to use as a new natural sanitizer in the poultry industry, reducing the microbial contamination of these main pathogens.

Lactic Acid Inhibits Lipopolysaccharide-Induced Mast Cell Function by Limiting Glycolysis and ATP Availability.

Sepsis has a well-studied inflammatory phase, with a less-understood secondary immunosuppressive phase. Elevated blood lactate and slow lactate clearance are associated with mortality; however, regulatory roles are unknown. We hypothesized that lactic acid (LA) contributes to the late phase and is not solely a consequence of bacterial infection. No studies have examined LA effects in sepsis models in vivo or a mechanism by which it suppresses LPS-induced activation in vitro. Because mast cells can be activated systemically and contribute to sepsis, we examined LA effects on the mast cell response to LPS. LA significantly suppressed LPS-induced cytokine production and NF-κB transcriptional activity in mouse bone marrow-derived mast cells and cytokine production in peritoneal mast cells. Suppression was MCT-1 dependent and reproducible with sodium lactate or formic acid. Further, LA significantly suppressed cytokine induction following LPS-induced endotoxemia in mice. Because glycolysis is linked to inflammation and LA is a byproduct of this process, we examined changes in glucose metabolism. LA treatment reduced glucose uptake and lactate export during LPS stimulation. LA effects were mimicked by glycolytic inhibitors and reversed by increasing ATP availability. These results indicate that glycolytic suppression and ATP production are necessary and sufficient for LA effects. Our work suggests that enhancing glycolysis and ATP production could improve immune function, counteracting LA suppressive effects in the immunosuppressive phase of sepsis.

Comparative study on effects of citric and lactic acid treatment on morphological, functional, resistant starch fraction and glycemic index of corn and sorghum starches

The present study isolated starch from corn and sorghum grains through wet milling procedure. Sorghum starch is considered an alternative to corn starch in future, due to similar functional properties. However, agronomically sorghum is a cheap input cost crop compared to sorghum and can grow in drought hit areas. Lactic acid and citric acid modifications along with heat-moisture treatments were performed on both sorghum and corn grains followed by their comparison in terms of functional, textural, thermal, pasting and digestibility characteristics. For both corn and sorghum starches, the resistant starch increased after chemical modifications. The RS content of acid and acid-heat moisture treated starches were in the range of 77.9–90%, significantly higher than those of native starches (64.6–68.8%). The modifications increased the gelatinization temperature, decreased the peak and cold paste viscosity of starches. Chewiness significantly reduced after lactic and citric acid treatment along with heat-moisture treatments. The crystallinity to amorphous ratio measured through Fourier Transform infrared reduced after all chemical treatments. Percent light transmittance was further reduced after heat-moisture treatments, however the effect on corn starch was more pronounced i.e. it declined from 16.5 to 5.2%. The acid-heat moisture treatments had considerably lowered the glycemic index of starch. The GI reduced from 74 to 49.7 and 60 to 48.5 when treated with acid in the presence of heat and moisture. Thus, these starches could be used in production of low-calorie foods.

Enhancing the hardness of potato slices after boiling by combined treatment with lactic acid and calcium chloride: Mechanism and optimization

Potatoes usually suffer from greatly decrease of hardness after boiling, which limits their processing potential in food industry. Moreover, methods for enhancing the hardness of potatoes after boiling are underexplored. In this study, the hardness of potato slices after boiling were increased from 288 g to 2342 g by the combined treatment of lactic acid (LA) and calcium chloride (CC). Through the analysis of the microstructure of the potato cells, the molecular weight distribution and natural sugar ratio of different soluble pectin fractions, and the enzymatic activities (polygalacturonase, PG and pectin methylesterase, PME), the possible mechanism behind the hardness enhancement by LA and CC pretreatment, namely the direct link between pectin and potato structure was revealed. The obtained results confirmed the target spot for enhancing the hardness of potatoes after boiling lay in PG activity and gelation of the pectin, which also could be used to help other plants resist the heat process if pectin existed in their cell wall.

Optimizing Chemical Wood Modification with Oligomeric Lactic Acid by Screening of Processing Conditions

When exposed to moisture, wood undergoes swelling and is susceptible to fungal degradation. Chemical modification via oligomeric lactic acid (OLA) treatment has been found to be a promising environmentally friendly solution to this disadvantage. In this study, wood was impregnated with OLA and then variously heat treated to polymerize the OLA in situ. The effect of curing temperature and time on OLA polymerization has been determined chemically. Dimensional stability was examined by water immersion and hygroscopicity measurements and biological decay resistance also evaluated. OLA impregnation followed by heat treatment enhanced wood properties. OLA cure at 160 °C for 48 h resulted in treated wood with greater dimensional stability and biological resistance.

Lactic acid suppresses LPS-induced mast cell cytokine production by limiting glycolysis and ATP availability

Abstract Sepsis, a life threatening response to infection, has a well-studied initial cytokine storm, with a less understood secondary immunosuppressive phase. Elevated blood lactate and slow lactate clearance are associated with mortality, however, any regulatory role is unknown. We hypothesized that lactic acid contributes to the late phase of sepsis and is not solely a consequence of bacterial infection. Thus far, no studies have examined the effect of lactic acid on sepsis models in vivo or a mechanism by which they suppress LPS activation in vitro. Because mast cells can be activated systemically and contribute to sepsis, we examined lactic acid effects on the mast cell response to the bacterial product LPS. Lactic acid significantly suppressed LPS-induced cytokine production and NFκB-mediated transcription in mouse bone marrow derived mast cells and cytokine production in peritoneal mast cells. Suppressive effects were MCT-1-dependent and observed with sodium lactate or formic acid. Further, lactic acid significantly suppressed cytokine induction following LPS-induced endotoxemia in mice. Because glycolysis is linked to inflammation and lactic acid is a by-product of this process, we examined changes in glucose metabolism. Lactic acid treatment reduced glucose uptake and lactate export during LPS stimulation. Lactic acid effects were mimicked by glycolytic inhibitors and reversed by increasing ATP availability. These results indicate that glycolytic suppression and ATP production are necessary and sufficient for lactic acid effects. Our work suggests that enhancing glycolysis and ATP production could improve immune function, counteracting lactic acid suppressive effects in the immunosuppressive phase of sepsis.

Inactivation of Salmonella Enteritidis on eggshells by lactic acid spray

Egg safety and quality is a long-standing concern for producers and consumers. Salmonella enterica serovar Enteritidis (Salmonella Enteritidis) is the prevalent egg-product-related foodborne pathogen. The treatment with organic acids, including lactic acid, for the elimination and control of foodborne pathogens is generally recognized as safe, and is widely applied in many foods. In this study, we found that spraying with 2% lactic acid on the eggshell surface effectively reduced Salmonella Enteritidis counts. Agar-filled eggs were used to study the bacterial penetration of the eggshell (eggshell and membranes), and the contamination of the whole egg contents was investigated. No significant differences were observed between the Salmonella Enteritidis penetration in lactic acid sprayed and unsprayed eggs stored at 4 °C. The Haugh unit, albumin pH, and eggshell strength values were similar in the sprayed and washed eggs. Average Haugh unit scores for sprayed eggs were still Grade A within 3 weeks. However, the lactic acid treatment decreased the eggshell strength and cuticle layer thickness. SEM observations confirmed that spraying of lactic acid damaged the cuticle integrity. The results from our research will indicate that lactic acid spray is highly effective in reducing Salmonella contamination on the eggshell surface, but trans-shell penetration was demonstrated in the eggs stored at room temperature. Consequently, low-temperature storage is important for the prevention of recontamination of the egg after spraying.

Soaking in lactic acid lowers the phytate-phosphorus content and increases the resistant starch in wheat and corn grains

The low availability of phytate phosphorus (Phy-P) from cereals for monogastric livestock can be enhanced using feed technological processes. The present objective was to investigate the effect of soaking of grains in lactic acid (LA) on the Phy-P disappearance and chemical composition in wheat and corn grains and whether changes in the nutrient profiles occurred when cereals were dried and stored for four weeks. Wheat, corn and a 50:50 mixture of both grains were soaked in 0, 10 and 25 g/kg LA (LA0, LA10, and LA25) for 0, 6, 12, 24 and 48 h. Thereafter, samples were either directly analyzed for their nutrient content or stored for 4 weeks at 21 °C until analyses. The effect of LA on the nutrient profiles in wheat, corn and, wheat-corn mixture was more evident with increasing LA concentration and soaking time, with the greatest effect with LA25 after 48 h of incubation. Soaking the cereals in LA25 for 48 h decreased (P < 0.05) the total phosphorus content by 9% across grains and decreased the Phy-P content by 24, 30 and 25% in corn, wheat and wheat-corn mix, respectively (P < 0.05), thereby correspondingly increasing the available phosphorus content. Phytase activity in corn grain represented one-tenth of the activity in wheat. End-product inhibition was indicated by the reduced phytase activity in wheat and wheat-corn mix after 48 h of soaking (P < 0.05). Moreover, crude ash and neutral detergent fiber decreased after soaking in LA, with the greatest change observed with LA25 and 48 h of treatment in LA. Although the LA treatment did not markedly affect the total starch content, soaking in LA25 increased the resistant starch content in wheat by 51%, whereas it decreased by 52 and 19% in corn and wheat-corn mixture, respectively (P < 0.05). Drying and storing the samples for four weeks increased the content of dry matter and crude ash, whereas neutral-detergent fiber, acid-detergent fiber, and non-resistant starch were reduced in the LA-treated grains after storage (P < 0.05). Storage also enhanced the Phy-P disappearance in LA-treated wheat and wheat-corn mix, thereby further increasing the available phosphorus fraction. In conclusion, soaking of grains in LA25 for 48 h demonstrated to be an effective strategy to improve the phytate-P availability in wheat and wheat-corn mix. Beneficial changes in the hemicellulose and resistant starch fractions caused by the LA treatment may have implications for the functional abilities of the LA-treated grains.

Effect of lactic acid and steam treatments on Campylobacter jejuni on chicken skin

Minimization of Campylobacter jejuni contaminations in poultry meats is important for public health. Certain chemical agents and physical processes to be used on carcasses to destroy pathogenic microorganisms. One of the most common used chemical is lactic acid. The bactericidal activity of different concentrations of lactic acid and hot steam on the C. jejuni populations on chicken skin samples were determined. Chicken breast skin samples were inoculated with C. jejuni and dipped into different lactic acid solutions and hot steam. reduction of C. jejuni and pH values were determined after 0., 1., 3. and 5 days of the storage at 4±1°C. according to microbiological analysis. Compared with the control group, reductions in C. jejuni populations were determined as 1.72 and 2.02 log at 22°C, as 1.91 and 2.34 log at 54°C on day 0, in 2%, 3% concentrations respectively. On the other hand, beginning from day 0, bacterial counts reached undetectable (&lt;1.0x102 cfu/g) levels after the decontamination treatments with 4% LA for 60 s at 22°C and 54°C, after the treatments with 2% LA followed by HS concentrations of 97±1°C for 15 s and 133±1°C for 3 s. It was determined that decontamination with lactic acid and hot steam application had a significant reduction effect on C. jejuni in chicken skin samples and the effect of lactic acid was increased depending on the concentration.

Combination effect of saturated or superheated steam and lactic acid on the inactivation of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes on cantaloupe surfaces

The purpose of this study was to evaluate the effectiveness of the combination treatment of lactic acid immersion and saturated or superheated steam (SHS) on inactivation of foodborne pathogens on cantaloupes. Saturated steam (SS) treatments were performed at 100 °C, while SHS treatments were delivered at either 150 or 200 °C. Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes-inoculated cantaloupes were exposed to 2% lactic acid or sterile distilled water for 1 min followed by a maximum of 20 s of SS or SHS. Populations of each of the three pathogens on cantaloupes were reduced to under the detection limit (1.0 log CFU/cm2) after the combination treatment of 2% lactic acid and 200 °C steam for 20 s. To compare the effect of the lactic acid treatment method, we conducted spray application with 2% lactic acid combined with SS or SHS treatment; however, no significant log reduction differences were found between immersion and spraying techniques. After combination treatment of cantaloupes for 20 s, color and maximum load values (a characteristic of texture) were not significantly different from those of untreated controls. The results of this study suggest that the combination treatment of lactic acid and SHS can be used as an antimicrobial intervention for cantaloupes without inducing quality deterioration.

Transcriptional profiling of lactic acid treated reconstructed human epidermis reveals pathways underlying stinging and itch

The incidence of sensitive skin with stinging and itch following chemical exposure in products such as cosmetics is increasing, but molecular mechanisms underlying this pathophysiology remain understudied. Here we performed transcriptional analysis of reconstructed human epidermis (RHE) 1, 6, and 24 h following topical lactic acid (LA) application, a known inducer of the sensitive skin reaction. Since little is known about the specific role of keratinocyte transcriptional changes in mediating stinging and itch, we performed pathway analysis using several publically available databases and then focused on significantly changed transcripts involved in stress responses and itch signaling using the Comparative Toxicogenomics Database. LA treatment induced damage-associated genes HSPA1A, DDIT3, IL1A, and HMGB2. Neurotrophic factors including BDNF, ARTN, PGE2, and chemokines were also upregulated. Stimulation of the RHE with 5% LA did not reduce cell viability, but reduced the trans-epidermal electric resistance, suggesting barrier dysfunction. Accordingly, skin barrier formation genes such as filaggrins (FLG, FLG2) and corneodesmosin (CDSN) were downregulated. To our knowledge, this is the first study focusing on transcriptional changes underlying the stinging response of keratinocytes upon LA stimulation. While follow-up research is needed, this study provides new insight into the mechanisms underlying the sensitive skin reaction.

Relative response of populations of Escherichia coli and Salmonella enterica to exposure to thermal, alkaline and acidic treatments

We evaluated the relative response of generic Escherichia coli (GEC), Shiga toxin-producing E. coli (STEC) and Salmonella enterica to heat, alkaline or acid treatments. GEC included strains from carcasses (n = 24) and trim (n = 25) at a small beef plant where no decontamination interventions are used and at a large plant where multiple decontamination interventions are used (carcass n = 25 and trim n = 25). STEC strains belonging to nine serogroups, included isolates from cattle (n = 53), beef (n = 16) and humans (n = 44). S. enterica strains belonging to 29 serotypes, included isolates from humans (n = 30), poultry (n = 26), pork (n = 10) and beef (n = 33). Strains were grown in Brain Heart Infusion (BHI) broth and subjected to the following treatments: 60 °C for 2 min, 5% lactic acid (pH 2.9) for 1 h at 4 °C, or NaOH (pH 11.0) for 2 h at 4 °C. Median log reductions of the GEC populations after heat, alkaline and acid treatment ranged from 2.3 to 3.8, 0.7 to 2.2 and 0.7 to 1.2 log CFU/mL, respectively. No statistically significant difference in reductions was observed between carcass GEC or trim GEC from the large or small plant, except for a greater reduction in trim GEC from the small plant. Median reductions of the STEC populations ranged from 3.3 to 3.5, 0.0 to 0.6, and 0.3 to 0.5 log CFU/mL after heat, alkaline and acid treatment, respectively. The median reductions were not dependent upon isolation source, except between STEC cattle and human isolates after alkaline treatment, where the reduction of the former was higher by 0.6 log unit. For the Salmonella populations, median log reductions ranged from 3.5 to 4.0, 1.7 to 2.4 and 3.7 to 4.1 log CFU/mL after heat, alkaline and acid treatment, respectively. The reductions were not isolation source related. The median log reductions were in the order GEC < STEC < Salmonella after heat treatment and STEC < GEC < Salmonella after alkaline or acid treatment. Overall, the relative response of GEC, STEC and Salmonella in the model system suggests that exposure to heat or pH-based decontamination interventions in meat plants is not associated with increased resistance among E. coli strains in these environments, and total E. coli counts on beef can be indicative of treatment efficacy for the control of Salmonella by heat, lactic acid and alkaline treatment and for the control of STEC subjected to heat.

Treatment of corn with lactic acid or hydrochloric acid modulates the rumen and plasma metabolic profiles as well as inflammatory responses in beef steers

BackgroundHigh-grain diets that meet the energy requirements of high-producing ruminants are associated with a high risk of rumen disorders. Mild acid treatment with lactic acid (LA) has been used to modify the degradable characteristics of grains to improve the negative effects of high-grain diets. However, the related studies mainly focused on dairy cows and explored the effects on rumen fermentation, production performance, ruminal pH and so forth. And up to date, no studies have reported the hydrochloric acid (HA) treatment of grains for ruminant animals. Therefore, based on metabolomics analysis, the aim of this study was to evaluate the effects of treatment of corn by steeping in 1% LA or 1% HA for 48 h on the rumen and plasma metabolic profiles in beef steers fed a high corn (48.76%) diet with a 60:40 ratio of concentrate to roughage. The inflammatory responses of beef cattle fed LA- and HA-treated corn were also investigated.ResultsBased on ultra-high-performance liquid tandem chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS) metabolomics and multivariate analyses, this study showed that steeping corn in 1% LA or 1% HA modulated the metabolic profiles of the rumen. Feeding beef steers corn steeped in 1% LA or 1% HA was associated with lower relative abundance of carbohydrate metabolites, amino acid metabolites, xanthine, uracil and DL-lactate in the rumen; with higher ruminal pH; with lower concentrations of acetate, iso-butyrate and iso-valerate; and with a tendency for lower ruminal lipopolysaccharide (LPS) concentrations. Moreover, the data showed lower concentrations of plasma C-reactive protein, serum amyloid A, haptoglobin, interleukin (IL)-1β and IL-8 in beef steers fed 1% LA- or HA-treated corn. The 1% LA treatment decreased the concentrations of plasma LPS, LPS-binding protein and tumour necrosis factor-alpha and the relative abundance of L-phenylalanine, DL-3-phenyllactic acid and tyramine in plasma. The 1% HA treatment decreased the relative abundance of urea in plasma and increased the relative abundance of all amino acids in the plasma.ConclusionsThese findings indicated that LA or HA treatment of corn modulated the degradation characteristics of starch, which contributed to improving the rumen and plasma metabolic profiles and to decreasing inflammatory responses in beef steers fed a high-concentrate diet.

Evaluation of the safety and efficacy of the organic acids lactic and acetic acids to reduce microbiological surface contamination on pork carcasses and pork cuts.

Studies evaluating the safety and efficacy of lactic and acetic acids to reduce microbiological surface contamination on pork carcasses pre‐chill and pork meat cuts post‐chill were assessed. Lactic acid treatments consisted of 2–5% solutions at temperatures of up to 80°C applied to carcasses by spraying or up to 55°C applied on cuts by spraying or dipping. Acetic acid treatments consisted of 2–4% solutions at temperatures of up to 40°C applied on carcasses by spraying or on cuts by spraying or dipping. The maximum treatment duration was 30 s. The Panel concluded that: [1] the treatments are of no safety concern, provided that the substances comply with the European Union specifications for food additives; [2] spraying of pork carcasses pre‐chill with lactic acid was efficacious compared to untreated control, but based on the available data, the Panel could not conclude whether lactic acid was more efficacious than water treatment when spraying of pork carcasses pre‐chill or pork meat cuts post‐chill. The Panel concluded that dipping of pork meat cuts post‐chill in lactic acid was more efficacious than water treatment. However, it could not conclude on the efficacy of acetic acid treatment of pork carcasses pre‐chill and/or pork meat cuts post‐chill; [3] the potential selection and emergence of bacteria with reduced susceptibility to biocides and/or resistance to therapeutic antimicrobials linked to the use of the substances is unlikely as long as Good Hygienic Practices are implemented; and [4] the release of both organic acids is not of concern for the environment, assuming that wastewaters released by the slaughterhouses are treated, if necessary, to counter the potentially low pH caused by lactic or acetic acid, in compliance with local rules.

Lactic acid treatment of by-products and phosphorus level in the diet modulate bacterial microbiome and the predicted metagenome functions using the rumen simulation technique

This study used a rumen simulation technique to evaluate the effects of soaking of by-product-rich concentrate (BPC) in 5% lactic acid (LAC; vol/vol) on the rumen microbiota, predicted metagenome, fermentation characteristics, and nutrient degradation without or with supplemented P. The diet was supplemented with 1.6 g of P in the form of monocalcium phosphate per kilogram of dry matter in addition to 284 mg of inorganic P/d per fermentor via artificial saliva. Fermentor fluid was collected for analyses of short-chain fatty acids, fermentation gases, redox potential, and microbiota and feed residues for calculation of nutrient degradation. The microbiota composition was assessed using paired-end Illumina (Illumina Inc., San Diego, CA) MiSeq sequencing of the V3 to V5 region of the 16S rRNA gene. Soaking in LAC reduced the contents of crude protein, neutral and acid detergent fibers, and organic matter fractions as well as ash and P content of the BPC. Both the LAC treatment of BPC and the inorganic P modified the relative bacterial abundances mainly within the predominant orders Bacteroidales and Clostridiales. Supervised DIABLO N-integration networking supported that operational taxonomic units related to BS11, Ruminococcaceae, Christensenellaceae, Eubacterium, and Selenomonas were the most discriminant for the LAC-treated BPC, whereas other operational taxonomic units related to BS11, RFN20, Ruminococcus, and Succiniclasticum were best correlated with the inorganic P supplementation. Integration networking also showed that carbohydrate and pyruvate metabolism, biosynthesis of unsaturated fatty acids, and degradation of several xenobiotics were stimulated by the LAC treatment of BPC. Those data supported the enhanced fermentation activity as indicated by increased total short-chain fatty acid concentration, especially propionate and butyrate, and methane, but decreased ruminal crude protein degradation, with the LAC-treated compared with control-treated BPC. In contrast, despite an increased abundance of imputed functions, such as inositol phosphate metabolism, phosphatidylinositol signaling, and fructose and mannose metabolism, the reduced abundance of the imputed Kyoto Encyclopedia of Genes and Genomes pathway "transcription machinery" as well as the decrease in total short-chain fatty acids and nutrient degradation indicated reduced bacterial metabolic activity with the inorganic P supplementation. In conclusion, soaking of BPC in LAC may favor the proliferation of certain fibrolytic bacterial taxa and stimulate their metabolic activity, whereas the supplemented P to a diet already meeting ruminal P needs may impair ruminal nutrient utilization.

The effect of organic acid and sodium chloride dips on the shelf-life of refrigerated Irish brown crab (Cancer pagurus) meat

Crab (Cancer pagurus) meat (white and brown) has a short shelf-life. Chemical treatments may inhibit microbial spoilage and extend shelf-life. The effect of 5% organic acids (lactic acid (LA), acetic acid (AA) and citric acid (CA)) and 5% sodium chloride (NaCl) on TVC (mesophiles and psychrophiles), Enterobacteriaceae, Pseudomonas spp. and lactic acid bacteria (LAB) were investigated during storage (2 °C for 12 days). AA was the most effective treatment for white meat, reducing the initial TVCm and TVCp by 1.6 and 1.8 log10 cfu/g, respectively, and extended the shelf life to 8–11.5 days, compared to 5 days for untreated control samples. LA treatment also significantly (P < 0.05) reduced the initial TVC, but the shelf life was only increased by 3 days. CA and NaCl treatments had no significant effect (P > 0.05). A similar pattern was observed for brown meat samples, although the shelf life was increased by a maximum of 1–3 days. The growth of Enterobacteriaceae, Pseudomonas spp. and LAB was significantly (P < 0.05) reduced on AA treated samples only. It was concluded that the shelf-life of crab meat may be extended by up to 3 days using lactic acid and more than doubled using acetic acid.

Effect of lactic acid and ajwain (Carum copticum) on the biogenic amines and quality of refrigerated common carp (Cyprinus carpio)

Common carp (Cyprinus carpio) samples treated with Carum copticum (0.5% and 1%) and lactic acid were examined for a period of 18 days. Samples were analysed for their total viable count (TVC), psychrotrophic count (PTC), pH, thiobarbituric acid reactive substances (TBARS), total volatile base nitrogen (TVN) and biogenic amines (histamine, cadaverine, and putrescine) to evaluate their quality and safety. The TVC, PTC, pH, and TVN values were significantly reduced (p < 0.05) by lactic acid treatment, as was the formation of biogenic amines. Lipid oxidation was significantly (p < 0.05) delayed in samples treated with Carum copticum. Moreover, in these samples, a reduction in the formation of biogenic amines was observed. Therefore, Carum copticum and lactic acid can be utilized as food preservatives to extend the shelf-life of fish.

Surface pH of Fresh Beef as a Parameter To Validate Effectiveness of Lactic Acid Treatment against Escherichia coli O157:H7 and Salmonella

The U.S. beef industry must provide documentation to the U.S. Department of Agriculture, Food Safety and Inspection Service (USDA-FSIS) that the antimicrobial interventions implemented or any subsequent changes in the process are effective under the actual conditions that apply in its operation. The main objective of this study was to determine whether surface pH after application of diluted lactic acid solution on surfaces of fresh meat can be used as a control measure indicator for the reduction of E. coli O157:H7 and Salmonella. Samples (240 each) of lean and adipose beef tissues were inoculated with cocktail mixtures of Escherichia coli O157:H7 and Salmonella. Application parameters were varied such that lean and adipose tissues were spray treated with either 2 or 4.5% lactic acid solution at either 38 or 60°C for 1 to 10 s. Lean and adipose tissues were collected before and after spray treatments for enumeration of the pathogens. Based on the conditions of this study, there was no difference between spray treatments at 38 or 60°C, but 4.5% lactic acid solution reduced pathogens more effectively ( P ≤ 0.05) than did 2% lactic acid solution. Spray treatment with lactic acid solution for 1 to 10 s reduced surface pH values of lean tissues (3 to 3.8) and adipose tissues (2.75 to 3.65). At surface pH values of 3.0 and 2.75, lactic acid reduced E. coli O157:H7 on surfaces of lean and adipose tissues by approximately 1.60 and 1.54 log CFU/cm2, respectively. At surface pH values of 3.8 and 3.65, lactic acid reduced E. coli O157:H7 on lean and adipose tissues by approximately 0.3 and 0.42 log CFU/cm2, respectively. The surface pH values after lactic acid treatment and the reductions of both pathogens showed a strong linear relationship; this indicates that a surface pH of 3.1 would provide at least 1-log reduction of E. coli O157:H7 and Salmonella, regardless of lactic acid application parameters. Therefore, surface pH after spray treatment with lactic acid could be used to validate pathogen reduction.