Fat contributes to the buffering capacity of chicken skin and meat but enhances the vulnerability of attached Salmonella cells to acetic acid treatment

Exploiting the microbiota of organic and inorganic acid-treated raw poultry products to improve shelf-life

Introduction

Targeted amplicon sequencing of the 16S rRNA delineates the complex microbial interactions that occur during food spoilage, providing a tool to intensively screen microbiota response to antimicrobial processing aids and interventions. The current research determines the microbiota and spoilage indicator (total aerobes and lactic acid bacteria; LAB) response to inorganic and organic antimicrobial intervention use on the shelf-life of fresh, never-frozen, skin-on, bone-in chicken wings.

Methods

Wings (n=200) were sourced from local processor and either not treated (NT) or treated with 15-s dips of tap water (TW), organic (peracetic acid; PAA), inorganic acids (sodium bisulfate; SBS), and their combination (SBS + PAA). Wings were stored (4°C) and rinsed in neutralizing Buffered Peptone Water (BPW) for 1 min on d 0, 7, 14, and 21 post-treatment. Spoilage indicators, aerobic mesophiles and LAB, were quantified from rinsates. Genomic DNA of d 14 and 21 rinsates were extracted, and V4 of 16S rRNA gene was sequenced. Sequences were analyzed using QIIME2.2019.7. APC and LAB counts were reported as Log10 CFU/g of chicken and analyzed in R Studio as a General Linear Model using ANOVA. Pairwise differences were determined using Tukey's HSD (P£0.05).

Results

Spoilage was indicated for all products by day 21 according to APC counts (>7 Log10 CFU/g); however, wings treated with SBS and SBS + PAA demonstrated a 7-day extended shelf-life compared to those treated with NT, TW, or PAA. The interaction of treatment and time impacted the microbial diversity and composition (p < 0.05), with those treated with SBS having a lower richness and evenness compared to those treated with the controls (NT and TW; p < 0.05, Q < 0.05). On d 14, those treated with SBS and SBS + PAA had lower relative abundance of typical spoilage population while having a greater relative abundance of Bacillus spp. (~70 and 50% of population; ANCOM p < 0.05). By d 21, the Bacillus spp. populations decreased below 10% of the population among those treated with SBS and SBS + PAA.

Discussion

Therefore, there are differential effects on the microbial community depending on the chemical intervention used with organic and inorganic acids, impacting the microbial ecology differently.

Effect of food structure and buffering capacity on pathogen survival during in vitro digestion

Even though a plethora of barriers are employed by the human gastrointestinal tract (GIT) to cope with invading pathogens, foodborne diseases are still a common problem. The survival of food pathogens in the GIT is known to depend on food carrier properties. The aim of this study was to investigate the influence of food buffering capacity and food structure on the survival of Salmonella Typhimurium and Listeria monocytogenes during simulated digestion, following contamination of different food model systems that had different combinations of fat and protein content. The results illustrated the strong protective properties of proteins, acting either as a strong buffering agent or as a physical barrier against gastric acidity, for both pathogens. In comparison, fat manifested a lower buffering capacity and weaker protective effects against the two pathogens. Intriguingly, a low fat content was often linked with increased microbial resistance. Nonetheless, both pathogens survived their transit through the simulated GIT in all cases, with S. Typhimurium exhibiting growth during intestinal digestion and L.monocytogenes demonstrating a healthy residual population at the end of the intestinal phase. These results corroborate the need for a deeper understanding regarding the mechanisms with which food affects bacterial survival in the human GIT.

Quality Characterization of Different Parts of Broiler and Ligor Hybrid Chickens

The quality characterization of different parts of male and female Ligor hybrid chickens was investigated and compared with those of commercial broiler. Genotypes, muscle types, and sex had effects on the composition, physicochemical, and textural properties of chicken samples. Ligor hybrid chicken contained higher percentages of protein, moisture, ash, and collagen content but lower fat content than those of commercial broiler (p < 0.05), except in the case of breast, where no significant difference in moisture and ash was observed (p ≥ 0.05). The pH in breast meat of both chickens was lower than that of thigh meat. The color (L*, a*, and b*) values of male and female chickens were not significantly different, except for the L* value of broiler chicken, which was higher in female chickens than in male chickens. Higher cooking loss and shear force were found in male Ligor hybrid chicken. A similar protein pattern was observed for the protein from the same muscle type, irrespective of sex and genotype tested. It was observed that Ligor hybrid chicken contained higher glutamic acid and aspartic acid than commercial broilers. Therefore, Ligor hybrid chicken is a promising new source of nutrition, which can be beneficial for consumers.

Buffering capacity of wet texturized plant proteins in comparison to pork meat

There is an increasing demand to develop and characterize high moisture extrudates from alternative plant proteins due to their increased use in various foods. In this study, wet texturized proteins from two pea isolates and four oilseed flours from pumpkin and sunflower were subjected to an acid titration to gain insights into their buffering capacity. Results were compared to pork meat with a special emphasis on compositional differences. Wet texturized pumpkin and sunflower proteins had the highest buffering capacity, especially in between pH7.0 and pH4.5, while pea protein extrudates and pork meat were more prone to acidification and similar in buffering capacity. A multiple linear regression model further revealed that ash and select minerals and amino acids are key influencing factors on the overall buffering capacity, while the effect of protein and non-protein nitrogen depends on the evaluated pH-regime. The obtained results underline the importance for a more in-depth physicochemical characterization of texturized plant proteins and their raw materials and suggest a need for recipe and process adjustment to achieve stable pH values.

Reduction of Salmonella Infantis on skin-on, bone-in chicken thighs by cetylpyridinium chloride application and the impact on the skin microbiota

Salmonella Infantis has been the etiological agent of numerous foodborne outbreaks of nontyphoidal Salmonella. Consequently, there is an emergent need to mitigate Salmonella Infantis among poultry. Thus, this study evaluated the efficacy of cetylpyridinium chloride (CPC) versus peroxyacetic acid (PAA), on bone-in, skin-on chicken thighs for the reduction of Salmonella and changes in the microbiota. Exactly 100 skin-on, bone-in chicken thighs (2 trials, 0 and 24 h, k = 5, n = 5, N = 50) were inoculated with 10⁸ CFU/mL of a nalidixic acid resistant strain of S. Infantis for an attachment of 10⁶ CFU/g. Thighs were treated with 20 s part dips (350 mL): a no inoculum, no treatment control (NINTC); no treatment control (NTC); tap water (TW); TW+CPC; TW+PAA. Following treatment, thighs were rinsed in 150 mL of nBPW, and rinsates were collected. Rinsates were spot plated for Salmonella and aerobic bacteria (APC). Log₁₀ transformed counts were analyzed using a mixed-effects model (random effect = trial) with means separated using Tukey's HSD (P ≤ 0.05). The genomic DNA of rinsates was extracted, and the 16S rDNA was sequenced on an Illumina MiSeq. Microbiota data were analyzed using QIIME2, with data considered significant at P ≤ 0.05 (main effects) and Q≤0.05 (pairwise differences). Treatment × time interactions were observed for both Salmonella and APC (P < 0.05). The treatment of thighs with PAA and CPC reduced Salmonella and APC in respect to the controls. Numerically, thighs treated with CPC had less Salmonella (4.29 log₁₀CFU/g) and less APC (4.56 log₁₀CFU/g) at 24 h than all other treatments (P > 0.05). Differences in diversity metrics were not consistently observed between treatments; however, in trial 2, the NTC treated thighs were different than those treated with CPC (P < 0.05; Q < 0.05). In both trials, ANCOM, the analysis of microbiome compositional profiles, revealed shifts at both the phylum and order levels with thighs being different in the relative abundances of Proteobacteria (P < 0.05). In conclusion, treatment of skin-on poultry parts with CPC may reduce the risk of foodborne outbreaks caused by Salmonella Infantis.

Inhibition of a spoilage exopolysaccharide producer by bioprotective extracts from Lactobacillus acidophilus CRL641 and Latilactobacillus curvatus CRL705 in vacuum-packaged refrigerated meat discs

The effect of bioprotective extracts (BEs) from Lactobacillus acidophilus CRL641 (BE-1) and Latilactobacillus curvatus CRL705 (BE-2) against the exopolysaccharide producer Latilactobacillus sakei CRL1407 in vacuum-packaged meat discs at 4 °C was evaluated. Lat. sakei CRL1407 was able to grow in control samples from 2.80 to 7.77 log CFU/g after 38 days. BE-1 and BE-2 reduced bacterial growth by 2.11 and 1.35 log CFU/g, respectively, but their combination led to a greater growth reduction (3.31 log CFU/g). The antimicrobial activity was detected in treated samples with BE-1 and BE-1 + BE-2 until day 16, while with BE-2 only at the initial time. The pH values remained constant in the discs treated with the BEs combination, whereas the greatest drop in pH was observed in control samples. The minor lipid oxidation without perceptible color changes was detected in the presence of BE-1 and BE-1 + BE-2. The combination of BEs as biocontrol agent plus conventional preservation barriers could extend the fresh meat shelf-life without quality loss.

Survival of Salmonella on Red Meat in Response to Dry Heat

ABSTRACT

Red meat is associated with Salmonella outbreaks, resulting in negative impacts for the processing industry. Little work has been reported on the use of dry heat as opposed to moist heat against Salmonella on red meat. We determined the effect of drying at 25°C and dry heat at 70°C with ∼10% relative humidity for 1 h against 11 Salmonella strains of multiple serovars on beef, lamb, and goat and rubber as an inert surface. Each strain at ∼108 CFU/mL was inoculated (100 μL) onto ±1 g (1 cm2) of each surface and allowed to attach for 15 min in a microcentrifuge tube. Samples were then exposed to 70 and 25°C with ∼10% relative humidity in a heating block. Surviving Salmonella numbers on surfaces were enumerated on a thin agar layer medium. If numbers were below the limit of detection (2.01 log CFU/cm2), Salmonella cells were enriched before plating to determine the presence of viable cells. Water loss (percent) from meat after at 25 and 70°C was determined. Whole genomes of Salmonella were interrogated to identify the presence-absence of stress response genes (n = 30) related to dry heat that may contribute to the survival of Salmonella. The survival of Salmonella at 25°C was significantly higher across all surfaces (∼6.09 to 7.91 log CFU/cm2) than at 70°C (∼3.66 to 6.33 log CFU/cm2). On rubber, numbers of Salmonella were less than the limit of detection at 70°C. Water loss at 70°C (∼17.72 to 19.89%) was significantly higher than at 25°C (∼2.98 to 4.11%). Salmonella cells were not detected on rubber, whereas survival occurred on all red meat at 70°C, suggesting its protective effect against the effect of heat. All Salmonella strains carried 30 stress response genes that likely contributed to survival. A multi-antibiotic-resistant Salmonella Typhimurium 2470 exhibited an increase in heat resistance at 70°C on beef and lamb compared with other strains. Our work shows that dry heat at 70°C for 1 h against Salmonella on red meat is not a practical approach for effectively reducing or eliminating them from red meat.

HIGHLIGHTS

Food buffering capacity: quantification methods and its importance in digestion and health

Understanding the influence of food properties on buffering capacity will have an impact on gastric secretions and breakdown during digestion.

Application of Amplon in combination with peroxyacetic acid for the reduction of nalidixic acid-resistant Salmonella Typhimurium and Salmonella Reading on skin-on, bone-in tom turkey drumsticks

Peroxyacetic acid (PAA) has become an important component of pathogen reduction in poultry processing, but there are potential concerns for continued exposure. The objective was to evaluate the effects of PAA and Amplon (AMP) used alone or in the combination. Bone-in tom turkey drumsticks (N = 100, n = 10, k = 5, 0 and 24 h) per study were obtained and inoculated with either nalidixic acid–resistant Salmonella Typhimurium or Salmonella Reading (64 μg/mL). The inocula were allowed to adhere to the drums at 4°C for 60 min for a final attachment of 10⁸ and 10⁷ cfu/g per S. Typhimurium and S. Reading, respectively. Drumsticks were treated with a no-treatment control; tap water, pH 8.5 (TW); TW+500 ppm PAA, pH 3.5 (PAA); TW+500 ppm AMP, pH 1.3 (AMP); TW + PAA + AMP (PAA + AMP). Treatments were applied as short duration dips (30 s) and allowed to drip for 2 min. After treatment, drums were stored at 4°C until microbial analyses at 0 and 24 h. Drums were rinsed in neutralizing buffered peptone water and spot plated for total aerobes and Salmonella. Bacterial counts were log₁₀ transformed and analyzed using n-way ANOVA. All treatments reduced S. Reading on turkey legs at both 0 and 24 h (P < 0.0001; P < 0.0001). At 24 h, drums treated with PAA + AMP (3.92 log₁₀ cfu/g) had less S. Reading than no-treatment control, TW, and AMP. Treatment by time interactions were observed for total aerobes among drums in both studies (P < 0.0001, P < 0.0001) and Salmonella among drums inoculated with S. Typhimurium (P < 0.0001). During the S. Reading and S. Typhimurium study, all treatments reduced Salmonella and total aerobes on drums. During the S. Typhimurium study, drums treated with PAA + AMP had the lowest numerical load of S. Typhimurium and total aerobes. The combination of AMP + PAA may exhibit a synergistic effect in reducing Salmonella on turkey drums, thus increasing the safety of turkey products for consumers.

Salmonella survival after exposure to heat in a model meat juice system

The effect of heat against eleven Salmonella strains in model meat juices was examined. Juices from beef, lamb and goat were made from either the fatty layer (FL), muscle (M) or a mixture of both (FLM). The pH of each FLM sample was altered to match the pH of PBS and vice versa to determine the pH effect on the survival of Salmonella against the effect of heat. Salmonella were exposed to either gradual heating to 70 °C in FLM, M and FL or heat shock at 70 °C for 5 min in FLM. Fat, fatty acid profile and iron content of the juices were determined. Gradual heat treatment significantly (p ≤ 0.05) reduced Salmonella as compared to the untreated controls (~1.92-7.61 log CFU ml^-1) while heat shock significantly (p ≤ 0.05) reduced Salmonella as compared to the untreated controls (~5.80-7.36 log CFU ml^-1). Survival of Salmonella was higher in lamb juices than other juices. The fat content in lamb FL (3.25%) was significantly higher (p ≤ 0.05) than beef (1.30%) and goat FL (1.42%). Iron content in lamb FLM (~127 mg kg^-1) was significantly (p ≤ 0.05) lower than beef (~233 mg kg^-1) and goat FLM (~210 mg kg^-1). The omega 6 and linoleic acid content in goat FLM (~36.0% and ~34.4%) was significantly higher (p ≤ 0.05) than beef (~29.1% and ~27.1%). Fat, fatty acids and iron may differentially protect Salmonella against the effect of heat in these juices.

Buffering capacity of commercially available foods is influenced by composition and initial properties in the context of gastric digestion

Buffering capacity in commercially available food products is mainly influenced by protein content, and by the interaction of protein and fat content, initial pH, and particle size distribution.

The addition of golden flaxseed flour (Linum usitatissimum L.) in chicken burger: Effects on technological, sensory, and nutritional aspects

Five different concentrations of golden flaxseed flour (0%: F0 (control), 5%: F1, 10%: F2, 15%: F3, 20%: F4) were used as a functional ingredient to replace the fat in chicken burgers. The products were analyzed for moisture, protein, carbohydrate, fat, ash, shear force, consumer acceptance, and their sensory and technological characteristics. The fat, carbohydrate, and protein contents of the raw hamburgers did not differ significantly. An increase in golden flaxseed flour concentration caused a decrease in moisture content and an increase in ash content. The addition of golden flaxseed flour positively affected the technological characteristics and increases in the yield and water retention capacity were observed, together with decreases in shrinkage and mechanical resistance. Formulation F1 presented the highest average acceptance, which did not differ from the F0, and the latter also did not differ from F2. The F3 and F4 formulations differed from the others, with lower average values for acceptance. The check-all-that-apply method revealed that the formulations F0, F1, and F2 were described by sensory terms that corresponded to the desired sensory characteristics. The addition of golden flaxseed flour improved the technological characteristics and the biofunctional potential arising from its bioactive compounds, making it an option as an ingredient for meat products.

The Efficacy of Sodium Bisulfate Salt (SBS) Alone and Combined With Peracetic Acid (PAA) as an Antimicrobial on Whole Chicken Drumsticks Artificially Inoculated With Salmonella Enteritidis

The presence of Salmonella spp. on poultry products is one of the leading causes of foodborne illness in the United States. Therefore, novel antimicrobial substances are being explored as potential interventions in poultry processing facilities. The objective of the current study was to evaluate the efficacy of varying concentrations of sodium bisulfate salt, SBS, alone or in combination with peracetic acid, PAA, in 15 s whole part dips. Ninety six drumsticks (4 replications, 8 treatments, 3 days) were inoculated separately in a 400 mL solution of nalidixic resistant (NA) Salmonella Enteritidis (10⁷ CFU/mL) and allowed to adhere for 60 to 90 min at 4°C for a final concentration of 10⁶ CFU/g. The experimental treatments included: a no treatment (control), and 15 s dips in 300 mL of tap water alone (TW) or with the addition of 1; 2; and 3% SBS; 1; 2; and 3% SBS+PAA. After treatment, drumsticks were stored at 4°C until microbial sampling was conducted. On d 0, l, and 3, drumsticks were rinsed in 150 mL of nBPW for 1 min, 100 μL of rinsate was serially diluted, spread plated on XLT4+NA (20 μg/mL), and incubated aerobically at 37°C for 24 h. Log-transformed counts were analyzed using a randomized complete block design (day) using One-Way ANOVA, polynomial contrasts, and pairwise comparisons with means being separated by Tukey's HSD with a significance level of P ≤ 0.05. A treatment by day interaction (P = 0.14071) was not substantial. Thus, the treatment effect was investigated separately by days. Over time, a linear trend was observed in S. Enteritidis concentration when SBS was increased (1 < 2 < 3%). The concentration of S. Enteritidis was different between 1% SBS and 1% SBS+PAA on d 0. However, the level of S. Enteritidis was not different among drumsticks treated in 2 and 3% SBS and 2 and 3% SBS+PAA across d 0, 1, 3. The application of 3% SBS alone or in combination with 200 ppm of PAA is capable of reducing the presence of Salmonella over a 3-d refrigeration period; potentially increasing the safety of poultry products for consumers.

Buffering capacity of protein-based model food systems in the context of gastric digestion

A standardized method to measure and quantify buffering capacity in the context of gastric digestion is proposed and the impact of protein content and surface area on buffering capacity was observed.

Food Grade Pimenta Leaf Essential Oil Reduces the Attachment of Salmonella enterica Heidelberg (2011 Ground Turkey Outbreak Isolate) on to Turkey Skin

Salmonella attached to the poultry skin is a major source of carcass contamination during processing. Once attached to the poultry skin, it is difficult to detach and inactivate Salmonella by commonly used antimicrobial agents since the pathogen is entrapped deeply in the feather follicles and the crevices on the skin. Essential oils could be natural, safe, and effective alternatives to synthetic antimicrobial agents during commercial and organic processing setup. The present study evaluated the efficacy of pimenta (Pimenta officinalis Lindl.) leaf essential oil (PEO), and its nanoemulsion in reducing Salmonella Heidelberg attachment on to turkey (Meleagris gallopavo) skin during simulated scalding (65°C) and chilling (4°C) steps in poultry processing. A multidrug resistant S. Heidelberg isolate from the 2011 ground turkey outbreak in the United States was used in the study. Results showed that PEO and the nanoemulsion resulted in significant reduction of S. Heidelberg attachment on turkey skin. Turkey skin samples treated with 1.0% PEO for 5 min resulted in >2 log10 CFU/sq. inch reduction of S. Heidelberg at 65 and 4°C, respectively (n = 6; P < 0.05). Similarly, skin samples treated with 1.0% pimenta nanoemulsion (PNE) for 5 min resulted in 1.5- and 1.8- log10 CFU/sq. inch reduction of S. Heidelberg at 65 and 4°C, respectively (n = 6; P < 0.05). In addition, PEO and PNE were effective in reducing S. Heidelberg on skin during short-term storage at 4 and 10°C (temperature abuse) (n = 6; P < 0.05). No Salmonella was detected in the dipping solution containing 0.5 or 1.0% PEO or PNE, whereas a substantial population of the pathogen survived in the control dipping solution. The results were validated using scanning electron -, and confocal - microscopy techniques. PEO or PNE could be utilized as an effective antimicrobial agent to reduce S. Heidelberg attachment to turkey skin during poultry processing.