Control of Alicyclobacillus acidoterrestris in fruit juices by a newly discovered bacteriocin

Alicyclobacillus acidoterrestris is one of the most spoilage-causing bacteria in fruit juices. Control of A. acidoterrestris in fruit juices by bificin C6165 (Pei et al. in J Appl Microbiol 114(5):1273-1284, 2013), a bacteriocin produced by Bifidobacterium animalis subsp. animalis CICC 6165, was described in this study. Activity spectrum of bificin C6165 was investigated and sixteen strains of A. acidoterrestris were sensitive to bificin C6165 in diluted Apple Juices. In the commercial fruit juices, vegetative cells of A. acidoterrestris were inactivated by bificin C6165 at 40 μg/ml. The inhibitory effect of bificin C6165 was better at lower pH (pH 3.5) and at a higher temperature of 45 °C. Furthermore, electron microscopy examination of the vegetative cells treated with bacteriocin revealed substantial cell damage and bacterial lysis. The result suggested that primary mode of action of bificin C6165 was most probably due to pore formation. Although no significantly activity of bificin C6165 was observed against the endospores of A. acidoterrestris in commercial apple juice, the addition of bacteriocin contributed to the reduction of the thermal resistance of A. acidoterrestris spores. Additionally, encapsulation of bificin C6165 with Ca-alginate gel was investigated. Encapsulation of bificin C6165 provided a promising method to control A. acidoterrestris in food juice industry.

Development and application of a method for the analysis of 9 mycotoxins in maize by HPLC-MS/MS

A reliable and sensitive liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous determination of aflatoxins (AFB1 , AFB2 , AFG1 , and AFG2 ), ochratoxin A (OTA), deoxynivalenol (DON), zearalenone (ZEA), fumonisin B1 (FB1 ), and T2-toxin in maize. The samples were first extracted using acetonitrile: water: acetic acid (79 : 20 : 1), and then further cleaned-up using OASIS HLB cartridge. Optimum conditions for the extraction and chromatographic separation were investigated. The mean recoveries of mycotoxins in spiked maize ranged from 68.3% to 94.3%. Limits of detection and quantification ranged from 0.01 to 0.64 μg/kg and from 0.03 to 2.12 μg/kg, respectively. The LC-MS/MS method has also been successfully applied to 60 maize samples, which were collected from Shaanxi Province of China. Twenty-four of the total 60 samples (40%) were contaminated with at least 1 of these 9 mycotoxins. Occurrence of mycotoxins were 6.7%, 1.7%, 3.3%, 6.7%, 1.7%, 23.3%, and 3.3% for AFB1 , AFB2 , OTA, ZEA, DON, FB1 , and T2-toxin, respectively. The results demonstrated that the procedure was suitable for the simultaneous determination of these mycotoxins in maize matrix.

Adsorptive removal of patulin from apple juice using Ca-alginate-activated carbon beads

This study aimed to investigate the adsorption of patulin from apple juice by Ca-alginate-activated carbon (Ca-alginate-AC) beads. The capacity of patulin was determined by high-performance liquid chromatography. The results showed that Ca-alginate-AC beads have significant ability to reduce patulin from contaminated apple juice. Furthermore, the adsorption process did not affect the quality of apple juice. The effects of contact time, initial patulin concentration, adsorbent dose, and temperature were assessed. The removal percentage of patulin increased with contact time, adsorbent dose, and temperature. A reduction was also noted to bind patulin at increased levels of contamination. The equilibrium data were fitted to Langmuir, Freundlich, and Temkin isotherm models and the isotherm constants were calculated at different temperatures. The adsorption equilibrium was best described by the Freundlich isotherm (R(2) > 0.990). The pseudo 1st-order model was found to describe the kinetic data satisfactorily. Thermodynamic parameters such as standard Gibbs free energy (ΔG◦◦), standard enthalpy (ΔH◦), and standard entropy (ΔS◦) were evaluated. The results showed that the adsorption was spontaneous and endothermic nature.

Purification and characterization of anti-Alicyclobacillus bacteriocin produced by Lactobacillus rhamnosus

Lactobacillus rhamnosus CICC 20975 produces a 6,502-Da bacteriocin, named bacteriocin RC 20975, active against Alicyclobacillus acidoterrestris, Lactobacillus acidophilus, Lactobacillus brevis, Bacillus subtilis, and Listeria innocua. This bacteriocin is not quite heat stable but is effective after refrigerated storage and freeze-thaw cycles. Bacteriocin RC 20975 was added at a concentration of 256 AU/ml to the endospores of A. acidoterrestris DSM 3922; no viable cells were detected after 24 h. The primary mode of action of bacteriocin RC 20975 seems to be the formation of pores, as indicated by K⁺ efflux from metabolically active cells of A. acidoterrestris. However, efflux of larger cytoplasmic content was not observed within the first 30 min after bacteriocin RC 20975 treatment. In addition, adsorption of bacteriocin RC 20975 to target cells at different temperatures and pH levels and in the presence of surfactants was studied. Finally, the effect that different media, media components, and addition of vitamins to the media had on bacteriocin RC 20975 production was also studied.

Chemometric classification of apple juices according to variety and geographical origin based on polyphenolic profiles

To characterize and classify apple juices according to apple variety and geographical origin on the basis of their polyphenol composition, the polyphenolic profiles of 58 apple juice samples belonging to 5 apple varieties and from 6 regions in Shaanxi province of China were assessed. Fifty-one of the samples were from protected designation of origin (PDO) districts. Polyphenols were determined by high-performance liquid chromatography coupled to photodiode array detection (HPLC-PDA) and to a Q Exactive quadrupole-Orbitrap mass spectrometer. Chemometric techniques including principal component analysis (PCA) and stepwise linear discriminant analysis (SLDA) were carried out on polyphenolic profiles of the samples to develop discrimination models. SLDA achieved satisfactory discriminations of apple juices according to variety and geographical origin, providing respectively 98.3 and 91.2% success rate in terms of prediction ability. This result demonstrated that polyphenols could served as characteristic indices to verify the variety and geographical origin of apple juices.

Alicyclobacillus contamination in the production line of kiwi products in China

Alicyclobacillus are spoilage microbes of many juice products, but contamination of kiwi products by Alicyclobacillus is seldom reported. This study aims to investigate the whole production line of kiwi products in China to assess the potential risk of their contamination. A total of 401 samples from 18 commercial products, 1 processing plant and 16 raw material orchards were tested, and 76 samples were positive, from which 76 strains of microbes were isolated and identified as 4 species of Alicyclobacillus, including Alicyclobacillus acidoterrestris, Alicyclobacillus contaminans, Alicyclobacillus herbarius and Alicyclobacillus cycloheptanicus, and another 9 strains as 3 species of Bacillus by sequencing of their 16S rDNA. Through phylogenetic tree construction and RAPD-PCR amplification, it was found that there exist genotypic diversities to some extent among these isolates. Four test strains (each from one species of the 4 Alicyclobacillus species isolated in this study) could spoil pH adjusted kiwi fruit juice and some commercial kiwi fruit products with producing guaiacol (11-34 ppb).

Purification and identification of five novel antioxidant peptides from goat milk casein hydrolysates

The present research described the preparation, purification, and identification of antioxidant peptides from goat milk casein (GMC). Goat milk casein was hydrolyzed by using a combination of neutral and alkaline proteases to obtain goat milk casein hydrolysates (GMCH) with high antioxidant activity. After desalting by nonpolar macroporous absorption resin, GMCH was isolated and purified by gel filtration chromatography and reversed-phase HPLC, respectively, and further identified by nanoliter electrospray ionization-tandem mass spectrometry. Antioxidant activities of GMC, GMCH, and pure peptides were evaluated and compared using free radical scavenging activity, metal ion chelating ability, and anti-lipid peroxidation ability. Compared with GMC, the free radical-scavenging ability and ferrous ion-chelating ability of GMCH increased significantly. The inhibition effect of lipid peroxidation of GMCH was much stronger than that of tert-butylhydroquinone and phytogermine and a little lower than that of ascorbic acid. The antioxidant activity of GMCH could be attributed to the high antioxidant activity of oligopeptides, especially 5 novel oligopeptides: Val-Tyr-Pro-Phe, Phe-Gly-Gly-Met-Ala-His, Phe-Pro-Tyr-Cys-Ala-Pro, Tyr-Val-Pro-Glu-Pro-Phe, and Tyr-Pro-Pro-Tyr-Glu-Thr-Tyr, which were first observed in GMCH. The antioxidant activity of these 5 novel oligopeptides and GMCH increased 3.59 to 380 times compared with GMC, combining anti-lipid peroxidation ability of GMCH, which indicated that GMCH and its purified fractions in different stages could be used as functional food ingredients, food additives, and pharmaceutical agents in the future.

Aflatoxin m1 in milk products in china and dietary risk assessment

This study was conducted to investigate the occurrence of aflatoxin M1 (AFM1) in milk products in China using the competitive enzyme-linked immunosorbent assay method and to estimate the dietary exposure to this toxin through a probabilistic approach. Based on the exposure assessment results, a quantitative cancer potency formula developed by the Joint Food and Agriculture Organization and World Health Organization Expert Committee on Food Additives was applied to assess the cancer risk. AFM1 was detected in 48.07% of the milk samples and 4.49% of the yoghurt samples. No samples contained AFM1 above the current regulatory limit in China. The simulated AFM1 intake (90% confidence interval) in various sex-age groups ranged from 0.023 (0.021 to 0.023) ng/kg of body weight per day for 30- to 45-year-old men to 0.382 (0.354 to 0.386) ng/kg of body weight per day for 2- to 4-year-old girls at the 99th percentile. The cancer risk of AFM1 to the general population of China was assessed to be 0.129 cancer cases per year per 10(8) persons at the 99th percentile. These results indicate that the health risk associated with AFM1 in milk in China is relatively low.

Characterization of bacteriocin bificin C6165: a novel bacteriocin

AIMS

To purify and primarily characterize an anti-Alicyclobacillus bacteriocin produced by Bifidobacterium animalis subsp. animalis CICC 6165, suggested to be named bificin C6165.

METHODS AND RESULTS

During purification of the bificin C6165, optimal recovery was achieved with ammonium sulfate precipitation followed by two chromatographic steps. Mass spectrometry analyses revealed a distinctive peak corresponding to a molecular mass of 3395·1 Da. This bacteriocin was heat stable, effective after refrigerated storage and freeze-thaw cycles. The primary mode of action of bificin C6165 is most probably due to pore formation, as indicated by the efflux of K(+) from metabolically active cells of Alicyclobacillus acidoterrestris. In the presence of 10 mmol l(-1) gadolinium, bificin C6165 did not affect cells of Alicyclobacillus acidoterrestris. This suggests that the mode of action of bificin C6165 relies on a net negatively charged cell surface.

CONCLUSIONS

Bificin C6165 is indeed a novel bacteriocin and it exhibited remarkable potency for Alicyclobacillus control.

SIGNIFICANCE AND IMPACT OF THE STUDY

Application of bacteriocins in preservation of fruit juices has seldom been studied. Bificin C6165 may be an alternative method to control juice spoilage by this Alicyclobacillus acidoterrestris and meet increasing consumer demand for nature and artificial chemical additive-free food products.

Binding mechanism of patulin to heat-treated yeast cell

AIMS

This study aims to assess the removal mechanism of patulin using heat-treated Saccharomyces cerevisiae cells and identify the role of different cell wall components in the binding process.

METHODS AND RESULTS

In order to understand the binding mechanism, viable cells, heat-treated cells, cell wall and intracellular extract were performed to assess their ability to remove patulin. Additionally, the effects of chemical and enzymatic treatments of yeast on the binding ability were tested. The results showed that there was no significant difference between viable (53·28%) and heat-treated yeast cells (51·71%) in patulin binding. In addition, the cell wall fraction decreased patulin by 35·05%, and the cell extract nearly failed to bind patulin. Treatments with protease E, methanol, formaldehyde, periodate or urea significantly decreased (P < 0·05) the ability of heat-treated cells to remove patulin. Fourier transform infrared (FTIR) analysis indicated that more functional groups were involved in the binding process of heat-treated cells.

CONCLUSIONS

Polysaccharides and protein are important components of yeast cell wall involved in patulin removal. In addition, hydrophobic interactions play a major role in binding processes.

SIGNIFICANCE AND IMPACT OF THE STUDY

Heat-treated S. cerevisiae cells could be used to control patulin contamination in the apple juice industry. Also, our results proof that the patulin removal process is based mainly on the adsorption not degradation.

Reduction of patulin in aqueous solution by lactic acid bacteria

This study aims to investigate the ability of lactic acid bacteria (LAB) to remove patulin (PAT) from aqueous solution with respect to the bacterial viability, initial PAT concentration, incubation time, temperature, and pH. The removal of PAT determined by high-performance liquid chromatography (HPLC) coupled with UV detector. The maximum PAT uptake was achieved by Bifidobacterium bifidum 6071 and Lactobacillus rhamnosus 6149 strains (52.9% and 51.1%) for viable and (54.1% and 52.0%) for nonviable cells after 24 h incubation. The highest removal of PAT was at pH 4.0 and 37 °C and increased with decreasing of toxin levels. The removal ability of selected strains could represent new strategies for a possible application in contaminated food products and animal feed.

Ability of inactivated yeast powder to adsorb patulin from apple juice

This study aimed to investigate the adsorption of patulin from apple juice, using two types of inactivated yeast powder: laboratory-prepared yeast powder (LYP) and commercial yeast powder (CYP). The effects of incubation time, pH, incubation temperature, adsorbent amount, and initial concentration of patulin and the stability of the yeast-mycotoxin complex were assessed. The results showed that the efficiencies of the two yeast types in adsorbing patulin were similar. The ability of the powders to remove patulin increased with longer incubation times, and patulin concentration was below detectable levels with LYP and CYP at approximately 36 and 30 h, respectively. The highest removal of patulin was achieved at pH 5.0 for both powder types, and there were no significant differences in patulin decrease at different temperatures (4, 29, and 37°C). Additionally, the adsorption percentage of patulin increased significantly with the increase of absorbent amount and decrease of initial concentration of patulin. Stability of the yeast-patulin complex was assessed, and patulin was more stable when washed in phosphate-buffered saline (pH 4.0) than in absolute ethyl alcohol. These results suggest that inactivated yeast powder has potential as a novel and promising adsorbent to bind patulin effectively.

Prevalence of Salmonella on raw poultry at retail markets in China

Data regarding Salmonella on raw poultry are very limited in China. The objective of this study was to determine the prevalence of Salmonella on raw poultry at the retail level in six provinces and two national cities in China. Whole chicken carcasses (n = 1,152) were collected from three types of retail markets (large, small, and wet). All samples were analyzed for the presence of Salmonella by using the U.S. Department of Agriculture, Food Safety Inspection Service method. Of 1,152 chicken samples, overall Salmonella prevalence was 52.2%. The highest prevalence was observed in Guangxi Province (65.3%), next in Guangdong Province (64.6%), and then in Beijing (63.9%), Shaanxi Province (50.7%), Henan Province (47.9%), Shanghai (44.4%), and Fujian Province (42.4%), and lowest prevalence was observed in Sichuan Province (38.9%). Salmonella prevalence was significantly different among the six provinces and two national cities. Salmonella prevalence was highest in the wet markets (54.4%) compared with the large markets (50.3%) and the small markets (52.1%), but differences were not significant (P > 0.05). Good manufacturing practices, good agricultural practices, and hazard analysis critical control point systems for Salmonella control in poultry production at the farm, processing, and retail level should be implemented.