Chloroanisoles as a cause of musty taint in chickens and their microbiological formation from chlorophenols in broiler house litters

The cause and origin of musty taint in chicken from broiler systems has been established as 2,3,4,6-tetrachloroanisole formed by microbial methylation of 2,3,4,6-tetrachlorophenol present as a wood preservative on shavings used as litter. At least three of the fungi found in poultry litter (Scopulariopsis brevicaulis, Aspergillus sydowi and Penicillium crustosum) can effect this methylation. 2,3,4,6-Tetrachloroanisole formed in the litter was taken up by the chickens. The levels in various chicken tissues and factors affecting uptake and loss have been investigated.     

Impedimetric Characterization of Adsorption of Listeria monocytogenes on the Surface of an Aluminum‐Based Immunosensor

The impedimetric characteristics of an immunosensor depend on the electrical properties of an immunosensor substrate. The impedimetric characteristics of an immunosensor compared with adsorption of Listeria monocytogenes were investigated on an aluminum surface insulated with an electrically resistive aluminum oxide layer. Antibody for L. monocytogenes (anti‐L. monocytogenes) was immobilized on an aluminum surface that was insulated with a native air‐formed aluminum oxide layer. The resistance of impedance (R) value of an aluminum‐based immunosensor decreased, especially at 10⁴ to 10⁶ Hz, where the effect of the reactance of impedance (X) was minimal when L. monocytogenes was adsorbed on the immunosensor surface. The R value of the immunosensor at 81 kHz decreased proportionally to the concentration of L. monocytogenes from 1.3 to 4.3 log CFU mL^?1. The adsorption of L. monocytogenes produced local protrusions on the immunosensor surface, causing physicochemical changes in the ionic layer formed on the immunosensor surface by a sinusoidal electrical signal input, which might help electrical current to flow and cause the R value to decrease.     

Autoxidation of methyl linolenate and methyl linoleate: The effect of α-tocopherol

α-Tocopherol substantially affects the distribution of peroxidic compounds formed during the autoxidation of methyl linolenate and methyl linoleate. In the autoxidation of both these unsaturated fatty acid esters the proportion of monohydroperoxides with conjugated double bonds in the trans, trans configuration is reduced until at high concentrations of α-tocopherol (5%) only cis, trans isomers are formed. In the autoxidation of methyl linolenate the proportion of hydroperoxy-epidioxides is reduced and only monohydroperoxides are formed when 5% α-tocopherol is present. The results are discussed in terms of recent findings concerning the mechanism of the autoxidation of unsaturated lipids.     

Impact of cosolvents on formation and properties of biopolymer nanoparticles formed by heat treatment of β-lactoglobulin–Pectin complexes

The purpose of this study was to determine the influence of neutral cosolvents on the formation and properties of biopolymer nanoparticles formed by thermal treatment of protein–polysaccharide electrostatic complexes. Biopolymer particles were formed by heating (85 °C, 20 min) an aqueous solution containing a globular protein (β-lactoglobulin) and an anionic polysaccharide (beet pectin) above the thermal denaturation temperature (T_m) of the protein under pH conditions where the biopolymers formed electrostatic complexes (pH 5). The impact of two neutral cosolvents (glycerol and sorbitol) on the self-association of β-lactoglobulin and on the formation of β-lactoglobulin–pectin complexes was examined as a function of solution pH (3–7) and temperature (30–95 °C). Glycerol had little impact on the pH-induced self-association or aggregation of the biopolymers, but it did increase the thermal aggregation temperature (T_a) of the protein–polysaccharide complexes, which was attributed to its ability to increase aqueous phase viscosity. Sorbitol decreased the pH where insoluble protein–polysaccharide complexes were formed, and greatly increased their T_a, which was attributed to its ability to increase T_m, alter biopolymer–biopolymer interactions, and increase aqueous phase viscosity. This study shows that neutral cosolvents can be used to modulate the properties of biopolymer nanoparticles prepared by thermal treatment of protein–polysaccharide electrostatic complexes.     

CHARACTERIZATION OF THE ACTION OF BACILLUS SUBTILUS ALPHA-AMYLASE ON SWEET POTATO STARCH,AMYLOSE AND AMYLOPECTIN1

The action pattern of Bacillus subtilis alpha-amylase on Jewel variety sweet potato starch, amylose and amylopectin was monitored using high performance size exclusion chromatography. A wide range of products, from high molecular weight polysaccharides to specific saccharides of low molecular weights, were observed. The hydrolysis pattern for amylose in starch was concealed by hydrolytic fragments formed from amylolysis of the greater quantity of amylopectin. Amylopectin was degraded to a more specific mixture of polysaccharide fragments. Changes in molecular size of hydrolytic fragments formed during amylolysis supported the cluster model previously proposed for amylopectin. These results also suggest that the action of alpha-amylase on sweet potato starch is generally a nonrandom process, primarily resulting from enzymatic action on amylopectin. To support this hypothesis, a more random pattern of hydrolysis was observed from acid treated starch.     

Formation of amino-imidazo-azaarenes and carbolines in fried beef patties and chicken breasts under different cooking conditions in Korea

The effect of cooking temperature and time on amino-imidazo-azaarenes (AIAs) and carbolines in fried ground beef patties and chicken breast under different cooking conditions in Korea was evaluated. Beef patties were fried at different temperatures (150, 180, and 230°C) for 4, 8, 12, and 16 min per each side and then the amount of AIAs and carbolines was evaluated by solid-phase extraction and HPLC-MS analysis. In fried ground beef patties, formations of 9H-pyrido [3,4-b]indole (Norharman) and 1-methyl-9H-pyrido [3,4-b]indole (Harman) were dramatically increased at 230°C for 16 min. Concentrations of Norhanrman and Harman formed at 230°C for 16 min/side were 12 and 40 times greater than level those of Norharman formed at same cooking condition. In fried chicken breasts, 2-amino-3,7,8-trimethylimidazo[4,5-f] quinoxaline (7,8-DiMeIQx) and 2-amino-3,4,7,8-tetramethylimidazo[ 4,5-f]quinoxaline (Tri-MeIQx) were not found at 150 and 180°C. Norhanrman formed at 230°C for 16 min was approximately 4 times higher than fried chicken breasts at 180°C. These results suggest that increase of cooking temperature and time was directly affected on AIAs and carbolines formation in Korean cooked meat.     

Influence of texture of suwari gels on kamaboko gels made from sardine (Sardina pilchardus) surimi

The textural characteristics and water holding capacity of suwari (set) and kamaboko (set and cooked) sardine surimi gels were examined in order to clarify the influence of the initial network formed in setting conditions (25, 35 and 40°C for 30 and 60 min) on the texture of the kamaboko gels. Although the texture of suwari gels set at 35°C improved with longer setting, both setting times ensured kamaboko gels with the highest gel strength. Suwari gels set at 25°C also improved with longer setting but the gel strength of both suwari and kamaboko gels was lower than at 35°C. For gels set at 40°C prolonged setting weakened the suwari networks formed, leading to kamaboko gels with poorer textural characteristics. ©1997 SCI     

The influence of pH on the thermal stability of 5-<Emphasis Type="Italic">O</Emphasis>-caffeoylquinic acids in aqueous solutions

Chlorogenic acid, the ester of caffeic acid with quinic acid, is a natural phenolic compound found in all higher plants. It is potentially useful in pharmaceuticals, foodstuffs, feed additives, and cosmetics due to recently discovered biomedical activity of this compound. This finding caused new interest in the properties of chlorogenic acid in its isomers and in its natural occurrence. It has been found that as many as fourteen compounds (chlorogenic acid derivatives and its reaction products with water) can be formed from 5-O-caffeoylquinic acid by heating its water solution at different pH. Four of them, two hydroxylated 3-O-caffeoylquinic acid derivatives and two hydroxylated 4-O-caffeoylquinic acid derivatives, have been not reported yet. The amount of each formed component depends on the heating time and pH. The transformation product can be mistakenly treated as a new component, not found before in the examined plant, or can be a cause of erroneous quantitative estimations of plant composition.     

Biofilm formation by Escherichia coli in hypertonic sucrose media

High osmotic environments produced by NaCl or sucrose have been used as reliable and traditional methods of food preservation. We tested, Escherichia coli as an indicator of food-contaminating bacterium, to determine if it can form biofilm in a hyperosmotic environment. E. coli K-12 IAM1264 did not form biofilm in LB broth that contained 1 M NaCl. However, the bacterium formed biofilm in LB broth that contained 1 M sucrose, although the planktonic growth was greatly suppressed. The biofilm, formed on solid surfaces, such as titer-plate well walls and glass slides, solely around the air–liquid interface. Both biofilm forming cells and planktonic cells in the hypertonic medium adopted a characteristic, fat and filamentous morphology with no FtsZ rings, which are a prerequisite for septum formation. Biofilm forming cells were found to be alive based on propidium iodide staining. The presence of 1 M sucrose in the food environment is not sufficient to prevent biofilm formation by E. coli.     

Effects of lard on the formation of volatiles from the Maillard reaction of cysteine with xylose

BACKGROUND: The presence of lipid oxidation products in the Maillard reaction pathway is of particular interest today. The objective of this study was to investigate the effect of lard and its oxidation products on the formation of volatiles from cysteine and xylose model systems. RESULTS: Headspace volatiles generated in reaction mixtures were examined by solid‐phase microextraction in combination with gas chromatography‐mass spectrometry. The addition of lipid had a suppressing effect on most of the sulfur‐containing compounds derived from the reaction between cysteine and xylose, especially for 2‐methyl‐3‐furanthiol, 2‐furanmethanethiol, 2‐methylthiophene, and 3‐methylthiophene. One of the intermediates—furfural—was also formed in much lower concentration when lard was present. In addition, cysteine and xylose modified lipid oxidation pathways, so that lipid‐derived alcohols, alkylfurans and aliphatic acids were formed rather than aldehydes. Compared with the lard heated alone, most aldehydes were formed at lower levels in the lard‐containing reaction mixtures, and several aldehydes including hexanal, heptanal, (2E)‐heptenal and (2E,4E)‐heptadienal were absent. CONCLUSION: The addition of lipid was inhibitory to the formation of most sulfur‐containing compounds in the Maillard reaction. Furthermore, Maillard reaction products influenced the formation of products from lipid oxidation. Copyright © 2011 Society of Chemical Industry     

DISTRIBUTION OF ESTERS PRODUCED DURING SUGAR FERMENTATION BETWEEN THE YEAST CELL AND THE MEDIUM

The distribution of the esters formed during sugar fermentations between the yeast cells and the medium was investigated in fermentations by 5 strains of Saccharomyces cerevisiae and 3 strains of S. uvarum (carlsbergensis). The esters studied included the acetates of isoamyl alcohol and phenethyl alcohol and the ethyl esters of the C₆-C₁₂ fatty acids. All of both acetates appeared in the medium. The proportion of the fatty acid ethyl esters transferred to the medium decreased with increasing chain length: all in the medium for ethyl caproate, 54–68% for ethyl caprylate, 8–17% for ethyl caprate, and all remaining in the yeast cell for ethyl laurate. A higher proportion of the esters formed appeared to remain in the cells of the S. uvarum strains than in cells of S. cerevisiae.     

Formation of two types of gels from bovine myosin

Myosin was isolated from bovine m. semimembranosus and gels were formed by heat treatment at different pH values and ionic strengths. The gels were subjected to rigidity measurements and their microstructure was studied by scanning electron microscopy. This article provides evidence that myosin can form two completely different gel structures in the pH range 5.5–6.0, depending on ionic strength. Fine stranded gel structures were formed at low ionic strength (0.25M KCl), whereas coarsely aggregated gel structures were formed at high ionic strength (0.6M KCl). The fine stranded structure had a higher rigidity than the coarsely aggregated structure. It was found that all fine strand myosin gels were formed from turbid solutions and the aggregate gels from clear solutions. When the pH was lowered to 4 in 0.6M KCl a strand-type gel structure formed spontaneously on dialysis, even without heat treatment. This structure did not change in character on heating. It was concluded that the conditions required for the formation of strand-type myosin gels were already present before the heat treatment and that the strands were made up of myosin filaments at certain pH and ionic strength combinations, which produced a turbid solution. The strand-type structures were considered specific with regard to myosin interactions which was not the case for the aggregated structures. Variation of the heating temperature in the range 55 to 65°C had no major effect on the type of structure formed.     

Isolation and Identification of a Novel β-Carotene Degrading Microorganism from Sea Buckthorn Juice

This study was designed to isolate and identify a novel β-carotene cleaving microorganism from sea buckthorn juice and to detect the carotenoid-derived aroma compounds catalyzed by the microbial enzyme. The strain was characterized based on morphological and biochemical properties, as well as part of its 16S rDNA sequence analysis. It was then identified using Basic Local Alignment Search Tool (BLAST) and classified as coagulase-negative Staphylococcus pasteuri (GeneBank Accession No. KP171185). β-Ionone and β-cyclocitral were formed as the main flavor products of β-carotene in submerged culture. When cell-free culture supernatant was applied for the conversion, nearly complete degradation of β-carotene (2 mg) was observed after 12 h. β-Ionone and β-cyclocitral were the main aromas, whereas β-ionone-5,6-epoxide, 2-hydroxy-2,6,6-trimethyl cyclohexanone and dihydroactinidiolide were formed in minor quantities. Moreover, the carotenoid-cleavage enzyme activities of S. pasteuri were partially characterized and partially purified enzyme possesses high activity in adverse industrial condition.     

High correlation of methylglyoxal with acrylamide formation in glucose/asparagine Maillard reaction model

α-Dicarbonyl compounds were highly reactive intermediates formed in Maillard reaction (MR), and o-phenylenediamine (OPD) was widely used as a trapping agent for α-dicarbonyl compounds. Both aqueous glucose/asparagine (Glc/Asn) and glucose/asparagine/o-phenylenediamine (Glc/Asn/OPD) model systems were heated at 150 °C for up to 30 min. The α-dicarbonyl compounds formed in MR were identified by HPLC/MS in our particular model system, indicating that 3-deoxy-2-hexosulose, 2,3-butanedione and methylglyoxal (MG) were three main α-dicarbonyl compounds. In this work, MG was chosen as a representative of α-dicarbonyl compound in MR to investigate the influence on the formation of acrylamide (AA). The concentrations of AA, MG and Asn were detected during MR by HPLC method. The results indicated that the formation of AA increased with the heating time, and nearly 80% of AA formed through participation of α-dicarbonyl compounds. These results were consistent with the changes of amounts of MG. The amounts of formation and consumption of MG increased with heating time, and from 9 min of reaction, the consumed amounts of MG accounted for 73–88% on basis of total amounts of MG formed in MR, suggesting that most of MG take part in the next reaction steps. Meanwhile, the Asn concentration decreased with heating time in both models. The formation of AA and consumption of Asn were highly correlated with MG. Indeed, as MG concentration in MG/Asn model system decreased during heating at 150 °C, the concentration of AA significantly increased. The coefficient of correlation between consumed amounts of MG and the formed amounts of AA is 0.931, again demonstrating that MG does play a role in AA formation.     

Radiation-Injured CIostridium Botulinurn Type E Spores: OutGrowth and Repair

Spores of Clostridium botulinum type E surviving irradiation doses of 0.1–0.4 Mrad were injured as evidenced by their inability to form typical macrocolonies at 10°C in the presence of polymyxin and neomycin, antibiotics which did not similarly affect growth of unirradiated spores. Several degrees of severity of injury were demonstrated. Radiation injury was not associated with the germination lytic system but with the post germination growth system. Radiation-injured spores formed aseptate filaments during outgrowth in microcultures. Some of these filaments lysed; others divided and formed microcolonies less dense than those formed by unirradiated cells. Radiation-injured spores repaired when incubated at 30°C for ca. 15 hr on TP-EY agar medium with polymyxin and neomycin, and formed typical macrocolonies when shifted to 10°C.     

MATERIALS FORMED BY YEAST DURING FERMENTATION

Extracellular polysaccharides, peptides and amino acids are formed by brewing yeasts (Saccharomyces cerevisiae) during fermentation of a synthetic medium consisting mostly of glucose and ammonium sulphate. Similar materials are formed also in fermentations of wort.     

Lactic Acid Fermentation of Saccharified Solution from Rice Flour

For the preparation of a tasty fermented beverage from rice flour, suitable amylases and lactic acid bacteria were explored and selected. A glucoa-mylase from Rhizopus commercially named as gluczyme formed less reducing sugars from gelatinized rice flour than glucoamylase from As-pergillus. However, saccharified solution prepared by gluczyme was well utilized by a lactic acid bacterium isolated from a kefir, which is considered to be a bacterium closely related to Leuconostoc mesenteroides. The substances such as amino acids formed by some contaminating enzymes like protease in gluczyme are presumed to stimulate the growth of the kefir-bacterium and contribute to the formation of a favorable fermented beverage.     

Extraordinary Heat Resistance of Talaromyces flavus and Neosartorya fischeri Ascospores in Fruit Products

Ascospores of three strains each of Talaromyces flavus, Neosartorya fischeri and Byssochlamys fulva/nivea were analyzed for resistance to thermal inactivation in five fruit-based (blueberry, cherry, peach, raspberry and strawberry) products. D_91°C values for two strains of T. flavus ranged from 2.9–5.4 min; D_88°C values ranged from 7.1–22.3 min. Ascospores of N. fischeri were somewhat less heat resistant; D_91°C values were < 2.0 min and D_88°C were 4.2–16.2 min. Ascospores of Byssochlamys spp. were considerably less heat resistant. The type of fruit product did not appear to substantially influence rates of thermal inactivation. No heat-resistant ascospores of T. flavus or N. fischeri, i.e., ascospores capable of surviving 15 min at 75°C, were formed on fruit products stored at 10°C for 137 days. However, T. flavus and N. fischeri formed ascospores on cherry substrate stored at 25°C within 65 and 137 days, respectively, that survived 15 min at 88°C.     

Impact of cranberry juice and proanthocyanidins on the ability of <Emphasis Type="Italic">Escherichia coli</Emphasis> to form biofilms

The effects of cranberry juice cocktail (CJC) and proanthocyanidins (PACs) on biofilm formation were investigated. Escherichia coli strain HB101pDC1 and nonfimbriated strain HB101 were grown in 10 wt% CJC or 120 μg/mL PACs for 12 consecutive cultures. Biofilm formation was investigated by incubating bacteria in 96-well polyvinyl chloride (PVC) plates and studying the optical density of the solution using the crystal violet method. We suspect that biofilm formation occurred due to non-specific interactions between the bacteria and the polymer. Both P-fimbriated E. coli HB101pDC1 and the non-fimbriated strain HB101 formed biofilms. E. coli strain HB101pDC1 formed a thicker and more mature biofilm. Cranberry juice inhibited biofilm formation after the first culture; however, for bacteria grown in PACs, a decrease in biofilm formation was observed with increasing number of cultures. The inhibitory effect was reversible. These results demonstrate that CJC is more effective than isolated PACs at preventing biofilm formation, possibly suggesting that other cranberry compounds also play a role in anti-biofilm activity.     

Assessment of bacterial biofilm on stainless steel by hyperspectral fluorescence imaging

Hyperspectral fluorescence imaging techniques were investigated for detection of two genera of microbial biofilms on stainless steel material which is commonly used to manufacture food processing equipment. Stainless steel coupons were deposited in nonpathogenic E. coli O157:H7 and Salmonella cultures, prepared using M9 minimal medium with casamino acids (M9C), for 6 days at 37 °C. Hyperspectral fluorescence emission images of the biofilm formations on the stainless coupons were acquired from 416 to 700 nm with the use of ultraviolet-A (320–400 nm) excitation. In general, emission peaks for both bacteria were observed in the blue region at approximately 480 nm and thus provided the highest contrast between the biofilms and background stainless steel coupons. A simple thresholding of the 480 nm image showed significantly larger biofilm regions for E. coli O157:H7 than for Salmonella. Viable cell counts suggested that Salmonella formed significantly higher density biofilm regions than E. coli O157:H7 in M9C medium. On the basis of principal component analysis (PCA) of the hyperspectral fluorescence images, the second principal component image exhibited the most distinguishable morphological differences for the concentrated biofilm formations between E. coli and Salmonella. E. coli formed granular aggregates of biofilms above the medium on stainless steel while Salmonella formed dense biofilm in the medium-air interface region (pellicle). This investigation demonstrated the feasibility of implementing fluorescence imaging techniques to rapidly screen large surface areas of food processing equipment for bacterial contamination. Company and product names are used for clarity and do not imply any endorsement by USDA to the exclusion of other comparable products.