GROWTH OF STAPHYLOCOCCUS AUREUS IN ACIDIFIED PASTEURIZED MILK1

1970 ◽  
Vol 33 (11) ◽  
pp. 516-520 ◽  
Author(s):  
T. E. Minor ◽  
E. H. Marth
Keyword(s):  
Staphylococcus Aureus ◽  
Acetic Acid ◽  
Lactic Acid ◽  
Hydrochloric Acid ◽  
Ph Value ◽  
The Other ◽  
Antagonistic Effects ◽  
Pasteurized Milk ◽  
Ph Values ◽  
Effect On Growth

The effect of gradually reducing the pH of pasteurized milk with acetic, citric, hydrochloric, lactic, and phosphoric acids over periods of 4, 8, and 12 hr on growth of Staphylococcus aureus 100 in this substrate was determined. In addition, 1: 1 mixtures of lactic acid and each of the other acids, and of acetic and citric acids were evaluated for their effect on growth of this organism. To achieve a 90% reduction in growth over a 12 hr period, a final pH value of 5.2 was required for acetic, 4.9 for lactic, 4.7 for phosphoric and citric, and 4.6 for hydrochloric acid. A 99% reduction during a 12 hr period was obtained with a final pH value of 5.0 for acetic, 4.6 for lactic, 4.5 for citric, 4.1 for phosphoric, and 4.0 for hydrochloric acid. A pH value of 3.3 was required for a 99.9% reduction with hydrochloric acid, whereas the same effect was produced at a pH value of 4.9 with acetic acid. Correspondingly lower pH values were required to inhibit growth within 8 and 4 hr periods. Mixtures of acids adjusted to pH values at the borderline for growth (12 hr period) exhibited neither synergistic nor antagonistic effects between two acids.

Effect of pH, Acidulant, Time, and Temperature on the Growth and Survival of Listeria monocytogenes

1989 ◽  
Vol 52 (8) ◽  
pp. 571-573 ◽  
Author(s):  
KENT M. SORRELLS ◽  
DAVIN C. ENIGL ◽  
JOHN R. HATFIELD
Keyword(s):  
Antimicrobial Activity ◽  
Acetic Acid ◽  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Citric Acid ◽  
Hydrochloric Acid ◽  
Malic Acid ◽  
Incubation Temperature ◽  
Growth And Survival ◽  
Ph Values

The effect of different acids, pH, incubation time, and incubation temperature on the growth and survival of four strains of Listeria monocytogenes in tryptic soy broth was compared. Hydrochloric acid (HCl), acetic acid (AA), lactic acid (LA), malic acid (MA), and citric acid (CA) were used to acidify tryptic soy broth to pH values 4.4, 4.6, 4.8, 5.0, and 5.2 pH. Incubation times were 1, 3, 7, 14, and 28 d at 10, 25, and 35°C. The inhibition of L. monocytogenes in the presence of high acidity appears to be a function of acid and incubation temperature. Based on equal pH values, the antimicrobial activity is AA > LA > CA ≥ MA > HCl at all incubation times and temperatures. When based on equal molar concentration, the activity appeared to be CA ≥ MA > LA ≥ AA > HCl at 35 and 25°C, and MA > CA > AA ≥ LA > HCl at 10°C. Greatest antimicrobial activity occurred at 35°C. Greatest survival occurred at 10°C and greatest growth occurred at 25°C. Final pH of the medium was as low as 3.8 in HCl at 28 d. All strains grew well at pH values lower than the minimum previously reported (5.5–5.6).

scholarly journals Nutritive value of broad-leaved dock (Rumex obtusifolius L.) and its effect on the quality of grass silages

2011 ◽  
Vol 49 (No. 4) ◽  
pp. 144-150 ◽  
Author(s):  
S. Hejduk ◽  
P. Doležal
Keyword(s):  
Acetic Acid ◽  
Lactic Acid ◽  
Fermentation Process ◽  
Nutritive Value ◽  
Ph Value ◽  
Red Clover ◽  
Rumex Obtusifolius ◽  
Ph Values ◽  
Grass Silage

The effect of broad-leaved dock (Rumex obtusifolius L.) on the impaired nutritive value of grassland herbages was studied together with the effect of dock and addition of microbial inoculant on the fermentation process in grass silages. The herbage of broad-leaved dock exhibits low DM content, CP and fibre contents comparable with red clover, yet its NEL concentration is low. Quality of silages made of dock at DM content over 300 g/kg is good but the silages show significantly lower contents of lactic acid (35.9%), acetic acid (70.0%) and higher pH values (4.69 vs. 4.35) as compared with the grass silage. Silages made of dock do not contain butyric acid and exhibit lower rates of proteolysis. The presence of broad-leaved dock in herbage poses a danger of slow wilting and low production of fermentation acids. The addition of lactic acid bacteria (LAB) showed in the studied set of silages and in dock silages by an increased content of lactic acid (+18.9% and +27.0%, resp.) and by a significant reduction of pH value (–0.17 and –0.14, resp.).  

Effect of Phage on Survival of Salmonella Enteritidis during Manufacture and Storage of Cheddar Cheese Made from Raw and Pasteurized Milk

2001 ◽  
Vol 64 (7) ◽  
pp. 927-933 ◽  
Author(s):  
RAJESH MODI ◽  
Y. HIRVI ◽  
A. HILL ◽  
M. W. GRIFFITHS
Keyword(s):  
Lactic Acid ◽  
Salmonella Enteritidis ◽  
Cheddar Cheese ◽  
Raw Milk ◽  
Final Concentration ◽  
Pasteurized Milk ◽  
Ph Values ◽  
Standard Procedures ◽  
Raw Milk Cheese ◽  
And Storage

The ability of Salmonella Enteritidis to survive in the presence of phage, SJ2, during manufacture, ripening, and storage of Cheddar cheese produced from raw and pasteurized milk was investigated. Raw milk and pasteurized milk were inoculated to contain 104 CFU/ml of a luminescent strain of Salmonella Enteritidis (lux) and 108 PFU/ml SJ2 phage. The milks were processed into Cheddar cheese following standard procedures. Cheese samples were examined for Salmonella Enteritidis (lux), lactic acid bacteria, molds and yeasts, coliforms, and total counts, while moisture, fat, salt, and pH values were also measured. Salmonella Enteritidis (lux) was enumerated in duplicate samples by surface plating on MacConkey novobiocin agar. Bioluminescent colonies of Salmonella Enteritidis were identified in the NightOwl molecular imager. Samples were taken over a period of 99 days. Counts of Salmonella Enteritidis (lux) decreased by 1 to 2 log cycles in raw and pasteurized milk cheeses made from milk containing phage. In cheeses made from milks to which phage was not added, there was an increase in Salmonella counts of about 1 log cycle. Lower counts of Salmonella Enteritidis (lux) were observed after 24 h in pasteurized milk cheese containing phage compared to Salmonella counts in raw milk cheese with phage. Salmonella Enteritidis (lux) survived in raw milk and pasteurized milk cheese without phage, reaching a final concentration of 103 CFU/g after 99 days of storage at 8°C. Salmonella did not survive in pasteurized milk cheese after 89 days in the presence of phage. However, Salmonella counts of approximately 50 CFU/g were observed in raw milk cheese containing phage even after 99 days of storage. In conclusion, this study demonstrates that the addition of phage may be a useful adjunct to reduce the ability of Salmonella to survive in Cheddar cheese made from both raw and pasteurized milk.

Bacterial Spoilage of Citrus Products at pH Lower than 3.51

1976 ◽  
Vol 39 (12) ◽  
pp. 819-822 ◽  
Author(s):  
B. J. JUVEN
Keyword(s):  
Acetic Acid ◽  
Lactic Acid ◽  
Thermal Resistance ◽  
Tartaric Acid ◽  
Lactobacillus Brevis ◽  
Acid Inhibition ◽  
Temperature Range ◽  
Ph Values ◽  
Sugar Syrup ◽  
Z Value

A strain of Lactobacillus brevis, L-3, was isolated from a blown can of grapefruit segments in sugar syrup; it caused spoilage of citrus products having pH values lower than 3.5. When inoculated into orange (pH 3.38) and grapefruit (pH 2.99) juices, after 5 h at 30 C L-3 produced 15 and 22 μg diacetyl/ml, respectively, and off-flavor was detectable. L-3 grew in APT broth acidified to pH 3.0 with citric, hydrochloric, phosphoric, or tartaric acid. However, its growth was inhibited at pH 3.6 if the acidulant was lactic acid, while with acetic acid inhibition occurred at a pH between 3.7 and 4.0. The thermal resistance of L-3 in orange serum (pH 3.4) was studied in the temperature range of 52 to 60 C: a z value of 8.3 was obtained. A simple and reliable capillary technique for studying the thermal resistance of gas-producing organisms in liquid foods and media is presented.

Pyrimidine Derivatives and Related Compounds, V Synthesis of Some Isoxazolo [2,3-a] pyrimidines. A New Ring System

1977 ◽  
Vol 32 (3) ◽  
pp. 311-314 ◽  
Author(s):  
Mohamed Hilmy Elnagdi ◽  
Ezzat Mohamed Kandeel ◽  
Kamal Usef Sadek
Keyword(s):  
Acetic Acid ◽  
Hydrochloric Acid ◽  
Ethyl Acetoacetate ◽  
Pyrimidine Derivative ◽  
Ring System ◽  
The Other ◽  
Acid Mixture ◽  
Pyrimidine Derivatives ◽  
Benzoyl Isothiocyanates ◽  
Related Compounds

3-Amino-5-phenyl-4-phenylazoisoxazole (1) reacts with ethyl acetoacetate to yield the corresponding ethyl isoxazolylaminocrotonate derivative (2) which could be thermally cyclized into the isoxazolopyrimidine derivative (4). On the other hand, condensation of 1 with ethoxymethylenemalononitrile has resulted in the formation of the aminoethylene derivative (5).Compound 1 reacted with acrylonitrile to yield the isoxazolo[2,3-a]pyrimidine derivative (6). The latter was converted into the corresponding exo derivative (8) by the action of acetic acid-hydrochloric acid mixture.Compound 1 also reacted with methoxycarbonyl-, ethoxycarbomyl- and benzoyl isothiocyanates to yield the isoxazolylthioureas (10a, b) and (11), respectively. The reaction of 2 with acetic acid-hydrochloric acid and with phenylhydrazine is reported.

CONTROL OF CLOSTRIDIUM BOTULINUM AND STAPHYLOCOCCUS AUREUS IN SEMI-PRESERVED MEAT PRODUCTS

1972 ◽  
Vol 35 (9) ◽  
pp. 514-523 ◽  
Author(s):  
Han's Riemann ◽  
W. H. Lee ◽  
C. Genigeorgis
Keyword(s):  
Staphylococcus Aureus ◽  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Clostridium Botulinum ◽  
Meat Product ◽  
Meat Products ◽  
Rapid Decline ◽  
Ph Values ◽  
And Staphylococcus Aureus ◽  
Brine Concentration

Clostridium botulinum and Staphylococcus aureus are naturally occurring contaminants in semi-preserved meat products. They can be inhibited by (a) storage below 3 C, (b) 10% sodium chloride (brine concentration), (c) pH values below 4.5, or (d) proper combinations of these factors. However, most meat products do not have the pH values and brine concentrations required to completely inhibit C. botulinum and S. aureus and there is always a risk of temperature abuse. Improved safety can be achieved by adding 1% or more glucose to the product. The glucose will, in the event of temperature abuse, generally be fermented to lactic acid by the indigenous microflora in the product. As a result, the pH value drops to a level at which the brine concentration is sufficient to inhibit C. botulinum and S. aureus. A better approach to safety is to add, together with glucose, a radiation-killed preparation of lactic acid bacteria, e.g., Pediococcus cerevisiae. Such preparations cause a rapid decline in pH only when the product is exposed to a high temperature, and they are stable during storage of meat products. Addition of irradiated lactic acid bacteria to meat products has not yet been officially approved. Another way to improve the safety of semi-preserved meat is to add sufficient glucono-delta-lactone to reduce the initial pH of the product to a level at which the salt concentration is inhibitory. Use of larger amounts of glucono-delta-lactone may result in flavor and color problems even when the meat product is kept at refrigeration temperatures.

Differentiation of Actinomyces propionicus from Actinomyces israelii and Actinomyces naeslundii by gas chromatography

1968 ◽  
Vol 14 (7) ◽  
pp. 749-753 ◽  
Author(s):  
Yu-Ying F. Li ◽  
Lucille K. Georg
Keyword(s):  
Gas Chromatography ◽  
Acetic Acid ◽  
Lactic Acid ◽  
Liquid Chromatography ◽  
Formic Acid ◽  
The Other ◽  
Gas Liquid Chromatography ◽  
Actinomyces Naeslundii ◽  
Actinomyces Species ◽  
End Products

Gas–liquid chromatography (g.l.c.) was used for the analysis of certain metabolic end products of Actinomyces propionicus, as an aid in the separation of this organism from the morphologically similar Actinomyces species, A. israelii and A. naeslundii. Profiles of the chromatograms for the major volatile acids of five strains of A. propionicus studied were found to be distinct from those of four strains of A. israelii and four strains of A. naeslundii. The ratio of propionic acid to acetic acid was approximately 50 times as great for A. propionicus as for the other Actinomyces species. Formic acid was present in significant amounts in both A. israelii and A. naeslundii, but was present only in trace amounts in A. propionicus.Two major nonvolatile acids, lactic and succinic, were identified for the A. israelii and A. naeslundii strains. One of the A. propionicus strains also showed both acids in significant amounts; however, the other four strains of A. propionicus showed succinic acid in large amounts, but only trace amounts of lactic acid.

Pickled Egg Production: Effect of Brine Acetic Acid Concentration and Packing Conditions on Acidification Rate

2014 ◽  
Vol 77 (5) ◽  
pp. 788-795 ◽  
Author(s):  
OSCAR ACOSTA ◽  
XIAOFAN GAO ◽  
ELIZABETH K. SULLIVAN ◽  
OLGA I. PADILLA-ZAKOUR
Keyword(s):  
Acetic Acid ◽  
Regression Analysis ◽  
Acid Concentration ◽  
Egg Production ◽  
Ph Value ◽  
Linear Regression Analysis ◽  
Multiple Linear Regression Analysis ◽  
Acetic Acid Concentration ◽  
Ph Values ◽  
Acidified Foods

U.S. federal regulations require that acidified foods must reach a pH of 4.6 or lower within 24 h of packaging or be kept refrigerated until then. Processes and formulations should be designed to satisfy this requirement, unless proper studies demonstrate the safety of other conditions. Our objective was to determine the effect of brine acetic acid concentration and packing conditions on the acidification rate of hard-boiled eggs. Eggs were acidified (60/40 egg-to-brine ratio) at various conditions of brine temperature, heat treatment to filled jars, and postpacking temperature: (i) 25°C/none/25°C (cold fill), (ii) 25°C/none/2°C (cold fill/refrigerated), (iii) 85°C/none/25°C (hot fill), and (iv) 25°C/100°C for 16 min/25°C (water bath). Three brine concentrations were evaluated (7.5, 4.9, and 2.5% acetic acid) and egg pH values (whole, yolk, four points within egg) were measured from 4 to 144 h, with eggs equilibrating at pH 3.8, 4.0, and 4.3, respectively. Experiments were conducted in triplicate, and effects were considered significant when P < 0.05. Multiple linear regression analysis was conducted to evaluate the effect on pH values at the center of the yolk. Regression analysis showed that brine concentration of 2.5% decreased the acidification rate, while packing conditions of the hot fill trial increased it. Inverse prediction was used to determine the time for the center of the yolk and the total yolk to reach a pH value of 4.6. These results demonstrate the importance of conducting acidification studies with proper pH measurements to determine safe conditions to manufacture commercially stable pickled eggs.

Organic sulfur compounds. VII. Some reactions of benzothiazine hydroxamic acids

1970 ◽  
Vol 48 (23) ◽  
pp. 3727-3732 ◽  
Author(s):  
R. T. Coutts ◽  
Sharon J. Matthias ◽  
E. Mah ◽  
N. J. Pound
Keyword(s):  
Acetic Acid ◽  
Hydrochloric Acid ◽  
Sodium Hydroxide ◽  
Unsaturated Acid ◽  
Hydroxamic Acids ◽  
Sulfur Compounds ◽  
The Other ◽  
Complex Reaction ◽  
Organic Sulfur Compounds ◽  
Derivatives Of

Treatment of (3,4-dihydro-4-hydroxy-3-oxo-2H-1,4-benzothiazin-2-yl)acetic acid (1a) with sodium hydroxide yields the corresponding lactam, i.e. (3,4-dihydro-3-oxo-2H-1,4-benzothiazin-2-yl)acetic acid, together with the α,β-unsaturated acid, 3,4-dihydro-3-oxo-2H-1,4-benzothiazine-Δ2,α-acetic acid. The 6-methyl- and 6-bromo-derivatives of 1a behaved similarly when reacted with sodium hydroxide but when 3,4-dihydro-4-hydroxy-3-oxo-2H-1,4-benzothiazine was so treated a more complex reaction occurred.Methyl (6-bromo-3,4-dihydro-4-hydroxy-3-oxo-2H-1,4-benzothiazin-2-yl)acetate was also treated with hydrochloric acid. The two products isolated were (6-bromo-3,4-dihydro-3-oxo-2H-1,4-benzothiazin-2-yl)acetic acid and (6-bromo-7-chloro-3,4-dihydro-3-oxo-2H-1,4-benzothiazin-2-yl)acetic acid.The action of hydrochloric acid on 3,4-dihydro-4-hydroxy-7-methyl-3-oxo-2H-1,4-benzothiazine also gave two products. One was the corresponding lactam; the other was unexpected and has been tentatively identified as bis[2-(3,4-dihydro-7-methyl-3-oxo-2H-1,4-benzothiazine].

Effects of Fermented Green Juice and Cellulase on the Silage Quality of Sugarcane Top

2012 ◽  
Vol 554-556 ◽  
pp. 1053-1056 ◽  
Author(s):  
Yi Fen Zhuang ◽  
Xin Zhu Chen ◽  
Zhao Xia Dong ◽  
Jian Guo Zhang ◽  
Wen Chang Zhang
Keyword(s):  
Acetic Acid ◽  
Lactic Acid ◽  
Moisture Content ◽  
Water Soluble ◽  
Soluble Carbohydrate ◽  
Moisture Contents ◽  
Ph Values ◽  
Silage Quality ◽  
Water Soluble Carbohydrate

Two moisture levels of sugarcane top (moisture contents 69.03% - MC1 and 56.38% - MC2) were treated with fermented green juice (FGJ) at 2 ml/kg and/or with cellulase (CEL) at 5000 U/kg raw matter, and ensiled in the laboratory at ambient temperature. All additive treatments significantly (P<0.01) increased lactic acid and water soluble carbohydrate (WSC) contents, and significantly (P<0.01) decreased pH and contents of NH3-N and acetic acid compared with the control. The treatment of FGJ and CEL mixture significantly (P<0.01) decreased pH and content of acetic acid (AA) compared with treatments of FGJ and CEL alone. All the MC2 silages had more extensive fermentation than MC1 silage, shown by higher contents of lactic acid, lower pH values and NH3-N contents. In conclusion, both FGJ and CEL addition significantly improved the silage quality of sugarcane top, and their mixture had better result than FGJ and CEL alone. Reducing the moisture content of sugarcane top could improve its silage quality.

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