Rennet coagulation properties of heated milk

Heating impaired the rennet coagulation properties of milk which deteriorated further during storage, i.e. rennet hysteresis occurred. Acidification to pH values ≤ 6.2 or addition of low concentrations of CaCl2 greatly improved the rennet coagulation properties of heated milk. Acidification of heated milk to pH values < 5.5 followed by neutralization to pH 6.6 to produce reformed micelles, resulted in greatly improved rennet coagulation properties except for severely heated milks (120°C for 10 min) which were not coagulable even after acidification/neutralization. Acidification of heated milk to pH values < 5.5 and storage at the low pH for 24 h before neutralization resulted in a further improvement in the rennet coagulation properties. Dialysis of heated milk that had been acidified and reneutralized against an excess of normal milk resulted in a dramatic deterioration of its rennet coagulability. Reheating milk that had been heated, acidified and reneutralized resulted in little change in RCT or gel firmness. Addition of heated milk to raw milk resulted in an increase in RCT of the latter and a reduction in gel firmness.

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

Journal of Food Protection ◽

10.4315/0362-028x-64.7.927 ◽

2001 ◽

Vol 64 (7) ◽

pp. 927-933 ◽

Cited By ~ 108

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.

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Statistical prediction of interactions between low concentrations of inhibitors on yeast cells responses added to the SD-medium at low pH values

Biotechnology for Biofuels ◽

10.1186/s13068-019-1453-4 ◽

2019 ◽

Vol 12 (1) ◽

Cited By ~ 2

Author(s):

Cecilia Laluce ◽

Longinus I. Igbojionu ◽

José L. Silva ◽

Clóvis A. Ribeiro

Keyword(s):

Low Ph ◽

Yeast Cells ◽

Statistical Prediction ◽

Ph Values ◽

Low Concentrations

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CHEDDAR CHEESE: COMPARISON OF EFFECTS OF RAW AND HEATED MILK ON QUALITY AND RIPENING

Journal of Milk and Food Technology ◽

10.4315/0022-2747-32.8.304 ◽

1969 ◽

Vol 32 (8) ◽

pp. 304-311 ◽

Cited By ~ 11

Author(s):

Walter V. Price ◽

Ara O. Call

Keyword(s):

Amino Nitrogen ◽

Raw Milk ◽

Water Soluble ◽

Soluble Nitrogen ◽

Heated Milk ◽

Storage Rate ◽

C 50 ◽

Raw Milk Cheese ◽

Short Time ◽

And Storage

Abstract2 Portions of identical milk of manufacturing quality were made into cheese: (a) without heating; (b) after pasteurizing by the holder method; (c) after short-time heating at 71 C; (d) over 71 C (74–87); and (e) less than 71 C (50–69). These variations in heating did not require extensive modifications of cheese-making operations. Measurements were made of moisture, pH, and salt. Cheese was cured at 7 C, scored at 1, 3, 6, and 12 months, and analyzed for total nitrogen, water-soluble nitrogen, and amino nitrogen at 3, 6, and 12 months. Milk pasteurized by the holder method or by heating to 71 C produced better cheese than raw milk or milk heated for a short time at less than 71 C. Raw-milk cheese cured most rapidly, had the most intense flavors, and was least stable in storage. Rate of curing and intensity of flavor decreased and storage stability increased with the severity of heat treatments. Changes in protein were less extensive in heated-milk cheese and were more extensive in cheese of lower grades. Although there are risks involved, markets for cheese with pronounced cheese flavor can be met with the products produced from milk heated for short times at less than 71 C.

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Rennet coagulation of heated milk: influence of pH adjustment before or after heating

Journal of Dairy Research ◽

10.1017/s0022029900026030 ◽

1988 ◽

Vol 55 (2) ◽

pp. 205-215 ◽

Cited By ~ 40

Author(s):

Harjinder Singh ◽

Samweul I. Shalabi ◽

Patrick F. Fox ◽

Albert Flynn ◽

Anne Barry

Keyword(s):

Heat Treatment ◽

Adverse Effect ◽

Adverse Effects ◽

Skim Milk ◽

Ph Adjustment ◽

Milk Samples ◽

Heated Milk ◽

Rennet Coagulation ◽

Low Concentrations ◽

Influence Of Ph

SummaryThe rennet coagulation times of infant milk formulae or fresh skim milk (milk) samples heated at temperatures in the range 70–140 °C for 1–10 min decreased on acidification, usually to pH < 6·0. Heated milk samples acidified to pH 5·5 and reneutralized to pH 6·6 retained good rennet coagulability. Acidification of such milk samples before heating also reduced the adverse effect of severe heat treatment (95 °C for 1 min) on rennet coagulation. Addition of low concentrations of CaCl2 to heated milks offset the adverse effects of heating. Acidification of heated milks increased the [Ca2+], and reneutralization of acidified milk only partly restored the [Ca2+], i.e. acidified/reneutralized milk had a higher [Ca2+] than normal milk, suggesting this as the mechanism via which acidification/neutralization improves the rennet coagulability of heated milk. Approximately 50% of the whey protein can be incorporated into rennet gels in heated milks while retaining good coagulability and curd tension; this may be a useful technique for increasing cheese yield.

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ELECTROKINETIC PHENOMENA

The Journal of General Physiology ◽

10.1085/jgp.21.6.729 ◽

1938 ◽

Vol 21 (6) ◽

pp. 729-744 ◽

Cited By ~ 5

Author(s):

Harold A. Abramson ◽

Laurence S. Moyer

Keyword(s):

Low Ph ◽

General Definition ◽

Crystal Length ◽

Alkyl Benzene ◽

Electrokinetic Phenomena ◽

Ph Values ◽

Aluminum Ions ◽

Low Concentrations ◽

Isoelectric Points ◽

Definition Of

1. Although the isoelectric points of dissolved cystine, tyrosine, and aspartic acid molecules lie at widely differing pH values, the isoelectric points of the surfaces of these substances in the crystalline state are all near pH 2.3. This was found to be true in solutions of hydrochloric acid and in acetate buffers of approximately constant ionic strength. 2. When suspended in gelatin, tyrosine and cystine crystals adsorb the protein and attain a surface identical in behavior with gelatin-coated quartz or collodion particles. 3. Aluminum ions at low concentrations reduce the electric mobilities of tyrosine crystals to zero in a manner analogous to their effect on other surfaces. 4. Alkyl benzene droplets also have their electric mobility reduced to zero at low pH values but, unlike the amino acids, a change in sign was never noticed. 5. The mobility of tyrosine crystals is independent of crystal length between 2–100µ. Below this size the mobilities are decreased. 6. These results are discussed in connection with the concept of the general definition of the isoelectric point and the behavior of certain insoluble proteins such as wool and silk fibroin.

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Identification of the co-existence of low total organic carbon contents and low pH values in agricultural soil in north-central Europe using hot spot analysis based on GEMAS project data

The Science of The Total Environment ◽

10.1016/j.scitotenv.2019.04.382 ◽

2019 ◽

Vol 678 ◽

pp. 94-104 ◽

Cited By ~ 5

Author(s):

Haofan Xu ◽

Alecos Demetriades ◽

Clemens Reimann ◽

Juan J. Jiménez ◽

Juliane Filser ◽

...

Keyword(s):

Organic Carbon ◽

Central Europe ◽

Agricultural Soil ◽

Hot Spot ◽

Low Ph ◽

North Central ◽

Ph Values ◽

Project Data ◽

North Central Europe ◽

Spot Analysis

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Adaptation of Lactobacillus plantarum IMDO 130201, a Wheat Sourdough Isolate, to Growth in Wheat Sourdough Simulation Medium at Different pH Values through Differential Gene Expression

Applied and Environmental Microbiology ◽

10.1128/aem.02668-10 ◽

2011 ◽

Vol 77 (10) ◽

pp. 3406-3412 ◽

Cited By ~ 15

Author(s):

Gino Vrancken ◽

Luc De Vuyst ◽

Tom Rimaux ◽

Joke Allemeersch ◽

Stefan Weckx

Keyword(s):

Gene Expression ◽

Lactobacillus Plantarum ◽

Differential Gene Expression ◽

Lipoteichoic Acid ◽

Low Ph ◽

Exponential Growth Phase ◽

Cellular Mechanisms ◽

Content Type ◽

Ph Values ◽

Differential Gene

ABSTRACTSourdough is a very competitive and challenging environment for microorganisms. Usually, a stable microbiota composed of lactic acid bacteria (LAB) and yeasts dominates this ecosystem. Although sourdough is rich in carbohydrates, thus providing an ideal environment for microorganisms to grow, its low pH presents a particular challenge. The nature of the adaptation to this low pH was investigated forLactobacillus plantarumIMDO 130201, an isolate from a laboratory wheat sourdough fermentation. Batch fermentations were carried out in wheat sourdough simulation medium, and total RNA was isolated from mid-exponential-growth-phase cultures, followed by differential gene expression analysis using a LAB functional gene microarray. At low pH values, an increased expression of genes involved in peptide and amino acid metabolism was found as well as that of genes involved in plantaricin production and lipoteichoic acid biosynthesis. The results highlight cellular mechanisms that allowL. plantarumto function at a low environmental pH.

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