Inter- and intra-species variability in heat resistance and the effect of heat treatment intensity on subsequent growth of Byssochlamys fulva and Byssochlamys nivea

The effect of continuous-flow microwave treatment of milk was estimated by using indicators of the heat treatment intensity (β-lactoglobulin denaturation, inactivation of alkaline phosphatase and lactoperoxidase). Results were compared with those obtained using a conventional process having the same heating, holding, and cooling phases. Continuous microwave treatment proved to be an effective system for pasteurizing milk, with the inclusion of a holding phase to maintain the time and temperature conditions required. At high pasteurization temperatures, the extent of thermal denaturation observed with the microwave treatment was lower than that obtained with the conventional system. This result could be attributed to a better heat distribution and the lack of hot surfaces contacting the milk in the case of the microwave unit.

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Carbonitration of a Tool for Pressing Stainless Steel Pipes

Journal of Engineering Sciences ◽

10.21272/jes.2020.7(2).c3 ◽

2020 ◽

Vol 7 (2) ◽

pp. C17-C21

Author(s):

I. V. Ivanov ◽

M. V. Mohylenets ◽

K. A. Dumenko ◽

L. Kryvchyk ◽

T. S. Khokhlova ◽

...

Keyword(s):

Heat Treatment ◽

Thermal Treatment ◽

Heat Resistance ◽

Alkali Metals ◽

Matrix Ring ◽

High Hardness ◽

Operating Conditions ◽

Matrix Rings ◽

Conventional Heat Treatment ◽

The Stability

To upgrade the operational stability of the tool at LLC “Karbaz”, Sumy, Ukraine, carbonation of tools and samples for research in melts of salts of cyanates and carbonates of alkali metals at 570–580 °C was carried out to obtain a layer thickness of 0.15–0.25 mm and a hardness of 1000–1150 НV. Tests of the tool in real operating conditions were carried out at the press station at LLC “VO Oscar”, Dnipro, Ukraine. The purpose of the test is to evaluate the feasibility of carbonitriding of thermo-strengthened matrix rings and needle-mandrels to improve their stability, hardness, heat resistance, and endurance. If the stability of matrix rings after conventional heat setting varies around 4–6 presses, the rings additionally subjected to chemical-thermal treatment (carbonitration) demonstrated the stability of 7–9 presses due to higher hardness, heat resistance, the formation of a special structure on the surface due to carbonitration in salt melts cyanates and carbonates. Nitrogen and carbon present in the carbonitrided layer slowed down the processes of transformation of solid solutions and coagulation of carbonitride phases. The high hardness of the carbonitrified layer is maintained up to temperatures above 650 °C. If the stability of the needle-mandrels after conventional heat treatment varies between 50–80 presses, the needles, additionally subjected to chemical-thermal treatment (carbonitration) showed the stability of 100–130 presses due to higher hardness, wear resistance, heat resistance, the formation of a special surface structure due to carbonitration in melts of salts of cyanates and carbonates. Keywords: needle-mandrel, matrix ring, pressing, heat treatment, carbonitration.

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Survey of the Furosine Content in Cheeses Marketed in Spain

Journal of Food Protection ◽

10.4315/0362-028x-63.7.974 ◽

2000 ◽

Vol 63 (7) ◽

pp. 974-975 ◽

Cited By ~ 7

Author(s):

MAR VILLAMIEL ◽

MARÍA ARIAS ◽

NIEVES CORZO ◽

AGUSTÍN OLANO

Keyword(s):

Heat Treatment ◽

Protein A ◽

Treatment Intensity ◽

Wide Range

The furosine content in 53 samples of different cheese types (fresh, ripened with molds, artisanal hard-pressed, industrial hard-pressed, and processed) marketed in Spain was analyzed. The lowest furosine values were observed in artisanal hard-pressed cheeses (4.8 to 10.2 mg per 100 g of protein) and ripened with molds cheeses (4.2 to 12.8 mg per 100 g of protein). Industrial hard-pressed cheeses showed furosine values between 3.5 and 43.8 mg per 100 g of protein. Differences between samples may be attributed to the heat-treatment intensity given to cheese milk and to cheesemaking conditions. The highest contents of furosine were observed in processed cheeses (20 to 366.6 mg per 100 g of protein). A wide range of furosine content was found in fresh cheeses (17.9 to 73.6 mg per 100 g of protein), which could be due to the different amounts of dried milk added during the manufacture of cheeses.

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Heat Resistance of Escherichia coli in Cow and Buffalo Milk

Journal of Food Protection ◽

10.4315/0362-028x-43.5.376 ◽

1980 ◽

Vol 43 (5) ◽

pp. 376-380 ◽

Cited By ~ 2

Author(s):

R. S. SINGH ◽

B. RANGANATHAN

Keyword(s):

Escherichia Coli ◽

Heat Treatment ◽

Heat Resistance ◽

Skim Milk ◽

Buffalo Milk ◽

Time Interval ◽

E Coli ◽

Heat Resistant ◽

Whole Milk

Three Escherichia coli cultures (0111:B4, 0127:B8 and NP) were selected to study their heat-resistant characteristics when in cow skim, cow whole and buffalo whole milk. The temperatures of heat-treatment included in this study were 50, 55, 60 and 63 C. The time interval during heat-treatment was 10 min at 50 and 55 C and 5 min at 60 and 63 C. Marked differences in heat-resistance were observed in the three E. coli cultures. The z-values obtained for strain 0111:B4 were 8.3, 9.0 and 10.2 when tested in cow skim milk, cow whole milk and buffalo milk, respectively. The z-values for 0127:B8 and NP were 17.5, 18.0 and 19.2 and 18.8, 19.0 and 20.3, respectively, for the three types of milk.

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Thermal Inactivation of Listeria monocytogenes in Chicken Gravy

Journal of Food Protection ◽

10.4315/0362-028x-55.7.492 ◽

1992 ◽

Vol 55 (7) ◽

pp. 492-496 ◽

Cited By ~ 15

Author(s):

I-PING D. HUANG ◽

AHMED E. YOUSEF ◽

ELMER H. MARTH ◽

M. EILEEN MATTHEWS

Keyword(s):

Heat Treatment ◽

Listeria Monocytogenes ◽

Heat Resistance ◽

Thermal Inactivation ◽

Refrigerated Storage ◽

Department Of Agriculture ◽

Large Numbers ◽

Z Value ◽

D Values ◽

The U.S

Heat resistance of Listeria monocytogenes strains V7 and Scott A in chicken gravy and changes in heat resistance during refrigerated storage were studied. After chicken gravy was made, it was cooled to 40°C, inoculated with 105 CFU L. monocytogenes per ml of gravy, and then stored at 7°C for 10 d. Gravy was heated at 50, 55, 60, and 65°C immediately after inoculation and after 1, 3, 5, and 10 d of refrigerated storage. The D values for strains Scott A and V7 in gravy heated at 50°C at day 0 were 119 and 195 min and at day 10 they were 115 and 119 min, respectively, whereas at 65°C comparable values at day 0 were 0.48 and 0.19 min and at day 10 they were 0.014 and 0.007 min. Heat resistance (expressed as D values) was greater at day 0 than at the end of refrigerated storage. The z values ranged from 3.41 to 6.10°C and were highest at the early stages of chill storage and then decreased at the later stages. Strain V7 was more heat resistant than Scott A at 50°C. Strain Scott A always had a higher z value than did strain V7 at the same storage interval. A heat treatment greater than the 4-D process recommended by the U.S. Department of Agriculture was required to inactivate the large numbers of L. monocytogenes that developed in chicken gravy during refrigerated storage.

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Growth and Heat Resistance of Clostridium SporogenesPA 3679 Spores Heated and Recovered in Acidified Media

Journal of Food Protection ◽

10.4315/0362-028x-58.6.656 ◽

1995 ◽

Vol 58 (6) ◽

pp. 656-659 ◽

Cited By ~ 5

Author(s):

T. SÁNCHEZ ◽

M. RODRIGO ◽

M. J. OCIO ◽

P. FERNÁNDEZ ◽

A. MARTÍNEZ

Keyword(s):

Heat Treatment ◽

Citric Acid ◽

Heat Resistance ◽

Medium Composition ◽

Colony Development ◽

Medium Ph ◽

Clostridium Sporogenes ◽

Ph Level ◽

Recovery Medium ◽

Heating Medium

The effect of subculture medium composition (pH, type of acidulant, presence of EDTA) on the germination of spores of Clostridium sporogenes PA 3679, both with and without heat treatment in phosphate buffer (30 s at l25°C), was studied. Additionally, the effect of the heating medium substrate and pH and subculture medium pH and composition on the heat resistance of the spores was evaluated. The results indicate that the pH of the recovery medium and the type of acidulant have significant effects (P ≤ 0.05) on counts of PA 3679. Adding EDTA only increases inhibition of this microorganism when the pH is near neutral. For a given pH level, citric acid provided greater inhibiting power than glucono-δ-lactone, although the percentage of undissociated acid was less for citric acid. No growth was observed at pH 5.7, although in the case of glucono-δ-lactone sporadic colony development was seen in some plates. The pH of the heating medium acidified with glucono-δ-lactone did not affect the heat-resistance parameters (D and z) of spores heated to temperatures between 121 and 140°C in relation to the unacidified extract. Nor did we see any significant influence of the composition and pH of the recovery medium on these heat-resistance parameters when comparing the results with those obtained using the usual recovery medium.

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HEAT TREATMENT OF PINEAPPLE: SUBSEQUENT GROWTH AND OCCURRENCE OF MEALYBUG WILT OF PINEAPPLE

Acta Horticulturae ◽

10.17660/actahortic.1993.334.43 ◽

1993 ◽

pp. 407-410 ◽

Cited By ~ 1

Author(s):

D.E. Ullman ◽

D.F. Williams ◽

H. Fleisch ◽

J.S. Hu ◽

D. Sether ◽

...

Keyword(s):

Heat Treatment ◽

Subsequent Growth ◽

Mealybug Wilt

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Effect of Water Activities of Heating and Recovery Media on Apparent Heat Resistance of Bacillus cereusSpores

Applied and Environmental Microbiology ◽

10.1128/aem.67.1.317-322.2001 ◽

2001 ◽

Vol 67 (1) ◽

pp. 317-322 ◽

Cited By ~ 55

Author(s):

Louis Coroller ◽

Ivan Leguérinel ◽

Pierre Mafart

Keyword(s):

Heat Treatment ◽

Heat Resistance ◽

Water Activity ◽

Effect Of Water ◽

Optimal Value ◽

Negative Effect ◽

The Difference ◽

D Values ◽

Recovery Medium ◽

Heating Medium

ABSTRACT Spores of Bacillus cereus were heated and recovered in order to investigate the effect of water activity of media on the estimated heat resistance (i.e., the D value) of spores. The water activity (ranging from 0.9 to 1) of the heating medium was first successively controlled with three solutes (glycerol, glucose, and sucrose), while the water activity of the recovery medium was kept near 1. Reciprocally, the water activity of the heating medium was then kept at 1, while the water activity of the recovery medium was controlled from 0.9 to 1 with the same depressors. Lastly, in a third set of experiments, the heating medium and the recovery medium were adjusted to the same activity. As expected, added depressors caused an increase of the heat resistance of spores with a greater efficiency of sucrose with respect to glycerol and glucose. In contrast, when solutes were added to the recovery medium, under an optimal water activity close to 0.98, a decrease of water activity caused a decrease in the estimated D values. This effect was more pronounced when sucrose was used as a depressor instead of glycerol or glucose. When the heating and the recovery media were adjusted to the same water activity, a balancing effect was observed between the protective influence of the solutes during heat treatment and their negative effect during the recovery of injured cells, so that the overall effect of water activity was reduced, with an optimal value near 0.96. The difference between the efficiency of depressors was also less pronounced. It may then be concluded that the overall protective effect of a decrease in water activity is generally overestimated.

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