Suitability of Animals' Purified Milk Caseins and Their Subunit Κ−caseins as Substrates for Subtilisin and Trypsin

Doğru, Mehmet; Baysal, Zübeyde; Aytekin, Çetin

doi:10.1081/pb-100103380

Cited by 3 publications

(2 citation statements)

References 7 publications

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“…The greatest reduction was noted in the κ-casein fraction, α-casein appeared the most stable. Similar results were reported by Ismail et al (1991) and Dogru et al (2001). The above-mentioned results imply that a storage temperature has a decisive effect on the degradation rate of casein fractions.…”

Section: Resultssupporting

confidence: 81%

Effect of Bacillus cereus Enzymes on Milk Quality following Ultra High Temperature Processing

2006

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Using a model case of contamination of long-life semi-skimmed milk with the spores of six B. cereus strains, isolated from the farm environment and raw milk, proteolysis was monitored by measuring changes in protein content by infra-red spectroscopy; free tyrosine was measured by the Lowry method according to Juffs, and the reduction in casein fractions by SDS-PAGE. Lipolysis was monitored by the dilution extractive method. At a storage temperature of 4 °C for 4 months no enzyme processes were observed, whereas at a storage temperature of 24 °C a marked enzyme activity was found during maximum 3 weeks as well as sensory changes of UHT milk. After three weeks of storage, a reduction in protein content from 34.55 g·1 -1 milk to 29.46 ± 2.00 g·1 -1 milk, and a reduction in the free tyrosine from 0.65 to 2.13 ± 0.28 mg·ml -1 was found, as well as increased molar contents of free fatty acids (FFA) from 41.97 to 1617.22 ± 68.17 mmol·kg -1 milk fat. After six days of storage, α-casein, β-casein and κ-casein dropped to 69 ± 10%, 56 ± 16% and 43 ± 10%, respectively. Majority of changes in UHT milk depended on the B. cereus strain used, initial microbial counts and the method of heat inactivation of spores. Bacillus cereus, spores, proteolysis, casein, lipolysisBacillus spp. are questionable components of raw milk microflora because of a difficult removal of their spores due to thermal resistance. They are significant contaminants of fresh milk in terms of hygiene, technology, and in the case of B. cereus of health, too. Brown (2000) described Bacillus spp. as microorganisms that cause significant economic losses.The spores of Bacillus spp. commonly occur in the barn environment and represent secondary contamination of milk during milking. The most frequently isolated Bacillus species from raw milk are B. licheniformis and B. cereus (Crielly et al. 1994), whereas other bacilli occur less frequently (Luká‰ová et al. 2001; Vyletûlová et al. 2001). Many researchers attribute the changes in Bacillus species distribution to seasonal influences (Sutherland and Murdock 1994). On the contrary, Luká‰ová et al. (2001) did not confirm the effect of seasonal factors on the incidence of Bacillus spp. in milk. Christiansson et al. (1999) pointed out an increased contamination of milk with B. cereus spores during the grazing season, associated with a higher incidence of spores in milk. On farms with good hygiene management, the spore counts in milk should lie within 0.2 -10 4 ·l -1 (Harmon and Kautter 1991). Bacillus spp. spores may occur also in UHT milk, as reported by B a h o u t (2000) who found the spores in 18.3% samples investigated at a count of 2.6 × 10 2 ·ml -1 and noted a presence of B. cereus. Vyletûlová (2001) monitored by ribotyping the incidence of B. cereus in milk, from raw milk to the final product (UHT milk). She assumed milk was contaminated either at the farm or recontaminated during processing.B. cereus is regarded as a psychrotrophic species. In 1998, B. weihenstephanensis was identified, previously designated as ...

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Section: Resultssupporting

confidence: 81%

Effect of Bacillus cereus Enzymes on Milk Quality following Ultra High Temperature Processing

2006

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“…The α-casein was assessed to be the most stable fraction. Identical results were obtained also by Ismail et al (1991), and Dogru et al (2001). Gallagher et al (1994) monitored the effects of protease of B. subtilis and its optimal temperature of 40 °C for casein fractions.…”

Section: Initial Concentrationsupporting

confidence: 76%

Influence of Bacillus spp. Enzymes on Ultra High Temperature-treated Milk Proteins

Dračková¹,

Vorlová²

2004

Acta Vet. Brno

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A model case of long-life half-fat milk contamination with spores of 15 strains of B. licheniformis, B. subtilis a B. cereus isolated from farm environment and from raw milk was used to determine proteolysis by measuring the changes in milk protein contents. The methods of infrared spectroscopy, free tyrosine using Lowry's method according to Juffs and setting of decrease in casein fractions using the SDS-PAGE were employed. Under storage temperature of 4 o C no proteolysis was recorded. However, under storage temperature of 24 °C the following changes in comparison with initial values were recorded after 3 weeks: a decrease in protein contents from 34.60 g⋅1-1 to 29.46-32.86 g⋅l-1 and increased free tyrosine contents from 0.65 mg⋅ml-1 to 2.13-1.59 mg⋅ml-1 depending on Bacillus spp. type. It was detected that milk heating at a temperature of 100 o C for 10 min and at 135 o C for 5 s, respectively, the spores of resistant strains Bacillus licheniformis may survive and show proteolytic activity. When monitoring the reduction of casein fractions it was found that the κ-casein was the most quickly broken down to 7.43%. The values of β-casein dropped to 27.53% and α-casein to 43.95%. Under storage temperature of 4 °C the reduction of all casein fractions was lower. A reduction to 79.42% for κ-casein, 78.30% for β-casein and 85.71% for α-casein was recorded. The intensity of changes was dependent on species and strain of Bacillus spp. used, on storage temperature and heat inactivation of spores. The initial spore concentration made itself felt, too.

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EXTRACTION, PURIFICATION, AND CHARACTERIZATION OF A TRYPSIN INHIBITOR FROM COWPEA SEEDS (Vigna unguiculata)

Wang

Xia

et al. 2013

Preparative Biochemistry and Biotechnology

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Protease inhibitors against trypsin were extracted from cowpea seeds, purified, and characterized. After the seed powder was defatted with hexane, the cowpea trypsin inhibitor (CpTI) was extracted with 0.15 M NaCl for 30 min. The crude extracts were then heated at 90°C for 10 min, followed by precipitation with 40-65% saturation ammonium sulfate, by which the protein purity increased approximately 15-fold. The CpTI had approximate 88-fold and 186-fold purification after anion-exchange chromatography (Super-Q) and gel filtration (Sephadex G-200), respectively. A broad band of the purified CpTI on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) indicates a degree of heterogeneity and partial denaturation of CpTI, having a molecular mass of ∼8000 kD. Multiple peaks between 7451 and 8898 by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectroscopy also suggest heterogeneity. The purified CpTI was stable at 90°C for 60 min, pH 5-10, and 0-3.0% of NaCl. The purification method described here can be used to obtain highly purified CpTI for its studies such as risk assessment of CpTI genetically modified foods.

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Suitability of Animals' Purified Milk Caseins and Their Subunit Κ−caseins as Substrates for Subtilisin and Trypsin

Cited by 3 publications

References 7 publications

Effect of Bacillus cereus Enzymes on Milk Quality following Ultra High Temperature Processing

Effect of Bacillus cereus Enzymes on Milk Quality following Ultra High Temperature Processing

Influence of Bacillus spp. Enzymes on Ultra High Temperature-treated Milk Proteins

EXTRACTION, PURIFICATION, AND CHARACTERIZATION OF A TRYPSIN INHIBITOR FROM COWPEA SEEDS (Vigna unguiculata)

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