Lactase and Starter Culture Survival in Heated and Frozen Yogurts1

1980 ◽  
Vol 43 (1) ◽  
pp. 26-28 ◽  
Author(s):  
M. L. SPECK ◽  
J. W. GEOFFRION
Keyword(s):  
Starter Culture ◽  
Lactase Activity ◽  
Large Numbers ◽  
Heat Treated ◽  
Frozen Yogurt

Yogurt customarily contains large numbers of viable starter culture, although some yogurt is heat-treated to inactivate the starter. It was found that heating to inactivate the starter also inactivated lactase. This could have a disadvantageous effect on lactose-intolerant consumers. Manufacture of frozen yogurt did not have any appreciable damaging effect on the yogurt culture or lactase activity.

scholarly journals Staphylococcal Food Poisoning Associated with Spray-Dried Milk

1955 ◽  
Vol 53 (4) ◽  
pp. 387-397 ◽  
Author(s):  
P. H. R. Anderson ◽  
Doris M. Stone
Keyword(s):  
Spray Drying ◽  
Clinical Features ◽  
Milk Powder ◽  
Food Poisoning ◽  
Skim Milk ◽  
Skim Milk Powder ◽  
Large Numbers ◽  
Heat Treated ◽  
Drying Chamber ◽  
Spray Dried

SummaryEight explosive outbreaks of food poisoning, occurring in school canteens in England during 1953 and affecting 1190 known cases, are described. The clinical features were characteristic of the toxin type of illness. No deaths occurred.The food causing all of these outbreaks was prepared from spray-dried skim milk powder. It was not subsequently heat-treated and was usually consumed 3–4 hr. after preparation.The spray-dried milk powder proved to contain a high content of bacteria, including large numbers of Staph. aureus, of a phage pattern often associated with food poisoning. The assumption was therefore made that these outbreaks were caused by staphylococcal enterotoxin.Because the food was often consumed within 3–4 hr. of reconstitution of the milk powder—before, in fact, the staphylococci had had time to grow—it is concluded that the poisoning must have been due mainly to pre-formed toxin.Consideration is given to the opportunities for the formation of toxin in a spray-drying plant, and reasons are brought forward for believing that it is formed mainly in the balance tank where the warm milk is kept, sometimes for several hours, before passing into the final drying chamber.The processing of the milk and the precautions for preventing contamination of the finished product are discussed.

The use of Lactobacillus plantarum as starter culture in heat-treated sucuk

2016 ◽  
Vol 231 ◽  
pp. S72 ◽  
Author(s):  
Fatma Yagmur Hazar ◽  
Zeynep Feyza Yilmaz ◽  
Kubra Fettahoglu ◽  
Guzin Kaban
Keyword(s):  
Lactobacillus Plantarum ◽  
Starter Culture ◽  
Heat Treated

scholarly journals Infectious and Whole Inactivated Simian Immunodeficiency Viruses Interact Similarly with Primate Dendritic Cells (DCs): Differential Intracellular Fate of Virions in Mature and Immature DCs

2002 ◽  
Vol 76 (6) ◽  
pp. 2936-2951 ◽  
Author(s):  
I. Frank ◽  
M. Piatak ◽  
H. Stoessel ◽  
N. Romani ◽  
D. Bonnyay ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Viral Rna ◽  
Virus Particles ◽  
Large Numbers ◽  
Heat Treated ◽  
Intact Virus ◽  
Immunodeficiency Virus ◽  
Spread Of Infection ◽  
Virus Interactions ◽  
Hiv 1

ABSTRACT As potential targets for human immunodeficiency virus type 1 and simian immunodeficiency virus (HIV-1 and SIV), dendritic cells (DCs) likely play a significant role in the onset and spread of infection as well as in the induction of antiviral immunity. Using the SIV-macaque system to study the very early events in DC-virus interactions, we compared chemically inactivated SIV having conformationally and functionally intact envelope glycoproteins (2,2′-dithiodipyridine [AT-2] SIV) to infectious and heat-treated SIV. Both human and macaque DCs interact similarly with SIV without detectable effects on DC viability, phenotype, or endocytic function. As assessed by measuring cell-associated viral RNA, considerable amounts of virus are captured by the DCs and this is reduced when the virus is heat treated or derived from a strain that expresses low levels of envelope glycoprotein. Immunostaining for SIV proteins and electron microscopy indicated that few intact virus particles are retained at the periphery of the endocytically active, immature DCs. This contrasts with a perinuclear localization of numerous virions in large vesicular compartments deeper within mature DCs (in which macropinocytosis is down-regulated). Both immature and mature DCs are capable of clathrin-coated pit-mediated uptake of SIV, supporting the notion that the receptor-mediated uptake of virus can occur readily in mature DCs. While large numbers of whole viruses were preferentially found in mature DCs, both immature and mature DCs contained similar amounts of viral RNA, suggesting that different uptake/virus entry mechanisms are active in immature and mature DCs. These findings have significant implications for cell-to-cell transmission of HIV-1 and SIV and support the use of AT-2 SIV, an authentic but noninfectious form of virus, as a useful tool for studies of processing and presentation of AT-2 SIV antigens by DCs.

VIRUS INACTIVATION AND COAGULATION FACTOR PREPARATIONS

1987 ◽  
Author(s):  
B L Evatt
Keyword(s):  
Hepatitis B ◽  
Hemophilia A ◽  
Viral Infections ◽  
Coagulation Factor ◽  
Viral Inactivation ◽  
Large Numbers ◽  
Heat Treated ◽  
B Virus ◽  
Immunodeficiency Virus ◽  
Hemophilia Treatment Centers

Nonheat-treated factor concentrates were used for the therapy of congenital and acquired coagulation deficiencies until 1984. These unheated factor crticentrates, which are manufactured from pooled plasma obtained from between 2500 and 25,000 blood or plasma donors, have been epidemiologically implicated in exposure of large numbers of hemophilia patients to several viral infections Including human immunodeficiency virus (HIV), hepatitis B, and non-A non-B hepatitis. Of these, HIV has been fdund to be very heat labile. After the introduction in 1984-85 of heat treatment of concentrates to reduce the risk of! hepatitis to recipients, several studies documented a lack of HIV serconversion in patients treated with clotting-fadtor concentrates. However, subsequent reports described a few hemophilia patients who had seroconverted to HIV! after receiving heat-treated concentrate from unscreened donors. To determine the significance of these seroconvers(ions, an international survey was conducted on 11 hemophilia treatment centers in Europe, Canada, and the United Kingdcpn whose total patient population comprised more than 2300 hemophilia A patients and 400 hemophilia B patients. Only three patients were found who seroconverted beyond a 6-month period after switching to heat-treated material, a(nd no seroconversions have occurred in these centers between November 1985 and February 1987. In addition no cases of seroconversion on donor screened heat-treated concentrate have been reported since its widespread introduction to the hemophilia patients during 1985-1986. Other modes of viral inactivation are currently being tested, and they appeiar to be effective in inactivating HIV and hepatitis B virus. Some of these methods have shown some promise for the inactivation of non-A and non-B hepatitis, but more data are needed for final assessment of these methods.

scholarly journals Specific heat-temperature curves of some age-hardening alloys

1938 ◽  
Vol 168 (933) ◽  
pp. 237-264 ◽  
Keyword(s):  
Low Temperatures ◽  
Lattice Parameter ◽  
Age Hardening ◽  
Second Stage ◽  
Large Numbers ◽  
Heat Treated ◽  
Or Groups ◽  
Set Up ◽  
Lower Temperature ◽  
Two Stages

In a recent paper Gayler (1937) has dealt with the various theories of age hardening and has put forward the view that ageing takes place in two stages: in the first stage the solute atoms diffuse to planes about which precipitation proper will ultimately take place, and this gives rise to an increase in resistance to deformation and an increase in electrical resistivity without change in lattice parameter. The second stage follows the first and takes place nearly simultaneously. Some of the diffusing atoms will form molecules gradually form groups which will tend to produce a gradual decrease in resistivity and a diminution in the rate of hardening. When the molecular groups have grown to such an extent that the parent solid solution can no longer withstand the stresses set up, release of these stresses is caused by rejection of the groups, i. e. precipitation proper takes place. Once precipitation has set in them, according to Gayler's view, softening should begin. This theory tends to combine the "Knot" theory (Gayler and Preston 1932), which states that age-hardening occurs due to the formation of clusters or groups of atoms inside the parent lattice (the first stage, according to Gayler), and the precipitation theory (Merica and other 1919) which attributed hardening to the presence of large numbers of precipitated particles, probably ultramicroscopic in size, dispersed throughout the material. Naturally the formation of clusters or knots will occur at a lower temperature than precipitation, so that at low temperatures hardening will occur by the mechanism of the first stage. At high temperatures hardening may take place due to precipitation, the first stage being masked entirely. The question as to which of the tow processes is likely to be more effective in any particular alloy when heat-treated to give the maximum hardness obtainable in the hardening range is not specifically dealt with by Gayler, although it is stated that the experimental evidence available suggests that the second stage is, in general, more important. The work of Cohen (1936) on the silver-copper alloy containing 7∙5 % copper supports this contention, since his results show that hardening due to knot formation even at low temperatures (100-150°C) is very small indeed.

scholarly journals The Impact of the Adjunct Heat-Treated Starter Culture and Lb. helveticus LH-B01 on the Proteolysis and ACE Inhibitory Activity in Dutch-Type Cheese Model during Ripening

Animals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2699
Author(s):  
Monika Garbowska ◽  
Anna Berthold-Pluta ◽  
Lidia Stasiak-Różańska ◽  
Antoni Pluta
Keyword(s):  
Proteolytic Activity ◽  
Inhibitory Activity ◽  
Starter Culture ◽  
Soluble Nitrogen ◽  
Ace Inhibitory Activity ◽  
Adjunct Cultures ◽  
Heat Treated ◽  
The Impact ◽  
Cheese Model ◽  
Ace Inhibitory

Adjunct cultures are used in cheesemaking to improve the sensory characteristics of the ripened cheeses. In addition, it is known that different adjunct cultures are capable of producing enzymes with the specificity to hydrolyze caseins, leading to the release of various bioactive compounds (bioactive peptides, amino acids, etc.). The objective of this study was to evaluate the effect of adjunct heat-treated starter XT–312 and a cheese culture Lb. helveticus LH-B01 on the proteolytic activity and angiotensin converting enzymes inhibitors (ACE) in cheese models during ripening. Seven different cheese models were evaluated for: proteolytic activity using the spectrophotometric method with ortho-phthaldialdehyde (OPA), soluble nitrogen (SN), trichloroacetic acid-soluble nitrogen (TCA-SN) phosphotungstic acid-soluble nitrogen (PTA-SN), total nitrogen (TN), pH, contents of water, fat, as well as for total bacteria count (TBC), count of Lactococcus genus bacteria, count of Lb. helveticus, and number of non-starter lactic acid bacteria (NSLAB). Presence of adjunct bacterial cultures both in the form of a cheese culture LH-B01 and heat-treated XT–312 starter promoted primary and secondary proteolysis, which resulted in acceleration of the ripening process. ACE inhibitory activity and proteolytic activity was the highest throughout of ripening for cheese model with LH-B01 culture. The cheese models with the adjunct heat-treated starter were characterized by lower TBC, NSLAB and lower count of Lactococcus genus bacteria during ripening, compared to control cheeses.

scholarly journals Effect of the microbial lactase (EC 3.2.1.23) activity in yoghurt on the intestinal absorption of lactose: An in vivo study in lactase-deficient humans

1990 ◽  
Vol 64 (1) ◽  
pp. 71-79 ◽  
Author(s):  
Philippe Marteau ◽  
Bernard Flourie ◽  
Philippe Pochart ◽  
Claude Chastang ◽  
Jehan-François Desjeux ◽  
...  
Keyword(s):  
Small Intestine ◽  
Intestinal Absorption ◽  
Transit Time ◽  
Terminal Ileum ◽  
Area Under Curve ◽  
Starter Culture ◽  
Breath Hydrogen ◽  
Lactase Activity ◽  
Perfusion Technique

Breath hydrogen excretion was measured in eight lactase (EC 3.2.1. 108)-deficient volunteers ingesting 18 g lactose in the form of milk, yoghurt and heated yoghurt. Total excess hydrogen excretion (area under curve) was significantly lower after yoghurt and heated yoghurt, than after milk: 103 (SE 29), 191 (SE 32), and 439 (SE 69) respectively (P < 0.001). The oro-caecal transit time of fermentable components from yoghurt and heated yoghurt (mainly lactose) was longer than that from milk: 165 (SE 17), 206 (SE 19), v. 103 (SE 19) min (P < 0.01). An intestinal perfusion technique was used in the same subjects after ingestion on two consecutive days of 18 g lactose in yoghurt and heated yoghurt. Significantly less lactose was recovered from the terminal ileum after yoghurt than after heated yoghurt meals: 1740 (SE 260) v. 2825 (SE 461) mg (P < 0.05), and approximately one-fifth of the lactase activity contained in yoghurt reached the terminal ileum. These findings indicate that more than 90% of the lactose in yoghurt is digested in the small intestine of lactase-deficient subjects and suggest that both the lactase activity contained in the viable starter culture and a slow oro–caecal transit time are responsible for this excellent absorption.

Prevalence of Campylobacter jejuni in Turkey Carcass Processing and Further Processing of Turkey Products

1986 ◽  
Vol 49 (9) ◽  
pp. 712-717 ◽  
Author(s):  
G. R. ACUFF ◽  
C. VANDERZANT ◽  
M. O. HANNA ◽  
J. G. EHLERS ◽  
F. A. GOLAN ◽  
...  
Keyword(s):  
Campylobacter Jejuni ◽  
Muscle Tissue ◽  
Abdominal Cavity ◽  
Frozen Storage ◽  
Campylobacter Coli ◽  
Processing Plant ◽  
Turkey Meat ◽  
Large Numbers ◽  
Heat Treated ◽  
Processed Products

Presence of Campylobacter jejuni was determined at various locations in turkey carcass processing and further processing of turkey products (wieners, ham and boneless breast). Contamination of turkey carcasses with C. jejuni, in most cases, occurred on the surface of the skin or on the surface of the abdominal cavity lining. No contamination of interior muscle tissue was observed. The percentage of turkeys containing C. jejuni upon entering the processing plant varied (50 to 100%). Large numbers of C. jejuni were killed during scalding of carcasses, but extensive recontamination occurred during mechanical defeathering. After scalding, numbers of C. jejuni peaked during evisceration, but dropped to lower levels after washing. Few or no C. jejuni were recovered from the carcasses after leaving the chill tank. No C. jejuni were detected on frozen turkey carcasses, including the drip, at the wholesale or retail level. However, Campylobacter coli was detected in the drip of a few carcasses that had been in frozen storage at the wholesale level for 2 wk and 3 months. Neither C. jejuni nor C. coli was detected on frozen turkeys at the retail level. Although, in some cases, C. jejuni were recovered from turkey meat during initial stages of further processing, no C. jejuni were recovered from heat-treated, further processed products.

Competition of Thermally Injured Listeria monocytogenes with a Mesophilic Lactic Acid Starter Culture in Milk for Various Heat Treatments

2002 ◽  
Vol 65 (4) ◽  
pp. 643-650 ◽  
Author(s):  
FINNY P. MATHEW ◽  
ELLIOT T. RYSER
Keyword(s):  
Lactic Acid ◽  
Lactococcus Lactis ◽  
Starter Culture ◽  
High Heat ◽  
Uht Milk ◽  
Lactococcus Lactis Subsp ◽  
Heat Treated ◽  
Tryptose Phosphate Broth ◽  
Fermentation Period ◽  
Ultrahigh Temperature

Overnight tryptose broth cultures of three L. monocytogenes strains were combined, centrifuged, suspended in 200 ml of tryptose phosphate broth, and heated at 56°C for 20 min and at 64°C for 2 min to obtain low-heat-injured (LHI) and high-heat-injured (HHI) cells, respectively, showing &gt;99.0% injury. Flasks containing 200 ml of raw, low-heat-treated (56°C for 20 min), high-heat-treated (64°C for 2 min), pasteurized, and ultrahigh-temperature (UHT) milk were tempered to 31.1°C and inoculated to contain 104 to 106 CFU/ml of LHI, HHI, or healthy L. monocytogenes cells and a commercial Lactococcus lactis subsp. lactis–Lactococcus lactis subsp. cremoris starter culture at levels of 0.5, 1.0, and 2.0%. Numbers of healthy and injured L. monocytogenes cells and starter organisms were determined using tryptose phosphate agar with or without 4.0% NaCl at selected intervals during 24 h of incubation at 31.1°C. The presence of L. monocytogenes did not adversely affect the growth of the starter culture at any inoculation level. Overall, L. monocytogenes survived the 24-h fermentation period and grew to some extent. In starter-free controls, 76 to 81% of LHI cells and 59 to 69% of HHI cells were repaired after 8 h of incubation, with the lowest repair rates being observed for raw rather than heat-treated or pasteurized milk. Increased injury was observed for healthy L. monocytogenes cells at the 1.0 and 2.0% starter levels, with less injury seen for LHI and HHI cells. Raw and subpasteurized milk allowed less of a decrease in the percentage of injury and also showed higher numbers of injured cells than did pasteurized and UHT milks. These findings may have important implications for the survival of Listeria spp. in certain cheeses that can be prepared from raw or heat-treated milk.

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