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At least 325 records · Page 18Linked to original sources
PubMed1999

Weak organic acid treatment causes a trehalose accumulation in low-pH cultures of Saccharomyces cerevisiae, not displayed by the more preservative-resistant Zygosaccharomyces bailii.

Weak organic acid food preservatives exert pronounced culture pH-dependent effects on both the heat-shock response and the thermotolerance of Saccharomyces cerevisiae. In low-pH cultures, they inhibit this stress response and cause strong induction of respiratory-deficient petites amongst the survivors of lethal heat treatment. In higher pH cultures, 25 degrees C sorbic acid treatment causes a strong induction of thermotolerance without inducing the heat-shock response. In this study we show that trehalose, a major stress protectant, accumulates rapidly in S. cerevisiae exposed to sorbate at low pH. In pH 3.5 cultures, a 25 degrees C sorbate treatment is as effective as a 39 degrees C heat shock in inducing trehalose. This weak-acid-induced trehalose accumulation is enhanced in the pfk1 S. cerevisiae mutant, indicating that it arises through inhibition of glycolysis at the phosphofructokinase step. The more preservative-resistant food spoilage yeast Zygosaccharomyces bailii differs from S. cerevisiae in that: (1) its basal thermotolerance is not strongly affected by culture pH; (2) it does not display trehalose accumulation in response to 25 degrees C sorbate treatment at low pH; and (3) there is no induction of respiratory-deficient petites during lethal heating with sorbate. This probably reflects Z. bailii being both petite-negative and better equipped for maintenance of homeostasis during weak-acid, pH or high-temperature stress.

Food Preservatives↗
PubMed2004

Freezing: an underutilized food safety technology?

Freezing is an ancient technology for preserving foods. Freezing halts the activities of spoilage microorganisms in and on foods and can preserve some microorganisms for long periods of time. Frozen foods have an excellent overall safety record. The few outbreaks of food-borne illness associated with frozen foods indicate that some, but not all human pathogens are killed by commercial freezing processes. Freezing kills microorganisms by physical and chemical effects and possibly through induced genetic changes. Research is needed to better understand the physical and chemical interactions of various food matrices with the microbial cell during freezing and holding at frozen temperatures. The literature suggests that many pathogenic microorganisms may be sublethally injured by freezing, so research should be done to determine how to prevent injured cells from resuscitating and becoming infectious. Studies on the genetics of microbial stress suggest that the induction of resistance to specific stresses may be counteracted by, for example, simple chemicals. Research is needed to better understand how resistance to the lethal effect of freezing is induced in human pathogens and means by which it can be counteracted in specific foods. Through research, it seems possible that freezing may in the future be used to reliably reduce populations of food-borne pathogens as well as to preserve foods.

Bacteria↗
PubMed1984

Radiation preservation of foods of plant origin. Part 1. Potatoes and other tuber crops.

In Part 1 of a planned series of articles on preservation of foods of plant origin by gamma irradiation, the current state of research on the technological, nutritional, and biochemical aspects of sprout inhibition of potatoes and other tuber crops are reviewed. These include varietal responses, dose effects, time of irradiation, pre- and postirradiation storage, and handling requirements; postirradiation changes in carbohydrates, ascorbic acid, amino acids, and other nutrients; respiration; biochemical mechanisms involved in sprout inhibition; wound healing and microbial infection during storage; formation of wound and light-induced glycoalkaloids and identification of irradiated potatoes. The culinary and processing qualities with particular reference to darkening of boiled and processed potatoes are discussed. The prospects of irradiation on an industrial scale as an alternative to chemical sprout inhibitors or mechanical refrigeration are considered.

Amino Acids↗
PubMed1980

[Various methods for the determination of preservatives in food. I. Extraction and spectrophotometric determinations (author's transl)].

In the Federal Republik of Germany formic acid, benzoic acid, propionic acid, sorbic acid and the esters of p-hydroxybenzoic acid were permitted as food-additives. They can be extracted together from acidified materials by means of perforation with ether. During distillation the preservatives are fixed by sodium hydroxide. The alkaline extract can then be used directly for various photometric (Part I) and chromatographic (Part II) determinations. All preservatives except propionic acid can be identified and determined by simple and specific color reaction. From the alkaline extract, benzoic acid, sorbic acid and the esters of p-hydroxybenzoic acid can be separated as the free acid by thin-layer chromatography on silica gel. Determination of the remission at 232 nm and 260 nm and of the reduction in fluorescence are employed for the photometric in situ evaluation of the thin-layer chromatograms.

Benzoates↗
PubMed2000

Effect of preservation techniques and food additives on staphylococcal thermonuclease.

Staphylococcal TNase was found to retain its activity fully even after exposure to chilling and refrigeration temperatures for 24 h. It was not inhibited by p-hydroxy benzoic acid, sorbic acid, methylpropyl p-benzoic acid and sodium nitrite in the concentration range of 0.04 to 0.5%, whereas it was inhibited by 100 ppm of butylated hydroxy anisole (BHA), 200 ppm of butylated hydroxy toluene (BHT), and 300 ppm of propyl gallate. There was not complete inhibition of S. aureus and TNase by tocopherol (TP) and ascorbic acid (AA) even at concentration of 300 ppm. These results indicate that TNase can be used as an index of potentially enterotoxin producing S. aureus contamination in foods subjected to chilling, refrigeration as well as in foods containing common preservatives and antioxidants.

Animals↗
PubMed1991

Nasopharyngeal carcinoma: epidemiology and dietary factors.

Nasopharyngeal carcinoma (NPC) is a disease with a remarkable racial and geographical distribution. It is very rare (incidence of less than 1 per 100,000 person-years) in most parts of the world, and in only a handful of populations does this low-risk profile deviate; these groups include people in southern China, Eskimos and other natives of the Arctic region, natives of south-east Asia, and the mainly Arab populations of North Africa and Kuwait. Convincing evidence implicates dietary factors as the primary cause of NPC among Chinese. A series of case-control studies conducted in various Chinese populations with distinct risks of NPC, ranging from the very high-risk Cantonese populations to the relatively low-risk northern Chinese, have suggested that ingestion of salted fish and other kinds of preserved foods constitutes the most important cause of NPC among these people. Preliminary data on Malays in south-east Asia, Eskimos in Alaska and Arabs of North Africa also suggests that ingestion of preserved foods by these population groups may be responsible for their raised incidence of NPC.

Animals↗
PubMed1990

Diet and nasopharyngeal carcinoma.

Nasopharyngeal carcinoma (NPC) is a disease with a remarkable racial and geographical distribution. It is very rare (incidence of less than 1 per 100,000 person-years) in most parts of the world and only a handful of populations are known to deviate from this low-risk profile, which include people of southern China. Eskimos and other natives of the Arctic region, natives of southeast Asia, and mainly Arab populations of north Africa and Kuwait. There is now convincing evidence implicating dietary factors as the primary cause of NPC among Chinese. A series of case-control studies conducted in various Chinese populations with distinct risks of NPC, ranging from the very high-risk Cantonese to the relatively low-risk Northern Chinese, have suggested that ingestion of salted fish and other kinds of preserved foods by the Chinese constitutes the most important cause of NPC development among these people. Preliminary data on Malays in southeast Asia, Eskimos in Alaska, and Arabs of north Africa also suggest that ingestion of preserved foods by these population groups may be responsible for their raised incidence of NPC.

Animals↗
PubMed1990

Diet and nasopharyngeal carcinoma.

Nasopharyngeal carcinoma (NPC) is a disease with a remarkable racial and geographical distribution. It is very rare (incidence of less than 1 per 100,000 person-years) in most parts of the world and only a handful of populations are known to deviate from this low-risk profile, which include people of southern China, Eskimos and other natives of the Arctic region, natives of southeast Asia, and the mainly Arab populations of north Africa and Kuwait. There is now convincing evidence implicating dietary factors as the primary cause of NPC among Chinese. A series of case-control studies conducted in various Chinese populations with distinct risks of NPC, ranging from the very high-risk Cantonese to the relatively low-risk Northern Chinese, have suggested that ingestion of salted fish and other kinds of preserved foods by the Chinese constitutes the most important cause of NPC development among these people. Preliminary data on Malays in southeast Asia, Eskimos in Alaska, and Arabs of north Africa also suggest that ingestion of preserved foods by these population groups may be responsible for their raised incidence of NPC. Regardless of race and geography, the commonest form of nasopharyngeal cancers are those that arise from the epithelial cells lining the nasopharynx. These carcinomas (commonly referred to as NPCs) constitute 75-95% of nasopharyngeal cancers in low-risk populations and virtually all nasopharyngeal cancers in high-risk populations (Ho, 1971; Sugano et al, 1978; Levine and Connelly, 1985).

Animals↗
PubMed1986

Radiation preservation of foods of plant origin. Part IV. Subtropical fruits: citrus, grapes, and avocados.

Current information on the use of ionizing radiation for improving the storage of subtropical fruits like citrus, grapes, and avocados is reviewed. The feasibility of applying radiation either alone or in combination with other physical or chemical treatments for the control of postharvest fungal diseases is considered. Irradiation effects on the physiology of the fruits as related to respiration, ethylene evolution, changes in major chemical constituents, and quality are discussed. The recent trends in the possible use of irradiation as an alternative treatment to chemical fumigants for disinfestation of citrus and avocados and the prospects for the future application of irradiation for preservation of some of these fruits are outlined.

Citrus↗
PubMed1998

Nasopharyngeal carcinoma in Malaysian Chinese: salted fish and other dietary exposures.

We interviewed 282 histologically confirmed cases of nasopharyngeal carcinoma (NPC) in Chinese residents of Selangor and the Federal Territory, Malaysia, and an equal number of Chinese age-, sex-, and length-of-residence-matched controls sampled from the general population. Consumption of 55 dietary items during childhood, and 5 years pre-diagnosis of NPC, was analyzed by univariate and multivariate methods. Four salted preserved foods (fish, leafy vegetables, egg and root), fresh pork/beef organ meats and beer and liquor consumption exhibited strong positive associations, and 4 vegetable/fruit combinations strong negative associations with NPC. Factor analysis and multivariable modeling using estimated factor scores strongly supported separate effects on NPC of vegetables/fruits, salted preserved foods, pork/beef organ meats and beer/liquor consumption. Multivariable modeling associated NPC most clearly with high consumption of salted fish, salted eggs, pork/beef liver and beer and low consumption of Chinese flowering cabbage, oranges/tangerines and shrimp. A strong residual association of social class with NPC remained after adjustment for diet, which is consistent with a substantial role for non-dietary environmental factors.

Adult↗
PubMed1996

Applications of the bacteriocin, nisin.

Nisin was first introduced commercially as a food preservative in the UK approximately 30 years ago. First established use was as a preservative in processed cheese products and since then numerous other applications in foods and beverages have been identified. It is currently recognised as a safe food preservative in approximately 50 countries. The established uses of nisin as a preservative in processed cheese, various pasteurised dairy products, and canned vegetables will be briefly reviewed. More recent applications of nisin include its use as a preservative in high moisture, hot baked flour products (crumpets) and pasteurised liquid egg. Renewed interest is evident in the use of nisin in natural cheese production. Considerable research has been carried out on the antilisterial properties of nisin in foods and a number of applications have been proposed. Uses of nisin to control spoilage lactic acid bacteria have been identified in beer, wine, alcohol production and low pH foods such as salad dressings. Further developments of nisin are likely to include synergistic action of nisin with chelators and other bacteriocins, and its use as an adjunct in novel food processing technology such as higher pressure sterilisation and electroporation. Production of highly purified nisin preparations and enhancement by chelators has led to interest in the use of nisin for human ulcer therapy, and mastitis control in cattle.

Animals↗
PubMed2005

Functional properties of edible agar-based and starch-based films for food quality preservation.

Edible films made of agar (AG), cassava starch (CAS), normal rice starch (NRS), and waxy (glutinous) rice starch (WRS) were elaborated and tested for a potential use as edible packaging or coating. Their water vapor permeabilities (WVP) were comparable with those of most of the polysaccharide-based films and with some protein-based films. Depending on the environmental moisture pressure, the WVP of the films varies and remains constant when the relative humidity (RH) is >84%. Equilibrium sorption isotherms of these films have been measured; the Guggenheim-Anderson-de Boer (GAB) model was used to describe the sorption isotherm and contributed to a better knowledge of hydration properties. Surface hydrophobicity and wettability of these films were also investigated using the sessile drop contact angle method. The results obtained suggested the migration of the lipid fraction toward evaporation surface during film drying. Among these polysaccharide-based films, AG-based film and CAS-based film displayed more interesting mechanical properties: they are transparent, clear, homogeneous, flexible, and easily handled. NRS- and WRS-based films were relatively brittle and have a low tension resistance. Microstructure of film cross section was observed by environmental scanning electron microscopy to better understand the effect of the structure on the functional properties. The results suggest that AG-based film and CAS-based films, which show better functional properties, are promising systems to be used as food packaging or coating instead of NRS- and WRS-based films.

Agar↗