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tom T. 64, nr 4
17-21
PL
Do dobrze znanych korzyści wynikających z ogrzewania mikrofalowego należy zaliczyć szybkie i bezpośrednie ogrzewanie produktu w całej masie oraz brak kontaktu z powierzchnią grzejną, a dzięki temu, zapobieganie przegrzewaniu produktu i blokowaniu przepływu. W artykule przedstawiono również wpływ ogrzewania mikrofalowego na jakość mleka. Retentat po mikrofiltracji mleka oraz śmietankę (28 % tłuszczu) poddano ogrzewaniu mikrofalowemu w systemie ciągłym w temp. 110-138°C przez 5 s. Po sterylizacji próbki przechowywano w temp. 5š1°C oraz 25š1°C do 5 dni. Stwierdzono, że ogrzewanie śmietanki i retentatu odpowiednio w temp. powyżej 125 i 130°C przez 5 s, było skuteczne do sterylizacji mikrofalowej tych produktów. Ogrzewanie mikrofalowe nie powodowało niekorzystnych zmian smaku i zapachu produktu.
EN
Microwave treatment has well known potential advantages, which are derived from the rapid and direct heat transfer to the product, even temperature distribution throughout the material and the lack of contact with hot surfaces, which avoids overheating of the product and formation of additional heat transfer resistance. In this paper the effects of microwave treatment on the quality of milk were also presented. Retentat after milk microfiltration and cream (28 % fat) were subjected to the continuous-flow microwave treatment at 110-138°C for 5 s. After heat treatment samples were stored at 5š1°C and 25š1°C for up to 5 days. It was observed that the heating temperatures above 125 and 130°C / 5 s for cream and retentat, respectively, were effective as microwave sterilization. Microwave heating had no adverse effects on product flavour.
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nr 02
50-51
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tom 63
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nr 03
336-339
EN
The aim of this study was to identify certain biochemical features in 691 B. cereus strains isolated from raw milk and the environment of milk production. At the first stage of the study the following abilities were observed in all the examined strains: the fermentation of D-glucose in facultative anaerobic conditions, the production of acetylmethylcarbinol (Voges-Proskauer reaction), the reduction of nitrates to nitrites, the production of acid from D-xylose, L-arabinose, D-mannitol and galactose, the hydrolysis of casein, gelatine and tributyrin and the ability of haemolysis. At the second stage, 142 chosen strains were subject to a detailed analysis of biochemical features with the application of API 50CH and API 20E tests (BioMerieux Polska Sp. z o.o.). The study confirmed the occurrence of the typical features for B. cereus as specified in Bergey’s taxonomy in all the examined strains: i.e. the ability of gelatine and casein hydrolysis, the fermentation of D-glucose, the production of acetoine, the reduction of nitrates to nitrites, and the lack of the ability of D-xylose and L-arabinose fermentation. 27% of the examined strains had an ability of lactose fermentation, which is untypical for B. cereus. 72% of the strains had the ability of tributyrin hydrolysis.
PL
Niniejszy artykuł dotyczy wpływu aktywności wody (aw) na procesy biologiczne oraz przemiany chemiczne i fizyczne w wybranych produktach mlecznych. W części I artykułu omówiono podstawowe zagadnienia i definicje dotyczące aktywności wody, a także scharakteryzowano i podzielono produkty mleczne pod względem wartości tego parametru. Szczególną uwagę zwrócono na praktyczne aspekty jakości i higieny produktów w powiązaniu z aktywnością wody (aw). Przedstawiono wpływ aktywności wody na ciepłooporność mikroorganizmów, reakcje oksydacji tłuszczów i nieenzymatycznego brunatnienienia w proszku mlecznym. Opisano także przemianę szklistą, w wyniku której przyspieszona jest krystalizacja amorficznej laktozy oraz jej wpływu na pogorszenie jakości mleka w proszku.
EN
This work presents a literature review pertinent to the effects of water activity (aw) on the course of biological processes, as well as chemical and physical changes in the selected dairy products. In the first part of this manuscript the fundamentals and definitions of the water activity as well as dairy products were discussed and characterized as well as classified in terms of value for the mentioned parameter. A special attention was paid to several key aspects of practical importance for dairy product quality and hygiene. The topics elaborated in detail include the effects of aw on: micro-organisms' heat-resistance, lipid oxidation reactions and non-enzymatic browning in milk powder. There was also characterized the glass transition process, which resulted in the acceleration of amorphous lactose crystallization, as well as the effect of this change on the deterioration of milk powder quality.
EN
The Bacillus cereus species of bacteria is commonly found in the environment, as well as in raw materials and foodstuffs. It may cause outbreaks of food-borne infections in humans. The course of the infection can be twofold: it can either take the form of intoxication - caused by ingestion of food containing B. cereus emetic toxin (cereulide) - or toxicoinfection, resulting from the presence of enterotoxic B. cereus strains in food which produce diarrheal type of toxins in the small intestine. The ability of B. cereus to adapt to certain stress conditions, such as low pH, can influence their survival in the gastrointestinal tract, mainly the stomach. These bacteria can initially adapt to low pH in the course of food production or in the original environment of their occurrence, i.e. in the soil. This behavior leads to a higher acid resistance of the cells and, consequently, in the case of contaminated food ingestion, it may facilitate the transit of the pathogen to the upper gastrointestinal tract. The article discusses various aspects of B. cereus survival inside the human gastrointestinal tract, paying special attention to its upper part. The issues of B. cereus capacity to counter adverse environmental conditions inside the human stomach, as well as the so called cross-resistance of the bacteria have been elucidated. The following factors have been taken into consideration: the biological state of bacteria (vegetative or spore form), growth temperature profile, phases of vegetative cell growth, as well as the possible prior exposure of the bacteria to low pH. The influence of these factors on the resistance of B. cereus spores and vegetative forms to high acidity has been examined. Finally, the effect of digestive enzymes (pepsin) on the survival of B. cereus spores and vegetative forms in the medium simulating the human stomach environment have been analyzed.
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nr 1
79-84
PL
Celem artykułu jest omówienie możliwości rozwoju w serach podpuszczkowych dojrzewających drobnoustrojów patogennych, takich jak: Listeria monocytogenes, Escherichia coli, Salmonella sp. oraz Staphylococcus aureus. Przeanalizowano wpływ różnych czynników technologicznych wpływających na rozwój patogenów w serach. Dokonano przeglądu piśmiennictwa dotyczącego jakości mikrobiologicznej serów rynkowych. Przedstawiono przypadki zatruć pokarmowych -wywołanych spożyciem serów dojrze¬wających, zanieczyszczonych drobnoustrojami chorobotwórczymi.
EN
The aim of the study was to review the possibilities of growth in rennet cheeses pathogenic microorganisms, such as: Li¬steria monocytogenes, Escherichia coli, Salmonella sp. and Staphylococcus aureus. The influence of some factors on the growth of pathogenic bacteria was analysed. The review of the literature concerning the microbiological quality of mar¬ket cheeses was made. The cases of foodpisonings, caused by consumption of rennet cheeses, contaminated with pathogenic bacteria were shown.
PL
Celem badań była ocena jakości mikrobiologicznej lodów z rynku warszawskiego w aspekcie wymagań PN-99/A-86431 i rozporządzenia Ministra Rolnictwa i Rozwoju Wsi z 5 lipca 2002 r. (Dz.U. Z 25 lipca 2002 r., Nr 117, poz. 1011). W 87 próbkach lodów pochodzących z rożnych punktów sprzedaży na terenie Warszawy oznaczono liczbę drobnoustrojów ogółem i liczbę bakterii z grupy coli. W 97,7% próbek ogólna liczba drobnoustrojów nie przekraczała limitów podanych w PN (m = 5x10⁴; M = 2,5x10⁵ j.t.k./g) oraz w rozporządzeniu MRiRW (m = lx10⁵; M = 5x10⁵ j.t.k./g). W 86% próbek liczba bakterii z grupy coli nie przekraczała 10 j.t.k./g. W porównaniu z wymaganiami PN dla bakterii z grupy coli w lodach (m = 10²; M = 10³), 6 próbek lodów nie spełniło kryterium m, z czego w jednej próbce lodów została przekroczona wartość M. Rozporządzenie MRiRW zaostrza wymagania odnośnie liczby bakterii z grupy coli w lodach (m = 10; M= 100). Wedle tych kryteriów przekroczenie wartości m odnotowano w 10 próbkach lodów.
EN
The target of present research was opinion of microbiological quality of ice creams in Warsaw market in aspect of requirements of the Polish Standard for the ice cream (PN-99/A-86431) and the Regulation of the Minister of Agriculture and Rural Development. A total of 87 samples of ice creams were analysed for standard plate count and coliform count. The results show that total bacterial count was considerably (in 97,7% of samples) below the limits of the Polish Standard (m = 5x10⁴; M = 2,5x10⁵ cfu/g) and of the Regulation of the Minister of Agriculture and Rural Development (m = 1x10⁵; M = 5x10⁵ cfu/g). 86% of the samples had a coliform count lower than 10 cfu/g. In refer to requirements of Polish Standard for coliform number in ice cream (m = 10²; M= 10³ cfu/g), 6 samples failed to meet the requirements of the m value for coliform bacteria, and additionally 1 sample - M value for coliform bacteria. The Regulation of the Minister of Agriculture and Rural Development quote sharpens requirements for coliform bacteria (m = 10; M= 100 cfu/g). According to this criteria, excess of the m value were noted down in 10 samples of ice creams.
EN
Bacillus cereus-mediated food poisoning of the diarrhoeal type is related to the production of the following extracellular factors by the bacteria: haemolysin BL (enterotoxin HBL), non-haemolytic toxin (NHE), and cytotoxin (CytK), as well as haemolysins IV and cereolysin O, both of which have been scarcely examined and discussed in the literature. This article reviews the literature containing current data that revise former theories on the pathogenesis of the diarrhoeal form of B. cereus-mediated food poisoning. The results of in vitro studies confirming the survival of vegetative cells in the stomach and intestine environment prove that the biological state of the examined bacteria does not have any influence on the occurrence of the diarrhoeal syndrome. After contaminated food has been ingested, B. cereus spores/vegetative cells pass the stomach and reach the small intestine. There the spores can germinate to become vegetative cells that multiply and produce enterotoxins. The enterotoxins, finally, affect the intestinal epithelium, which results in diarrhoea. So far this type of food poisoning has been attributed to enterotoxin activity, excluding any kind of interaction between the host and the microorganism. However, according to the results of the latest research, the interaction between the epithelial cells and the cells of B. cereus contributes to the occurrence of infection symptoms, and the adhesion of B. cereus to the intestinal epithelium is prerequisite for the onset of the diarrhoeal syndrome. This article illustrates different aspects of B.cereus survival inside the human gastrointestinal tract, paying special attention to its lower part, i. e. the small intestine. The effect of exposure to bile salts and other factors, as well as to the indigenous microflora of the gastrointestinal tract, on B.cereus survival has been discussed. The article also elucidates issues relating to the mechanism of bacterial-epithelial cell cross-talk (interaction), which is induced when a pathogen comes into contact with enterocytes.
PL
Na podstawie przebadanych w latach 1995-2001 254 próbek krajowych jogurtów i biojogurtów rynkowych (naturalnych i smakowych) w 97% próbek stwierdzono, że liczba mikroflory charakterystycznej dla jogurtu wynosiła powyżej 10⁷ j.t.k./g. Liczba bifidobakterii jako mikroflory dodatkowej była zadowalająca (powyżej 10⁶ j.t.k./g) tylko w 35% badanych próbek biojogurtów. W latach 1995-2001 wyraźnie poprawiła się jakość higieniczna jogurtów i biojogurtów określana na podstawie obecności bakterii z grupy coli. Bakterie te były nieobecne w 0,01 g jogurtu we wszystkich badanych próbkach od 1998 r. Obecność pleśni i drożdży powyżej 10 j.t.k. w 1 g jogurtu lub biojogurtu w latach 1995-1997 stwierdzono w 73% próbek, a w latach 2000-2001 w 19% próbek.
EN
The microbiological quality of 254 samples of yoghurt obtained from retail trade of Warsaw market was surveyed in 1995- 2001. It was found that number of characteristic yoghurt microflora exceeded 10⁷ CFU/g in 97% of samples. The number of bifidobacteria as additional microflora was fair (more than 10⁶ CFU/g) in 35% samples of yoghurt. The hygienic quality of yoghurt was improved distinctly. From 1998 coliform bacteria were not detected in 0,01 g of any tested samples. The number of yeast and moulds above 10 CFU/g of yoghurt was detected in 73% and 19% of the samples examined in 1995-1997 and 2000-2001, respectively.
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