Ultra-high Temperature Treated Milk Research Articles

Changes occurring in stabilized ultra-high-temperature-treated whole milk during storage.

This Research Communication describes the relationship between casein, free fatty acids (FFAs) and the storage period of ultra-high temperature-treated (UHT) whole milk observed for a period of 120 d of labelled shelf-life. Moreover, we aim to estimate the daily rate of casein degradation in UHT whole milk, and the total length of time estimated for its full degradation. With this aim, ten sets of samples were evaluated from batches of UHT milk manufactured by a dairy processing plant in Parana State, Brazil on 10 different days. Each set was comprised of one liter of raw milk and 12 units of 1 litre cartons of UHT milk, and represented one batch of production. Total mesophilic (TMC), psychrotrophic (TPC), and somatic cell counts (SCC) of raw milk were assessed. UHT milk was assessed for fat (%), sialic acid (mg/l), casein (%), and FFA contents. TMC ranged from 3·5 × 106 to 3·1 × 107 CFU/ml; TPC, from 106 UFC/ml and higher; and SCC, from 18 × 104 SC/ml to 4·83 × 105 CS/ml. Casein (r = -0·991; R2 = 0·9822) and FFA (r = 0·962; R2 = 0·9245) contents, and storage time of UHT milk were correlated (P < 0·05). The rate of casein hydrolysis was estimated as 0·021 g/100 g UHT whole milk/day. A complete breakdown of casein was estimated to occur by the 560th day post-manufacture. Although age gelation was not observed in our study, the report herein corroborates the understanding that the microbiological quality and SCC of raw milk are important components involving the integrity of casein and lipids of UHT milk during shelf-life.

Survival analysis, consumer perception and physico-chemical analysis of low fat UHT milk stored for different time periods

Survival analysis based on consumers' acceptance or rejection of milk of different storage ages, was used to validate the shelf-life of low fat ultra-high temperature treated (UHT) milk in high density polyethylene bottles, as previously determined by a multivariate accelerated shelf-life test (MASLT). UHT milk between 120 and 290 d of storage were evaluated. Based on 50% of consumers rejecting the product, the shelf-life was estimated to be 214 d, validating the shelf-life of 211 d estimated by the MASLT. In addition, consumers completed check-all-that-apply attribute questions and rated the acceptability of the milk. The consumers noted positive sensory attributes more frequently in fresher milk samples with an increase in negative attributes with storage. Along with this, hedonic scores for the milk decreased and physicochemical and enzymatic reactions associated with the deterioration of UHT milk increased with storage.

Differences in Sensitivity of Milk Fermentation to Lactating Cow and Dry Cow Intra-mammary Antimicrobial Agents

Antimicrobial agents for treatment of mastitis in dairy cows may result in drug residues in milk, suppressing production of fermented dairy products. The objective of this study was to compare the effects of lactating cow and dry cow intra-mammary antimicrobial preparations on fermentation of milk. Samples of ultra-high temperature-treated milk + starter culture (Lactococcus lactis subsp. lactis), were prepared. Using serial double dilution, erythromycin-trimethoprim lactating cow formula was added to five samples at 62.5-1000 mg/L and cloxacillin benzathine dry cow preparation to another five at 75-1200mg/L. A negative control with neither starter culture nor antimicrobial agent, and a positive control with starter culture but no antimicrobial agent were included. All samples were incubated at 30° C for two days and osmolarity (mOsmoles/L) monitored by a cryoscopic osmometer. From a starting value of 301±1.72 for fresh milk, osmolarity of non-inoculated milk did not rise beyond 314±7.07. Maximum osmolarity of inoculated milk attained in the presence of erythromycin-trimethoprim was 328±0.97, in contrast to 507±35.53 in the presence of cloxacillin benzathine. Hence hydrophilic lactating cow antimicrobial formulas exert a highly significant inhibitory effect on milk fermentation compared to hydrophobic dry cow antimicrobial preparations.

Storage-induced changes in the sensory characteristics and volatiles of conventional and lactose-hydrolyzed UHT processed milk

Storage-induced changes are known to be more prominent in lactose-hydrolyzed (LH) milk compared to conventional milk. Therefore the present study aimed at identifying off-flavors resembling from formation of volatiles during storage of ultra-high temperature treated (UHT) LH milk and conventional UHT milk. Further, the influence of heat processing, indirect or direct, on UHT LH milk was also examined. Storage-induced changes in sensory attributes, volatiles and primary amines were investigated during a 4 months period. Conventional UHT milk (with 5 % lactose) processed using indirect heat treatment (CONVI) and two types of UHT LH milk (with less than 0.01 % lactose) produced using either direct heat treatment (LHD) or indirect heat treatment (LHI) were represented in the study. Sensory descriptive analysis showed that fresh samples of CONVI, LHI and LHD differed in sensory properties and the samples could be differentiated according to boiled and stale aroma as well as color saturation. Differentiation of the fresh samples based on the volatile gas chromatography–mass spectrometry profile was not achievable. During storage, samples developed differently with respect to sensory characteristics, volatiles and the amount of primary amines. Partial least squares models (PLS1) including only methyl ketones and aldehydes showed that 2-butanone, 2-pentanone, 2-heptanone, 2-nonanone, heptanal, octanal and nonanal predicted stale flavor. Bitter taste, on the other hand, correlated with the amount of primary amines (Pearson’s correlation, r 2 = 0.71). This finding indicates that storage-induced changes in sensory characteristics, volatiles and primary amines depend on both differences in lactose content and the applied heat processing.

Application of osmometry in quality analysis of milk

The aim of this study was to evaluate osmometry as a tool in quality analysis of milk. The osmolality of raw milk, sterilized milk, skimmed UHT (ultra-high temperature-treated) milk, pasteurized milk, standardized UHT milk and fermented milk (Lactococcus lactis culture) was determined by freezing point osmometry. The relationship between osmolality and pH of fermented milk was further investigated during spontaneous fermentation of UHT milk at 37°C for 48h. Average osmolality values (mean ± SD) were raw milk-290.2 ± 7.98, sterilized milk-290.2 ± 5.84, skimmed UHT milk-290.8 ± 3.31, pasteurized milk-283.6 ± 2.28, standardized UHT milk-281 ± 4.59 and fermented milk-466.0 ± 17.30 mOsmoles kg(-1). For fresh milk samples, 88% showed normal osmolality, 8% were hypo-osmotic and 4% hyper-osmotic. Fermentation studies revealed a high negative correlation between osmolality and pH, with a correlation coefficient of -97.49%. Hypo-osmotic milk shows mixing of milk with water along the production chain. Hyper-osmotic milk indicates fermentation of milk at high ambient temperatures or with prolonged storage. It may also reveal adulteration of fresh milk with a soluble substance. Osmolality was highest for fermented milk owing to production of lactic acid during fermentation. This was confirmed by the high negative correlation between osmolality and pH of milk in fermentation studies. Hence the osmolality of fermented milks may be used as an index of the extent of fermentation.

Aflatoxin M1 in raw, UHT milk and dairy products in Sicily (Italy)

A survey on 73 milk samples from different animal breeds and 24 dairy products samples from Sicily, Italy, was carried out for the presence of aflatoxin M1 (AFM1) by LC-fluorescence detection after immunoaffinity cleanup. AFM1 was detected in 48% and 42% of the milk and dairy samples at concentration ranges between <5.0–16.0 and <5.0–18.0 ng L−1, respectively. Within the raw milk samples, 92% had an AFM1 content below 5.0 ng L−1, in 7% of the cases it was in the range 5.0–10.0 ng L−1 and 1% was contaminated between 10.0 and 20.0 ng L−1. For the dairy products, ultra-high-temperature treated (UHT) milk, milk cream and cheese, the incidence was 42%, of which 83% contained less than 5.0 ng L−1 and 17% contained 10.0–20.0 ng L−1 AFM1. The levels of contamination found justify continuous monitoring for public health and to reduce consumer exposure.

Formation, Stability, and Properties of an Algae Oil Emulsion for Application in UHT Milk

This study aimed to develop a technology for producing ultrahigh temperature ultrahigh temperature-treated (UHT) milk enriched with docosahexaenoic acid. Starch hydrophobically modified with octenyl succinic anhydride (OSA starch) was used as an emulsifier to make algae oil emulsion in UHT milk. In this study, the stability of oil-in-water emulsions was examined. The emulsification of 10 % algae oil model emulsion with 10 % OSA starch and 40 % corn syrup had small droplets and was completely stable. Milk enriched with unsaturated fatty acids was heated using an indirect UHT treatment, and the milk was then stored at different temperatures. The oxidative stability of fish oil-enriched milk was investigated by measuring peroxide value, measuring volatile secondary oxidation products, and carrying out sensory analysis. All of the milk samples were stable. In summary, fish oil-enriched milk is resistant to oxidation. Algae oil-enriched drinking milk is a stable product during 11 weeks of storage. Application of high storage temperature (40 °C) does not significantly increase the oxidation process. The present study suggested that stable algae oil emulsion can be formed by OSA starches with corn syrup, and a food formulation test confirmed the successful application of algae oil emulsion to extend the shelf life of milk.

Application of osmometry in monitoring fermentation of milk.

Fermentation of milk yields many other products apart from lactic acid. This study was carried out to monitor the progress of fermentation by measuring the total solute concentration i.e. osmolality in fermenting milk. Five samples each of raw milk, pasteurised milk and UHT (ultra-high temperature treated) milk were incubated aerobically without starter culture at 37°C for 3 days. Osmolality was measured by freezing point depression at the beginning of incubation and at exactly the same time for the next 3 days. Osmolality of raw milk (mean±SD) increased from 290.2±8.0 to 405.6±31.06 mOsmoles kg in one day and stabilized around this 1

Occurrence of aflatoxin M1 in some samples of UHT, raw & pasteurized milk from Indian states of Karnataka and Tamilnadu

Aflatoxin M1 (AFM1) is a toxic metabolite found in the milk of lactating animals which have consumed feedstuffs contaminated with aflatoxin B1. Ultra high temperature treated (UHT) milk is a product which is becoming popular in developing countries like India as there is a lack of proper cold storage or refrigeration facilities. In this study, 45 samples of UHT milk of popular brands prevalent in the market were analyzed for the presence of AFM1 by reversed phase HPLC using fluorescent detector after cleanup of sample with immunoaffinity columns. All samples of plain UHT milk were positive for AFM1 and 38% of these contained levels more than 0.5μg/kg, the maximum permitted limit prescribed by the Codex Alimentarius Commission and by the mandatory regulations of the country, the FSSAI Regulations, 2011. In 62.5% of flavored UHT milk, AFM1 was below detectable levels (0.02μgL−1). However, 12.5% of these samples also contained levels exceeding the maximum permitted limits. AFM1 was present in 61.6% of the 52 raw milk samples analyzed from the two states of Karnataka and Tamilnadu with a range of 0.1–3.8μgL−1. 17.3% of these samples also exceeded the regulatory limits of the country.

Cloning and Characterisation of a Δ-prfA Listeria monocytogenes Strain Containing an Artificial Single Copy Genomic Internal Amplification Control (IAC) for Use as Internal Sample Process Control (ISPC)

Conventional internal amplification controls (IAC) are DNA-based controls which monitor the amplification reaction of real-time PCR in food pathogen detection. Food pathogen detection using real-time PCR, however, includes necessarily sample preparation and DNA isolation/purification. This modular structure leads to an analytical chain. To cover the whole analytical chain, the concept of the IAC has to be extended to internal sample process controls (ISPCs) which include supporting pre-analytical steps. One concept for such ISPCs is the use of recombinant bacterial cells comprising a deleted target and an artificial competitive target instead, which are derived from the actual target strain. In this work, we present an ISPC for the molecular detection of Listeria monocytogenes. A Δ-prfA L. monocytogenes EGDe strain was cloned with a pPL2 phage insertion vector to include a single copy artificial DNA target, resulting in a fluorescence signal not interfering with the respective signal of the L. monocytogenes EGDe wild-type strain during real-time PCR. The recombinant strain was confirmed and characterized with conventional and real-time PCR including sequencing. Microbiological examination revealed a distinct phenotype pattern on selective plate media which enables discrimination of Δ-prfA L. monocytogenes EGDe from wild-type L. monocytogenes EGDe and Listeria innocua. The ISPC was applied in an examination of artificially contaminated ultra high temperature-treated milk to demonstrate its analytical suitability. The resulting corrected recovery values of the ISPC as obtained by the whole molecular quantification procedure correspond to the respective values determined for the actual target strain (P ≤ 0.05).

The effect of hydrogen peroxide on the growth of thermophilic lactic starter and acid gelation of UHT milk

The influence of H 2O 2 pre-treatment (10–250 mg L −1) of ultra-high temperature treated (UHT) milk devoid of lactoperoxidase activity on the growth of thermophilic starter in the process of yoghurt production was studied using isothermal batch microcalorimetry and dynamic rheological measurements. Typical dual-peak power-time curves of diauxic growth of starter bacteria in milk were registered. Even the lowest concentrations of H 2O 2 added into milk 1 h before inoculation hindered the growth of thermophilic bacteria, retarded the onset of milk gelation, and resulted in formation of weaker gels. UHT milk samples treated with H 2O 2 and subsequently with catalase showed certain bacteriostatic influence of H 2O 2 pre-treatment on the second exponential growth phase. However, hardly any difference in gelation and no changes in rheological characteristics of mature gels in milk free of residual H 2O 2 due to catalase treatment prior to inoculation in comparison with H 2O 2-free control samples were observed.

Assessment of aflatoxin M1 levels in selected dairy products in north‐western Iran

The purpose of this survey was to evaluate the natural occurrence and content of aflatoxin M1, AFM1, in dairy products marketed in Urmia. During September 2007, 40 samples of pasteurised milk, 40 samples of ultra high temperature‐treated (UHT) milk, 40 samples of creamy cheese and 40 samples of Iranian Feta cheese were collected from different supermarkets in Urmia city. AFM1 contents were determined by the competitive enzyme‐linked imunosorbent assay (ELISA) technique. All milk samples analysed showed a mean of AFM1 concentrations lower than the permissible level of 50 ng/kg in Iran (23.22 and 19.53 ng/kg in pasteurised milk and UHT milk respectively). The mean levels of AFM1 contamination were 43.31 ng/kg in Feta cheeses and 21.96 ng/kg in creamy cheeses. The potential risk of human exposure to aflatoxin M1 via consumption of milk and milk products is well known. Dairy products must therefore be evaluated for aflatoxin and kept free from fungal contamination as much as possible.

Competence of the housefly, Musca domestica, as a vector of Microsporum canis under experimental conditions

The role of Musca domestica Linnaeus as a vector of the dermatophyte Microsporum canis was investigated under experimental laboratory conditions. About 400 4-day-old M. domestica flies were divided into two groups. Group A consisted of about 200 infected flies and group B comprised about 200 uninfected flies that were used as controls. Each trial was run three times. Flies from group A were fed for 24 h with a solution of ultra-high temperature-treated (UHT) milk containing about 10(6) colony-forming units (CFU) per mL of M. canis (infected milk inoculum [IMI]). The control group (group B) was fed with only UHT milk spiked with a teaspoon of honey. Microsporum canis was detected from faeces, vomitus, external surfaces and internal organs of 20 adult flies, eggs, first-, second- and third-stage (L1, L2, L3) larvae and pupae of each group, as well from 20 adult newly emerged flies (NEFs; from infected generations only). Samples were collected at 2, 4, 6 and 24 h post-infection (p.i.) (i.e. the times at which IMI was available) and on 2, 5, 7 and 8 days p.i. from adult flies, faeces and vomitus. Eggs, L1, L2, L3 and pupae were processed as soon as they appeared. Equivalent samples were taken from group B. All the samples were individually cultured. Microsporum canis was not isolated from the control group, from eggs, larvae, pupae or NEFs, or from faeces and vomitus, although it was detected on the body surface (26.2%) and internal organs (26.9%) of adult flies. The highest positivity for M. canis was detected on flies within the first 6 h p.i. (i.e. 57.2% on the body surface and 71.6% in the internal organs). No M. canis was isolated at 24 h p.i., but it was isolated from the body surface only at 2 and 5 days p.i. The results presented provide evidence that M. domestica transmits M. canis mechanically with its outer body surface for up to 5 days p.i., but does not do so through its vomitus and faeces or transovarially. The role played by M. domestica in the epidemiology of human and animal dermatophytoses is discussed.

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

Jan‰tova, B., J. Luka‰ova, M. Draakova, L. Vorlova: Influence of Bacillus spp. Enzymes on Ultra High Temperature-treated Milk Proteins. Acta Vet. Brno 2004, 73: 393-400. 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. Proteolysis, Bacillus spores, Bacillus licheniformis, casein

The growth and interaction of yeasts and lactic acid bacteria isolated from Zimbabwean naturally fermented milk in UHT milk

Nine yeast and four lactic acid bacterial strains, previously isolated from Zimbabwean traditionally fermented milk, were inoculated into ultra-high temperature treated (UHT) milk in both single and yeast–lactic acid bacteria co-culture. The lactic acid bacteria (LAB) strains consisted of Lactococcus lactis subsp. lactis biovar. diacetylactis C1, L. lactis subsp. lactis Lc39, L. lactis subsp. lactis Lc261 and Lactobacillus paracasei subsp. paracasei Lb11. The yeast strains used were Candida kefyr 23, C. lipolytica 57, C. lusitaniae 63, C. lusitaniae 68, C. tropicalis 78, Saccharomyces cerevisiae 71, S. dairenensis 32, C. colliculosa 41 and Dekkera bruxellensis 43. After 48-h fermentation at 25°C, the samples were analysed for pH, viable yeast and bacterial counts, organic acids, volatile organic compounds (VOC) and carbon dioxide. The Lactococcus strains reduced the pH from about 6.6 to between 4.0 and 4.2, while Lb. paracasei subsp. paracasei Lb11 reduced the pH to about 5.4. Most of the yeasts, however, did not affect the final pH of the milk except for C. kefyr 23, which reduced the pH from 6.6 to 5.8. All the Lactococcus strains grew two log cycles during the 48-h fermentation period, while Lb. paracasei subsp. paracasei Lb11 grew about one log cycle. S. cerevisiae 71, C. colliculosa 41 and D. bruxellensis 43 showed poor growth in the milk in both single and co-culture. The other species of yeast grew about two log cycles. Candida colliculosa 41, S. dairenensis 32 and D. bruxellensis 43 showed reduced viability when in co-culture with Lb. paracasei subsp. paracasei Lb11. The samples in which C. kefyr 23 was used were distinct and characterised by large amounts of acetaldehyde, carbon dioxide and ethanol. However, in the samples where S. dairenensis, C. colliculosa, D. bruxellensis, C. lusitaniae, C. tropicalis, C. lipolytica and S. cerevisiae were used in co-culture, the final pH and metabolite content were mainly determined by the corresponding LAB strain. From the observations, it was concluded that C. kefyr 23 grows well in UHT milk and produces VOC that may be important to the flavour profile of the fermented milk. Enhancement of production of some flavour compounds such as acetaldehyde and malty compounds in some yeast–LAB co-cultures was presumed to be indicative of interaction between the microorganisms.

Aflatoxin M1 in raw and ultra high temperature-treated milk commercialized in Portugal

During June to September 1999, 31 samples of raw milk were obtained from individual farms and 70 samples of ultrahigh-temperature-treated (UHT) milk (18 samples of whole milk, 22 of semi-skimmed and 30 samples of skimmed milk) were collected in supermarkets in Lisbon, Portugal. The total number of samples analysed was 101. The incidence of aflatoxin M1 (AFM1

The Combined Effect of High Hydrostatic Pressure and Mild Heat on Inactivation of Pathogens in Milk and Poultry

The combined effects of high hydrostatic pressure and heat on the inactivation of Escherichia coli O157:H7 NCTC 12079 and Staphylococcus aureus NCTC 10652 in poultry meat and ultra-high-temperature-treated (UHT) milk were investigated. The simultaneous application of high pressure and mild heating was more lethal than either treatment alone. The substrate was found to have a significant effect on the survival of the pathogens during treatment. For E. coli O157:H7, a 15-min treatment of 400 MPa at 50°C resulted in approximately a 6.0-log10 reduction in CFU/g in poultry meat and a 5.0-log10 reduction in UHT milk; however, a < 1-log10 reduction was achieved with either treatment alone. In contrast, for S. aureus, a 15-min treatment of 500 MPa at 50°C was required to achieve a 5.0-log10 reduction in poultry meat and a 6.0-log10 reduction in UHT milk. As before, a <1-log10 reduction in numbers was achieved with either treatment alone. The pressure-temperature inactivation curves of each organism, in each substrate, were fitted using the Gompertz equation. Polynomial expressions derived from the Gompertz variables were used to devise simple models which predicted the inactivation of each pathogen at various pressure-temperature combinations. Thus, a number of different pressure-temperature conditions could be chosen to achieve a desired inactivation level. The use of such models will provide flexibility in selecting optimum pressure processing conditions without compromising microbiological safety.

DIGESTIBILITY AND ANTIGENICITY OF β-LACTOGLOBULIN IN DIFFERENT HEAT PASTEURIZED COMMERCIAL COW'S MILKS DIGESTED BY PEPSIN AND PANCREATIN

Allergenicity of food proteins is generally dependent on their heat-stability and resistance to digestive enzymes. Using the methods of ELISA inhibition assay and immunoblots, we assessed peptic-and pancreatic-digestibility of β-lactoglobulin (β-LG) and its antigenecity after the treatment with digestive enzymes in three types of commercially available heat pasteurized cow's milks (low temperature long time-treated milk (LTLT), high temperature short time-treated milk (HTST) and ultrahigh temperature-treated milk (UHT)). Digestibility of β-LG was resistant to both single and sequential peptic- and pancreatic-digestions in the LTLT and HTST, but not in the UHT. In the LTLT, boiling of the milk for 15min lead β-LG to lost of the digestive resistance. These results suggested that the UHT may be superior than the LTLT and HTST in the point of gastrointestinal digestibility of β-LG, and that consideration of cooking for menus composed of the cow's milks may improve digestibility of β-LG in the stomach and intestines.

Sensitivity of Vegetative Pathogens to High Hydrostatic Pressure Treatment in Phosphate-Buffered Saline and Foods

The effect of high hydrostatic pressure (up to 700 MPa) at 20°C on the survival of vegetative pathogens was investigated in 10mM phosphate buffer (pH 7.0), ultra high-temperature-treated (UHT) milk, and poultry meat. In buffer, Yersinia enterocolitica was most sensitive, with a pressure of 275 MPa for 15 min resulting in more than a 105 reduction in numbers of cells. Treatments of 350 MPa, 375 MPa, 450 MPa, 700 MPa, and 700 MPa for 15 min were needed to achieve a similar reduction in Salmonella typhimurium, Listeria monocytogenes, Salmonella enteritidis, Escherichia coli O157:H7, and Staphylococcus aureus respectively. A significant variation in pressure sensitivity was observed between different strains of both L monocytogenes and E. coli O157:H7. The most resistant strains (L. monocytogenes NCTC 11994 and E. coli O157:H7 NCTC 12079) were chosen for further studies on the effect of substrate on pressure sensitivity. In both cases the organisms were more resistant to pressure when treated in UHT milk than in poultry meat or buffer. There was evidence, assessed by differential plating using trypticase soy agar with and without additional NaCl, that sublethally injured cells were present at pressures lower than were required for death. This information may be of value if pressure is combined with preservation treatments such as mild heating. The variation in results obtained with different organisms and in different substrates should be recognized when recommendations for the pressure processing of foods are being considered.

Multiplication of Bacteria in Bottled Milk Storing in Cold Place

The keeping quality of Ultra High Temperature-treated milk in cold place and the multiplication of bacteria, especially psychrophilic bacteria, in bottled milk storing in cold place were discussed. Pasteurization of milk was carried out for 2seconds at temperature of 130°C (the U.H.T. method). One samples were taken into the sterilized flask with a cotton cap from the cooling part of pasteurizer and were poured into the sterilized bottle in the laboratory. Another samples poured into the ordinary pasteurized bottle were taken immediately after stopping with a paper cap on daily process.The sterilized bottled milk did not changed during the store for 60days and all samples were to drink. The ordinary pasteurized bottled milk were different from the above mentioned. On the 10th day of the store. we found the multiplication of psychrophilic bacteria in three-tenth of samples and they were abnormal taste. On the 20th day of the store, two-tenth of samples did not indicate the presence of psychrophiles and four-tenth were to drink. The presence of psychrophilies in samples was recognized at the high rate on 30th, 40th, 50th, and 60th day, but there were few of samples which did not changed in all.