Thesis (MScVoedselwet)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Milk has been identified as having the potential of being a carrier of human pathogens, and it is thus essential to eliminate or reduce the likelihood of milk borne contamination. This problem of milk contamination is generally solved by the process of pasteurisation which is achieved by heating the "raw" material for a sufficient period of time to destroy any pathogenic and spoilage bacteria which may be present at a temperature of below 100°C. Presently, there are two basic methods of pasteurisation in use in the dairy industry, the LTLT and the HTST methods, where the applied heat treatment is considered sufficient to ensure public safety and adequate keeping quality. In addition to these, there is another method, the "pot" pasteurisation, to be found in Southern Africa that was designed to eliminate potential pathogenic and spoilage bacteria present in raw milk. As far as it is known no thermal studies have been done on the "pot" pasteurisation method. The objectives of this study were to determine the impact of different milk pasteurisation temperature and time combinations on the survival of selected microbes. The accuracy of the "pot" pasteurisation method and how it differs from the other pasteurisation methods was also determined using the same selected microbes. The six selected microbes were thermally inactivated by using the LTLT, HTST and the "pot" pasteurisation methods at low and high inoculum levels of 104 and 106 cfu.ml-1. The thermal death curves were constructed for each selected species. The selected microbes included the strains Bacillus cereus (S4), Chryseobacterium meningosepticum (S5), Pseudomonas putida (S6), Acinetobacter baumannii (C3), Escherichia coli (58) and Candida lipolytica (G1). Survivors were enumerated after heating for 0, 5, 10, 15, 20, 25, 30, 35 and 40 min for both the LTLT and HTST pasteurisation methods and after heating for 0, 10, 20 and 30 min for the "pot" pasteurisation method. The results from this study showed that with the exception of the B. cereus strain, the other selected microbes at both high and low concentration levels did not survive the LTLT or the HTST pasteurisation methods. It was found that for all the organisms used in this study, there was a rapid initial death rate just before the required pasteurisation temperatures of 63°, 72° and 90°C were reached, during the "come-up" period. In contrast, the results from the "pot" pasteuriser showed that theB. cereus (S4), Chr. meningosepticum (S5), P. putida (S6), A. baumannii (C3) and E. coli (58) strains survived the pasteurisation conditions applied. From these results it was thus concluded that the "pot" pasteuriser under the conditions evaluated in this study, did not pasteurise effectively. Therefore, it is recommended that the manufacturer improves the heating quality of the "pot" pasteuriser. As it was found that only the B. cereus (S4) strain survived all the different pasteurisation methods, future research needs to be done to determine at which temperature this heat resistant bacterial strain will be destroyed. This is very important because there is a need to destroy all the spoilage microorganisms that can lead to the deterioration of food products. / AFRIKAANSE OPSOMMING: Melk is 'n potensiële draer van mikrobes wat patogenies is vir die mens. Dit is dus essensiëel om die besmetting van melk te verlaag of te elimineer. Die probleem van melkbesmetting word opgelos deur die proses van pasteurisasie. Die proses word toegepas deur verhitting van die rou material vir 'n voldoende periode om patogeniese en bederf organismes te vernietig. Temperature onder 100°C word gebruik. In die suiwelbedryf word twee basiese metodes gebruik: die LTLT (lae temperatuur, lang tyd) metode en die HTKT (hoë temperatuur, kort tyd) metode. Albei hittebehandelings is voldoende om publieke veiligheid en 'n genoegsame rakleeftyd te verseker. 'n Derde metode, "pot" pasteurisasie, word in Suidelike Afrika gebruik. Die metode is ontwikkel om potensiële patogene en bederf organismes in rou melk te elimineer. Die probleem is dat daar geen navorsing op die temperatuur eienskappe van die “pot" metode gedoen is nie. Die doelwitte van hierdie navorsing was om die effek van verskillende temperatuur:tyd kombinasies op die oorlewing van sekere mikrobes te bepaal. Die akkuraatheid van die "pot" metode en die manier hoe dit van ander metodes verskil, is ook in ag geneem. Die navorsing is ten alle tye gebaseer op die geselekteerde mikroorganismes. Die ses geselekteerde spesies van mikrobes is vernietig deur middel van die LTLT, HTKT en "pot" pasteurisasie metodes. Die mikrobes is geïnaktiveer teen lae en hoë inokulums van 104 en 106 kve.ml-1. Terminale dodings kurwes is opgestel vir elke geselekteerde spesie. Die mikrobes van belang is Bacillus cereus (S4), Chryseobacterium meningosepticum (S5), Pseudomonas putida (S6), Acinetobacter baumannii (C3), Escherichia coli (58) en Candida lipolytica (G1). Die oorlewende mikroorganismes is na hitte behandelings van 0, 5, 10, 15, 20, 25, 30, 35 en 40 minute vir beide die LTLT en die HTKT pasteurisasie metodes en na hitte behandelings van 0, 10, 20, en 30 minute vir die "pot" pasteurisasie metode getel. Die resultate van die navorsing dui aan dat, behalwe vir B. cereus, die geselekteerde mikrobes teen beide lae en hoë konsentrasies nie die LTLT en die HTKT metodes oorleef het nie. Daar is gevind dat, vir al die organismes, vinnige aanvanklike dodingstempos teenwoordig was net voor die noodsaaklike pasteurisasie temperatuur van 63°, 72° en 90°C bereik is, gedurende die "come-up" periode. Inteenstelling hiermee het die resultate van die "pot" metode bewys dat B.cereus (S4), Chr. meningosepticum (S5), P. putida (S6), A. baumannii (C3) en E. coli (58) stamme die pasteurisasie toestande oorleef het. Uit die resultate is ’n gevolgtrekking gemaak dat die "pot" pasteurisasie metode nie effektief was nie. Daar word dus aanbeveel dat die vervaardiger die verhittings-kwaliteit van die "pot" pasteurisasie apparaat verbeter. Aangesien net die B. cereus (S4) stam al drie pasteurisasie metodes oorleef het, moet toekomstige navorsing gedoen word om die vernietigings temperatuur van dié hittebestande stam te bepaal. Die navorsing is van belang weens die behoeftes om alle bederf mikroorganismes wat tot die agteruitgang van voedsel produkte kan lei, te vernietig.

Made available in DSpace on 2014-06-11T19:32:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-05-04Bitstream added on 2014-06-13T18:44:24Z : No. of bitstreams: 1 vicente_hig_dr_jabo.pdf: 1044940 bytes, checksum: 1e6202c64e317099b4cf8015b4128b59 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Este trabalho teve como objetivo determinar a prevalência de Escherichía calí produtoras de shigatoxinas e E. calí dos sorogrupos 0157, 0111 e 0113 em rebanhos leiteiros do Município de Jaboticabal-SP. A presença de seqüências stx1, stx2e eae foi detectada pela reação em cadeia da polimerase (PCR) em amostras de fezes, água, leite, mão de ordenhador, insuflador de ordenhadeira e teto. Todas as amostras stx e eae positivas foram submetidas a uma nova reação de PCR para detecção das seqüências rfb 0157, 0111 e 0113. Observou-se uma alta prevalência (72,16%) de seqüências stx nas fezes dos bovinos. Os coeficientes de prevalência das seqüências rfb 0157, 0111 e 0113 nas fezes dos bovinos foram, respectivamente, 14,77%, 0,2% e 30,83%. Detectaram-se seqüências stx em amostras de água (19,51 %), leite (33,33%), mão de ordenhador (3,57%), e teto (7,14%). Ainda nas amostras de água e leite foram detectadas Escheríchía colí 0157 e 0113. Por meio da separação imunomagnética, isolou-se 53,62% das amostras PCR 0157 positivas, sendo destas 72,97% produtoras de enterohemolisina. Foram isoladas 25% das amostras PCR 0113 positivas. Animais de todos os rebanhos (100%) apresentaram em suas fezes STEC e E. calí 0113 e os sorogrupos 0157 e 0111 foram observados em 60,0% e 10,0% dos rebanhos, respectivamente. Concluiu-se que a alta prevalência de STEC detectada em rebanho leiteiro evidenciou que as fezes de bovinos desempenham um papel importante na contaminação ambiental e podem oferecer risco de agravo à saúde pública. / The objective of this study was to determine the prevalence of Shigatoxigenic Escherichía colí (STEC) and STEC serogroups 0157, 0111 and 0113 in feces, water, milk, milkman's hands, teat and teatcup sampled in dairy farms in Jaboticabal-SP. Samples were collected from 10 herds and assessed for the presence of the virulence genes stX1, stX2 and eae by polymerase chain reaction (PCR). Ali stx and eae positive samples were submitted to a second PCR reaction targeting the sequences rfb 0157, rfb 0111 and rfb 0113. High prevalence of stx was detected (72,16%) in fecal samples, whereas the prevalence of sequences rfb 0157, rfb 0111and rfb 0113 were 14,77%, 0,2% and 30,83%, respectively. Sequence stx was detected in water (19,51 %), milk (33,33%), milkman's hands (3,57%) and teat samples (7,14%). It was also detected Escheríchía colí 0157 and 0113 in water and milk samples. It was isolated, by immunomagnetic separation, 53,62% of the PCR positive samples, from these, 72,97% were enterohaemolytic. 25% of the 0113 PCR positive samples were isolated. STEC was identified in ali herds (100%), and serogroups 0157, 0111 and 0113 were observed in 60%, 10% and 100% of the herds, respectively. In conclusion, the high STEC prevalence detected in dairy herds evidences that bovine feces might play an important role as a contamination source in the region of Jaboticabal.

The aim of the study was to evaluate the total viable count and detects each microorganism by the use of mass spectroscopy. In the period of June to December 2017 35 samples of pasteurized milk from two vending machines (Hodkovice, Suchdol) were tested. For comparison samples were divided to warmer season (June-Septemeber) and colder season (October-December) sampling. The total amount of microorganism was determined in each sample of milk and total viable count was estimated by the use of mass spectroscopy MALDI-TOF. The total viable count in the tested pasteurized milk were from 3,27 log KTJ/ml up to 7,35 log KTJ/ml. The mass spectroscopy detected 210 microorganisms belonging to 20 families of gram-positive and gram-negative bacteria and one species of eukaryot organism. The most often identified species belong the Enterobacteriaceae family.

Orientador: Luiz Augusto do Amaral / Banca: Elma Pereira dos Santos Polegato / Banca: Naiá Carla Marchi de Rezende Lago / Banca: Raul José Silva Gírio / Banca: Maria da Gloria Buzinaro / Resumo: Este trabalho teve como objetivo determinar a prevalência de Escherichía calí produtoras de shigatoxinas e E. calí dos sorogrupos 0157, 0111 e 0113 em rebanhos leiteiros do Município de Jaboticabal-SP. A presença de seqüências stx1, stx2e eae foi detectada pela reação em cadeia da polimerase (PCR) em amostras de fezes, água, leite, mão de ordenhador, insuflador de ordenhadeira e teto. Todas as amostras stx e eae positivas foram submetidas a uma nova reação de PCR para detecção das seqüências rfb 0157, 0111 e 0113. Observou-se uma alta prevalência (72,16%) de seqüências stx nas fezes dos bovinos. Os coeficientes de prevalência das seqüências rfb 0157, 0111 e 0113 nas fezes dos bovinos foram, respectivamente, 14,77%, 0,2% e 30,83%. Detectaram-se seqüências stx em amostras de água (19,51 %), leite (33,33%), mão de ordenhador (3,57%), e teto (7,14%). Ainda nas amostras de água e leite foram detectadas Escheríchía colí 0157 e 0113. Por meio da separação imunomagnética, isolou-se 53,62% das amostras PCR 0157 positivas, sendo destas 72,97% produtoras de enterohemolisina. Foram isoladas 25% das amostras PCR 0113 positivas. Animais de todos os rebanhos (100%) apresentaram em suas fezes STEC e E. calí 0113 e os sorogrupos 0157 e 0111 foram observados em 60,0% e 10,0% dos rebanhos, respectivamente. Concluiu-se que a alta prevalência de STEC detectada em rebanho leiteiro evidenciou que as fezes de bovinos desempenham um papel importante na contaminação ambiental e podem oferecer risco de agravo à saúde pública. / Abstract: The objective of this study was to determine the prevalence of Shigatoxigenic Escherichía colí (STEC) and STEC serogroups 0157, 0111 and 0113 in feces, water, milk, milkman's hands, teat and teatcup sampled in dairy farms in Jaboticabal-SP. Samples were collected from 10 herds and assessed for the presence of the virulence genes stX1, stX2 and eae by polymerase chain reaction (PCR). Ali stx and eae positive samples were submitted to a second PCR reaction targeting the sequences rfb 0157, rfb 0111 and rfb 0113. High prevalence of stx was detected (72,16%) in fecal samples, whereas the prevalence of sequences rfb 0157, rfb 0111and rfb 0113 were 14,77%, 0,2% and 30,83%, respectively. Sequence stx was detected in water (19,51 %), milk (33,33%), milkman's hands (3,57%) and teat samples (7,14%). It was also detected Escheríchía colí 0157 and 0113 in water and milk samples. It was isolated, by immunomagnetic separation, 53,62% of the PCR positive samples, from these, 72,97% were enterohaemolytic. 25% of the 0113 PCR positive samples were isolated. STEC was identified in ali herds (100%), and serogroups 0157, 0111 and 0113 were observed in 60%, 10% and 100% of the herds, respectively. In conclusion, the high STEC prevalence detected in dairy herds evidences that bovine feces might play an important role as a contamination source in the region of Jaboticabal. / Doutor

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The aim of this study was to determine the rate of transfer of melamine as fertilizer ingredient to kikuyu pastures and if melamine would be transferred from the fertilized pasture to cow’s milk. Three trials were conducted in the study, viz. a pilot pot plant trial, an applied pasture trial and a milk production trial. Melamine is a commercially available industrial chemical with a high nitrogen content. Large quantities of melamine waste can sometimes be incorporated into crop and pasture fertilizers due to the high N content. An initial pot plant trial with kikuyu was conducted to determine whether melamine would be absorbed as such from the soil to the plant material. The pots were fertilized in the form of melamine adulterated Chinese maize Gluten 60, at a rate equivalent to 8.8 kg of melamine/ha. Results indicated that melamine was indeed absorbed and 7 days after fertilization, the concentration of melamine in the grass was 228 mg/kg. An applied pasture trial was then conducted were three pastures of 0.3 ha each were used. One pasture served as a control and received N fertilization in the form of LAN at a rate of 40 kg N/ha. The other two pastures also received LAN, but with 10% (Treatment 1) and 20% (Treatment 2) of the LAN-N substituted with melamine-N. All three pastures also received P-fertilization in the form of Single Superphosphate at a rate of 20 kg P/ha and KCl fertilizer at a rate of 50 kg K/ha. Pasture samples were taken once a week for 10 weeks, each time at the exact same spot in each camp. Samples were dried and finely milled before analysis via LC-MS/MS for melamine content. The initial concentration of melamine in the grass of Treatment 2 was higher than that in the grass of Treatment 1. The rate at which melamine decayed in the plant material was found to be quite similar for the two melamine treatments. In this trial, melamine took around 10 weeks to reach undetectable levels in the grass. It was concluded that melamine was absorbed as such from the soil by pasture grass when included in a fertilizer. For the milk production study, eighteen lactating Holstein cows, 60 ± 5.1 (SE) DIM, with a daily milk production of 36.5 ± 2.0 (SE) kg/d and weighing 609 ± 12.8 (SE) kg, were stratified according to milk production and then randomly allocated to three groups of six cows. The groups were then randomly allocated to the three pastures used in the applied pasture trial. Cows were kept on the melamine fertilized pasture for 9 days, in which they were allowed to graze the pasture for approximately 10 hours each day. After the 9 day period, melamine was withdrawn by placing the cows on the control pasture that did not receive melamine contaminated fertilization for another 7 days. During these 16 days, milk was collected twice a day, viz. during the morning and afternoon milkings. Milk samples of each cow were sub-divided into two samples, one was preserved with potassium dichromate and analysed for milk composition and the other was frozen until analysed for melamine by LC-MS/MS. For the duration of the trial, melamine containing milk was destroyed in order to prevent it from contaminating milk collected from the rest of the herd. Results from the analysis for melamine confirmed that melamine was transferred from melamine fertilized pasture to milk. In this study, it took 6 days from melamine withdrawal for melamine to reach undetectable levels in the milk. It was also found that the melamine fertilized pasture did not have any significant effect on the average milk production and milk composition of the cows. The aim of the study was met and it was confirmed that melamine can be transferred from fertilizer to the soil, to the pasture and to the milk of cows grazing these pastures. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die tempo van oordrag van melamien as bemestingstof na Kikuyu weiding te bepaal, asook om te bepaal of melamien oorgedra sal word vanaf die bemeste weiding na melk. Drie proewe is uitgevoer wat ‘n potplant loodsproef, ‘n toegepaste weidings proef en ‘n melkproduksie proef ingesluit het. Melamien is ʼn kommersieël-beskikbare industriële chemikalieë met ʼn hoë stikstof inhoud. Groot hoeveelhede van melamien-afval kan soms in kunsmis ingesluit word vir die bemesting van gewasse en weidings, weens die hoë stikstof inhoud van melamien. ʼn Potplant loodsproef met Kikuyu is uitgevoer om te bepaal of melamien vanaf die grond deur die plantmateriaal geabsorbeer word. Melamienbemesting is in die vorm van vervalste Chinese mieliegluten 60 toegedien teen ʼn hoeveelheid gelykstaande aan 8.8 kg melamien/ha. Die resultate van hierdie proef het getoon dat melamien wel deur die plantmateriaal geabsorbeer is en 7 dae nadat bemesting toegedien is, was die konsentrasie van melamien in die gras 228 of mg/kg. ʼn Toegepaste weidingstudie is uitgevoer waar drie kampe van 0.3 ha elk gebruik is. Een van die kampe het as ʼn kontrole gedien en het stikstof bemesting in die vorm van KAN teen 40 kg N/ha ontvang. Die ander twee kampe het KAN bemesting ontvang waar 10% (Behandeling 1) en 20% (Behandeling 2) van die KAN-N deur melamien-N vervang is. Al drie kampe het ook fosfaatbemesting in die vorm van Enkel Superfosfaat ontvang teen 20 kg P/ha, asook KCl kunsmis teen 50 kg K/ha. Weidingmonsters is eenmaal per week op dieselfde plek in elke kamp geneem vir 10 weke nadat bemesting toegedien is geneem. Monsters is gedroog en daarna fyngemaal voordat dit vir melamieninhoud geanaliseer is met behulp van LC-MS/MS. Die aanvanklike melamienkonsentrasie in die gras van Behandeling 2 was hoër as die in die gras van Behandeling 1. Die tempo waarteen die melamienkonsentrasie in die plant materiaal afgeneem het, was baie dieselfde vir Behandelings 1 en Behandeling 2. Dit het ongeveer 10 weke geneem voordat die melamien in die gras nie-waarneembare vlakke bereik het. Die gevolgtrekking is gemaak dat melamien wat in die vorm van kunsmis toegedien word, as sodanig uit die grond geabsorbeer word deur die gras. Vir die melkproduksiestudie is agtien lakterede Holsteinkoeie, 60 ± 5.1 (SE) dae in melk, met ‘n daaglikse melkproduksie van 36.5 ± 2.0 (SE) kg/dag en ‘n liggaamsmassa van 609 ± 12.8 (SE) kg, volgens hul melkproduksie gerangskik en ewekansig in drie groepe van ses koeie elk ingedeel. Die groepe is daarna ewekansig aan die drie kampe, wat in die toegepaste weidingstudie gebruik is toegedien. Die koeie is vir 9 dae op die melamienbemeste weidings gehou, waartydens hulle toegelaat is om vir ongeveer 10 ure elke dag te wei. Na die tydperk van 9 d, is die koeie vanaf die melamienbemeste weidings onttrek deur hulle op die kontroleweiding te plaas vir ʼn verdere 7 dae. Gedurende hierdie 16 dae is melkmonsters tweekeer per dag geneem, tydens die oggend- en die middagmelkings. Die melkmonsters van elke koei is vervolgens onderverdeel in twee monsters, waarvan een met kaliumdichromaat gepreserveer is vir die beplaing van melksamestelling, terwyl die ander een gevries is totdat dit later vir melamien inhoud ontleed is met behulp van LC-MS/MS. Melk van die koeie wat op die melamienweidings gewei het, is weggegooi om te voorkom dat melk van die res van die kudde gekontamineer kon word. Die resultate van die melamienanalises het getoon dat melamien oorgedra word vanaf die melamienbemeste weiding na die melk. Tydens hierdie studie het dit 6 dae geneem vandat koeie vanaf die melamienbemeste weidings onttrek is, totdat die melkmelamien nie-bepaalbare vlakke bereik het. Daar is bevind dat melamienbemeste weidings geen betekenisvolle uitwerking op die gemiddelde produksie en samestelling van die melk gehad het nie. Die doel van hierdie studie is bereik en daar is getoon dat melamien vanaf kunsmis na die grond, na die gras en na die melk oorgedra kan word wanneer koeie op weidings geplaas word wat melamienbemeste kunsmis ontvang het.

Thesis (PhD (Food Science))--University of Stellenbosch, 2007. / Thermal pasteurisation failures in the dairy industry have often been found to cause end-products of poor quality and short shelf-life. Therefore, alternative methods to eliminate microbial contaminants in raw milk are being studied. Ultrasonication is one such non-thermal technology that could offer the dairy industry an alternative to traditional pasteurisation. The main objective of this dissertation was to evaluate the use of high-power lowfrequency ultrasound (20 kHz, 750 W, 124 μm) applied in batch mode to eliminate a selection of spoilage and potentially pathogenic microbes, commonly associated with milk. These included Gram-positive and negative microbes, comprising of rods and cocci, an endospore-former, and a yeast (Escherichia coli, Bacillus cereus, Chryseobacterium meningosepticum, Lactobacillus acidophilus, Lactococcus lactis, Listeria monocytogenes, Micrococcus luteus, Pseudomonas fluorescens and Saccharomyces cerevisiae). Three strains of E. coli (1 x 106 cfu.ml-1) tested, viz. ATCC 11775, a wild strain from raw milk, and an O157:H7 strain from milk were sensitive to ultrasonication. Complete elimination of viable cells occurred within 10 min. Viable counts of P. fluorescens were reduced by 100% within 6 min of ultrasonication and L. monocytogenes was reduced by 99.0% within 10 min. Lactococcus lactis was reduced by 97.0% and M. luteus, B. cereus and C. meningosepticum by 88.0%, 87.0% and 85.0% respectively. Lactobacillus acidophilus showed the most resistance to ultrasound with only 78.0% of viable cells being eliminated. Under similar conditions, S. cerevisiae was reduced by 99.7%. Microbial cell morphology, size and Gram status did not necessarily influence the efficacy of ultrasonication. Sterile saline solution and UHT milk were used as the suspension media, and the reputed protective effect of milk fat was not observed under the parameters used in this study. A higher wave amplitude (100%; 124 μm) was found to be more efficient in eliminating microbes than a lower wave amplitude (50%; 62 μm). Pulsed-ultrasonication did not enhance the efficiency of ultrasonication indicating that standing waves were absent. Limited success was achieved by ultrasonication itself, and the long batch treatment time (10 min or more) was found to be unrealistic for industrial implementation. Hence the simultaneous application of ultrasound and heat (thermoultrasonication) was examined. Thermo-ultrasonication proved to be more effective than either an ultrasonic or heat treatment with all viable M. luteus cells being eliminated within 4 min (100% amplitude at 72°C). Similarly, to eliminate E. coli and Lb. acidophilus from milk, only 2 min and 4 min thermo-ultrasonication was required, respectively. Bacillus cereus endospores remained resistant and after a 10 min thermo-ultrasonic treatment only 78.04% were eliminated. During this investigation both extensive surface (SEM) and internal (TEM) cell damage caused by ultrasonication were observed in E. coli, Lb. acidophilus and S. cerevisiae. Hence ultrasonication physically/mechanically damages these microbial cells causing cell death/injury. Microbial proteins and DNA released from cells into the environment after an ultrasonic treatment was measured and an increase in released microbial proteins and DNA was found to be indicative of a decrease in the number of viable cells, providing that the initial cell concentration was high enough. It was, however, not possible to correlate the concentration of released microbial proteins and DNA with the exact number of viable cells eliminated, rendering it an ineffective quality indicator for the industry. Ultrasonication had no statistically significant influence on the protein, fat and lactose content of both raw and pasteurised milk. The somatic cell count of raw and pasteurised milk was found to decrease after ultrasonication. Unlike with heating, activity of alkaline phosphatase and lactoperoxidase were not reduced by ultrasonication. Hence neither enzyme can be used to indicate a successful ultrasonic treatment of milk. This study has demonstrated that ultrasonication offers a viable alternative to pasteurisation as it is effective in eliminating microbes, and does not alter native milk components. However, to attain a more effective killing, thermo-ultrasonication is recommended for the treatment of milk to be used for the production of different dairy products.

Thesis (Ph.D.) -- University of Western Sydney, Hawkesbury, 1998. / "A thesis presented to the University of Western Sydney for the degree of Doctor of Philosophy, September, 1998" Bibliography: leaves 193 - 219.

Thesis (M. Tech. (Biomedical Technology)) -- Central University of technology, Free State, 2013 / The objective of this study was to determine the prevalence of Listeria monocytogenes and also to assess the general hygiene of fresh milk in the Maseru area, Lesotho. A total of 200 milk samples (40 pasteurised and 160 raw milk samples) were used for the research. Raw milk samples were collected from the local farmers at the Dairy reception as they bring it for selling. Pasteurised milk samples were bought from different milk selling points in the Maseru area. The total aerobic plate count, total coliform count and total E. coli count for 160 raw milk samples and 40 pasteurised samples were performed to determine the quality of milk. Milk was enriched in selective broths to increase detection sensitivity and was directly plated on selective agars for direct bacterial enumeration. About 54.4% of the of the raw milk samples had total aerobic plate counts greater that 200 000 cfu/ml while 55.6% (89/160) of the raw samples had high counts of greater than 20 cfu/ml for total coliforms, and 21.9% (35/160) of the samples had higher than expected total E. coli counts. High total coliform count was detected in 17.5% (7/40) of the pasteurised milk samples and about 67.5% (27/40) of these samples exceeded the limit for total aerobic plate counts. The counts exceeded the milk standards for pasteurised milk. Phosphatase activity was detected in seven pasteurised milk samples, whereas 33 tested negative for phosphatase activity. Some pasteurised milk samples tested positive for coliform counts which exceeded the maximum limits according to national standards for pasteurised milk. However, most of the pasteurised samples (82.5%) had acceptable counts of less than 20 cfu/ml. API and PCR were used for confirmation and amplification of the isolated Listeria strains. The prevalence of Listeria was found to be (3.75%). Listeria species were found in 6 out of 200 samples tested (160 raw milk samples and 40 pasteurised milk), and were only detected in the raw milk samples. Five species belonged to Listeria monocytogenes and one was Listeria innocua. None of the Listeria was detected in the pasteurised milk samples. Serotyping was done through multiplex PCR with D1, D2, FlaA and GLT primers to determine the serovar groups of L. monocytogenes. All six isolates revealed 214 bp gene which identifies the serotypes in Lineages I or III. The genetic fingerprinting of the isolated Listeria was also determined. Enterobacterial Repetitive Intergenic Consensus (ERIC) sequence-based PCR was used to generate DNA fingerprints with ERIC specific primers. On the basis of ERIC-PCR fingerprints, three different DNA patterns could be discriminated among the analysed isolates. Three L. monocytogenes isolates showed similar DNA banding patterns, while two isolates both had different profiles. A questionnaire was used to determine consumption of raw (unpasteurised) milk or pasteurised milk and its products and it was completed by 300 households from the community. Although there was no indicated prevalence of raw (unpasteurised) milk consumption from the community, participants indicated symptoms alleged to consumption of pasteurised milk and/or milk products. According to community perception some of the dairy products consumed were allegedly implicated in food poisoning illnesses experienced. Participants indicated more symptoms with both fresh and sour milk consumption than in cheese and yogurt consumption.

CAPES / O leite é um alimento com poder nutricional considerável e, por ser rico em componentes nutritivos, apresenta-se como um ótimo meio de crescimento para microrganismos. Portanto, o leite “cru”, deve passar por um tratamento térmico para reduzir ou eliminar as bactérias nocivas. O consumo de leite que tenha passado por um tratamento inadequado pode levar a infecções devido a diversos agentes patogênicos como, por exemplo, a Salmonella spp.. Por ser altamente nociva, a presença desta bactéria em alimentos é intolerável, tornando obrigatórios os testes microbiológicos de amostras de alimentos para determinar a presença deste microrganismo. Os métodos convencionais para a detecção da Salmonella spp. são lentos e trabalhosos, exigem o uso de volumes consideráveis de meios líquidos e sólidos e reagentes. Desta forma, metodologias alternativas que apresentem vantagens, tais como um custo relativamente baixo, rapidez, não ser destrutiva, ser livre de uso de reagentes, e consequentemente, não gerar Q Residuals, são demandas urgentes no controle de qualidade deste tipo de alimento. Assim, esta pesquisa teve como objetivo oferecer uma metodologia alternativa baseada em Espectroscopia no Infravermelho Próximo (NIR) para discriminar entre presença e ausência de Salmonella spp. em leite integral e desnatado UHT (Ultra High Temperature). Para isso, foram adquiridas diferentes amostras de leite integral e desnatado, ambos tratados de forma UHT. O tratamento dos dados foi realizado em software Matlab®, utilizando-se ferramentas do PLS toolbox®. Os modelos PLS-DA obtidos foram centrados na média, utilizando-se validação cruzada com algoritmo “deixe um fora”. O modelo para a discriminação de amostras de leite desnatado foi construído utilizando-se 4 variáveis latentes e apresentou RMSEC = 0,1639; RMSECV = 0,2084 e RMSEP = 0,0971. Já para leite integral, o modelo foi construído utilizandose 6 variáveis latentes com valores de RMSEC = 0,1351; RMSECV = 0,2076 e RMSEP = 0,0928. Os resultados mostraram que a metodologia sugerida foi capaz de discriminar as amostras contaminadas das não contaminadas com êxito, apresentando potencial para implementação no setor de controle de qualidade deste tipo de alimento. / Milk is a food with significant nutritional value and for being rich in nutritional constituents is presented as a great growth medium for microorganisms. Therefore, the "raw" milk, must undergo a thermal treatment to reduce or eliminate the most harmful bacteria. The consumption of milk that has passed through improper treatment, can lead to infections due to various pathogens such as, Salmonella spp.. For being highly detrimental, the presence of these bacteria in food is intolerable, making the microbiological food testing’sto determine the presence of this microorganism, absolutely required. Conventional methods to detect Salmonella spp. are laborious, requiring the use of significant amounts of liquid and solid media and reagents, besides demanding time-consuming procedures. Therefore, alternative methods which provide advantages, such as, relatively low cost, fast, non-destructive, free of reagents and, consequently, which does not generate waste are urgent demand did to the quality control of this kind of food. Thus, this research aimed to offer an alternative methodology based on Near Infrared (NIR) spectroscopy to discriminate between the presence and absence of Salmonella spp. in whole and skimmed UHT milk. Different samples of whole and skimmed milk, both treated through UHT were submitted to data analysis conducted in Matlab ® software, using PLS toolbox® tools. The PLS-DA models were median centered and cross-validated using leave one out algorithm. The model to discriminate skimmed milk samples was constructed using four latent variables and presented RMSEC = 0.1639; RMSECV = 0.2084 and RMSEP = 0.0971. To the whole milk, the model was built using six latent variables with RMSEC = 0.1351 values; RMSECV = 0.2076 and RMSEP = 0.0928. The results showed that the suggested methodology was able to differentiate between contaminated and uncontaminated samples successfully, presenting potential to be implemented in the quality control sector of milk industry.

CNPQ / O leite é uma das principais fontes de nutrientes da dieta humana e é um alimento que acompanha o ser humano durante toda a vida, tanto como leite de consumo como através de seus derivados. O leite pode apresentar contaminação oriunda de diversas fontes, relacionados desde a ordenha até o processo de beneficiamento do mesmo. Dentre esses contaminantes, destacam-se as micotoxinas, que são metabólitos tóxicos produzidos por fungos em condições de estresse. Estudos correlacionam a ocorrência de micotoxinas em leite e derivados lácteos, com ênfase na aflatoxina M1 (AFM1) que é regulamentada pela legislação vigente. Apesar da maior parte da literatura afirmar que a aflatoxina B1 (AFB1) é completamente convertida em AFM1, resultados preliminares tem sugerido que isso não é verdadeiro, o que vem a justificar que a mesma passe, também, a ser analisada, uma vez que a toxicidade da AFB1 é maior que a da AFM1. Na área de leite e derivados lácteos, estudos têm sugerido que as aflatoxinas, em especial a AFM1, localizam-se predominantemente nas frações proteicas. Porém, a elucidação da interação entre AFM1 e fração proteica permanece sem conclusão definitiva, o que sugere um campo amplo de estudo nesta área. Ainda, tendo em vista que a concentração de aflatoxinas é predominante na fração proteica e que pode haver uma interação química entre esta fração e aflatoxinas, os tratamentos térmicos aos quais o leite é submetido podem causar alterações significativas nas estruturas dessas proteínas e, por conseguinte, nas interações entre proteínas e AFM1 e AFB1. Portanto, o entendimento da natureza das ligações entre as AFM1 e AFB1 às proteínas do leite é imprescindível para a compreensão da biodisponibilidade dessas micotoxinas em animais e seres humanos. Desta forma, o objetivo do trabalho foi verificar o efeito do tratamento térmico e da digestibilidade sobre a interação proteína-aflatoxina. Para isso, foram contaminados amostras de solução de caseína bovina e leite desnatado com AFB1 (200 µg.L-1) e AFM1 (20 µg.L-1), posteriormente submetidas a pasteurização e digestão in vitro. As determinações realizadas consistiram na quantificação das AFLB1 e M1 por Cromatografia à Líquido de Ultra Alta Eficiência, Espectroscopia na região do infra vermelho (FTIR), Calorimetria Exploratória Diferencial (DSC) e Espectroscopia de fluorescência. Não houve redução da concentração de AFB1 e AFM1 após o tratamento térmico e a bioacessibilidade foi de 91,2% 70,5% e 90,9% e 69,7%, respetivamente, para caseína bovina e leite desnatado. Avaliando quantitativamente as estruturas secundárias da solução de caseína bovina e leite desnatado contaminados com AFB1 e AFM1 as principais mudanças ocorreram nas estruturas β-volta, β-anti e β-folha. Com a análise de DSC observou-se picos exotérmicos para ambos os ensaios, com variação de entalpia (∆H) após cada ensaio. Em relação aos espectros de fluorescência, foi possível verificar que as AFB1 e AFM1 promoveram redução da fluorescência original das proteínas lácteas. Pelos resultados obtidos, é possível concluir que a concentração das AFB1 e M1 não foram reduzidas pela temperaturaempregada, provavelmente pela interação proteínas do leite-aflatoxina, resultando numa bioacessibilidade relativamente elevada. / Milk and derivates are one of the main sources of nutrients of the human diet and is a food that follow's man during all of your life. The milk may be contaminated from several sources, related since milking until the beneficiation process. Among these contaminants, highlights are the mycotoxins, which are toxic metabolites produced by fungus in conditions of stress. Studies related to the occurrence of mycotoxins in milk and milk products, with the emphasis on aflatoxin M1 (AFM1) which is ruled by Brazilian law. While most of the literature stating that aflatoxin B1 (AFB1) is completely converted into AFM1, preliminary results have suggested that this is not true, justifying that it passes also to analyze because the toxicity of AFB1 is greater than the AFM1. In the milk and dairy products, studies have suggested that aflatoxins, in particular AFM1, are located predominantly in protein fractions. However, the elucidation of the interaction between AFM1 and protein fraction remains without definitive conclusion, suggesting a large broad field of study in this area. Also considering that the concentration of aflatoxins are prevalent in the protein fractions and can have a chemical interaction between these fractions and aflatoxins, the thermal treatments that the milk is subjected can cause significant changes in these proteins structures and consequently in interactions between proteins and AFM1 and AFB1. Therefore, the knowledge of nature of the links between AFM1 and AFB1 to milk proteins is indispensable for understanding the bioavailability of these mycotoxins in animals and humans. Thus, the aim of this study was to investigate the effect of thermal treatment and the digestibility of the interaction protein-aflatoxin. For this, samples of bovine casein solution and skimmed milk were contaminated with AFB1 (200 μg.L-1) and AFM1 (20 μg.L-1), and then submitted to pasteurization and in vitro digestion. The carried analyzes consisted in quantifying AFB1 and AFM1using high performance liquid chromatography, Fourier transform infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and fluorescence spectroscopy. There was no reduction in the concentration of AFB1 and AFM1 and after the thermal treatment the bioaccessibility was 91.2% and 70.5%, 90.9% and 69.7%, respectively, for bovine casein and skim milk. In quantitative assessments of the secondary structures of bovine casein and skim milk contaminated with AFB1 and AFM1 the major changes occurred in the β-turn structures, β-anti and β-sheet. With the DSC analysis was observed exothermic peaks for both tests, the change of enthalpy (∆H) after each test. Regarding the fluorescence spectra, we found that AFB1 and AFM1 promoted reduction of the original fluorescence of milk proteins. From the results, it may be concluded that the concentration of AFB1 and M1 not been reduced by the temperature applied, probably by the interaction between milk protein and aflatoxin, resulting in a relatively high bioaccessibility.