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Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 5 uppsatser.

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.

Ultra high temperature (UHT) processing can extend shelf life of milk to several months without refrigeration, which is more convenient and energy saving than pasteurized milk. However, the poor acceptance caused by "cooked" flavors limits its marketing growth, especially in United States. Ohmic heating, which has a more uniform and rapid heating than conventional UHT process, may minimized the flavor change during the thermal treatment. Flavor composition between Ohmic heated UHT milk and other traditionally processed UHT milk (direct steam injection and indirect plate heating) during 36 weeks storage were investigated in this study. A total of 20 volatile compounds were analyzed based on their importance to UHT milk as well as their representation to different chemical classes including sulfur-containing compounds, ketones, lactones, aldehydes and others. Dimethyl sulfide (DMS) and methyl ketones were significant different among three types of UHT heated milk. δ-lactones showed higher amount in Ohmic heating after stored for four weeks, which might generate creamy, fruity intermediate aroma. Other compounds showed no significant difference among three heating processes. Aroma recombination test revealed that the overall aroma of the ultra pasteurized (UP) milk could be mimicked by recombining 15 important reference odorants in the same concentrations as they occurred in the UHT milk using commercial pasteurized milk as the matrix. / Graduation date: 2012

Qualitative and quantitative research methods were employed to evaluate the acceptability and feasibility of HIV-1 infected, urban South African mothers being able to feed their infants heat-treated expressed breast milk (HTEBM). Nutritional status assessment of HIV-infected breastfeeding mothers (n=84) indicated that maternal status was not compromised; mean body mass index 26.8 (4.0) kg/m2, triceps skinfold 14.8 (5.50) mm and hemoglobin 11.6 (1.49) g/dL. However, severely immunocompromised mothers (CD4 + < 200 cells/mm3) were more likely to be anemic. Breastmilk viral loads were also higher in mothers with lower CD4+ cell counts. Community based inquiry on the acceptability of HTEBM was accomplished through in-depth interviews of participants (n=31), at the individual (mothers), family (partners, grandparents, mothers-in-law) and at the community level (traditional healers, daycare worker, health care counselors). Although an unfamiliar concept for all interviewed, overall, HTEBM was found to be an acceptable feeding choice regardless of respondents' gender, age, maternal status, family or community role. Further, data indicated mothers rarely received quality infant feeding counseling, consequently mixed feeding, a high risk for HIV transmission, was a common practice. In a pilot longitudinal study, using mixed-methods, the feasibility of mothers successfully implementing a modified breastfeeding intervention (6 months exclusive breastfeeding (EBF), cessation of breastfeeding, followed by use of HTEBM with complementary diet) was evaluated. The majority of mothers (36/66) practiced EBF for 6 months, 42% of whom also used HTEBM, expressing a range of approximately, 65 ml to 600 ml of breastmilk daily, for varying durations (2 weeks to 5 months). Mothers did not experience breast pathology. Home visits were highly enabling as was disclosure of HIV status to a partner. This is the first study to demonstrate that use of HTEBM is a feasible infant feeding option for HIV infected women. HTEBM may offer one solution to reduce vertical transmission of HIV and help maintain nutritional adequacy, as a component of complementary feeding.

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