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Southern Illinois University at Carbondale (2021)

EFFECTS OF THERMAL AND NON-THERMAL METHODS ON THE CHEMICAL COMPOSITION AND BACTERIAL INACTIVATION OF CAMEL MILK

Dhahir, Namariq

Titre : EFFECTS OF THERMAL AND NON-THERMAL METHODS ON THE CHEMICAL COMPOSITION AND BACTERIAL INACTIVATION OF CAMEL MILK

Auteur : Dhahir, Namariq

Université de soutenance : Southern Illinois University at Carbondale

Grade : Doctor of Philosophy (PhD) in the field of Agricultural Sciences 2021

Résumé
Understanding the composition of camel milk coupled with studying the effects of thermal and non-thermal treatments on its components and bacterial inactivation were the general objectives of this dissertation. In the first study (Chapter 2), the gross composition of camel milk including milk protein, fat, casein, total solids, lactose, ash, and mineral content were analyzed. In addition, fatty acid profile, amino acid profile, protein fractions, and volatile compounds were evaluated as well. Our results revealed that camel milk has its unique nutrients profile. These findings make it easier for the researchers and consumers to understand some of the nutritional attributes of camel milk.The impact of non-thermal ultrasound treatment (900 W, 20 kHz, 100% power level) on some milk-borne microorganisms and the components of camel milk was studied in Chapter3. We reported that continuous ultrasound processing was efficient in inactivating Escherichia coli (E.coli) O157 : H7 and Salmonella Typhimurium (S. Typhimurium) in camel milk without detrimental effects on milk fatty acids profile, lipid peroxides, and protein fractions except for some changes in milk volatile compounds (VC). In Chapter 4, another non-thermal technique, ultraviolet-C (UV-C) light, was applied to camel milk to study the effects of different UV-C light doses on the viability of E. coli O157:H7 and S. Typhimurium and the chemical changes to milk components. The main findings of this study were : (i) UV-C treatment at a dose of 12.45 mJ/cm2 resulted in only 3.9-log10 for both bacterial strains which did not meet the Food and Drug Administration (FDA) requirements for the 5-log pathogen reduction ; (ii) the UV-C treatment at the above dose, had limited effects on camel milk components. Thermal pasteurization of milk was first introduced to prevent milk-borne infectious diseases, however, its effects on camel milk components and quality are still unknown. Therefore, in Chapter 5, we investigated the efficacy of three previously reported thermal methods : PAST-1 (65ºC/30 min), PAST-2 (72ºC/5 min), and PAST-3 (80ºC/5 min) on bacterial inactivation and some camel milk components such as the fatty acid profile, lipid peroxidation, VC, and milk protein fractions. Complete elimination (6 log10 CFU/ml reduction) of E. coli O157 : H7 was achieved using all pasteurization methods, however, only 3.4 log10 CFU/ml reduction of the total viable counts was reported using PAST-1 and PAST-3 methods. We also reported that the PAST-1 and PAST-3 methods did not affect the chemical composition of camel milk. In conclusion, we assessed the main components of camel milk along with the amino fatty acid profile, acid profile, volatile compounds, and protein fractions. Thermal methods were more effective than the non-thermal methods in terms of microbial inactivation and most camel milk components were not significantly influenced by thermal and non-thermal methods.

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Page publiée le 7 décembre 2022