Call number: LD2668 .T4 1948 J3 / Master of Science

LD2668 .T4 1954 R87 / Master of Science

Ruminant products, meat and milk, were long ago discovered to contain a high content of saturated fat associated with various chronic diseases in human, including coronary heart disease. Increased consumption of n-3 fatty acids, linolenic (LNA; 18:3n-3), eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) by man has been linked with reduced incidences of these diseases. Therefore, in vitro experiments carried out in this thesis investigated the possibility that the dietary inclusion of essential oil compounds (EOC) might modify ruminal biohydrogenation of polyunsaturated fatty acids (PUFA), and thereby improve the fatty acid profiles of ruminant derived foods. In the first experiment, twenty EOC were screened, of which carvacrol, thymol, cis/trans-citral, geraniol, nerol, (+)-α-pinene, l-menthone, linalyl acetate and (R)-(+)-pulegone were most effective at protecting the PUFA from biohydrogenation. The reduced accumulation of stearic acid with concomitant increases in vaccenic acid following the addition of the EOC confirmed their capacity to inhibit biohydrogenation of both LA and LNA. However, the observed decreases in total volatile fatty acids concentrations suggested that the inclusion of these compounds at 300 mg l-1 also suppressed microbial fermentation. Of these EOC, carvacrol and thymol were the most potent inhibitors of fermentation as they decreased total VFA concentrations by ≥60% from those of the control. In the second experiment, selected EOC, namely linalyl acetate, l-menthone and (+)-α-pinene, were tested at lower doses. It was observed that these EOC when added at 100 and 200 mg l-1 also inhibited biohydrogenation with minimal effect on VFA concentration. In experiment 3, pure culture work was undertaken to assess the effects of EOC on three key Butyrivibrio spp., involved in the biohydrogenation process, namely B. fibrisolvens, B. hungatei and B. proteoclasticus. The EOC inhibited biohydrogenation through their bacteriostatic effects on these bacteria. In conclusion, these studies revealed that EOC have the potential to modify ruminal biohydrogenation to varying extents depending on the type of compound used and the dose applied. Consequently, they might be useful at improving the healthiness of ruminant products, however their effects have to be confirmed in vivo and ensure that they do not cause significant inhibition of fibre digestion.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

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The number of foodborne disease outbreaks related to fresh produce has increased in recent years. This has coincided with a growing public demand for minimally processed fruits and vegetables. Effective produce sanitizers are therefore needed that are at least as effective as chlorine, currently the most commonly used sanitizer. Natural antimicrobials from plant extracts and essential oils are a possible alternative. These are highly effective and may also be used in situations in which chlorine is not advantageous; for instance, in situations in which chlorine has limited efficacy or because of concerns over the production of harmful by-products resulting from chlorine use. Plant derived essential oils have been shown to be antibacterial, antiviral, and antifungal. In this study we examined the use of natural antimicrobials from plant extracts and essential oils as possible alternative sanitizers. We examined these antimicrobials for their efficacy against Escherichia coli. In addition, since many of these natural compounds are believed to be membrane active, silver ions were added to some of the tests to assess the potential for synergy between the antimicrobials. Silver ions, although slow-acting on their own, often exhibit a synergistic antimicrobial effect when combined with other membrane active antimicrobials such as oxidizing agents. These studies reveal that plant derived antimicrobials are effective sanitizers with the potential to replace commonly used chlorine

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