Doctoral Degrees (Microbial, Biochemical and Food Biotechnology)

Permanent URI for this collection

http://hdl.handle.net/11660/446

Browse

Now showing 1 - 4 of 4

Open Access
The chemical, microbial and sensory evaluation of lucerne (Medicago sativa L.) for human consumption and acceptability
(University of the Free State, 2014-06) Mielmann, Annchen; Hugo, C. J.; Bothma, C.
English: Lucerne (Medicago sativa L.) has not recently been investigated as an alternative protein source for human consumption in SA. The chemical (degrees Brix, macro- and micro-minerals, protein, AA, dry matter, moisture, ash, fat, fibre, carbohydrates and energy content) composition, microbial content, and shelf-life of three lucerne cultivars, ‘SA Standard’ (‘SAS’), ‘WL525’ and ‘WL711’, were investigated. It was compared to SB (Beta vulgaris var. cicla L.), to identify the lucerne cultivar to use for future research purposes. The Brix content of the lucerne cultivars was significantly (p<0.01) higher than SB. Raw lucerne cultivars had significantly (p<0.01; p<0.001) higher Ca and S contents than raw SB. The K, S and Mn content for the raw lucerne cultivars were significantly (p<0.001) higher than the cooked cultivars. The protein content of the raw lucerne cultivars were significantly (p<0.001) higher than the raw SB. Cooked ‘SAS’ and ‘WL525’ had significantly (p<0.001) higher protein contents than cooked SB. Both raw and cooked ‘SAS’ had a significantly (p<0.001) higher carbohydrate and energy contents than both raw and cooked ‘WL525’, ‘WL711’ and SB. The lucerne cultivars contained higher values of essential and non-essential AA than SB. The total bacterial count, coliform count, lactic acid bacteria count and mould count conformed to standards, while cooking significantly (p<0.001) reduced the bacterial load. The shelf-life of cooked lucerne and SB samples were of satisfactory microbiological quality until day seven. The sensory descriptive attributes of the three lucerne cultivars were determined, by using GDA, and consumers’ acceptance (degree of liking for aroma, taste, mouthfeel and overall acceptability). ‘SA Standard stew’ showed the lowest value, of the lucerne samples, for fibrous appearance, chewy and fibrous mouthfeel, bitter taste, and bitter and metallic aftertaste. Principal component analysis showed that, three stew samples (SB, ‘SAS’ and ‘WL525’) and plain SB displayed ‘positive’ attributes, such as soft and wet appearance, spinach beet aroma and salty taste. ‘WL711 stew’ and three plain samples (‘SAS’, ‘WL525’ and ‘WL711’) were associated with ‘negative’ descriptors, namely grassy aroma, fibrous and chewy texture, fibrous appearance, bitter taste, and bitter and metallic aftertaste. ‘SA Standard stew’ was the most preferred lucerne cultivar, as it’s values for degree of liking for aroma, mouthfeel, taste and overall acceptability were numerically higher than ‘WL525’ and ‘WL711’. External preference mapping indicated that three consumer clusters, with different lucerne preferences, were obtained by AHC. ‘SA Standard stew’ was the lucerne sample preferred by all the consumers, except those with some primary education and a yearly income of R501 000 – R750 000 per year, who indicated only a high acceptance for this sample. While 63.1% of the respondents knew what lucerne was, 77% was unfamiliar with the term ‘alfalfa’ and 90.3% never consumed lucerne before. Younger respondents of the white population group, with a grade 12 or higher education, were significantly (p<0.001) more knowledgeable about lucerne. The predictors, sensory qualities and synonyms, contributed significantly (p<0.001) to consumers’ attitudes towards lucerne. While respondents believed that ‘health general’ (40.1%) was the most important advantage of eating lucerne, ‘sensory properties’ (35.4%) and ‘vegetables spinach’ (24.5%) were regarded as the most important disadvantage and association, respectively. The differences in lucerne knowledge of respondents from different demographic backgrounds indicated a need to inform SA consumers, on the benefits of consuming lucerne. Based on these findings, lucerne could be implemented as an alternative vegetable protein and therefore, cultivar ‘SAS’ was proposed for future studies and product development.
Open Access
The effect of sodium reduction on the chemical, microbial and sensory quality of prominent South African processed meat products
(University of the Free State, 2016-08) Cluff, MacDonald; Hugo, A.; Hugo, C. J.
English: In light of the recent South African regulations limiting the sodium content of processed meat products, the latest draft of these regulations were used to establish to what extent commercial processed meat products deviated from these limits and required reformulation, two and a half years in advance of the first reduction limits coming into effect. Almost 60% of product labels already included information on sodium content almost three years before the applicable labelling regulations came into effect. Surveying nationally and regionally available products allowed for the identification of the five largest product classes. A comparison between labelled and determined Na content revealed that processors tended to overestimate Na content as a precautionary measure. A generous tolerance of 20% for underestimating the Na content, as stated in the labelling regulations draft, showed that only a small number of products would at the time, have exceeded the futuredated regulatory limits. Bacon, polony and pork bangers, representing the three most populous classes were used to evaluate the efficacy of the two-part regulatory limits as intermediate added NaCl levels without replacers or alterations in processing. Water activity, pH and moisture content were inconsistently affected with no definite links to deviations in dependent parameters such as microbial stability. Microbial and oxidative stability and sensory quality results were encouraging. Current processing techniques and ingredients other than NaCl maintained quality and stability. Changes in bacon and banger colour were found, although subjective evaluation is needed to grasp the implications. Polony texture was deemed acceptable, both quantitatively and qualitatively. Total Na levels better matching the regulatory limits may further limit the minor deviations in quality and stability. The relative success of using only 1% NaCl (w/w) in the pork bangers prompted the use of various compounds, either alone or in combination, to address the gaps in functionality of the 1% NaCl removed from the original formulation. Potassium chloride (1% w/w), K-gluconate (1% w/w), KCl (0.8% w/w) with YE (1% w/w) and lastly, KCl (0.8% w/w) with K-lactate (0.2% w/w) were compared to 1% NaCl and 2% NaCl controls. Treatments containing KCl had improved cooking losses over that of the controls. The use of K-containing compounds increased the K-content in addition to reducing Na-content. Basic chemical parameters were similar to that of the 2% NaCl control with only water activity being more similar to that of the 1% NaCl control. These replacers did not improve lipid oxidative stability and the use of YE actively deteriorated lipid oxidative stability. Colour was the most affected multi-component parameter and consumers had less favourable hedonic responses towards the use of K-gluconate. Partial replacement with 1% KCl was the most suitable solution when additional factors such as price-point, similarity to NaCl, and ease-of-use were taken into account. Lastly, the efficacy of the reduction and/or partial replacement of NaCl against the growth and survival of E. coli and S. aureus inoculated into banger batters were monitored. No effects on E. coli were observed beyond the bacteriostatic effect of sub-optimal temperatures (4 °C and 10°C) and the anti-microbial effects of the other additives in the formulations. At reduced NaCl levels, S. aureus was unable to grow and survival rate ultimately decreased. Partial replacement led to limited growth although survival rates eventually decreased. Survival rates were highest at 1% NaCl, 1% KCl and 0.2% K-lactate. Sub-optimal temperatures and other anti-microbial effects overrode that of partial NaCl replacement. Beyond the initial inoculation levels, reduction and/or partial replacement of NaCl did not increase the food safety risk of these bacterial species. This research showed that conformation with the regulatory limits warrants a back-to-basics strategy using multiple approaches that deliver better results when these approaches are linked to one another.
Open Access
The taxonomy and significance of Chryseobacterium isolates from poultry
(University of the Free State, 2012-01) Charimba, George; Hugo, C. J.; Jooste, P. J.
Species of the genus Chryseobacterium (family Flavobacteriaceae) occur widely in clinical, environmental and industrial ecosystems. In the clinical environment, they are uncommon etiologic agents, but their infections may be serious in immunocompromised patients. They are often resistant to multiple antimicrobial agents making infections due to these organisms potentially difficult to treat. In the food environment, they are known to cause spoilage of foods such as canned products, milk and dairy products, fish, meat and poultry. It is therefore necessary to be able to solve or anticipate and avert possible problems caused by Chryseobacterium species. This genus also has positive characteristics which include synthesis of a number of enzymes potentially useful in industry (e.g. keratinolytic enzymes), medicine (e.g. prion degradation) and turnover of organic matter in soil, water and sewage plants. Taxonomic studies are key to solving such problems by characterization and identification of such organisms. This also sets the foundation for investigation of the organism’s beneficial roles and applications. In this study, some Chryseobacterium strains isolated from poultry feather waste and raw chicken, were phenotypically characterized and identified using conventional tests and the BIOLOG Omnilog Gen II system. Phylogenies of seven selected isolates were determined using the 16S rRNA gene sequence analysis and they were further characterized using the BIOLOG Omnilog Gen III identification system. They fell into four taxonomic groups (Group 1: 1_F178; Group 2: 5_R23647; Group 3: 6_F141B and 7_F195; and Group 4: 8_R23573, 9_R23581 and 10_R23577) which did not show affiliation to any currently recognised type species of the genus Chryseobacterium suggesting that these groups were possible representatives of novel species. Three selected strains (8_R23573, 9_R23581 and 10_R23577) were subjected to a polyphasic taxonomic study to determine their exact taxonomic identities. Results of the predominant respiratory menaquinone, fatty acid methyl esters and DNA base composition supported the affiliation of the strains to the genus Chryseobacterium. When subjected to DNA-DNA hybridization, the strains gave relatedness values of more than 81% among the three strains and less than 57% similarity between the strains and their two nearest phylogenetic neighbours C. shigense (DSM 17126T) and C. luteum (LMG23785T). A novel species emerged after a comparison of the phenotypic, chemotypic and genotypic results. The new species was described and the name Chryseobacterium carnipullorum sp. nov. was proposed. Analysis using the BIOLOG Phenotype MicroArray (PM) system, revealed that C. carnipullorum has the potential to cause food spoilage mainly by utilizing carbohydrates, carboxylic acids and amino acids by producing metabolites which lead to souring, butyric spoilage defects, alkalinisation, bitter tastes and sulphide spoilage. The organism was also shown to have potential for biotechnological applications in food and stockfeed technology; coffee extraction, oil drilling and detergent industries; manufacture of artificial antigens and chemical diagnostic agents and release of oligosaccharides and oligopeptides in (ultra) oligotrophic freshwater environments. It was found that the new species was able to produce extracellular keratinases that were able to extensively degrade chicken feather waste in 48 h. This has the potential of contributing toward solving the disposal problem which is experienced by the poultry industry that produces huge amounts of the recalcitrant feather waste as a by-product. Currently, a very small percentage of feather waste is steamed, treated chemically and ground to form dietary protein supplement for stockfeeds. Degradation of feathers using keratinolytic organisms is a more economical and environmentally friendly alternative. Chryseobacterium carnipullorum also has the potential for application in other biotechnological processes involving keratin hydrolysis. Hydrolysed feathers can be converted to fertilizers, glues, films, and they can be used as the source of rare amino acids, such as serine, cysteine and proline.
Open Access
Taxonomy, spoilage, and virulence characteristics of 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 species isolated from fish
(University of the Free State, 2023) Gavu, Masabata Lydia; Hugo, C. J.; Hitzeroth, A. C.
In previous studies at the University of the Free State, aerobic, Gram-negative bacteria were isolated from Cape hake (𝘔𝘦𝘳𝘭𝘶𝘤𝘤𝘪𝘶𝘴 𝘤𝘢𝘱𝘦𝘯𝘴𝘪𝘴), intended for human consumption. Although some of these isolates could be identified, six isolates remained unidentified. The purpose of this study was to determine the genomic and phenotypic characteristics of these isolates to assign them to the correct genus, to describe novel species, if present, to determine the significance of these isolates in terms of pathogenicity and/or spoilage, and to isolate bacteriophages against the bacterial strains for possible biocontrol strategies. Based on 16S rRNA gene sequences, phylogenetic analysis confirmed that the six unidentified bacterial strains used in this study represented members of the genus 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢. Four of these six isolates were further characterized to determine whether they were novel species. Using genomic and phenotypic techniques, the DNA G+C content of strains SH 11-4(b), SH 19-2(b), SH 20-4 and SH 40-3 supported their affiliation with the genus 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢. Digital DNA-DNA hybridization, average nucleotide identity and amino acid identity values, and phenotypic characteristics demonstrated that strains SH 11-4(b), SH 19-2(b) and SH 40-3 represented novel species of the genus 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢. Results for strain SH 20-4 confirmed that it was not a novel species but represented another member of 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 𝘤𝘢𝘳𝘯𝘪𝘴. The names of the novel species were proposed as 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 𝘮𝘦𝘳𝘭𝘶𝘤𝘤𝘪𝘪 SH 11-4(b), 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 𝘱𝘪𝘴𝘤𝘪𝘴 SH 19-2(b), and 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 𝘧𝘳𝘪𝘨𝘪𝘥𝘪𝘱𝘪𝘴𝘤𝘪𝘴 SH 40-3. The potential pathogenicity and/or food spoilage capability of the six 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 fish isolates and reference strains were then evaluated by determining the production of siderophores, the production of a variety of enzymes that function as virulence factors, evaluating their antimicrobial resistance patterns, their ability to form biofilms, as well as the determination of their resistance to antibiofilm compounds. All the 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 isolates produced Siderophores indicating their ability to sequester iron for survival. Gelatinase, whose expression has been linked to enhanced biofilm formation, was produced in the most significant amounts by most organisms in this study. ‘𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 𝘮𝘦𝘳𝘭𝘶𝘤𝘤𝘪𝘪’ SH 11-4(b) could be regarded as a potential pathogen since it produced more than 4/8 virulence enzymes. 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 strains SH 11-3(a) and ‘𝘒. 𝘧𝘳𝘪𝘨𝘪𝘥𝘪𝘱𝘪𝘴𝘤𝘪𝘴’ SH 40-3 were the most resistant to antimicrobials. The antimicrobial resistance/susceptibility of the 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 and 𝘊𝘩𝘳𝘺𝘴𝘦𝘰𝘣𝘢𝘤𝘵𝘦𝘳𝘪𝘶𝘮 species in this study was determined using the Kirby-Bauer disc diffusion susceptibility method. The antimicrobial tests concluded that the fluoroquinolone and cephem antimicrobials would be the most effective in treating 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 infections. 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 𝘤𝘢𝘳𝘯𝘪𝘴 SH 20-4 was regarded as a strong biofilm former since it gave positive results for biofilm formation using three different methods, while strains SH 11-3(a) and ‘K. 𝘮𝘦𝘳𝘭𝘶𝘤𝘤𝘪𝘪’ SH 11-4(b) were the least successful at forming biofilms. This study revealed that 100 mM D-glucose was the most effective biofilm inhibition compound against the 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 test strains. Organisms whose biofilms showed the most resistance towards the inhibition compounds included K. 𝘤𝘢𝘳𝘯𝘪𝘴 SH 20-4 and ‘K. 𝘧𝘳𝘪𝘨𝘪𝘥𝘪𝘱𝘪𝘴𝘤𝘪𝘴’ SH 40-3 and susceptibility to the inhibition compounds mainly was observed in SH 11-3(a), SH 11-3(b), ‘K. 𝘮𝘦𝘳𝘭𝘶𝘤𝘤𝘪𝘪’ SH 11-4(b) and ‘K. piscis’ SH 19-2(b). Another aim of this study was to isolate lytic bacteriophages against the 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 species that may be pathogenic to fish or may cause food spoilage by using a two-fold agar overlay in a plaque experiment. Thirty-four phage isolates were obtained from the sewage and fishpond water samples. Strains SH 11-3(a) and SH 11-3(b) showed sensitivity toward a few phage isolates while ‘K. 𝘱𝘪𝘴𝘤𝘪𝘴’ SH 19-2(a) displayed the greatest resistance towards phage infection. Phage strains 11-3(b)-S2 showed a broader host spectrum than other phage isolates because they displayed lytic activity against 5/12 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 isolates. Most of the isolated phages were identified by transmission electron microscopy as members of the 𝘊𝘰𝘳𝘵𝘪𝘤𝘰𝘷𝘪𝘳𝘪𝘥𝘢𝘦, 𝘗𝘭𝘢𝘴𝘮𝘢𝘷𝘪𝘳𝘪𝘥𝘢𝘦, 𝘔𝘪𝘤𝘳𝘰𝘷𝘪𝘳𝘪𝘥𝘢𝘦, 𝘚𝘪𝘱𝘩𝘰𝘷𝘪𝘳𝘪𝘥𝘢𝘦 𝘢𝘯𝘥 𝘛𝘦𝘤𝘵𝘪𝘷𝘪𝘳𝘪𝘥𝘢𝘦 families. The three new members of the genus 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 were accurately classified, described, and named. The role of the six 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 species in virulence was determined. Some isolated phages can potentially prevent, eliminate, or reduce 𝘒𝘢𝘪𝘴𝘵𝘦𝘭𝘭𝘢 infections in fish.

Browse

Browsing Doctoral Degrees (Microbial, Biochemical and Food Biotechnology) by Advisor "Hugo, C. J."

Results Per Page

Sort Options