Faculty of Applied Sciences
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Item The development of a method for the analysis of Mahewu(1994) de Goede, Richard Goodwin; Adamson, J. H.; Neethling, D. N.A comparison was made of various methods for the analysis of the odoriferous components of Mahewu, a fermented mealie meal porridge. The most satisfactory procedure was found to be that of dynamic headspace sampling. This technique, used in conjunction with gas chromatography and mass spectrometry, allowed the positive identification of several components .Item Quality and storage stability of yoghurt produced from pigeon pea milk supplemented with Propionibacterium freudenreichii(2017) Yusuf, Amina Osizemeyele; Ijabadeniyi, Oluwatosin Ademola; Shode, Francis O.Pigeon pea (Cajanus Cajan) is consumed in many parts of Africa as a source of protein and carbohydrate. It is underutilised and mainly grown for subsistence. Researching on pigeon pea may enhance value addition and increase its utilization. In this study, a non-dairy probiotic yoghurt was prepared from pigeon pea milk. Yoghurt samples were prepared, using 100% pigeon pea milk, pigeon pea/soy milk in the ratio 50:50 and 100% soy bean milk. The yoghurts were inoculated with yoghurt starter cultures and divided into two equal parts. One part inoculated with Propionibacterium freudenreichii was referred to as probiotic yoghurt, while the other part served as the control. The nutritional, sensory and some functional properties of the yoghurt were determined. The microbiological quality of yoghurt samples stored at 4, 10 and 21°C, respectively, for 4 weeks, were monitored and analysed for aerobic spores’ formers, E. coli, total plate counts, mould and Propionibacterium freudenreichii weekly. The protein contents of the yoghurt samples varied from 4.54-5.85% for 100% soymilk and 100% pigeon pea yoghurt respectively. The probiotic yoghurt showed slightly lower protein content than pigeon pea yoghurt alone. All the yoghurt samples had considerably high total solids (16.04-17.41%) and were fairly good sources of amino acids. Essential amino acids in the yoghurt samples were comparable to the FAO/WHO (2007) recommended amino acid requirement for adults. Anti-nutritional factors of yoghurt samples were significantly lower (P≤0.05) than their milk counterparts, which may be attributed to the fermentation process. Probiotic yoghurt samples showed higher firmness than non-probiotic samples. Total plate counts (log 7.01- 7.46 CFU/ml) samples stored for 2 weeks at 4° C were similar. Predominant organisms were LAB and Propionibacterium freudenreichii. Storage temperature of yoghurt samples had an influence on the total plate count and LAB. Total plate count and LAB significant increased approximately by log 2 CFU/ml for the first two weeks of storage. However, moulds and E. coli were not detected in all samples. Beyond 2 weeks of storage, there was significant decline in total plate counts and LAB, while mould grew and increased. Aerobic spore formers and moulds were observed in the control yoghurt. However, E. coli was not found in all yoghurt samples throughout storage period. The pH of the milk in which yoghurt mixtures were formulated, ranged from pH 7 to 6.8 for pigeon pea and soymilk declined significantly as a result of acidification. Decline in pH at 4, 10 and 21°C was significant (p≤0.05) with the rate higher at 21, 10 than 4° C. Decline in pH resulted in increased TTA values over storage temperatures and periods. Samples stored at 21°C and 10°C had significantly higher TTA values than samples stored at 4° C. The colour values evaluated were recorded as L*, b*, a* and ∆E* during 4 weeks storage at 4, 10 and 21° C. Significantly high values (p≤0.05) were recorded for L* yoghurt samples with soymilk. The colour scale defines positive (red) and negative (green) for a* and b* positive (yellow) and negative (blue). All a* values both positive and negative were less than 3. There was no negative value recorded for b*. Colour difference ∆E* values trends increased as storage time and temperature increased. There were significant (p≤0.05) differences between samples stored at same and different storage temperatures and periods. Water holding capacity was significantly different (p≤0.05) in all the yoghurt samples stored at 4, 10 and 21°C for 4 weeks. Formulation with 100% soymilk recorded higher values. Soy yoghurt and probiotic yoghurts (100 %) showed higher water holding capacity compared to pigeon pea yoghurt and pigeon pea/soymilk yoghurt. The addition of Propionibacterium freudenreichii did not significantly affect sensory properties of the yoghurts. Acceptable yoghurt was produced from pigeon pea with comparable quality to soy which serves as control. Proximate composition was comparable to previous reports. Microbial quality and profile of all the yoghurt samples were similar. The absence of pathogenic bacteria in all the yoghurt samples confirm their safety. Soy yoghurt was most acceptable amongst the yoghurt samples but all the samples had comparable ratings, and these ratings are within commercially acceptable range (4 to 9) for yoghurt. Storage at 4oC should be the most acceptable, as storage at 21oC encourage proliferation of contaminantItem Development of a starter culture for the production of Gari, a traditional African fermented food(2010) Edward, Vinodh Aroon; Singh, Suren; Franz, Charles M. A. P.; Van Zyl, Petrus J.Cassava, (Manihot esculenta Crantz), is used for the production of a variety of West African foods and ranks fourth in the list of major crops in developing countries after rice, wheat and maize. Gari is one of the most popular foods produced from cassava. Cassava may contain high levels of linamarin, a cyanogenic glucoside, which in its natural state is toxic to man. Therefore, some processing methods that can enhance the detoxification of cassava and lead to the improvement of the quality and hygienic safety of the food are vitally important for less toxic products to be obtained. Quality, safety and acceptability of traditional fermented foods may be improved through the use of starter cultures. There has been a trend recently to isolate wild-type strains from traditional products for use as starter cultures in food fermentation. A total of 74 bacterial strains and 21 yeast strains were isolated from a cassava mash fermentation process in a rural village in Benin, West Africa. These strains were assessed, together with 26 strains isolated at the CSIR from cassava samples sent from Benin previously, for phenotypic and technological properties. Twenty four presumptive lactic acid bacteria (LAB) were selected for further phenotypic, genotypic and technological characterization during a research visit to the BFE (now Max Rubner Institute of Nutrition and Food). After assessment, the strains VE 20, VE 36, VE 65b, VE 77 and VE 82 were chosen for further study as starter cultures. These L. plantarum strains were chosen on the basis of predominance and possession of suitable technological properties. The investigation of this study was complemented by further, similar studies on further Gari isolates in Germany by the BFE. That study was done independently from this study, but both studies served to select potential starter cultures for cassava fermentation for the production of Gari, as this was the common goal of the project. Thus, a wider final selection of potential starter cultures was decided on at the project level and this selection was further tested in fermentation experiments. A total of 17 strains were grown in optimized media in 2 L fermenters. These strains were freeze-dried and thereafter tested in lab-scale cassava mash fermentation trials. xiii The strains performed well in the small scale bucket fermentations. There was a rapid acidification evidenced by the increase in titratable acidity, ranging from 1.1 to 1.3 % at 24 hours, and 1.3 to 1.6 % at 48 hours. The effect of the starter was obvious in that it lowered the pH much faster and to lower levels than the control. It appeared that both the processing and starter culture addition played a role in the removal of cyanide during processing of the cassava into Gari. This was evident from the lower cyanide values obtained for fermentations that included starter cultures. The study also showed that especially the L. plantarum group strains could be produced as starter cultures at lower costs than compared to L. fermentum, W. paramesenteroides or L. mesenteroides strains. Overall the results of this study were crucial for the project in showing that a starter culture which is easy and economical to produce and which has the desired attributes is a feasible possibility for application in the field.