Effects of Feed Moisture Content, Soybean Ratio and Barrel Temperature on Physical and Functional Properties of Extruded Maize-Soybean Flour Blends

The effects moisture content, temperature and soybean ratio on expanded product characteristics of extruded maize-soybean blends were studied. Response surface methodology was used to study the effects of extrusion conditions on extrudate properties taking barrel temperature (BT), feed moisture content (FM) and soybean flour ratio (SR) as factors. Expansion ratio (ER), water absorption index (WAI), water solubility index (WSI), hardness and colour (b* - (+) yellowness) of the extrudates were determined. BT and FM had significant effects on ER (p < 0.05). At low FM levels, ER increased with BT. It was observed that both FM and BT significantly affected WAI and WSI. WAI increased as FM increased. Increasing FM to 20% resulted in a decrease in WSI, beyond which an increase was observed. Hardness increased significantly as feed moisture content increased. High SR content significantly increased the extrudate hardness. FM had no significant effect on colour. Colour increased as the SR and BT increased. Significant regression models explained the effects of SR, FM, and BT on all response variables. All of the response variables' R2, were higher than 0.89. Keywords: Maize, Soybean, moisture content, extrusion

APPLICATION OF REFRIGERATED AND FROZEN SORGHUM MALT SLURRIES IN THE PRESERVATION OF STARTER CULTURES FOR OBUSHERA FROM UGANDA

Industrial production of traditional fermented beverages is limited by lack of quality commercial starter cultures. Saccharomyces cerevisiae MNC21Y and Lactobacillus plantarum MNC21 can be used to ferment cereal beverages such as Obushera.  These cultures are unavailable as commercial starters due to lack of appropriate propagating and distributing procedures. The purpose of this study was to evaluate the use of refrigerated and frozen sorghum slurries as carrier media for the starters. Starters were propagated in sorghum slurries (30°C for 24 h) and stored at 5°C and -18°C for 90 days. Viability of Saccharomyces cerevisiae and Lactobacillus plantarum was determined by cell counts after surface plating and pour plating, respectively. Fermentation ability was determined by inoculating sorghum slurries with starters and monitoring pH, acidity and flavor development. Viability was higher for starters stored at 5°C (S. cerevisiae: 6 log cfu.g-1 and Lb. plantarum: 7-9 log cfu.g-1during 90 days) than those at -18°C (S. cerevisiae: 2 cfu.g-1 and Lb. plantarum: 4 log cfu.g-1after 30 days). Refrigerated starters acidified Obushera (pH £ 4.5) faster (10-20 h) than frozen ones (18-24 h). Refrigerated or frozen S. cerevisiae + Lb. plantarum starters in sorghum malt slurries can remain viable for at least one or three months, respectively and produce Obushera with characteristic flavors

Kombucha Production in Uganda: Quality Aspects and Compliance With Standards

Kombucha is a mildly sweet and acidic fermented tea beverage. Its production and consumption in Uganda have expanded dramatically as a result of its purported nutritional and health benefits. However, there has been little research into the quality and safety of commercially produced Kombucha in Uganda. This study evaluated the quality and safety of certified (n = 27) and uncertified (n = 16) Kombucha on the market. It also assessed the knowledge and practices of Kombucha processors with certified (n = 4) and uncertified (n = 4) products in Uganda. A HACCP plan for Kombucha processing was also developed and validated with one processor. All products passed the Kombucha requirements for Staphylococcus aureus, Escherichia coli, Salmonella spp., and heavy metals (lead, arsenic, mercury, and cadmium). However, 60.47% of the products did not meet the quality and safety specifications for Kombucha failing to meet the acidity (n = 3), alcohol content (n = 14), and yeasts and molds (n = 15). The majority of the processors (n = 6) had very good scores (&gt; 75%) for knowledge and practices related to food safety but did not know the importance of sanitizing equipment. Half of the processors did not know about HACCP, its prerequisites, and the Kombucha specification. Four processors did not use objective methods to test product readiness. Half of the processors did not follow the Kombucha specification and had no HACCP plan. A HACCP plan with three CCPs and five CPs was developed and validated. This study, therefore, informs Kombucha processors and regulators on the safety and quality of Kombucha on the market and the importance of HACCP plan development and implementation in achieving product quality.</p

Survival and Acidification Potential of Lactobacillus Plantarum MNC 21 Stored in Air-Dried Sorghum Flours

Increased commercialization of indigenous fermented foods requires availability of affordable starter cultures. The starters should also maintain functionality when stored at ambient conditions, especially where erratic power supply makes constant refrigeration unachievable. This study evaluated the survival of Lactobacillus plantarum MNC 21 starter culture air-dried (at 25 or 30°C) in sorghum flour and stored at 25°C for 30 days. Two sorghum varieties (malted and un-malted) were used. To determine their fermentation efficiency during storage, sterile sorghum malt slurries were inoculated with the dried culture and fermented at 30°C for 24 h. Acidification potential was determined at 5 days intervals by measuring microbial counts, pH and titratable acidity. Microbial concentrations dropped from 8-9 log cfu/g on day 0 to 1 log cfu/g on day 30. Sorghum variety and whether it was malted or un-malted did not affect culture survival. Culture dried at 25°C had better survival during the first 10 days (8-9 log cfu/g) than that dried at 30°C (8 log cfu/g) but survival between days 20-30 was similar (1-4 log cfu/g). The acidification potential (ability to reduce pH to ≤4.5) decreased with storage time: 4 h (day 0), 24 h (day 15), &gt; 24 h (day 20) to no acidification (days 25-30). Air drying of starter cultures in sorghum flours coupled with storage at ambient temperatures could be adopted as a short-term preservation method. This low-cost technology is suitable for processors in developing countries where maintenance of a cold chain is hampered by unreliable electricity supply.</p

Effect of sweet potato endogenous amylase activation on in vivo energy bioavailability and acceptability of soy‐enriched orange‐fleshed sweet potato complementary porridges

Energy bioavailability can be influenced by food matrix factors and processing conditions or treatments. In this study, the effects of endogenous sweet potato amylase enzyme activation and slurry solids content of soy‐enriched orange‐fleshed sweet potato (OFSP) porridges on in vivo energy bioavailability (energy, weight gain, and feed efficiency ratio) and porridge acceptability were determined. Fifty‐six weanling albino rats were randomly assigned to two blocks each having eight groups of seven rats. The rats were housed in individual cages in a well‐ventilated animal house. The intervention block had rats fed on activated porridges (held at 75°C for 15 min), while rats in the control block were fed on nonactivated porridges (boiled at 90–95°C for 10 min). The rats were fed for 28 days on 50 ml of porridge per rat per day. The four groups per block were each fed on porridges with varying amounts of total solids content (10%, 15%, 20%, and 25%). Weight gain, energy bioavailability, and feed efficiency ratio were determined at the end of the feeding period. Consumer acceptability of activated and nonactivated porridges at 25% solids content was determined using a nontrained human panel (n = 40). Activation of amylases did not significantly (p &gt; .05) affect the bioavailable energy, cumulative weight gain, and feed efficiency of the rats. Increasing slurry solids content of activated and nonactivated porridges significantly (p &lt; .05) increased feed efficiency ratio (−14.6 ± 11.7 to 102.3 ± 2.3), weight gain (−1.4 to 5.6 g ± 1.9 g), and bioavailable energy (702.8 ± 16.2 to 1242.8 ± 12.2 kcal). Activation of amylases reduced porridge viscosity but did not significantly influence the overall acceptability. This work demonstrates the opportunity of utilizing sweet potato amylases to facilitate the preparation of complementary porridges with appropriate viscosity and increased energy density

Sorghum Malt Extract as a Growth Medium for Lactic Acid Bacteria Cultures: A Case of Lactobacillus plantarum MNC 21

Cultivation of lactic acid bacteria cultures is vital for research and commercial production of fermented foods. However, the conventional growth media used are generally costly. Malt extracts from four sorghum varieties (SESO 1, SESO 3, Epuripur, and Eyera) were evaluated as alternative low-cost growth media for Lactobacillus plantarum MNC 21. Saccharified sorghum malt extracts were inoculated with 4 log cfu/mL MNC 21 and incubated at 30°C for 24 h. MRS broth was the reference medium. Microbial counts, pH, titratable acidity (TA), free amino nitrogen (FAN), and total sugars were measured. Maximum microbial counts in the extracts and MRS broth were 9 and 10 log cfu/mL, respectively. Maximum growth rate in the extracts was 0.7–0.9 log cfu/mL/h and 0.8 log cfu/mL/h in MRS broth. The final pH of the extracts was 3.5–3.6, with an overall increase in TA of 1.2% in Epuripur and 0.2% in other varieties. Final pH and TA of MRS broth were 4.1 and 1.3%, respectively. Total sugars dropped by 95.2% and FAN by 2.1% in MRS broth. In contrast, total sugars and FAN dropped by 5.6–9.1% and 24.9–32.7% respectively, in the extracts. Sorghum malt extracts can be adopted as alternative low-cost growth media for lactic acid bacteria cultures

Probiotic Potential of Lactic Acid Starter Cultures Isolated from a Traditional Fermented Sorghum-Millet Beverage

The purpose of this study was to establish the probiotic potential of lactic acid bacteria (LAB) starter cultures, Lb. plantarum MNC 21, L. lactis MNC 24, and W. confusa MNC 20, isolated from a traditionally fermented sorghum-millet beverage from Uganda. The cultures were examined for tolerance to acid and bile salts, bile salt hydrolase (BSH) activity, antibiotic susceptibility, biogenic amine production, mucin degradation, hydrophobicity, auto-aggregation, adherence to the ileum, coaggregation, and antimicrobial properties against selected pathogenic species. Lb. rhamnosus yoba 2012, a known probiotic, was the reference. The isolates were tolerant to acid (pH = 3) and bile (1%). W. confusa MNC 20 and Lb. plantarum MNC 21 exhibited medium BSH activity (11–15 mm diameter of hydrolysis zone) while L. lactis and Lb. rhamnosus yoba 2012 exhibited low BSH activity (<10 mm diameter of hydrolysis zone). All isolates lacked mucolytic activity. Lb. plantarum MNC 21 and W. confusa MNC 20 produced agmatine. The candidate and reference microorganisms were resistant to 10 of 21 and 5 of 21 antibiotics, respectively. The isolates exhibited hydrophobic, auto-aggregation and coaggregation properties. These three properties were exhibited more (p<0.05) by the reference than the potential probiotics. The ability of the potential probiotics to attach onto the goat ileum (7.3–8.0 log cfu/cm2) was comparable to that of Lb. rhamnosus yoba 2012 (7.6 log cfu/cm2). The four LAB inhibited E. coli, S. aureus, and S. enterica to the same extent (p<0.05). The findings indicated potential probiotic activity of the starter cultures. However, further in vivo examination of these isolates is required to confirm their probiotic capabilities