Effect of high pressurized carbon dioxide on Escherichia coli

Carbon dioxide at high pressure can retard microbial growth and sometimes kill microorganisms depending on values of applied pressure, temperature and exposure time. In this study the effect of high pressurised carbon dioxide (HPCD) on Escherichia coli was investigated. Culture of E. coli was subjected to high pressurised carbon dioxide at 15, 25 and 35 bar, and varying exposure times of 20, 40, 60 and 90 minutes at room temperature (27 oC). Microbial inactivation increased with pressure and exposure time. For the first 20 minutes reduction of viable microbial cells was 18%, 30% and 36% at 15, 25 and 35 bar, respectively. Higher microbial inactivation values were achieved at 40, 60, and 90 minutes. Decimal reduction times were 127, 93 and 75 minutes at 15, 25, and 35 bar, respectively. The pH values of treated samples decreased with increasing pressure and treatment time from approximately neutral to 5.71 at 15 bar, and 5.02 at 35 bar. It was concluded that high pressurised carbon dioxide has antimicrobial effect on E. coli bacteria. With further studies, HPCD microbial deactivation can be used for foods preservation as a alternative technology to conventional heat pasteurisation and sterilization

Co-composting of banana peel and orange peel waste with fish waste to improve conversion by black soldier fly (Hermetia illucens (L.), Diptera: Stratiomyidae) larvae

Black soldier fly (BSF) larvae composting is a promising waste treatment that can add value to available biodegradable waste. However, substrates that have low protein content and contain complex molecules (e.g. fruit peels) are not easily degraded by the larvae. This study evaluated the impact on the BSF larvae composting efficiency of co-composting different mixtures of banana and orange peels with incremental increase of fish waste. Mixtures (in total 50 distinct mixtures) of varying proportions of banana peels, orange peels and fish waste were evaluated. BFSL fed on orange peel and banana peel mixtures, containing no fish waste, resulted in a lower biomass conversion efficiency (4.5% +/- 1.3) on a volatile solids (VS) basis (BCEvs). Co-composting the fruit peels with fish waste increased the biomass conversion efficiency and the highest BCEvs (25%) was attained when 75% fish waste was included. However, the BCEvs varied greatly (18.0% +/- 5.8), likely due to varying fish waste composition. A 25% fish waste inclusion resulted in more than twice as high BCEvs (12.3% +/- 2.1) compared to when no fish waste was included. As the conversion efficiency variance increased with increasing fish waste inclusion, it was recommended to keep the inclusions of the fish waste to around 25% of the total mixture, in order to increase the reliability of the BSF larvae composting efficiency

Food industry waste - An opportunity for black soldier fly larvae protein production in Tanzania

Black soldier Ily larvae composting is an emerging treannent option with potential to improve biowaste valorization in cities of low-income countries. This study surveyed the current generation and management status of food industry biowaste and their availability and suitability as potential feedstock for black soldier Ily larvae (BSFI.) composting treatment in three Tanzania cities, Dar es Salaam, Mwanza, and Dodoma. Biowaste-generating food industry companies (n = 29) in the three cities were found to produce banana peels, mango seeds, sunflower press cake, brewery waste, and coffee husks in large quantities (similar to 100,000-1,000,000 kg y(-1)). Around 50 % of these companies (16/29), primarily vegetable oil companies (10/11), either sold or gave away their waste as animal feed, while most companies (9/11) with unutilized food industry waste landfilled the generated biowaste. Multi-criteria analysis based on substrate availability criteria identified banana peels, mango seeds, and coffee husks with total score points of a >= 10/12 as the most suitable feedstock for BSFL composting. However, multi-criteria analysis based on physicalchemical criteria identified brewery waste and sunflower press cake with total score points of a >= 11/15 as the most suitable feedstock. Combined availability and physical-chemical properties of individual biowastes showed that all identified types of food industry biowaste can be suitable feedstock for producing BSFL biomass for protein production, but certain waste streams needed to be mixed with other waste streams prior to BSFL-composting to ensure sufficient availability and provide a balanced nutritional profile compared with the single-source biowastes. This study concluded that large volumes of food industry waste are being generated from food industry companies in Tanzania and there is need to establish new biowaste management interventions for resource recovery. Furthermore, for interested stakeholders in the waste management business, multi-stream BSFI.-composting can be a suitable solution for managing and closing nutrient loops of the unutilized food industry biowaste in Tanzania and in other similar settings globally

Effect of cultivar and ripening on the polyphenol contents of East African highland bananas (Musa spp.)

East African highland bananas (EAHBs) contain high amount of phenolics especially tannins, and are used to produce low-viscosity banana juice by a purely mechanical process. Occasional juice failure and cloudy appearance are the major problems facing juice production. The present work thus examined the variations in phenolic content of EAHB cultivars and their changes during ripening. The aim was to obtain a better knowledge of the various forms and amounts of phenolic compounds in different EAHBs, and how these properties may affect the ability of cultivars to produce low viscosity banana juice. Eleven banana cultivars including juice-producing and cooking bananas were harvested at the green maturity stage and analysed for total phenolic content (TPC), tannin content (TC), and tannin monomers at different ripening stages for five days. Analyses of TPC and TC were performed using the Folin-Ciocalteu method, whereas tannin monomers were identified by High-Performance Liquid Chromatography (HPLC) with UV detection. Multivariate analysis of variance was used to evaluate the relationship between cultivar, ripeness stage, and TPC/TC. A substantial difference in TPC was observed between juice-producing and cooking cultivars. The highest TPC was found in the juice-producing cultivar Kibungara (360.68 +/- 17.12 mg GAE/100 g) at day 5 (the ripe stage), while the lowest TPC (8.67 +/- 0.22 mg GAE/100 g) was observed in the cooking cultivar Malindi at ripening day 5. The results revealed that TPC and TC of banana pulp seemed to be more related to cultivar (p <= 0.05) than physiological changes during ripening (p >= 0.05). Further, HPLC analysis showed that among the individual catechins, gallocatechin was the predominant monomer in juice-producing cultivars, whereas in cooking cultivars, gallic acid was dominant. The present work indicated that high amount of total phenolic such as tannins especially gallocatechin in juice-producing banana cultivars favour the release of banana juice, and that analysis of phenolic compounds will provide a basis in the selection of banana cultivars with high potential for juice production