Tonna A. Anyasi

Effect of organic acid pretreatment on some physical, functional and antioxidant properties of flour obtained from three unripe banana cultivars

Unripe banana flour (UBF) obtained from organic acid pretreatment of pulp from three non-commercial cultivars were profiled for physical, functional and antioxidant properties. UBF showed marked significant differences (p<0.05) in colour (CIEL(∗)a(∗)b(∗) and CIELCH) and water holding capacity with no significant difference in oil holding capacity. The total polyphenol content (TPC) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) differed significantly with M-red UBF recording high TPC (1130.39 ± 27.26 mg GAE/100g d.w.) at 10 g/L citric acid pretreatment. Correlation analysis between TPC and DPPH showed very strong positive correlation for Mabonde UBF in citric and lactic acid pretreatment (r = 0.999, p < 0.01; r = 0.985, p < 0.01), while inverse correlation was recorded in M-red UBF for ascorbic and lactic acid pretreatment (r = -0.031; r = -0.137). Organic acid pretreatment enhances the physical and antioxidant properties of UBF hitherto absent in composite food formulations.

Functional Properties and Postharvest Utilization of Commercial and Noncommercial Banana Cultivars

Banana (Musa spp.) is one of the worlds most important crops cultivated in tropical and subtropical regions of the world. Banana is a major source of macro-elements, especially potassium, and contains health-beneficial ingredients such as resistant starch, total dietary fibers, rapidly digestible starch, and slowly digestible starch. Oligosaccharides (fructooligosaccharides and inulin) and polyphenols ((+)-catechin, (-)-epicatechin, (-)-epigallocatechin, and gallic acid) are other ingredients present in bananas that have found application in the prevention of muscular contractions, regulation of blood pressure, prevention of colon cancer and diabetes, and in the cure of intestinal disorders when unripe. This review identifies the different commercial and noncommercial banana cultivars and their utilization. Commercial cultivars include Williams (M. acuminata cv. Williams), Dwarf Cavendish (M. acuminata cv. Petite Nain), Chinese Cavendish (M. acuminata cv. Chinese Cavendish), Grand Nain (M. acuminata cv. Grand Nain), and Goldfinger (M. acuminata cv. Goldfinger), with Mabounde and Luvhele identified as noncommercial varieties. Banana postharvest utilization includes its use as functional foods, prebiotics, probiotics, nutraceuticals, and processing into value-added products.

Morphological, physicochemical, and antioxidant profile of noncommercial banana cultivars

Banana cultivars––Luvhele (MusaABB), Mabonde (MusaAAA), and Muomva-red (Musa balbisiana) ––were characterized for morphological, physicochemical, and antioxidant properties. All three cultivars varied significantly (P < 0.05) in their morphology, pH, titratable acidity and total soluble solids with no significant difference in their ash content. Individual cultivars showed variations in flour starch granule when observed using a scanning electron microscope. Characterization of cultivars for total polyphenols (TPs) and antioxidant activity upon pretreatment with ascorbic, citric, and lactic acid shows that the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay of samples varied significantly as Muomva-red cultivar (1.02 ± 0.01 mg GA/g) expressed the highest DPPH activity at lactic acid concentration of 20 g/L. Total polyphenol content was also highest for Muomva-red [1091.76 ± 122.81 mg GAE/100 g (d.w.)]. The high amount of TPs present in these cultivars make them suitable source of bio-nutrients with great medicinal and health functions.

Some physical and functional properties of finger millet (Eleusine coracana) obtained in sub-Saharan Africa

The study determined the physical properties of finger millet (FM) (Eluesine coracana) grains and the functional properties of FM flour. Physical properties such as colour attributes, sample weight, bulk density, true density, porosity, surface area, sample volume, aspect ratio, sphericity, dimensional properties and moisture content of grain cultivars were determined. Water absorption capacity (WAC), bulk density (BD), dispersibility, viscosity and micro-structure of FM flours were also evaluated. Data collected were analyzed using SPSS statistical software version 23.0. Results showed that milky cream cultivar was significantly higher (p<0.05) than other samples in sample weight, bulk density, true density, aspect ratio and sphericity. However, pearl millet, used as a control, was significantly different from FM flour on all dimensional properties. Moisture content of milky cream showed higher significant difference for both grains and flours as compared to brown and black grain/flours. Milky cream cultivar was significantly different in L*, b*, C*, H* values, WAC, BD and dispersibility for both FM grains and flours. Data showed that brown flour was significantly higher in viscosity than in milky and black flours. Microstructure results revealed that starch granules of raw FM flours had oval/spherical and smooth surface. The study is important for agricultural and food engineers, designers, scientists and processors in the design of equipment for FM grain processing. Results are likely to be useful in assessing the quality of grains used to fortify FM flour.

Phenolics and essential mineral profile of organic acid pretreated unripe banana flour

Banana fruit (Musa spp) though rich in essential minerals, has also been implicated for the presence of phytochemicals which nonetheless beneficial, can also act as mineral inhibitors when in forms such as phenolic compounds, phytates and tannins. This study assayed the essential macro and trace minerals as well as phenolic compounds present in unripe banana flour (UBF) obtained from the pulp of four different cultivars. Unripe banana flour was processed by oven drying in a forced air oven dryer at 70°C upon pretreatment with ascorbic, citric and lactic acid. Organic acid pretreatment was done separately on each unripe banana cultivar at concentrations of 10, 15 and 20g/L. Phenolic compounds were profiled using liquid chromatography mass spectrometry electrospray ion (LC-MS-ESI) while essential minerals were determined using inductively coupled plasma atomic emission spectroscopy (ICP-AES) and mass spectroscopy (ICP-MS) respectively. Results of LC-MS-ESI assay of phenolics revealed the presence of flavonoids: epicatechin and myricetin 3-O-rhamnosyl-glucoside in varying concentrations in UBF. Essential mineral profile indicated that Zinc had the least occurrence of 3.55mg/kg (p<0.05), while potassium was the most abundant mineral at 14746.73mg/kg in UBF of all four banana cultivars. Correlation between phenolic compounds and essential minerals using Pearsons Correlation Coefficient test revealed weak and inverse association between flavonoids and most macro and trace minerals present in UBF samples. Organic acid pretreatment thus exhibited little effect on phenolics and essential minerals of UBF samples, though, inhibitory influence of phenolic compounds was recorded on essential minerals.

Microbial Safety of Street Vended Foods Sold in Thohoyandou, South Africa

Abstract Street vended foods (SVFs), if prepared under hygienic and regulated conditions, play a significant role in feeding the urban population with cheap, accessible and nutritious diet. This study investigated the microbial safety of 28 food samples obtained from four different locations in Thohoyandou. Standard microbiological methods were used for enumeration of Staphylococcus aureus and Coliforms. Results of the study show that isolated S. aureus was < 2.4771 log10 cfu/g in all samples and locations, while there was no significant difference (p > 0.05) in total coliform count (<2.1761 log10 cfu/g) among samples and across all locations. Microbial contamination of SVFs using the total plate count method was observed in the food samples except fried potato chips, with marked significant difference (p < 0.05) recorded across locations in cereals and meat samples. Majority of SVFs obtained from all locations met the microbiological standard of ready-to-eat foods.