Olufunmilola A. Abiodun

Effect of delayed harvesting and pre-treatment methods on the antinutritional contents of trifoliate yam flour

Effects of delayed harvesting and pre-treatment methods on the anti-nutritional contents of trifoliate yam flour were examined. Trifoliate yam tubers were washed, peeled, sliced and subjected to pre-treatment methods, such as soaking, pre-cooking and blanching/soaking. The phenols, phytate, oxalate, tannin and alkaloid profiles of the flours were evaluated and the values of phenols, tannin, oxalate and phytate contents were 0.02-0.32, 0.04-0.53, 0.11-4.32 and 0.20-1.05mg/100g, respectively. The predominant alkaloids in trifoliate yam flour were dioscorine and dihydrodioscorine. The white trifoliate yam flour had higher levels of anti-nutrients than the yellow trifoliate yam flour. Alkaloid contents of trifoliate yam flour increased slightly with delayed harvesting periods. Blanching/soaking method drastically reduced the anti-nutrient contents of trifoliate yam flour than other methods.

Effect of harvesting periods on the chemical and pasting properties of trifoliate yam flour

The effects of delayed harvesting on the chemical and pasting properties of trifoliate yam flour were studied. The tubers were harvested at 7, 8, 9, 10 and 11months after maturity and were processed into flours. Chemical and pasting properties of the flours were determined. White trifoliate yam flour at 11months was significantly different (p<0.05) from other flours in dry matter and fibre contents but the lignin content (1.83%) was not significant different (p>0.05) from yellow trifoliate yam flour at 11months. Amylose and starch contents decreased while the sugar contents increased with harvesting periods. Yellow trifoliate yam flour had higher amylose at 10months while the white trifoliate yam flour had higher starch at 9months and sugar contents at 11months. Potassium and sodium were the major minerals found in the yam with higher values in yellow trifoliate yam flours. Peak viscosity and breakdown decreased while the holding strength and final viscosities increased with harvesting periods. Harvesting trifoliate yam tubers at 7-9months produced flour with high quality and prevents post harvest losses.

Physical and Functional Properties of Trifoliate Yam Flours as Affected by Harvesting Periods and Pre-treatment Methods

The physical and functional properties of trifoliate yam flours processed using different pre-treated methods at varying harvesting periods were examined. The flours were subjected to physical (bulk density) and functional (water absorption, solubility and swelling power) analyses. The bulk density values for the trifoliate flours ranged from 0.54-1.03 g/cm3. The parboiled flours had higher bulk densities in both cultivars of trifoliate yam flour. The parboiled white trifoliate yam flour harvested at 10 months had higher water absorption capacity (4.52 ml H2O/g) and was significantly different (p>0.05) from other flours harvested at other periods. Soaked (60°C) flours harvested at 11 months had the least solubility (3.49%) while the parboiled trifoliate yam flour had higher solubility. At 60-80°C, parboiled flours had higher swelling power values than the other flours while at 90°C, the raw flours harvested at 7 and 9 months had higher values which was significantly different (p<0.05) from other flour samples. The physical and functional properties of trifoliate yam flours were more dependent on the pre-treatment methods rather than the harvesting periods.

Physico-chemical, microbial and sensory properties of kunu zaki beverage sweetened with black velvet tamarind (Dialium guineense)

This work determined the physicochemical, microbial and sensory characteristics of kunu zaki sweetened with black velvet tamarind (Dialium guinnense) flour. The outer covering and seed of black velvet was removed while the pulp was pulverized to obtain the flour. The tamarind pulp was analysed for its proximate and sugar contents. Kunu zaki was prepared according to standard method and 10, 20, 30, 40 and 50 g of the black velvet pulp was added to 1000 ml each of kunu zaki along with a control sample. The kunu zaki samples were stored at refrigeration temperature (4 oC) for a period of 5 days. The physicochemical properties (pH, obrix, total titratable acidity), color, beta-carotene and vitamin C, microbial load and sensory attributes of the kunu zaki were analysed. The black velvet tamarind pulp had 42.01 g/100 g of total solid. The addition of black velvet tamarind (Dialium guinnense) to kunu zaki lowered the pH, thereby improving the keeping quality of the kunu zaki samples. The pH of kunu zaki ranged from 2.69-4.15 while the titratable acidity ranged from 5.44-10.06 %, the betacarotene and vitamin C content were high with a range of 3.10–36.6 mg/100 g and 4.73–47.25 mg/100 g respectively. The bacterial count ranged from 1-8.8 × 10 cfu/mL and a fungal count of 1-4.9 × 10 cfu/mL. Kunu zaki with 50 g of black velvet tamarind was the most preferred in terms of taste, appearance, aroma and general acceptability.

Metal hazard on the health safety of the people of two towns in the oil producing area of Akwa-Ibom State

Garri processed from cassava, one of the most common staple crop throughout tropical Africa, Asia and South America, were traditionally done. The effect of processing methods on the chemical pollutant loads were studied using twenty four matured, male wistar rats fed with blends of garri, while the control rats fed with rat ration only. The raw cassava and smoked fish used for the experiment were examined to assess the level of their contamination. Garri processed from the raw materials sourced from the two towns were compared by evaluating the effect the processing had in reducing the concentration of the pollutants. It was shown from the results that the feed had metal pollutants that would ultimately affect consumers of the food and, equally the effect of processing on the reduction of the metal pollutant load of the various feed ratios. The results also showed the prospect of processing on the safety of the foods and invariably, the health of consumers. Keywords: Garri, Consumers health, metal – pollutants, food safety, processing methods

Microbiological evaluation of watermelon juice treated with serendipity berry (Dioscoreophyllum cumminsii) extract

Watermelon (Citrullus lanatus) fruit is among numerous fruits that has a high moisture content and is therefore desirable for human consumption. In order to ensure its availability all through the year, processing into juice and other valuable processes are being carried out in order to reduce the rate of spoilage and watermelon juice losses. The high moisture content in fruits makes them highly susceptible to spoilage. Watermelon juice and extract of serendipity berry (Dioscoreophyllum cumminsii) were blended together in the following ratios: sample A (100 ml+10 ml), sample B (100 ml+20 ml), sample C (100 ml+30 ml), sample D (100 ml+40 ml), and sample E (100 ml+50 ml) respectively, while pure watermelon juice served as a control sample. Microbial and sensory analyses of the samples were evaluated over twelve weeks of storage. Over the period of storage, the results showed that microbial load of the control sample ranged between 1.1x10-9.7.6x10 cfu/ml, while treated samples ranged between 0.2 x10 1.4x10 cfu/ml, with some of the treated samples having negligible growth <10 cfu/ml. Results from the study confirmed that pure watermelon juice was highly susceptible to a microbial attack due to the absence of a preservative, and large volume of microbial loads was recorded, while the treated samples that included serendipity berry extract, which functioned both as a sweetener and a preservative, had fewer microbial loads over same period of storage. The sensory evaluation result showed that sample C (100 ml watermelon juice + 30 ml of serendipity berry extract) was rated the best in terms of taste, aroma and general acceptability, while sample D (100 ml watermelon juice + 40 ml of serendipity berry extract) was rated highest for colour.

Comparative study of the effect of dry and wet ginger (Zingiber officinale Roscoe) spice on the proximate and microbial safety of soybean beverage

Soybean beverage, most common nutritious local beverage in Nigeria and in the world, is a high protein beverage used as a dairy milk substitute with the limited utilization due to natural or ambient conditions that serve as growth medium for microorganisms. Hence, it has a short shelf life. This study examines the shelf life of soybean beverage preserved with the ginger spice (dried at 70 ̊C, 80 ̊C, 90 ̊C and 100 ̊C, and 2 g and 4 g of fresh/wet ginger respectively) over 7-week period. The samples were (A: plain soybean beverage; B: 200 ml soybean beverage + 2 g of ginger dried at 100 ̊C; C: 200 ml soybean beverage + 2 g ginger dried at 90 ̊C; D: 200 ml soybean beverage + 2 g ginger dried at 80 ̊C; E: 200 ml soybean beverage + 2 g ginger dried at 70 ̊C; F: 200 ml soybean beverage + 2 g fresh ginger; and G: 200 ml soybean beverage + 4 g fresh ginger respectively). The proximate, pH, microbial and sensory analyses of samples ranged as follows: 87.35% 90.83% for the moisture content; 0.58% 0.65% ash content; 4.65% 4.96% protein; 0.10%-0.26% fibre content; 2.06% 2.98% crude fat and 1.68% 4.17% carbohydrate, and pH values ranged from 6.2 6.5. Microbiological analysis over storage period showed that the control sample ranged from 0.4×10 6 -8.3×10 6 cfu/ml, and treated samples from 0.4×10 6 to 2.4×10 6 cfu/ml. Low values of the samples treated with dry ginger spice were preserved better than others, probably due to preservative and anti-microbial properties of the spice. Sensory evaluation, carried out by twenty-eight persons, showed that the sample E: (200 ml soymilk+ 2 g ginger dried at 70 ̊C) was most preferred (with respect to taste, aroma and overall acceptability), while there was a significant difference in the appearance of the samples.

Evaluation of colour in white and yellow trifoliate yam flours in relation to harvesting periods and pre-processing methods

Colour is one of the important sensory properties that determine the acceptability of food products. Therefore, this work determines the colour in white and yellow trifoliate yam flours in relation to harvesting periods and pre-processing methods. Freshly harvested trifoliate yam tubers were prepared into flour using four pretreatment (untreated, soaking at ambient temperature, soaking at 60 o C and parboiling at 98 o C±2) methods. The flour colour was analyzed and the whiteness index was determined. L (brightness) value ranged from 68.90 in parboiled yellow trifoliate yam harvested at 8 months to 96.57 in the raw white trifoliate flour harvested at 9 months. Parboiled trifoliate yams from the two cultivars harvested at 11 months were darker in colour than other flour. Parboiled yellow trifoliate yam flours were significantly ( p >0.05) different from other samples in colour. The intensity of colour of the parboiled yellow trifoliate yam flour was more pronounced than others. However, the colour of the flour became deeper with prolonged harvesting periods and prominent in parboiled samples at 11 months. Keywords: Colour, Harvesting periods, Pre-treatment, White trifoliate yam, Yellow trifoliate yam