Nigerian Food Journal最新文献

Microbiological, functional, chemical and sensory properties of flours of two (2) cultivars of orange-fleshed sweet potato (centinnial and CIP 440293) being multiplied for distribution in South East and South-South Nigeria were investigated using standard techniques. The flours were observed to have good functional properties and high dry matter contents which were respectively 88.09 ± 0.00% and 86.0 ± 0.00%. The respective values for fat content (0.85 ± 0.00% and 1.75 ± 0.00 %), ash content (2.04 ± 0.00% and 2.40 ± 0.42%) and crude fibre content (2.90 ± 0.28% and 2.67 ± 0.00%) were low but the respective levels of carotenoids values (3.74 ± 0.00 and 5.28 ± 0.00 μg/g) were high indicating a promising source of pro-vitamin A. The sensory evaluation had no statistical difference among the parameters. The flours had high nutritive values with good functional and sensory properties. The microbial loads were within the acceptable limit of < 10⁵ recommended by ICMSF, making the flour samples microbiologically safe and with appropriate packaging, the shelf life could be extended under good storage conditions.

Flour from mucuna beans (Mucuna pruriens) were used in producing texturized meat analogue using a single screw extruder with the intention to monitor modifications on some functional properties of the extrudate. Response surface methodology based on Box Behnken design at three levels of barrel temperature (110, 120, 130°C), screw speed (100, 120, 140 rpm) and feed moisture content (44, 47, 50%) were used in 17 runs. Regression models describing the effect of process variables on the product quality attributes were obtained. Result obtained showed that the moisture contents of the meat analogue samples decreased from 13.23 to 6.53%. Increasing feed moisture content resulted in extruded meat analogue with a higher density (0.988), water absorption index (WAI) (2.30), oil absorption index (OAI) (2.350), swelling power (3.47) and lower lateral expansion (0.84). Lateral expansion, OAI and swelling power increased as barrel temperature increased with peak values of 1.39, 2.39 and 3.47 respectively, while bulk density and WAI decreased. The product functional responses with coefficients of determination (R²) ranging between 0.658 and 0.894 were most affected by changes in barrel temperature and feed moisture and to lesser extent by screw speed. Optimization results based on desirability concept indicated that a barrel temperature of 120.15°C, feed moisture of 47% and screw speed of 119.19 rpm would produce meat analogue of preferable functional properties.

An experiment was conducted to evaluate the effect of various levels of poultry manure application on the nutritional value and functional properties of Dioscorea bulbifera. The experiment was a randomised complete block design on a plot size of 8 m² with a planting space of 50 cm × 1 m, using 5 levels of poultry manure: 0, 1, 2, 3 and 4 tonnes/ hectare. Standard analytical methods were used to determine the proximate and mineral composition as well as the functional properties of the bulbils. Poultry manure application significantly increased the starch content. The highest starch yield (13.50%) was observed at 4 tonnes/hectare poultry manure application. The dry matter and fat contents were not significantly affected by poultry manure application. Crude fibre, ash and crude protein contents were significantly affected by poultry manure application. Ash content ranged from 3.41 – 4.68% with 4 t/ha level of application having the highest ash content. The crude protein content ranged from 2.48 – 6.28%. The highest crude protein content was observed at 3 t/ha. The total carotenoid content was not significantly affected by poultry manure application. The phosphorus, calcium and magnesium contents were significantly affected by poultry manure application. Water and oil absorption capacity increased with increase in the level of poultry manure while the bulk density was not significantly affected by the level of poultry manure. Application of poultry manure was found to significantly influence the nutrient content and functional properties of D. bulbifera.

In a study aimed at ascertaining whether boiling or frying best conserves nutrients; since the two methods are commonly adapted in Nigeria, the effect of boiling and frying on total carbohydrate, vitamin C and mineral contents of Irish (Solanum tuberosum) and sweet (Ipomea batatas) potato tubers were investigated. The determination of total carbohydrate was carried out using the phenol-sulphuric acid method and the spectrophotometric method was used to determine vitamin C content at 520 nm. The minerals evaluated are iron, zinc, magnesium, sodium, calcium and copper. These were determined by the atomic absorption spectrophotometric method. There was no significant difference (p > 0.05) in the total carbohydrate content of the boiled and fried sweet and Irish potatoes compared with their raw tubers. There was significant difference (p < 0.05) in the vitamin C content of the boiled and fried potato tubers. Boiling and frying of Irish potato resulted in a loss of 37.34 mg/100 ml (63.90%) and 30.44 mg/100 ml (53.90%) vitamin C respectively. Boiled sweet potato lost 51.16 mg/100 ml (72.37%) and fried lost 43.05 mg/100 ml (60.90%) of vitamin C. The mineral compositions of the boiled and fried Irish and sweet potatoes were significantly different (p < 0.05) from their raw tubers. Boiling retained more iron and copper while frying retained more zinc, magnesium, sodium and calcium in both Irish and sweet potato tubers. Boiling retained more carbohydrate while frying retained more vitamin C and minerals.

Phenolic constituents (total phenols, flavonoids, tannins, and anthocyanins), comparative antiradical potency and cytotoxicity of processed mango (Mangifera indica) kernel (PMK), processed bush mango (Irvingia gabonensis) kernel (PBMK) and their mixture (MKK) at 50:50 were evaluated. Antiradical assay of the samples was conducted using three different methodologies (lipid peroxidation, nitric oxide and ferric reducing anti-oxidant power (FRAP)). The three samples contained negligible amounts of anthocyanins (< 0.67 ng/g) compared with the other constituents (1.4 to 2.2 mg/g), largely of gallotannins and flavonoids. However, PBMK had the least flavonoid content, averaging 43%. Due to relative sensitivity of assay techniques to phenolic composition of sample extracts, results from FRAP assay favourably complemented those of another technique to give better reflection of sample’s radical scavenging capacity. Mean inhibitory concentration (IC₅₀) values obtained, showed that the three samples had higher antioxidant capacity than reference quercetin. Similarly, the mean lethal concentration (LC₅₀) values obtained from cytotoxicity assay indicated that the phenolic acid and flavonoid content of the three processed kernel samples were more tolerable physiologically compared with reference dichromate. Both observations were statistically significant (p < 0.05). Processed kernels of mango (Mangifera indica) (PMK) and bush mango (Irvingiagabonensis) (PBMK), therefore, could find application as neutraceuticals and antimicrobials.

Yam is a popular root and tuber crop which is important as a dietary staple and potential export crop. Storage of yam tubers is an age long practice in yam growing communities of West Africa, while pasting characteristic is an important indicator of potential utilization of yam tubers. The study was carried out to investigate effect of storage of the tubers on their pasting characteristics. Six varieties each of D. alata and D. rotundata were used for the study. At harvest, the tubers were divided into two groups. The first group was stored in a conventional open-air yam barn for four months, while tubers in the second group were not stored. Pasting characteristics of both fresh and stored tubers were determined by Rapid Visco Analyser (RVA). The result showed that the effect of storage on the yam tubers were species dependent. In D. alata there was an increase in peak viscosity (231.36 to 257.56 RVU), breakdown (71.68 to 122.47 RVU), setback (42.58 to 65.99 RVU), while there was a decrease in most of the parameters except break-down and setback viscosities in D. rotundata. Generally, a decrease in peak viscosity, holding strength, final viscosity and peak time of the yam tubers during storage was observed, while the breakdown and setback viscosities of the tubers increased significantly (p < 0.05) on storage. The industrial implication of this is that starches of stored tubers may have high retrogradation tendencies but more resistance to shear-thinning and have more paste stability during processing.

Rheology has been applied as sensitive tool for material characterisation since flow behaviour correlates closely with composition, molecular weight and molecular weight distribution. Pure honey was serially diluted with different percentages of sucrose: 10%, 50%, 70% and 90% and each were analysed rheologically at two different temperatures. Pure honey exhibits thixotropic time dependent rheological behaviour, while the behaviour of sucrose tends towards Newtonian. The addition of adulterant to honey drags the viscosity of the resulting fluid towards Newtonian. The rheological curve fitting was done using the Power Law and Carreau-Yasuda models. The results show that the Carreau-Yasuda model fitted better the rheology of pure honey samples. Conversely, the rheology of sucrose solution was predicted better with Power Law model.

The effects of pre-treatment in osmotic salt solution followed by oven-drying on the moisture removal, and β-carotene content of yellow-fleshed sweet potato were investigated. Potato rings of 3 cm diameter and thicknesses of 2 mm, 3 mm and 4 mm were soaked in NaCI solutions of 10, 15, 20, 25 and 30% w/v, for varying time of 20, 40, 60, 80 and 100 minutes. The pre-treated slices were then oven-dried in a convective oven at 60 °C. Moisture diffusivity was determined by the method of slopes, while β-carotene was measured by UV/VIS- spectrophotometer. Moisture diffusivity values during drying were between 3.648 × 10^− 7 m²/s and 1.459 × 10^− 6 m²/s, while losses in β- carotene ranged from 47 to 86%. The amount of water removed by pre-treatment with NaCl solution decreased significantly as the concentration and the time soaking increased, however, the water out flow was found to increase significantly with increase in thickness of the samples, where the 4 mm size had the highest (1.535 g H₂O/g sample) and 2 mm the least (1.434 g H₂O/g sample) Osmotic pre-treatment in salt solution had no effect on β-carotene, but subsequent oven-drying however degraded the β-carotene.

Comparative studies on the quality of honey obtained from different floral locations in Nigeria were investigated. Parameters such as physical properties, chemical, mineral, microbial contents and antimicrobial activity as well as organoleptic quality were evaluated. The results of the physico-chemical properties show the following range of values for acidity (1.36 − 1.55%), soluble solids (80.96 − 82.00%), specific gravity (1.41 − 1.44) and sweetness index (52.52 − 62.73). While the proximate values were: moisture (15.69 − 18.41%), protein (0.90 − 1.15%), fat (0.12 − 0.21%), ash (0.26 − 0.38%) and carbohydrate (79.94 − 82.71%). Potassium (55.31 mg/100 g) and calcium (5.14 mg/100 g) were the dominant minerals in the honey samples. The highest microbial count was observed in sample NSK (1.4 ± 0.14 × 10 cfu/100 g). There were no observable coliform growths in all the samples. All the honey samples exhibited antibacterial activities with clear zones that range from 2.05 − 6.10 mm. Honey samples KAD and ABJ had the best overall acceptance scores of 8.49 and 8.27 respectively.