No abstract

The effect of solvent polarity, polar and non-polar solvents, on pumpkin (Cucurbita maxima) seed oil yield and quality based on selected physicochemical properties was investigated. Five different solvents, like petroleum ether, hexane, cyclohexane, acetone and ethanol were used on a laboratory scale in this study. Results showed that both physicochemical properties and oil yield extracted from the pumpkin seed were influenced by solvent polarity. Oil yield ranged from 4.12 to 27.93%, with higher yield registered in petroleum ether and lowest in ethanol. Results on the physicochemical properties were as follows: Refractive index ranged from 1.437 (cyclohexane) to 1.466 (hexane), acid value, in mg KOH/g oil, ranged from 1.80 (cyclohexane) to 43.54 (ethanol), Peroxide value ranged, in meq O 2 /kg, from 6.70 (hexane) to 58.11 (ethanol), Iodine value, in g I 2 /g, ranged from 1.20 (petroleum ether) to 36.73 (ethanol), Saponification value, in mg KOH/kg, ranged from 30.54 (hexane) to 121.14 (acetone). The findings have demonstrated that solvent polarity significantly influenced physicochemical properties and oil yield extracted from pumpkin seed and therefore can assist in selecting solvents required in oil extraction to maximize yield and enhance or maintain oil quality.

The study investigated the effect of 10% aqueous extracts of ginger ( Zingiber officinale L.), garlic ( Allium sativum L.) and onion ( Allium cepa L.) on the quality of frozen chevon and pork as reflected by changes in values of 2-thiobartituric Acid Reactive Substances (2-TBARS), pH and total volatile basic nitrogen (TVB-N) over a 14 day storage under frozen conditions.  Fresh samples each weighing 2 kg from chevon and pork were bought from the local slaughter houses in two locations 24hrs after slaughtering while ginger roots, garlic and onion bulbs were purchased from Mitundu local market in Lilongwe district, Malawi.  The pH, total 2-TBARS and TVB-N of the thigh chevon and pork were measured from frozen storage at -20 o C after 14 days. The 10% aqueous extracts resulted in low pH values of 5.63, 5.79 and 5.67 at 14 d for chevon mixed with ginger, garlic and onion respectively. However, treated pork had higher pH content compared to treated chevon at 14 d. At day14 of frozen storage, the 2-TBARS expressed as mg MDA/kg meat, for chevon mixed with ginger, garlic and onion aqueous extracts were 2.62±0.01, 0 and 4.71±0.03 which was lower compared to the value of 5.93±0.01 for raw chevon. The TBARS values of chevon and pork mixed with ginger, garlic and onion and control chevon decreased from day 0 to 7 which eventually increased on 14 d. On 14 d, pork mixed with garlic extracts had lower TBARS value of 2.13±0.01 compared to 3.50±0.20, 2.26±0.01 and 3.92±0.01 for pork mixed with extracts of onion, ginger and control pork sample respectively. TVB-N, in mg/100g, was highest in control raw chevon and pork registering 95.70±0.32 and 84.00±0.40 at 14 d. Low values of TVB-N of 7.24±0.23, 12.37±0.23 and 16.61v±0.50 were registered in chevon mixed with aqueous extracts of ginger, garlic and onion compared to the values of 14.23±0.62, 22.87±0.47 and 18.86±0.14 for pork mixed with aqueous extracts of ginger, garlic and onion. The results of the study have revealed that natural aqueous antioxidant extracts of ginger, garlic and onion have antioxidative effect on lipid peroxidation in frozen stored fresh chevon and pork signifying that the use of these extracts can maintain quality.

In this study, oil quality with respect to physicochemical and phytochemical characteristics extracted from nonconventional seed oil namely Moringa oleifera, Adansonia digitata, Parinari curatellifolia and Cajanus cajan and conventional seed oil namely soybean (Glycine max) and groundnut (Arachis hypogaea) was assessed and compared. Results showed that there were significant differences in various quality parameters such as saponification number, peroxide value, free fatty acids in oils extracted from non-conventional and conventional sources. Oil yield ranged from 4.71 to 46.05% with pigeon peas registering the lowest yield and P. curatelifolia registering the highest yield. The following range of values in quality parameters were obtained: values in saponification number ranged from 55.91 mg KOH/g (C. cajan) to 220.54 mg KOH/g (groundnut): Peroxide value ranged from 2.79 meq O 2 /kg (M. oleifera) to 10.47 meq O 2 /kg (C. cajan): Free fatty acids ranged from 1.11 mg/100 g (P. curatelifolia) to 4.80 mg/100 g (pigeon peas): Specific gravity ranged from 0.87 (P. curatelifolia) to 0.91 (groundnuts): Oxalate ranged from 75.41 mg/100 g (groundnuts) to 632.56 mg / 100 g (pigeon peas): Acid value ranged from 2.21 mg KOH/g (P. curatelifolia) to 9.53 mg KOH/g (Pigeon pea): Iodine value ranged from 35.53 g/100 g (P. curatelifolia) and alkaloids ranged from 58.28 mg/g (M. oleifera) to 123.60 mg/g (groundnuts). Irrespective of the source of the oils, it was observed that the values in most of the oil quality parameters were within the acceptable levels. The findings in this study have demonstrated that nonconventional sources of oil have the potential to adequately supplement oils used for domestic consumption as well as industrial use in Malawi and therefore reduces the volumes of imported oils hence safeguarding foreign reserves.

In this study, proximate composition, physical characteristics and mineral content of fruit, pulp and seeds of Parinari curatellifolia (Maula) fruits from Bunda forests in Central Malawi were determined. Proximate composition included crude protein, crude fat and crude fiber, while physical characteristics included mass, length, thickness of whole fruit and kernels and minerals included potassium, magnesium, manganese, copper, zinc, iron and phosphorus. Total carbohydrate contents were also determined. All the results have been presented on dry matter basis. Results on crude protein ranged from 3.9±0.03 to 15.61±0.05% with pulp registering the lowest values (P<0.05) while the highest values were registered in kernels. Results on crude fat revealed that kernels had the highest values (46.05±0.19%) compared to values obtained in pulp or a mixture of pulp and peels while for crude fiber, the highest values (21.39±0.28%) were obtained in whole fruit. Furthermore, results on ash content showed that the highest values (5.71±0.25 %) were obtained in fruit peels while the lowest values (1.58±0.15 %) were registered in whole fruit. Lastly, results on carbohydrate content revealed that the highest values (84.95±0.14%) were obtained in the pulp while the lowest values (34.34±0.21%) were registered in kernels. The findings from this study have shown that there are significant differences in nutrient and mineral composition in the whole fruit, seeds and pulp of P. curatellifolia from Central Malawi and therefore these findings can be useful in nutritional planning regarding consumption of the P. curatellifolia fruit.