The economic impact of cowpea research in West and Central Africa: A regional impact assessment of improved cowpea storage technologies

Researchers from the Bean/Cowpea Collaborative Research Support Program (CRSP), a program supported by the USAID, developed several non-chemical cowpea grain storage technologies in the 1980s. These included hermetic storage in airtight containers, improved ash storage, and the solar heater. Impact studies conducted at the country level showed that the research program was economically a good investment. As the CRSP new storage technologies spread throughout West and Central Africa, a regional assessment including spillover effects became necessary to fully comprehend the impact and guide future research investments. Therefore, this study sought to measure the economic impact of the new CRSP cowpea storage technologies at a regional level. Surveys in seven countries were used to estimate storage technology adoption. Economic surplus was used to estimate annual benefits and internal rate of return (IRR), and net present value (NPV) were calculated to summarize the net benefits. From the perspective of recipients' countries the project was a good investment. The IRR, is found to be much greater than the cost of capital. The regional IRR was found to be about 29%, much higher than the real interest rate on government bonds in West Africa at the time. For example the real interest rate on bonds issued by the government of Ghana in 2004 and 2005 was 8.9% and 5.4% respectively. The IRR is also higher than the private bank real lending rates in West Africa. From the perspective of the principal donor, the US government, the project was a good investment given that the average real interest rate on US government’s bonds was 4.8% during the period. The net present value of the investment amounts to more than 295 million US dollars which yields an annualized value of about 17 million.     

不同储藏温度下油菜种子生活力的基因型差异

以发芽率为指标,研究了40份甘蓝型、白菜型和芥菜型油菜在-20℃、4℃、25℃、37℃、60℃温度储藏3个月、6个月、12个月后种子生活力的变化。结果显示：-20℃和4℃储藏下,不同基因型间种子发芽率变异较小,而25℃、37℃和60℃储藏下,基因型间种子生活力存在明显差异,选择60℃高温储藏不同时间的种子进行生活力鉴定,从甘蓝型、白菜型和芥菜型油菜中均筛选得到耐储藏的基因型。     

Nutritional and medicinal properties of underexploited legume trees from West Africa

Abstract

This review concerns three legume trees (family Fabaceae, subfamily Caesalpinioideae) from West Africa, namely Detarium microcarpum, Parkia biglobosa and Dialium guineense, and illustrates their nutritional value and therapeutic properties. These species are an important source of nutrition for West African populations, but their agricultural exploitation is still incomplete. The survey was conducted on Scopus, Web of Science, and Medline, using scientific and common English names of the species as keywords and then selecting papers related to nutritional and medicinal properties. Main food products are fruit pulp and seeds, though leaves can also be used. Most relevant dietary features are high protein, vitamin, and micronutrient contents. Various therapeutic and nutritional benefits of these plants have been documented by ethnobotanical and experimental studies, stimulating an interest for their possible use as functional food or drug sources. Most studied medicinal properties include antidiabetic and antimicrobial activities of D. microcarpum, cardiovascular protective and antidiabetic activities of P. biglobosa, and bilharzia-preventing molluscicidal activity of D. guineense. Phytochemical characterizations have revealed potential sources of active drugs, such as D. guineense saponins and D. microcarpum diterpenes. Scientific results support popular uses of these legume trees, indicating a prominent nutritional and health value.     

The influence of storage practices on aflatoxin contamination in maize in four agroecological zones of Benin, west Africa

Aflatoxin level in 300 farmers’ stores in four agro-ecological zones in Benin, a west African coastal country, were determined over a period of 2 years. At sampling a questionnaire was used to evaluate maize storage practices. Farmers were asked what storage structure they used, their storage form, storage period, pest problems in storage and what was done against them. Beninese farmers often changed their storage structures during the storage period, transfering the maize from a drying or temporary store to a more durable one. Most of the farmers complained about insects damaging stored maize. Often, storage or cotton insecticides were utilized against these pests. Regression analysis identified those factors that were associated with increased or reduced aflatoxin.

Maize samples in the southern Guinea and Sudan savannas were associated with higher aflatoxin levels and the forest/savanna mosaic was related to lower toxin levels. Factors associated with higher aflatoxin were: storage for 3–5 months, insect damage and use of Khaya senegalensis-bark or other local plants as storage protectants. Depending on the agroecological zone, storage structures that had a higher risk of aflatoxin development were the “Ago”, the “Secco”, the “Zingo” or storing under or on top of the roof of the house. Lower aflatoxin levels were related to the use of storage or cotton insecticides, mechanical means or smoke to protect against pests or cleaning of stores before loading them with the new harvest. Fewer aflatoxins were found when maize was stored in the “Ago” made from bamboo or when bags were used as secondary storage containers.     

贮藏时间和温度对甘蓝型油菜种子活力及脂肪酸含量的影响

研究了甘蓝型油菜种子在低温和常温干燥条件下,密闭贮藏过程中种子脂肪酸组成分含量、含油量及发芽能力的变化。结果表明：随着贮藏年限增加,甘蓝型油菜种子油酸、二十碳烯酸、芥酸的含量逐渐增加,亚麻酸、亚油酸含量则逐渐下降,棕榈酸和硬脂酸含量变化不明显;在冷藏1～5年里脂肪酸成分含量变化较快,之后变化缓慢;低芥酸材料在贮藏过程中芥酸含量增加速率高于高芥酸材料。随着贮藏时间延长,种子含油量逐渐下降,含油量高的材料下降更快;种子发芽率和发芽势均下降,后者下降幅度大;在同样冷藏条件下,套帐自交的种子比开放授粉种子的发芽率和发芽势下降均快且幅度大,而常温贮藏的开放授粉种子发芽能力下降速度明显比冷藏的快,6年后发芽率几近于零。     

The effects of the combined use of stabilizers containing locust bean gum and of the storage time on Kahramanmaraş-type ice creams

This study was aimed primarily at determining the suitability of locust bean gum and various stabilizers in the production of Kahramanmaraş-type ice creams, the physical, chemical and sensory properties of the ice creams produced, and the stabilizer combination that could produce the best quality ice cream. With a total amount of stabilizer of 1.0%, ice creams of four different combinations containing locust bean gum, carboxymethyl cellulose, guar gum and sodium alginate were produced and their properties during a 6-month storage period compared with the control sample produced using only salep extract ( Orchis orchida ).
  The ice cream produced using only the salep extract had significantly higher ( P  < 0.05) levels of titratable acidity, lower pH and viscosity values, and were harder and less resistant to melting compared to those produced with the stabilizer combinations. The stabilizer mixtures containing locust bean gum yielded better results than those with the salep extract. An analysis of the effect of storage time on the properties of the ice creams indicated that, of the physical properties examined, only the decrease in the penetrometer values was significant ( P  < 0.05). Apart from the difference observed in the third month during the storage of the ice creams produced with the salep extract, the differences during the storage time were not found to be significant ( P  > 0.05).     

Resistance to aflatoxin accumulation in kernels of maize inbreds selected for ear rot resistance in West and Central Africa

Thirty-six inbred lines selected in West and Central Africa for moderate to high resistance to maize ear rot under conditions of severe natural infection were screened for resistance to aflatoxin contamination using the previously established kernel screening assay. Results showed that more than half the inbreds accumulated aflatoxins at levels as low as or lower than the resistant U.S. lines GT-MAS:gk or MI82. In 10 selected aflatoxin-resistant or aflatoxin-susceptible inbreds, Aspergillus flavus growth, which was quantified using an A. flavus transformant containing a GUS-beta-tubulin reporter gene construct, was, in general, positively related to aflatoxin accumulation. However, one aflatoxin-resistant inbred supported a relatively high level of fungal infection, whereas two susceptibles supported relatively low fungal infection. When kernels of the 10 tested lines were profiled for proteins using sodium dodecyl sulfate-polyacrylamide gel electrophoresis, significant variations from protein profiles of U.S. lines were observed. Confirmation of resistance in promising African lines in field trials may significantly broaden the resistant germplasm base available for managing aflatoxin contamination through breeding approaches. Biochemical resistance markers different from those being identified and characterized in U.S. genotypes, such as ones inhibitory to aflatoxin biosynthesis rather than to fungal infection, may also be identified in African lines. These discoveries could significantly enhance the host resistance strategy of pyramiding different traits into agronomically useful maize germplasm to control aflatoxin contamination.     

原料牛乳贮存温度引起亚硝酸盐含量变化的研究

研究了贮存温度引起牛乳亚硝酸盐含量的变化。结果表明，牛乳亚硝酸盐的含量变化主要受贮存温度和受污染情况的影响、次之是pH值、贮存时间、贮存时微生物数量的多少而变化。研究表明，对牛乳亚硝酸盐的控制首先使新榨出的乳尽快地降到5℃，同时尽量避免外界污染及缩短贮存时间是避免原料牛乳亚硝酸盐升高的最好措施。     

Effect of cold storage and ozone treatment on physicochemical parameters,soluble sugars and organic acids in Actinidia deliciosa

The production of kiwi fruits is a dynamic agricultural activity in Corsica (France). The fruits are either consumed directly or used to produce kiwi wine. They are often stored for 4–6 months in industrial freezer chambers at 0 °C or industrial ozone chambers. The aim of this study was to measure physical, chemical and fungicidal parameters, soluble sugars and non-volatile organic acids during storage in each of these types of chamber. Various standard and instrumental methods (physicochemical techniques, HPLC) in conjunction with statistical analysis were used. During storage, the kiwi mass, firmness and acidity decreased, whereas reducing sugar, °Brix and pH increased. There were statistical differences between the two chambers regarding reducing sugar and acidity. The ozone gas treatment had a fungicidal effect on Botrytis cinerea. The major soluble sugar present in the kiwi fruit was fructose, followed by glucose and sucrose. The concentrations of these sugars increased during storage in both air at 0 °C and ozone-enriched air. Organic acids are one of the important factors influencing fruit flavour. Citric and quinic acids predominated over malic, tartaric and ascorbic acids. During storage in the ozone chamber, concentrations of non-volatile organic acids decreased sharply after 25 weeks. Storage at 0 °C enabled better retention of organic acids.     

Responses and genetics of maize germplasm resistant to the maize weevil Sitophilus zeamais Motschulsky in West Africa

The maize weevil, Sitophilus zeamais Motschulsky causes considerable damage to maize grain during storage in the tropics. The objectives of this study were to determine through two experiments the genetic basis of resistance to S. zeamais in African maize germplasm of open-pollinated cultivars, lines and hybrids. The first experiment tested for resistance of 20 maize cultivars (10 white and 10 yellow-grained) developed for lowland Africa grown in three relatively weevil-free savanna locations. The second experiment tested two sets of diallel crosses without reciprocals of 66 F₁ progeny from 12 inbred lines and 78 F₁ crosses from 13 inbred lines of subtropical and temperate origins. Variables studied for the first experiment included husk cover, grain texture, number of egg plugs, number of weevils produced, and number of grains damaged by the weevil. Results showed highly significant differences among the 20 maize cultivars tested. Significant cultivar×location interactions for egg plug and weevil production indicate the importance of environmental effects and complexity in weevil resistance. Of the 20 cultivars tested, Ikenne 83-TZSR-W-1 (open pollinated) and 8329-15 (hybrid) were the most promising for restricted weevil production and minimal grain damage. The results of genetic studies in the second experiment with 144 crosses indicated the presence of genetic differences in maize lines to weevil attack. General combining ability (GCA) and specific combining ability mean squares were highly significant, suggesting that the maize weevil resistance was controlled by both additive and non-additive gene actions and the inheritance was quantitative and polygenic. Among the lines used in the crosses, the two most weevil resistant lines with high GCA effects were TZi 30 (International Institute of Tropical Agriculture) and FLA2BT 106 (Florida).     

Effects of postmortem storage time on color and mitochondria in beef

To assess the effects of aging time (0, 15, 30, and 45 d) and temperature (0 or 5 °C) on beef mitochondria and steak color, vacuum packaged longissimus (n = 15) and cardiac muscles were assigned to 1 of 6 temperature × time combinations. As time increased, initial red color intensity increased whereas both mitochondrial oxygen consumption and color stability decreased. The decrease in mitochondrial oxygen consumption associated with longer aging times will increase initial color intensity. However, this improvement in color development will be negated by the decreased color stability that results from the effects of storage on mitochondria.     

Changes in carotenoids during processing and storage of pumpkin puree

Changes in the contents of carotenoids and their true retentions (% TR) during the production of puree of Cucurbita moschata ‘Menina Brasileira’ and of Cucurbita maxima ‘Exposição’ pumpkins and the stability of such compounds during 180 days of storage were monitored by liquid chromatography coupled with a photodiode array detector. Cooking caused higher losses than commercial sterilisation. High losses of xanthophylls such as lutein and violaxanthin were noted during processing and storage of pumpkin puree. Such losses show the low stability of these compounds. The major carotenoids, pro-vitamin A carotenes, namely, α-carotene and all-trans-β-carotene for C. moschata ‘Menina Brasileira’ and all-trans-β-carotene for C. maxima ‘Exposição’ obtained high retentions (>75%) after processing. A slight degree of isomerisation of β-carotene was noted in the puree samples, but with low concentrations of cis-isomers. Storage for 180 days did not significantly affect (P ? 0.05) the concentrations of these carotenoids.     

The effect of preliminary processing and period of storage on the quality of frozen Boletus edulis (Bull: Fr.) mushrooms

This paper investigates the effect on the quality of frozen Boletus edulis (Bull: Fr.) mushrooms of blanching or soaking and blanching in aqueous solutions containing combinations of added substances safe for human consumption, or period of frozen storage. During 12 months of storage, sensory evaluations, instrumental colour measurements and chemical analyses of the frozen products were carried out every four months. Based on the results of the sensory evaluation, a maximum storage period of four months was set for the frozen product obtained from unblanched mushrooms. Frozen products having undergone preliminary processing retained good sensory quality for up to 12 months. Soaking, blanching and freezing resulted in the appearance of colours, such as yellow, honey and pink–violet. As a result of freezing, decreases in the contents of thiamine, riboflavin and vitamin C were noted. Blanching in water, as a method of pre-processing, was sufficient for maintaining acceptable sensory quality.     

Modeling changes in rheological properties of potatoes during storage under constant and variable conditions

The changes in rheological properties of potatoes stored at 5, 15, 25 °C and variable (fluctuating) temperature for 16 or 26 weeks were evaluated in terms of elasticity and viscosity parameters using axial compression and creep tests. Cylindrical test specimens (15 mm diameter and 30 mm long) were used. A third-degree polynomial best fitted the force-deformation curves in axial compression test (R²=0.98-0.99) whereas a four-element (Burgers) mechanical model adequately described the creep response of potatoes (R²=0.95-0.99). The tangent modulus of elasticity in axial compression and elasticity and viscosity parameters in creep tests in general decreased significantly (P<0.05) with increase in storage time both under constant and variable storage conditions. The changes in rheological properties of potatoes stored under constant storage condition were sufficiently described by a modified exponential model (R²=0.89-0.96) except for the viscosity parameter of the Maxwell component of the four-element model. The logarithm of degradation rate constant, k, and the constant, n, were linearly related to storage temperature. For the variable storage condition, a bulk mean temperature (T_bm) was calculated to account for a series combination of storage time and temperature to which the potatoes were subjected. The changes in rheological properties due to variable storage temperature were then described as a function of T_bm and storage time, t_s, using stepwise multiple regression. The result indicated that except the viscosity parameter of the Maxwell component of the four-element model, it was possible to describe the changes in rheological properties as a function of T_bm and t_s (R²=0.84-0.99).     

Stability of anthocyanins and ascorbic acid in sonicated strawberry juice during storage

The stability of anthocyanins and ascorbic acid in sonicated strawberry juice during storage was investigated. Strawberry juice was sonicated at varying acoustic energy densities (AEDs) ranging from 0.33 to 0.81 W/mL and treatment times of 0–10 min. The degradation kinetics of sonicated samples followed first-order kinetics. Degradation rate constants were linearly correlated with AED (R ² > 0.91). Selected samples were stored for 10 days at 4 and 20 °C. A second-order polynomial model was employed to investigate the effects of storage time and processing variables. During storage higher loses were observed at a storage temperature of 20 °C compared to 4 °C. Predictive models developed for anthocyanins and ascorbic acid content were highly significant (P < 0.0001) and closely correlated to the experimental data (R ² > 0.91). Degradation mechanisms for anthocyanins and ascorbic acid due to sonication and storage are proposed.     

Effect of storage temperatures on antioxidant capacity and aroma compounds in strawberry fruit

The antioxidant capacity (measured as oxygen radical absorbance capacity, ORAC), total anthocyanins, total phenolics, aroma compounds, and postharvest quality of strawberry fruit (Fragaria x ananassa cv. Chandler) kept at 0°C, 5°C, and 10°C were investigated. Strawberry fruit stored at 10°C or 5°C showed higher antioxidant capacity, total phenolics, and anthocyanins than those stored at 0°C. However, the postharvest life based on overall quality was longer at 0°C than at 5°C or 10°C. The production of aroma compounds was markedly influenced by storage time and temperature. Individual aroma compounds were affected differently. For example, ethyl hexanoate, hexyl acetate, methyl acetate, and butyl acetate increased, while 3-hexenyl acetate and methyl hexanoate decreased during storage. In general, strawberries stored at 10°C or 5°C produced higher levels of these volatiles than those stored at 0°C. In conclusion, strawberries stored at 0°C retained an acceptable overall quality for the longest storage duration; however, berries stored at temperatures higher than 0°C showed higher content of aroma compounds and antioxidant capacity during the postharvest period.     

Effect of storage time and heat processing on the volatile profile of Senegalese sole (Solea senegalensis Kaup, 1858) muscle

The effect of heat treatment and the presence or absence of fish skin on the volatile composition of Senegalese sole muscle was studied. The volatile profile of Senegalese sole at different storage periods was also evaluated. All samples were analysed by HS-SPME–GC–IT/MS and subjected to sensory evaluation. As expected, cooking enhanced the production/liberation of volatile compounds. Fish with the skin present, after cooking, had higher levels of sulphur compounds, 2-nonanone, ethyl octanoate and lower contents of hexanol and heptanol than skinned fish; moreover, the samples with the skin had a better overall sensory acceptability. During storage, changes on the volatile composition of Senegalese sole samples were found. The major differences were obtained after 2 weeks of storage. Compounds such as hexanal, heptanal, octanal, decanal, (E)-2-hexenal, (E)-2-decen-1-al, (E,Z)-2,6-nonadienal, benzaldehyde, 4-ethyl-benzaldehyde, 1-penten-3-ol, heptanol and (E)-2-octen-1-ol decreased after 2 weeks of storage, and other compounds, such as 3-methyl-1-butanal, 2-methyl-1-butanal, 2-heptanone, dimethyl trisulphide, dimethyl tetrasulphide and 2-methyltetrahydrothiophen-3-one increased. These differences were confirmed by sensory evaluation. Principal component analysis was applied to the chemical data.     

Changes in phenolic composition and antioxidant activity of white wine during bottle storage: Accelerated browning test versus bottle storage

Polyphenol content, antioxidant activity, reducing power, colour and changes during storage over nine months in bottles and after accelerated browning were studied in selected Hellenic varietal white wines. The following phenolic compounds were identified in the wines: Caftaric, coutaric, fertaric, ferulic, caffeic, p-coumaric and gallic acids, (+)-catechin and (−)-epicatechin. The results showed that the contents of most of the phenols diminished with time, with the exception of caffeic, ferulic and p-coumaric acids. Antioxidant activity increased with storage whereas reducing power remained significantly unaffected. Accelerated browning did not significantly alter the concentrations of tartaric acid esters but it increased the concentrations of the hydroxycinnamic and gallic acids. (+)-Catechin concentration was not affected while (−)-epicatechin decreased. Antioxidant activity did not show any significant change but reducing power was reduced after the end of the browning test. As for the absorbance at 420 nm, it remained unchanged during storage, but it was significantly increased after accelerated browning.     

Mycological and physical parameters for selecting suitable packaging material for pre- and post-irradiation storage of cereal grains in Ghana

Owing to the rough warehouse handling of storage sacks in tropical areas in Africa, a suitable storage sack should not support de novo growth of fungal spores because this would reduce the tensile strength of the packaging material and act as a springboard for infecting grain contents. This paper reports the effect of activity of saprophytic fungi on the tensile strength of jute and woven polypropylene sacks. New woven polypropylene sacks carried lower levels of fungal spores (1.3×10¹ cfu/72 cm²) than jute sacks (3.0×10³ cfu/72 cm²). The natural mould penetration and growth was examined on sections (4×5 cm) of both jute and woven polypropylene after previous incubation at relative humidities of 55, 60, 65, 70, 75, 80, 90 and 95% for 10 weeks by placing them on Sabouraud's Agar. There was a significant difference (P = 0.05 level of significance) between the higher penetration of mould growth on jute sacks and that obtained on woven polypropylene sacks. Saprophytic fungi (Aspergillus candidus, A. flavus, A. fumigatus, A. niger, A. japonicus, A. parasiticus, A. ustus, Fusarium oxysporium, F. moniliforme, Penicillium verucosum var. cyclopium, Rhizopus oryzae and Trichoderma viride) isolated from jute sacks reduced tensile strength, measured by an Instron Model 1026, by 50–75% after 10 weeks at 90% R.H. Same fungal species on woven polypropylene sacks did not alter the tensile strength. Woven polypropylene sacks did not absorb moisture whilst the moisture content of jute sacks increased by 5.3–6.0% in 10 weeks at 90% R.H. with concomitant increase in mould and yeast counts by 1–2 log cycles. Evidence is presented to show that there was a positive correlation between the final mycoflora on jute sacks and loss in tensile strength. No correlation, however, was found between the total aerobic bacteria on jute sacks and the concomitant reduction in tensile strength. Fungi therefore play a major role in the reduction of tensile strength of jute sacks. Sterilization by gamma irradiation (8.0 kGy) of jute and woven polypropylene sacks did not affect their intrinsic tensile strength. Woven polypropylene sacks therefore have many microbiological and physical advantages over the traditional jute sacks to merit their use for grain storage in tropical areas like Ghana.     

Effects of blanching and storage conditions on soluble sugar contents in vegetable soybean

Vegetable soybean is becoming increasingly popular in the U.S. because of its rich source of isoflavones, folic acid, and other nutrients. The objective of this study was to investigate various blanching and storage conditions in order to identify the proper post-harvest management strategy in preserving sugar composition of vegetable soybean during storage. Fresh soybean pods of two vegetable soybean genotypes were stored at 4 °C for 30 days or 25 °C for 8-12 days in fresh air or nitrogen atmosphere. Shelled seeds and intact pods were blanched in boiling water or steamed at 100 °C for 10 min. All blanched soybean was stored at −20 °C and sampled monthly for 6 months for sugar analysis. Glucose, fructose and sucrose decreased gradually in fresh soybean when stored at 4 °C in air or nitrogen atmosphere for 28 days. Soybean stored at 25 °C in open air showed a rapid decrease of sucrose in the first 24 h, and then followed by a gradual increase; whereas oligosaccharides accumulated significantly during storage. Significant degradation in all sugars was found in soybean stored in nitrogen atmosphere at 25 °C. Soluble sugars decreased from leaching during the water blanching and cooling treatment of vegetable soybean seeds. Steam blanching and the presence of pod effectively retained soluble sugars in vegetable soybean during thermal treatment.