Oviposition preference and development of azuki bean weevil,Callosobruchus chinensis,on five different leguminous seeds

This study was conducted to determine the oviposition preference and development of azuki bean weevil, Callosobruchus chinensis (L.) (Coleoptera: Bruchidae) on five different leguminous seeds a) cowpea cultivar Yeonbundongbu, b) white kidney bean cultivar Hwanghyubilho, c) soybean cultivar Daepung, d) mung bean cultivar Seonhwanogdu, and e) azuki bean cultivar Hongeon. A multiple-choice test and a no-choice test were conducted to record the number of eggs laid, total developmental time, number of adults emerged, and adult longevity of C. chinensis on the five different leguminous seeds. Both choice and no-choice tests revealed cowpea seed as the most preferred oviposition substrate. Total developmental time from egg to adult stage ranged from 28 to 31 days; developmental time was shortest on the cowpea. Successful development of C. chinensis was not observed on soybean or on kidney bean. Rate of adult emergence was higher on azuki and mung bean seeds with longer adult longevity of those emerged from azuki bean and cowpea. Higher egg laying preference and shorter developmental time with longer adult longevity of the beetle on cowpea probably signifies importance of physical as well as chemical attributes of the seed as an oviposition substrate other than evolutionary history of the insect.     

Interactive effects of temperature and relative humidity on oviposition and development of Callosobruchus chinensis (L.) on azuki bean

The effects of three temperatures, 20 °C, 25 °C and 30 °C, and four relative humidity (RH) levels, 30–35%, 50–55%, 70–75%, and 90–95%, on oviposition and development of Callosobruchus chinensis (L.) (Coleoptera: Bruchidae) were investigated. C. chinensis were introduced to 30 g azuki bean seeds (cultivar Hongeon) one day post emergence. Five pairs of male and female beetles were used for each combination of temperature and RH, and replicated ten times. The introduced adults were allowed to lay eggs for 72 h. Temperature significantly influenced oviposition with increased number of eggs at 30 °C. Relative humidity had no effect on egg laying. Development time was affected by both temperature and RH. Development time was shortest at 30 °C and 70–75% RH. Adult emergence rate was affected by both temperature and RH; adult emergence rate increased with the increase in temperature and RH (up to 70–75%) levels. The results suggest that rather than the interactive effect of temperature and RH, individual effects of temperature and RH on C. chinensis are profound and C. chinensis is likely to cause greater damage to azuki bean seeds stored at 30 °C and 70–75% RH.     

Microwaves to control Callosobruchus maculatus in stored mung bean (Vigna radiata)

Disinfestation of stored grains using microwaves can be an alternative to chemical methods for controlling insects in grains and pulses. Mung bean of 12% moisture content (m.c.) was infested with different life stages of the cowpea weevil (Callosobruchus maculatus) and exposed to 200, 300 or 400 W microwave power levels for 14, 28 and 42 s. One hundred percent insect mortality for all life stages (egg, young larva, old larva, pupa and adult) was achieved with exposure to 400 W power level for 28 s, which caused a surface temperature of mung bean of 68.1 °C. Eggs were the most susceptible and adults were the least susceptible life stages to microwave treatments. No significant difference was observed between mortality of larvae and pupae stages and their mortality was between eggs and adults. Mung bean temperatures increased and germination decreased with increased power level or exposure time.     

Genetic analysis of seed resistance to Callosobruchus chinensis and Callosobruchus maculatus in cowpea

Callosobruchus chinensis (azuki bean weevil) and Callosobruchus maculatus (cowpea weevil) are the most destructive pests that cause significant losses to cowpea (Vigna unguiculata) seeds during storage. Development of cultivar(s) resistance to bruchids is a major goal in cowpea breeding program. Cowpea accession “TVu 2027” has been identified as moderately resistant to C. maculatus. Genetic studies of the seed resistance in this accession using strains of C. maculatus from Africa and America have demonstrated that the resistance is controlled by one or two recessive genes. However, there is no reports on genetics of the resistance to C. chinensis and to strain(s) of C. maculatus from Asia. Therefore, the objective of this study was to investigate genetics of the resistance to C. chinensis and C. maculatus in TVu 2027. TVu 2027 (P₂) and PK2015VTN001 (P₁; susceptible cowpea) were used to develop six basic generations (populations), viz. P₁, P₂, F₁ (P₁ × P₂), F₂ (P₁ × P₂), BC₁P₁ (P₁ × F₁) and BC₁P₂ (P₂ × F₁). The population were evaluated for percentage of damaged seeds (PDS) and area under the disease progress stairs (AUDPS; indicating infestation severity) by C. chinensis and C. maculatus. The results showed that TVu 2027 was moderately resistant to both bruchid species. Broad-sense heritability for PDS and AUDPS was moderate, being 70% and 73% for C. chinensis, respectively, and 64% and 61% for C. maculatus, respectively. Number of genes controlling C. chinensis resistance and C. maculatus resistance was two genes and one gene, respectively. Generation mean analysis revealed that genes with additive effect and additive × dominance gene interaction are involved in the resistance to both bruchid species. Correlation analysis suggested that the genes controlling resistance to C. chinensis and those conferring resistance to C. maculatus are unlinked.     

Efficacy of ozone for Callosobruchus maculatus and Callosobruchus chinensis control in cowpea seeds and its impact on seed quality

The insecticidal efficacy of ozone was evaluated against the adults of Callosobruchus maculatus (F.) and C. chinensis L. on stored cowpea seeds under laboratory conditions. Ozone was assessed at concentrations of 0.25, 0.5, 1.0, 1.5, and 2.0 g/m³. The effect of ozone treatments on the adult mortality after 1, 3, 5 and 7 days of treatment, progeny production after 45 days, cowpea seed weight loss, seed germination and chemical constituents of cowpea seeds were determined. Adult mortality of C. maculatus and C. chinensis was improved with the increase in ozone concentration. Thus, all tested concentrations caused complete adult mortality of C. chinensis after 7 days of treatment, while the concentrations of 1.0, 1.5, and 2.0 g/m³ caused complete adult mortality of C. maculatus after the same periods. Progeny of both species was significantly decreased in all ozone concentrations after 45 days of treatment. Nevertheless, strong suppression in progeny production was achieved at the highest concentration of ozone (2.0 g/m³). Also, the ozone treatment at the highest concentration protected the cowpea seeds from damage caused by C. maculatus and C. chinensis for 45 days. In addition, there was no significant effect of ozone treatments on the cowpea seed germination compared with untreated seeds. Moreover, the chemical analysis of treated cowpea seeds showed a slight decrease in protein, fat, carbohydrate, moisture, total phenolics, total flavonoids and tannins contents, and a slight increase in fiber and ash contents compared with untreated cowpea seeds. Our findings suggest the ozone can be effectively used for the control C. maculatus and C. chinensis and can provide sufficient protection of stored cowpea seeds.     

Effect of different legume seeds on life table parameters of cowpea weevil,Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae)

The cowpea weevil, Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) is one of the most important storage pests of legume seeds. The effect of various legume species including chickpea (Cicer arietinum L.) (cultivars Hashem and Mansour), cowpea (Vigna unguiculata L.) (cultivars Mashhad and 1057), green gram (Vigna radiata L.) (cultivar Parto), lentil (Lens culinaris Medikus) (cultivar Bilehsavar) was studied on the life history and life table parameters of C. maculatus at 30 ± 1 °C, relative humidity of 65 ± 5% and complete darkness. The developmental time was longest on lentil and shortest on cowpea 1057. The fecundity (number of eggs laid per reproductive period) of the pest was the lowest on lentil. The longest oviposition period was observed on chickpea Hashem. The gross and net reproductive rates were the highest on chickpea Mansour and lowest on lentil. The intrinsic rate of increase and finite rate of increase were the lowest when C. maculatus was reared on lentil and highest when it was reared on other hosts. The longest and shortest mean generation times were observed on lentil and cowpea 1057, respectively. According to the obtained results, lentil was relatively resistant and the other tested legumes were more susceptible hosts for feeding and population increase of C. maculatus. It is concluded that the resistant host cultivar can be proposed to be incorporated into breeding programs to minimize the economic losses incurred by C. maculatus.     

Trehalose and proline failed to enhance cold tolerance of the cowpea weevil,Callosobruchus maculatus (F.) (Col.: Bruchidae)

The cowpea weevil, Callosobruchus maculatus (F.) (Col.: Bruchidae) is a cosmopolitan field-to-store pest ranked as the major post-harvest pest of cowpea in tropical regions. The cold tolerance of an insect species can vary as a result of abiotic features including food resources. In this study, C. maculatus larvae were fed with proline and trehalose (10, 20, and 40 mmol) treated cowpea seeds to determine the effects of these potential cryoprotectants on the supercooling (SCP) and cold hardiness of the upcoming adult beetles. The SCPs of the control, proline-fed and trehalose-fed adults non-significantly changed from −18.2 °C for the control to −17.2 °C for trehalose-fed adults. The cold hardiness (24 h at 0, -5.0, −7.5, −10.0, and −12.5 °C) of the adults was almost the same for control and treatments. Median lethal times (LT₅₀; lethal time for 50% mortality) were 6.3, 6.0, and 5.4 h, respectively. Moreover, feeding the larvae with proline and trehalose-treated seeds did not affect the proline and trehalose contents of the adult beetles. Our results showed that C. maculatus could not tolerate subzero temperatures well above their SCP, indicating that this species might be a chill-susceptible insect.     

Effects of developmental stage,cold acclimation and diet on the cold tolerance of three species of Cryptolestes (Coleoptera: Laemophloeidae)

Flat grain beetles (Coleoptera: Laemophloeidae) are common stored-product insect pests in Canada, infesting cereals in grain bins, equipment and end products in flour mills. We studied the cold tolerance of the three most common flat grain beetles: Cryptolestes ferrugineus, Cryptolestes turcicus and Cryptolestes pusillus, by measuring the survival at −10 °C and supercooling point (SCP) for different life stages (egg, young larva, old larva, pupa and adult) reared on flour mixed with brewer’s yeast. Probit analysis was used to estimate the lethal time for 50 and 95% mortality. This was done with non-acclimated individuals (only held at 30 °C) or cold-acclimated individuals (held at 18, 10 and 5 °C, for 1 week/temperature). In general, adults were the most cold-hardy stage for each of the species. Acclimated insects were anywhere from no increase in cold tolerance to 14-fold more cold-tolerant than the corresponding non-acclimated stage and species. Cryptolestes ferrugineus was most cold-tolerant species (58 d at −10 °C to reach 95% mortality for acclimated adult), C. turcicus was the next most cold-tolerant, (39 d) and C. pusillus was the least cold-tolerant (11 d). The cold tolerance of adults reared on three diets was measured both for acclimated and non-acclimated insects. The adults reared on grain diet (whole wheat kernels, cracked wheat kernels and wheat germ (90:5:5 mass ratio) were the most cold-tolerant, adults reared on white-wheat flour and brewer’s yeast diet (95:5 mass ratio) had the next highest cold tolerance followed by the adults reared on 100% white-wheat flour. Supercooling point (SCP) of insects ranged from −20.6 to −26.7 °C. In general, acclimated insects had slightly lower SCP than non-acclimated insects.     

Legume type and temperature effects on the toxicity of insecticide to the genus Callosobruchus (Coleoptera: Bruchidae)

Three bruchid pest species, Callosobruchus maculatus, Callosobruchus chinensis and Callosobruchus rhodesianus, were studied for their response to insecticide toxicity taking into account the separate and interactive effects of temperature and pre-adult food. The food types used were cowpea (Vigna unguiculata) and mungbean (Vigna radiata). Callosobruchus maculatus was the most tolerant to malathion and the least affected by temperature change while C. rhodesianus was the least tolerant. Over a 4 °C range (23°, 25°, 27 °C), there was generally a significant impact of temperature on the tolerance of the three species to the insecticide. The food type on which the insects developed influenced considerably the degree of insecticide tolerance. Callosobruchus maculatus and C. chinensis populations reared on mungbean had higher tolerance to malathion than their counterparts reared on cowpea, but the opposite was observed in C. rhodesianus populations. The food influence in this study suggested an ancestral cause or fitness cost depending on the species. The interaction of food-by-temperature had no significant effect on malathion toxicity to this genus. Correlation analysis showed C. chinensis to be relatively less sensitive to insecticide concentration over the range studied compared with the other two species.     

Legume seed vicilins (7S storage proteins) interfere with the development of the cowpea weevil (Callosobruchus maculatus (F))

Vicilins (7S storage proteins) isolated from the seeds of the legumes Vigna unguiculata (cowpea), Vigna angularis (adzuki bean), Canavalia ensiformis (jack bean), Glycine max (soybean), Phaseolus vulgaris (common bean) and Phaseolus lunatus (lima bean) were shown to be immunologically related and to bind to a chitin matrix. The effect of the isolated vicilins on the development of the cowpea weevil Callosobruchus maculatus was examined. Vicilins from all non-host seeds, including those of the C maculatus-resistant cowpea line IT81D-1045, strongly inhibited larval development (ED₅₀ of 1·07±0·32% to 2·22±0·64%). Vicilins from the C maculatus-susceptible cowpea CE-31 and adzuki bean seeds were the exception with ED₅₀ of 6·25±0·75% and 5·40±1·54%, respectively. These results correlate well with the host range of C maculatus and are possibly a reflection of the low digestibility of vicilins by insect midgut proteinases in addition to the ability they show in binding to chitin-containing structures like the ones found in the bruchid midguts. © 1998 SCI.     

Effect of Dry Heat Pre-Treatment (Toasting) on the Cooking Time of Cowpeas (Vigna unguiculata L. Walp)

Four cowpea varieties (Brown beans, Oloka beans, IAR48 and IT89KD-288) were toasted at 105 °C, and used to study the effect of dry heat treatment on the cooking time and nutrient composition of cowpea seeds and also its effect on the functional properties of resultant flour of the cowpea seed varieties. Toasting reduced the cooking time for brown and oloka cowpea varieties from 55.00–31.00 and 70.67–51.67 min, respectively. The cooking time for IAR48 and IT89KD-288 cowpea varieties increased from 104.67 to 106.00 and 88.00 to 88.67 min, respectively. The results indicate that the cooking time of cowpea seeds can be reduced significantly on toasting, while maintaining their potential as functional agents in the food industry for nutrition and utilisation. Correlation between the amount of water imbibed by cowpea seeds and their cooking time was -0.74, but was not significant at p ≤ 0.05, suggesting that there is no significant relationship between the amount of water imbibed by cowpea seeds and their cooking time.     

Semiochemical modulation of host preference of Callosobruchus maculatus on legume seeds

Host preference of Callosobruchus maculatus (F.) on seeds of three legume cultivars, Ife-brown and black-eyed cowpeas [Vigna unguiculata L. (Walp)], and soybean (Glycine max L.), was investigated. Mated female C. maculatus showed high (90–95%) attraction to the three legume cultivars in Y-tube bioassays. However, the weevils discriminated among the cultivars in four-choice tests and showed greater attraction to Ife-brown cowpea (50%) than to soybean (30%) and black-eyed cowpea (15%). Coupled gas chromatography-electroantennography (GC-EAD) and GC–MS analyses of the headspace volatile organic compounds (VOCs) emitted by the legume seeds identified 2-ethyl hexanol as the principal EAD active component. Emission of 2-ethyl hexanol was two-fold greater in Ife-brown cowpea (∼0.54 μg g⁻¹ seeds) compared with black-eyed cowpea (∼0.23 μg g⁻¹ seeds) and soybean (∼0.21 μg g⁻¹ seeds). Synthetic 2-ethyl hexanol attracted 68% of female C. maculatus at 0.01 μg dose in Y-tube bioassays. These results demonstrated that host preference in C. maculatus is odor-mediated, and identified 2-ethyl hexanol as a potential attractant for C. maculatus.     

Characterization of Callosobruchus chinensis (L.) resistance in Vigna umbellata (Thunb.) Ohwi & Ohashi

Resistance to azuki bean weevil, Callosobruchus chinensis, was studied in a series of field and laboratory experiments in two accessions of rice bean (Vigna umbellata (Thunb.) Ohwi & Ohashi), one accession of black gram (V. mungo (L.) Hepper), and one accession of mungbean, (V. radiata (L.) Wilczek). Weevil damage to immature pods of the rice bean accessions, ‘Menaga’ and ‘Miyazaki’, was significantly less than to the susceptible mungbean, VC1973A. In mature pods, the pest damage to the pod wall of Menaga was significantly higher than to VC1973A, whereas the damage to Miyazaki was similar to VC1973A. Seeds within the pods of both rice bean accessions were resistant no matter when the pods were harvested. When the insects were exposed directly on dry seeds, both rice bean accessions and a black gram accession VM2164 were resistant to them. In artificial seeds made by mixing flour of the individual resistant Vigna accessions with VC1973A and subsequently exposed to bruchid oviposition, the higher the quantity of resistant Vigna flour the lower the number of bruchids that emerged from such seeds. No bruchids emerged from artificial seeds containing crude starch fraction from the three resistant Vigna accessions when such seeds were exposed to bruchid infestation, whereas many insects emerged from the seeds containing starch of VC1973A or flour of VC1973A alone. In artificial seeds made by mixing crude protein fractions of the three resistant Vigna accessions with flour of VC1973A, as the concentration of protein increased the number of C. chinensis adults that emerged decreased. Fractionation of crude proteins into acetone-precipitable proteins and peptide and amino acid portions resulted in the loss of antibiosis effect. Artificial seeds made from purified starch-polysaccharides fraction, however, exhibited antibiosis effects if prepared from the rice bean seed of Menaga and Miyazaki but not if made from the black gram seed, VM2164.     

Life cycle of Ulomoides dermestoides (Fairmaire, 1893) (Coleoptera: Tenebrionidae) under laboratory conditions

Ulomoides dermestoides (Fairmaire, 1983) is a beetle that feeds on stored grains such as peanuts, oats and corn. It is widely used in traditional medicine for the treatment of various respiratory diseases such as bronchial asthma. The aim of this study was to assess the life cycle of U. dermestoides using the peanut (Arachis hypogaea L) as food, under laboratory conditions. Twenty-five adult pairs were put together in glass vials for mating, employing broken peanut kernels as substrate. After the adults mated, 30 eggs were selected and monitored until the adult stage. The length of time each life stage took was recorded, including adult fecundity. The life cycle of U. dermestoides from egg to adult stage lasts for about 67.6 ± 0.2 days and consists of four stages: egg, larva, pupa and adult. Adult females laid eggs during 135 days after their emergence, and the average fecundity was 261 eggs per female. The duration of the larval stage was 60 ± 0.10 days and it passed through seven instars, and finally the semi-mobile pupae stage lasted 3–5 days.     

Deterrent and insecticidal properties of bean seed (Phaseolus vulgaris L.) whole meal or protein extract incorporated into the diet of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Callosobruchus maculatus, a pest that causes serious damage to chickpea Cicer arietinum, cannot develop in the seeds of Phaseolus or Vigna spp. which contain lectins. The insecticidal activity towards C. maculatus in these seeds is attributed both to lectins with specific affinity to N-acetylglucosamine, the major component of insect chitin, and to alpha-amylase inhibitors (lectin-like proteins). The insecticidal properties of bean meal or bean protein extracts from different sources towards different pest species are variable and need to be experimentally evaluated. The main objective of this study was to determine through a feeding trial on artificial chickpea seed the potential of bean seed meal from a wild bean Vigna caracalla, four varieties of Phaseolus vulgaris, and of a protein extract of P. vulgaris seed, to alter different life history traits of C. maculatus. The chickpea weevil was set up on artificial chickpea seeds containing different amounts of bean meal to observe the effects on female oviposition, percentage of development to adulthood and juvenile development time. These traits were combined in a composite index measuring the alteration of the multiplication rate of C. maculatus fed on artificial seed. The activity of lectin-like extracts was observed on chickpea artificial seed spiked with bean seed extract. Incorporation of bean flour at a rate of 10 and 20% in chickpea artificial seed significantly decreased C. maculatus female fecundity, percentage of adult emergence, and greatly increased the development time. Feeding trials with protein extracts of P. vulgaris reduced fecundity and survival of C. maculatus. Incorporation of 10% V. caracalla bean seed meal in chickpea artificial seed, reduced the multiplication potential of C. maculatus by over 90% showing that bean seed lectin extracts are worthy of further investigation for post-harvest infestation control.     

Temperature-dependent development and reproduction of the cowpea weevil,Callosobruchus maculatus F., in mungbean: Estimating a target temperature for its control using aeration cooling

The bruchid, Callosobruchus maculatus F., commonly known as the cowpea weevil, infests stored mungbean and other legumes. Aeration cooling has potential as a non-chemical means of managing this species in stored legumes. Population growth of C. maculatus in mungbean was investigated at nine constant temperatures (15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5 and 35 °C) at 60% RH so that a target temperature for cooling could be estimated. We used two laboratory strains: Strain 1 and Strain 2 that had been in culture for 16–17 years and 1–2 years respectively. The results for the two strains were very similar. Egg to adult development occurred between 20 and 35 °C for Strain 1 and 17.5 and 35 °C for Strain 2. The optimal temperature for population growth was estimated to be 32.2 and 33.7 °C for Strains 1 and 2, respectively. The estimated lower threshold for population growth, i.e. the temperature at which population growth is zero, was 17.5 °C for Strain 1 compared with 17.1 °C for Strain 2. Based on our results, we recommend a target temperature of 17 °C for aeration cooling to manage C. maculatus infestations in mungbean during storage.     

Desiccant drying prior to hermetic storage extends viability and reduces bruchid (Callosobruchus chinensis L.) infestation of mung bean (Vigna radiata (L.) R. Wilczek) seeds

Seeds of mung bean (Vigna radiata (L.) R. Wilczek) are subject to loss of viability due to aging and damage from pulse beetles (or bruchids; Callosobruchus spp.) infestation during storage. We investigated whether seed drying using desiccants and hermetic packaging would prevent or ameliorate these consequences of storage. Sun-dried mung bean seeds at a moisture content of 10% were subjected to further drying for 72 h using five different desiccants: Drying Beads® (a zeolite-based desiccant), silica gel, sodium aluminum silicate, activated alumina, and cow-dung ash (a traditional desiccant). Seeds were subsequently stored in hermetic plastic containers in the presence of these desiccants under ambient conditions along with sun-dried seeds stored in cloth bags or in hermetic containers. In addition, parallel samples of each treatment were inoculated with one pair of bruchid beetles (C. chinensis L.) and stored under the same conditions. The seed drying treatments did not affect initial seed quality (germination percentage and seedling vigor) significantly. After storage for 9 months at ambient temperatures, seeds dried using Drying Beads, silica gel, sodium aluminum silicate and activated alumina had higher germination percentages, seedling vigor indices and soil emergence, and lower electrical conductivity (leakage upon imbibition) and fungal infestation compared to other conditions. In addition, the mung bean seeds inoculated with bruchids and stored with these effective desiccants had less damage, oviposition, and insect respiratory activity in the hermetic containers and maintained higher seed germination and seedling vigor after six months of storage compared to other treatments and controls. The results demonstrate the superior ability of desiccants to quickly and safely dry seeds prior to and during storage and the benefits of such drying and hermetic storage conditions for preventing seed deterioration and insect damage during storage.     

Radio frequency heating as a disinfestation method against Corcyra cephalonica and its effect on properties of milled rice

Radio frequency (RF) heating has the potential to be developed as an alternative non-chemical disinfestation method. In contrast to microwave (MW), RF exhibited higher penetration depth, which helps RF to be a useful technique in disinfesting packaging foods. A 3 kW, 27.12 MHz RF system was used to validate the practical of radio frequency technology for rice moth (Corcyra cephalonica) control in milled rice. Rice samples were placed in the polystyrene bag and moved at a speed of 0.8 m/min, and heated in the RF system with intermittent mixing. Four electrode gaps and five sample thicknesses were chosen to confirm the optimal conditions of RF treatment. The results showed that the sample thickness of 15 mm and electrode gap of 40 mm could provide the optimum heating rate for rice. Mortality of each stage (adult, larva, egg) of C. cephalonica increased with increasing heating temperature and reached 100% while RF heated 180 s (45.8 °C), 300 s (56.9 °C), and 420 s (70 °C), respectively. No C. cephalonica was determined in the samples during 45 days storage incubation period at RF treatment to 70 °C. There were no significant differences between control and RF treated samples in quality parameters (moisture, protein, fat, gelatinization, and sensory attributes). Therefore, RF treatment may provide a practical and effective method for disinfesting milled rice without affecting product quality.     

Effect of Several Germination Treatments on Phosphatases Activities and Degradation of Phytate in Faba Bean (Vicia faba L.) and Azuki Bean (Vigna angularis L.)

Abstract: Two assays were conducted to investigate the changes of faba bean (Vicia faba L.) and azuki bean (Vigna angularis L.) phosphatases (phytase [Phy] and acid phosphatase [AcPh]) and the degradation of its substrates (inositol phosphate esters) during seed germination. The 1st assay was to establish the optimal germination conditions of faba bean and azuki bean to improve the endogenous phosphatases and increase the hydrolysis of phytate and, in the second assay, to determine the different lower phosphate esters of myo‐inositol produced during the germination process. In the 1st assay, seeds were soaked for 12 and 24 h and germinated for 3 and 5 d with and without the addition of gibberellic acid (GA₃). In the second assay, seeds were soaked for 12 h and germinated for 1, 3, and 5 d with GA₃. Phy (up to 3625 and 1340 U/kg) and AcPh (up to 9456 and 2740 U/g) activities, and inositol hexaphosphate (IP6) (8.23 and 7.46 mg/g), inositol pentaphosphate (IP5) (0.55 and 0.82 mg/g), and inositol tetraphosphate (IP4) (0.26 and 0.01 mg/g) were detected in ungerminated faba bean and azuki bean, respectively. The germination process caused a significant increase of Phy and AcPh activities in faba bean (up to 147% and 210%) and azuki bean (up to 211% and 596%) and a reduction in the phytate phosphorus content (up to 81% and 63%, respectively). Phytate phosphorus content was affected only by soaking time in the case of faba bean. Finally, during the course of germination, IP6 and IP5 were rapidly degraded in faba bean (88% and 39%) and azuki bean (55% and 56%), and IP4 was only a short‐living intermediate, which was increased during hydrolysis and degraded to inositol triphosphate. In this manner we could obtain a low‐phytate, endogenous phosphatase‐rich ingredient for enhancing human nutrition.     

Physicochemical Characterization of Mexican Cowpea (Vigna unguiculata) Tailing Starch

A physicochemical characterization was made of tailing starch isolated from cowpea (Vigna unguiculata), a legume. Proximate composition was 1.6% protein, 3.1% fiber, 0.7%, 0.6% ash and 94.0% carbohydrates as nitrogen‐free extract. Total dietary fiber content was 14.1%, soluble fiber was 12.1%, and insoluble fiber was 2.0% as determined by the Prosky method. Amylose content was 22.9%. Gelatinization temperature ranged from 73.5°C to 86.3°C, the peak temperature being 79.3°C. Gelatinization enthalpy was 12.9 J/g. Swelling power ranged from 6.1 g water per gram starch at 60°C to 26.3 g water per gram starch at 90°C. Solubility, analyzed within the same temperature interval, ranged from 4.3% to 23%. Water absorption capacity was 5.8 g water per gram starch at 60°C and 19.4 g water per gram starch at 90°C. Initial pasting temperature was 78°C, breakdown was ‐68 Brabender Units (BU), consistency was 265 BU, and setback was 197 BU. Clarity, expressed as transmittance, was 13.4%. Syneresis in a 6% gel stored for 24 h at 4°C was 6.6% and 22.5% at −10°C. The physicochemical properties of Mexican cowpea tailing starch indicate that it is a good source of dietary fiber which can be included in food systems that require thermal treatments as bakery products.