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.     

Survey of mycoflora counts, aflatoxin production and induced biochemical changes in walnut kernels

Fungal infection and mycotoxin contamination in fresh and stored kernels of walnut (Juglans regia) collected from different localities of Uttaranchal (India) were investigated. Fresh samples carry a combination of field as well as storage fungi. Species of Alternaria, Aspergillus and Penicillium were predominant. Thirty-nine percent of Aspergillus flavus isolates were toxigenic and produced up to 2170 μg/l of aflatoxin B₁ in the liquid media. Aflatoxin B₁ was the most common mycotoxin encountered as a natural contaminant in the stored samples. Twenty-one percent of fresh samples contained aflatoxin B₁ in low concentrations. The concentration of aflatoxin B₁ in fresh as well as stored samples was in the range of 140–1220 μg/kg. Characteristic rotting was observed in fresh as well as stored samples. The walnut kernels exhibited significant reductions in the levels of oil, starch and protein content during fungal infection.     

Laboratory evaluation of three novel insecticides inhibiting cuticle formation against some susceptible and resistant stored products beetles

The insecticidal activity of three 1-(2.6-disubstituted-benzoyl)-3-phenylureas was evaluated against a number of susceptible and resistant stored products beetles. The compounds were DU 19111 (1-(2,6-dichlorobenzoyl)-3-(3,4-dichlorophenyl)-urea), PH60-38 (1-(2,6-dichlorobenzoyl)-3-(4-chlorophenyl)-urea), and PH60-40 (1-chlorophenyl)-3-(2,6-difluorobenzoyl)-urea).

PH60-40 was found to be the most effective compound against susceptible strains of Sitophilus granarius, Sitophilus oryzae, Tribolium castaneum and Lasioderma serricorne. All three compounds were ineffective against Stegobium paniceum. A strain of T. castaneum (Kuala Lumpur strain) showing malathion-specific resistance was found to be more susceptible to PH60-40 than its “susceptible” strain. A non-specific resistant strain of T. castaneum (CTC12 strain) showed approximately two times tolerance to PH60-40 compared with the “susceptible” strain.

PH60-40 was shown to have ovicidal properties and also killed young larvae of T. castaneum after short exposure periods. Oviposition was not affected.

Wheat sprayed with an emulsifiable formulation of PH60-40 at 2, 5 or 10 ppm was found to be protected against susceptible T. castaneum, S. granarius and Oryzaephilus surinamensis and against resistant S. oryzae and T. castaneum (Kuala Lumpur strain) following 40 weeks storage at 20°C and 44 weeks storage at 35°C.

Preliminary toxicological data indicates that PH60-40 is of a sufficient order of safety for consideration for grain admixture. The compound is therefore of potential interest as a replacement for the more conventional grain protectants especially in situations where resistance is producing increasing control problems.     

Antilisterial activity of lactic acid bacteria isolated from "Alheiras" (traditional Portuguese fermented sausages): In situ assays

A total of 226 lactic acid bacteria (LAB) isolated from “Alheira”, a traditional Portuguese fermented sausage, were screened for antagonistic activity against some pathogenic microorganisms, including Listeria monocytogenes. The objective was to isolate LAB with antibacterial activity from “Alheiras” and to select strains that could be used in “Alheira” production. Isolates displaying antibacterial activity against Listeria innocua and L. monocytogenes were investigated for the nature of the antibacterial compounds active against these microorganisms. Results showed that two LAB cultures retained activity in the supernatants after neutralization and catalase treatment. These two strains were both identified as Pediococcus pentosaceus. The final aim of this work was to test the antilisterial activity of these two strains during storage of “Alheira mass” (sterilized), at 4 °C. The growth of L. innocua population was significantly suppressed in the paste of “Alheira” when the samples were co-inoculated with the LAB strains, in comparison with the paste only inoculated with L. innocua or co-inoculated with a bacteriocin negative strain of Ped. pentosaceus (ca. 1 × 10⁷ CFU/g after 28 days of incubation).     

A comparison of sugar-accumulating patterns and relative compositions in developing fruits of two oriental melon varieties as determined by HPLC

Sugar-accumulating patterns and compositions were compared between two oriental melon varieties, “Huangjingua” (Cucumis melo var. makuwa Makino) and “Yuegua” (Cucumis melo var. conomon Makino). Sucrose and reducing sugars were measured in different mesocarp tissues of developing fruits. They were all characterized by enhanced accumulation of glucose and fructose during early fruit development with almost no sucrose detectable. However, a transition of sucrose enhancement was accompanied by fruit maturing in the variety “Huangjingua”, while no such transition was observed in the variety “Yuegua” that merely had a sucrose content throughout development. In “Huangjingua”, both sucrose and total sugar gradients were observed, ascending from mesocarp adjacent to pedicle, middle part of mesocarp, and up to mesocarp adjacent to umbilicus. However, no obvious gradient in sucrose accumulation was seen among three mesocarp tissues examined. In terms of sweetness index, fructose is the chief contributor to sugar accumulation in both varieties. Also, the melon variety “Huangjingua” could be comparatively considered as a high-sucrose accumulator and “Yuegua” a minor-sucrose accumulator.     

Warner-Bratzler shear evaluations of 40 bovine muscles

Forty muscles from each of 20 beef carcass sides were used to perform Warner–Bratzler shear (WBS) force determinations for within and among muscle effects. The M. triceps brachii differed (P <0.05) in WBS values between the caput longum and caput laterale, and the M. gluteobiceps differed (P <0.05) in WBS values between the vertebral, cranial, and caudal portions. The M. trapezius did not differ between the pars cervicalis and pars thoracica. Larger muscles were evaluated for location effects within muscles. The M. pectoralis profundus, M. infraspinatus, M. triceps brachii (caput longum), psoas major, and M. semimembranosus all had significant location effects. Muscles were allocated into “very tender,” “tender,” “intermediate” or “tough” categories. Those muscles considered “very tender” (WBS <3.2 kg) were the diaphragm (outside skirt or wing of diaphragm), M. spinalis, M. infraspinatus, M. iliacus, M. psoas major, M. serratus ventralis, M. biceps brachii, M. obliquus internus abdominis, and M. vastus medius. Muscles considered “tender” (3.2 kg M. tensor fasciae latae, M. pectorales superficiales, M. teres major, M. longissimus lumborum, M. biventer cervicis, M. longissimus thoracis, M. splenius, M. subscapularis, M. rectus femoris, M. gluteus medius, M. gracilis, M. complexus, M. rectus abdominis, M. rhomboideus, and M. triceps brachii. Muscles classified as “intermediate” (3.9 kg M. gastrocnemius, M. supraspinatus, M. gluteobiceps, M. obliquus externus abdominis, M. semitendinosus, M. adductor, M. vastus lateralis, M. deltoideus, M. latissimus dorsi, M. transversus abdominis, and M. semimembranosus. Muscles classed as “tough” (WBS > 4.6 kg) were the M. extensor carpi radialis, M. trapezius, M. brachialis, M. pectoralis profundus, and M. flexor digitorum superficialis (hind limb). The diaphragm muscle was the most tender (WBS=2.03 kg), and the M. flexor digitorum superficialis was the toughest (WBS=7.74 kg). Tenderness, as measured by WBS, varied among and within bovine muscles, and knowledge of this variation allows for more appropriate use for specific purposes in the marketplace.     

Mycobiota in the processing areas of two different meat products

Mould growth is not accepted on most types of North European meat products and is considered as both an economic and aesthetic problem for the producers. In order to determine the mycobiota in processing areas of fermented sausage and liver pâté, filamentous fungi were isolated from air, equipment and raw materials in the processing areas of two fermented sausage processing plants and two liver pâté processing plants. A total of 336 samples were examined. The diversity of filamentous fungi in the processing areas was high; at least 17 different genera were identified. The main isolated genera were identified as Aspergillus, Botrytis, Cladosporium, Epicoccum, Eurotium, Penicillium, Phaeoacremonium and Phoma. Of these, Penicillium and Eurotium were the most important for contamination of fermented sausage, whereas Penicillium and Cladosporium were most important for liver pâté. Cladosporium was isolated more frequently in the processing plants examined in the autumn than in the spring. The seasonal variation indicates that outdoor air is an important source for this contamination. Eurotium was isolated frequently at one of the fermented sausage plants. Penicillium was isolated frequently at all four processing plants and was in addition found on moulded meat products. Sixteen Penicillium species were identified. The most frequently isolated were P. brevicompactum and the closely related P. bialowiezense, P. solitum, P. palitans, P. fagi and a new, not described species named P. “milanense” (ined.; Frisvad, 2007 personal com.). Isolation of a new species illustrates that the mycobiota in the processing areas of North European meat products has not yet been intensively investigated. Several mycotoxin producing species were isolated; the most prevalent were P. brevicompactum/P. bialowiezense and P. palitans. A screening for secondary metabolites showed that isolates of these species consistently produced mycophenolic acid and cyclopiazonic acid, respectively. Presence of these toxinogenic species in the processing areas implies a risk of mycotoxin contamination of the products if they are or has been subjected to mould growth. The ochratoxin A producing species P. nordicum and P. verrucosum were not isolated during the study. It was concluded that Penicillium species are the most important contaminants of the meat products because of their high prevalence in the production environment, their presence on meat products and their toxinogenic properties.     

Inhibition of Listeria monocytogenes by a bacteriocinogenic Lactobacillus sake strain in modified atmosphere-packaged Brazilian sausage

Lactobacillus sake 2a is a bacteriocinogenic strain isolated from “lingüiça frescal”, a Brazilian sausage. The combined effect of modified-atmosphere (MA) packaging (100% CO₂ and 50% CO₂/50% N₂) and addition of L. sake 2a on inhibition of growth of Listeria monocytogenes was evaluated in “lingüiça” stored at 6 °C. By the end of the first week, the inhibition of L. monocytogenes due to MA was significant (P0.05) while the presence of L. sake 2a did not influence significantly the growth of the pathogen. After 14 days, a reduction of 1.3–1.4 log in counts of L. monocytogenes was observed in samples containing L. sake 2a only or MA packaged only, while a reduction of 3.5 log was detected in those submitted to both treatments. Results indicate that inhibition of L. monocytogenes in “lingüiça frescal” by the bacteriocinogenic L. sake 2a is enhanced by the packaging of the product in MA.     

Use of isotope analysis to characterize meat fromIberian-breed swine

We describe a method based on isotope analysis (δ¹³C) for characterization and differentiation of Iberian pork meat as a function of the diet of the animal. Using adipose tissue, it is possible to classify unknown samples in group of animals designated “acorn-fed”, “recebo=mixed-fed” and “feed raised” according the δ¹³C value obtained, from the calibration straight line of y=−22.12–0.35x, with a correlation coefficient r=0.982 and s=0.1‰; where y=δ¹³C and x=arrobas of acorn and range forage received by the animals during the fattening period. Stress should be placed on the economic and industrial importance of Iberian-breed swine because the market prices of Iberian swine products depends on the classification of the animals according to the type of feeding regimen which they are subjected to.     

Biochemical and physical factors affecting discoloration characteristics of 19 bovine muscles

Steaks from muscles (n = 19 from nine beef carcasses) were evaluated over the course of retail display (0-, 1-, 2-, 3-, 4- or 5-d) for objective measures of discoloration (metmyoglobin, oxymyoglobin, L*-, a*-, and b*-values), reducing ability (metmyoglobin reductase activity (MRA), resistance to induced metmyoglobin formation (RIMF), and nitric oxide metmyoglobin reducing ability (NORA)), oxygen consumption rate (OCR), oxygen penetration depth, myoglobin content, oxidative rancidity, and pH. Muscles were grouped according to objective color measures of discoloration. M. longissimus lumborum, M. longissimus thoracis, M. semitendinosus, and M. tensor fasciae latae were grouped as “high” color stability muscles, M. semimembranosus, M. rectus femoris, and M. vastus lateralis were grouped as “moderate” color stability muscles, M. trapezius, M. gluteus medius, and M. latissimus dorsi were grouped as “intermediate” color stability muscles, M. triceps brachi – long head, M. biceps femoris, M. pectoralis profundus, M. adductor, M. triceps brachi – lateral head, and M. serratus ventralis were grouped as “low” color stability muscles, and M. supraspinatus, M. infraspinatus, and M. psoas major were grouped as “very low” color stability muscles. Generally, muscles of high color stability had high RIMF, nitric oxide reducing ability, and oxygen penetration depth and possessed low OCRs, myoglobin content, and oxidative rancidity. In contrast, muscles of low color stability had high MRA, OCRs, myoglobin content, and oxidative rancidity and low RIMF, NORA, and oxygen penetration depth. Data indicate that discoloration differences between muscles are related to the amount of reducing activity relative to the OCR.     

Mycotoxin problem in Africa: current status, implications to food safety and health and possible management strategies

Mycotoxins are toxic secondary metabolites of fungal origin and contaminate agricultural commodities before or under post-harvest conditions. They are mainly produced by fungi in the Aspergillus, Penicillium and Fusarium genera. When ingested, inhaled or absorbed through the skin, mycotoxins will cause lowered performance, sickness or death on humans and animals. Factors that contribute to mycotoxin contamination of food and feed in Africa include environmental, socio-economic and food production. Environmental conditions especially high humidity and temperatures favour fungal proliferation resulting in contamination of food and feed. The socio-economic status of majority of inhabitants of sub-Saharan Africa predisposes them to consumption of mycotoxin contaminated products either directly or at various points in the food chain. The resulting implications include immuno-suppression, impaired growth, various cancers and death depending on the type, period and amount of exposure. A synergistic effect between mycotoxin exposure and some important diseases in the continent such as malaria, kwashiorkor and HIV/AIDS have been suggested. Mycotoxin concerns have grown during the last few decades because of their implications to human and animal health, productivity, economics of their management and trade. This has led to development of maximum tolerated limits for mycotoxins in various countries. Even with the standards in place, the greatest recorded fatal mycotoxin-poisoning outbreak caused by contamination of maize with aflatoxins occurred in Africa in 2004. Pre-harvest practices; time of harvesting; handling of produce during harvesting; moisture levels at harvesting, transportation, marketing and processing; insect damage all contribute to mycotoxin contamination. Possible intervention strategies include good agricultural practices such as early harvesting, proper drying, sanitation, proper storage and insect management among others. Other possible interventions include biological control, chemical control, decontamination, breeding for resistance as well as surveillance and awareness creation. There is need for efficient, cost-effective sampling and analytical methods that can be used for detection analysis of mycotoxins in developing countries.     

Nutrition as a factor influencing hypopus formation in the Acarus siro species complex (Acarina, Acaridae)

Three species of mites, Acarus siro L., A. farris Oud. and A. immobilis Griffiths, were tested under optimum physical conditions (90% r.h. and 20°C). In most experiments hypopus production was estimated by comparing the number of protonymphs which developed promptly to tritonymphs with the number which developed to hypopi.

Hypopus formation appeared to be favoured by malnutrition in the presence of a certain minimum quantity of B vitamins. The period of response embraced the active larval and active protonymphal stage and the response appeared to be cumulative. It scemed to remain reversible through the larval stage but at some point during the active protonymphal period it became irreversible. The developmental period of those protonymphs which became hypopi was much extended compared with the developmental period of those which proceeded directly to tritonymphs. It is concluded that this extension is associated with physiological and developmental changes peculiar to the hypopus and not with starvation.

Acarus immobilis and Acarus farris, which have been shown to be mainly field species, produced more hypopi than the storage species Acarus siro, one population of which could not be induced to produce any hypopi. It is concluded that previously published records of the “Flour mite” motile hypopus from field habitats are probably based on the A. farris hypopus and the records of the “Flour mite” motile hypopus occurring in food stores are scarce because the storage species A. siro has a poor potential for hypopus formation or rarely encounters starvation conditions. Misidentifications, coupled with interspecific differences in hypopus production, may explain some of the conflicting results published by previous workers testing the same physical factors.     

Influence of storage period and packaging method on sliced dry cured beef "Cecina de Leon": Effects on microbiological, physicochemical and sensory quality

Quality aspects of sliced dry-cured beef “Cecina de León” preserved in vacuum and gas mixtures (20%/80% CO₂/N₂ and 80%/20% CO₂/N₂) were studied. The evolution of microbiological, physicochemical and sensory parameters were analysed during storage (210 days) at 6 °C. Although microbial counts at 60 days of the gas-packaged samples were lower than the vacuum-packed ones, they were never higher than the spoilage limit (7 log ufc/g). A slight increase (p < 0.05) in pH was observed throughout storage of “Cecina de León” packaged under vacuum and in gas mixtures. However, a decrease (p < 0.05) in a_w was observed during storage of “Cecina de León” packaged under vacuum but a_w did not vary (p > 0.05) during storage in the gas-packaged samples. No changes were observed (p > 0.05) in lightness (L^*), redness (a^*) and yellowness (b^*) in vacuum and gas packaged samples during storage. However, sensorially evaluated colour showed lower values in gas packaged samples during 30 days storage. This difference was decisive in establishing the shelf-life of “Cecina de León” slices preserved in gas mixtures (20%/80% CO₂/N₂ and 80%/20% CO₂/N₂). Therefore, from a microbiological point of view, gas mixtures are more effective in extending the shelf-life of “Cecina de León” slices. It is concluded that vacuum packaging allows longer storage than gas-packaging as it maintains a good visual appearance of “Cecina de León”, the main parameter in consumers’ perception of meat quality.     

Ecophysiology of ochratoxigenic Aspergillus ochraceus and Penicillium verrucosum isolates. Predictive models for fungal spoilage prevention - a review

Ochratoxin A (OTA) is a secondary metabolite produced by several species of Aspergillus and Penicillium; among them Aspergillus ochraceus and Penicillium verrucosum are two ochratoxigenic species capable of growing in different climates and thus contamination of food crops with OTA can occur worldwide. OTA can be found in a wide range of foods such as cereals, coffee, cocoa, spices, beer, wine, dried vine fruit, grapes and meat products. OTA is toxic to animals, it presents neurotoxic, immunotoxic and nephrotoxic effects. It has been implicated in a human kidney disorder known as Balkan Endemic Nephropathy. This review focuses on the ecophysiology of ochratoxin-producing Aspergillus ochraceus and Penicillium verrucosum, the effect of environmental factors on their germination, mycelial growth, and OTA production. Knowledge of environmental conditions required for sucessive stages of fungal development represent the first step towards preventing mycotoxin formation. Predictive models for different stages of fungal development are presented, which allow prediction of the time before spoilage as a function of the abiotic factors. Finally, the implications of these studies in management of barley, coffee and grapes are described. This can help to identify the critical control points in their production, storage and distribution processes.     

Variety differentiation of virgin olive oil based on n-alkane profile

An on-line LC–GC method was used to assess the n-alkane composition of 40 olive oil samples obtained from three different cultivars from a restricted grove zone in Croatia. Olive samples were handpicked at three different ripening stages during four consecutive years. No significant differences were found in relation to the variable “period of harvesting”, while the effects “variety” and “year” as well as their interaction caused significant differences for most of the n-alkane components (p0.05). Despite the influence of the production year, linear discriminant analysis based on the n-alkane components was able to correctly identify the variety of 97.5% of the samples.     

Maintaining dryness during storage contributes to higher maize seed quality

Smallholder farmers in Pakistan store their seeds and grains in porous polypropylene (woven) and jute bags or in bulk. Seed stored in these containers is susceptible to fluctuating seasonal relative humidity and temperature, which promote mold and insect growth. The present study assessed the performance of Purdue Improved Crop Storage (PICS) bags for maize seed storage during a two-month period. Seed moisture content increased in polypropylene bags while it remained constant in PICS bags. No change in germination was observed in maize seeds stored in PICS bags while in polypropylene bags it was reduced in half when compared to the initial germination. Seed stored in polypropylene bags had higher insect damage with a weight loss of 35% while in PICS bags the infestation was minimal with a weight loss of about 3%. Higher aflatoxin contamination levels were observed in seeds stored in polypropylene than PICS bags. PICS bags are effective at preserving the dryness of maize seed in storage during high relative humidity conditions, which leads to maintenance of seed quality.     

Effect of Storage on the Biochemical Structure and Processing Quality of Adzuki Bean (Vigna angularis)

Storage of adzuki beans and other pulse grains causes biochemical and physical changes that affect the hydration properties of the beans. This affects the quality of products made from the beans such as the Japanese bean paste “ann.” Storage, particularly under unfavourable conditions, leads to the “hard shell” phenomenon, where beans fail to imbibe water when soaked and remain hard, and the “hard-to-cook” phenomenon where the seeds hydrate normally, but the cotyledon fails to hydrate and soften during cooking. The hard shell phenomenon is attributable to impermeability of the seed coat to water, which is due to biochemical changes in the seed coat, such as the formation of protein-tannin complexes, and biophysical changes such as reduction in size or closure of the straphiole aperture in the hilum area—the main area for water entry into the adzuki bean. The hard-to-cook phenomenon is due to changes in the cotyledon tissue, which include formation of insoluble pectinates, lignification of the cell wall and middle lamella, interaction of condensed tannins with proteins and starch, and changes to the structure and functionality of the cellular proteins and starch.     

Spectral analyses of fluorescences in dent maize infected with Aspergillus flavus and Aspergillus parasiticus

Bright greenish yellow (BGYF) and blue white (BWF) fluorescences were associated with Aspergillus flavus and A. parasiticus infected maize. The fluorescences were studied spectrofluorometrically, the BGYF exhibiting a peak wave length between 480–485 nm and the BWF between 440–445 nm. Neither fluorescence varied in maize stored under different moistures and temperatures.

BWF was similar spectrally to the fluorescence of the endosperm of sound kernels but × 5 20 more intense. The spectrum of BWF was similar to Aflatoxin G₁ or a mixture of aflatoxin B₁, B₂, G₁ and G₂ when they were spotted on endosperm tissue. A color reference for BGYF was similar in peak wave length to BGYF. Amsoy soybeans without the seed coat fluoresced with a peak 470–475 nm and the intensity was low compared to BGYF in maize. A fluorescence of maize kernels visually similar to BGYF but not associated with Aspergillus infection or aflatoxin contamination was also investigated. This “false BGY” fluorescence was spectrally similar to the BGYF in infected kernels.