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.     

Mycobiota and mycotoxin contamination of maize flours and popcorn kernels for human consumption commercialized in Spain

Mycobiota and co-occurrence of aflatoxins, citrinin, ochratoxin A and zearalenone in 30 samples of maize flours and 30 of popcorn kernels purchased in Spain for human consumption were determined. The mycotoxin-producing ability of Aspergillus, Fusarium and Penicillium spp. was also studied.     

Influence of γ‐irradiation and maize lipids on the production of aflatoxin B1 by Aspergillus flavus

The effect of γ‐irradiation and maize lipids on aflatoxin B₁ production by Aspergillus flavus artificially inoculated into sterilized maize at reduced water activity (a_w 0.84) was investigated. By increasing the irradiation doses the total viable population of A. flavus decreased and the fungus was completely inhibited at 3.0 kGy. The amounts of aflatoxin B₁ were enhanced at irradiation dose levels 1.0 and 1.5 kGy in both full‐fat maize (FM) and defatted maize (DM) media and no aflatoxin B₁ production at 3.0 kGy γ‐irradiation over 45 days of storage was observed. The level in free lipids of FM decreased gradually, whereas free fatty acid values and fungal lipase activity increased markedly by increasing the storage periods. The free fatty acid values decreased by increasing the irradiation dose levels and there was a significant enhancement of fungal lipase activity at doses of 1.0 and 1.50 kGy. The ability of A. flavus to grow at a_w 0.84 and produce aflatoxin B₁ is related to the lipid composition of maize. The enhancement of aflatoxin B₁ at low doses was correlated to the enhancement of fungal lipase activity.     

The effect of storage temperature and time on the consistency and color of sterilized processed cheese

The effect of sterilization (117 °C for 20 min) on the color and consistency of processed cheeses was evaluated. The sterilization resulted in a darker shade (darker color) and increased firmness and elasticity of processed cheeses (P < 0.05). During the storage period (24 months) of sterilized processed cheeses, their color as well as consistency changed depending on the temperature tested (8 and 23 °C). The color change of sterilized processed cheeses was more significant at a higher storage temperature (23 °C) in comparison with the products kept at cold storage temperature (8 °C) (P < 0.05). The firmness of sterilized processed cheeses stored at 8 °C increased during the 24 months. The rise in firmness achieved in the products stored at 23 °C was followed by its decrease in the second year of storage.     

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).     

The effect of modified atmosphere packaging with carbon monoxide on the storage quality of master-packaged fresh pork

Modified atmosphere packaging with carbon dioxide is effective for prolonging shelf-life of fresh meat. Addition of carbon monoxide to the system provides the advantage of enhancing meat colour. The study objective was to determine the effect of CO₂-MAP + 0.4% CO, vs. 100% CO₂-MAP, on the bacteriology and colour of retail-ready fresh pork stored for 8 weeks in a master-package system. Total plate counts were not affected and listeria was present on meat from both treatments. Colour was enhanced with the inclusion of CO, while no effect on lipid oxidation was observed. Use of CO in MAP provides sufficient storage life and product colour quality to permit shipment of fresh pork to distant markets. However, given the stable fresh colour of CO-treated meat and the lack of inhibition of pathogen growth by CO, there is concern that CO-MAP under certain conditions may pose a food safety risk.     

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.     

Impact of mechanical shelling and dehulling on Fusarium infection and fumonisin contamination in maize

Mechanical shelling and dehulling methods were tested to evaluate their impact on Fusarium infection and fumonisin contamination in maize. All shelling methods which were tested were found to damage the grains. The IITA® sheller caused the highest level (up to 3.5%) of damage. Fusarium populations were higher on damaged grains, the highest being recorded from grains damaged by the IITA® sheller (2533.3 cfu g^-1). Fumonisin levels were higher in damaged grains, the highest being in maize shelled with the IITA® sheller (2.2 mg kg^-1). Fumonisin levels were positively and significantly correlated with the percentage of damage caused by the shelling methods, and with the number of Fusarium colonies in maize. Mechanical dehulling methods significantly reduced fumonisin levels in maize, resulting in a mean reduction of 62% for Mini-PRL, 65% for Engelberg, and 57% for the attrition disc mill. It is important for farmers to choose appropriate shelling methods to reduce mycotoxin contamination. Dehulling should be widely promoted for the reduction of mycotoxins in maize.     

Public information campaign on aflatoxin contamination of maize grains in market stores in Benin, Ghana and Togo

Rotary International with the International Institute of Tropical Agriculture (IITA) conducted an information campaign from 2000 to 2004 to increase public awareness of aflatoxin in Benin, Ghana and Togo. Key informant interviews with 2416 respondents showed poor baseline knowledge of aflatoxin and its health risks. The campaign included monitoring of aflatoxin contamination in maize grains from market stores in 38 cities and towns. Aflatoxin concentration in contaminated samples ranged from 24 to 117.5 ng g^-1 in Benin, from 0.4 to 490.6 ng g^-1 in Ghana, and from 0.7 to 108.8 ng g^-1 in Togo. The campaign significantly increased public awareness that populations were exposed to high levels of aflatoxin. The number of maize traders who were informed about the toxin increased 10.3 and 3.2 times in Togo and Benin, respectively; at least 33% more traders believed the information in each of Benin and Togo; 11.4 and 28.4% more consumers sorted out and discarded bad grains in Benin and Ghana, respectively. This paper concludes that sustained public education can help reduce aflatoxin contamination.     

The effect of storage temperature on drip loss from fresh beef

The effect of post rigor storage temperature on drip loss of two bovine muscles (M longissimus thoracis and M semimembranosus) was examined using 12 Dutch Friesian Holstein bulls. Drip loss of both longissimus and semimembranosus muscles was influenced by post rigor storage temperature. Higher storage temperatures resulted in increased drip losses, probably caused by a decrease in viscosity of the drip. The increase was most marked for the M longissimus thoracis. The relationship between drip loss and storage temperature was not linear; drip loss was found to be less affected by storage temperature as the latter was increased. The observed relationship could not be explained by a decrease in viscosity of the drip at higher temperatures alone. It was thought that faster ageing of the meat at elevated temperatures might increase the myofibrillar water-holding capacity, resulting in a decreased drip loss. However, this hypothesis requires further research. © 1998 Society of Chemical Industry.     

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.     

The effect of ball milling treatment on structure and porosity of maize starch granule

Maize starch was mechanically treated by a planetary ball mill at 500 rpm for 1, 2 and 3 h. The effect of ball-milling treatment on structure and porosity of maize starch granule was studied. The SEM and TEM analyses indicated that starch granule surfaces were significantly changed and cavities in the central region of distorted granules were observed in the company with disappearance of alternate growth rings. The FT-IR analysis showed that ball milling treatment significantly increased the intensity of band 3382 cm⁻¹ and decreased the ratio of 1047/1018 cm⁻¹ and 995/1018 cm⁻¹ corresponding to the crystalline/amorphous part of starch structure. Special surface area (S_BET), cumulative volume (V_BJH), average diameter pores (D_BJH), span and median diameter (D_{v, 0.5}) increased rapidly and then decreased gradually. The XRD patterns, FT-IR and ¹³C CP/MAS NMR spectra showed that the crystallinity of starches and content of double helices of starch chains were decreased, respectively.

Industrial relevance

Ball milling is one kind of physical modified method in polymer industry. It can be used in a variety of applications, including nanomatrix composites, dispersed alloy materials, metallic refinery, ore treatment, waste disposal, and synthesis of organic materials. Starch is a natural carbohydrate polymer, it contributes greatly to the textural properties of many foods and is widely used in food and industrial applications as a thickener, colloidal stabilizer, gelling agent, bulking agent and water retention agent. However, limitations such as low solubility, high viscosity, shear resistance, thermal resistance, thermal decomposition and high tendency toward retrogradation limit its use in some food and non-food systems.After ball milling treatment, the reactivity of starch is increased. Furthermore, milled starches exhibit the adsorptive capacity which can offer new opportunity for starch application, for example as sorbent in food or pharmaceutical.     

贮存温度和贮存时间对复原乳稳定性的影响

研究了贮存温度和贮存时间对复原乳的pH值、流变特性、粒径、乳析率和离心沉淀率的影响,在此基础上分析了贮存过程中乳浊液粒径与乳析率、离心沉淀率之间的相关性。结果表明:随着贮存温度的升高,复原乳的pH值与表观黏度逐渐降低,而随着贮存时间的延长,二者均先升高后降低,其中25℃和37℃下贮存在第15天时达到最大值,而55℃下贮存在第7天时达最大值;贮存过程中乳浊液顶部粒径d4,3与乳析率有较好的相关性(P<0.05),二者均随着贮存温度的升高和贮存时间的延长而增大;贮存过程中乳浊液底部粒径d4,3与离心沉淀率有很好的相关性(P<0.05),二者随着贮存温度的升高先增大后减小,在37℃时达最大值,随着贮存时间的延长均有所增大。     

Characteristics of moisture-absorbing film impregnated with synthesized attapulgite with acrylamide and its effect on the quality of seasoned laver during storage

Moisture-absorbing film impregnated with synthesized attapulgite with acrylamide (ATPGAA) was developed. The effects of ATPGAA concentrations of 0.5%, 1%, 2%, and 4% (w/w) in a linear low-density polyethylene polymer (LLDPE) matrix on the film properties were determined by measuring the physical properties, the oxygen and water vapor barriers, and moisture absorbency. The 4% ATPGAA film had high moisture absorbing efficiency. A packaging system fabricated from ATPGAA-impregnated films was applied to a dried-seasoned laver to evaluate its change in quality during storage. Seasoned laver packaged with ATPGAA-impregnated films had significantly greater crispness in texture and a lower peroxide value during storage than that packed with LLDPE film. The surface color of the seasoned laver packaged by ATPGAA-impregnated films was more stable than the control film. This study shows that moisture-absorbing films could serve as a packaging system to improve the storage quality of moisture-sensitive products.     

Effects of nitrite levels,endpoint temperature and storage on pink color development in turkey rolls

The objective of this research was to determine the relationship between minimum nitrite level, endpoint temperature and storage period on pink discoloration of turkey rolls. Rolls were prepared with 0, 3 or 5 parts per million (ppm) NO₂^–, cooked to an endpoint temperature of 75 °C or 85 °C and stored at 4 °C. During the 13-day storage period, on the 0th, 4th, 8th and 13th days cured pigment, total pigment, residual nitrite and color parameters were measured and sensory color was evaluated. At each endpoint temperature, addition of 3 ppm or 5 ppm NO₂^– significantly increased cured pigment and total pigment levels. Cured pigment levels of turkey rolls cooked to 75 °C were higher than rolls cooked to 85 °C, regardless of the NO₂^– level. There was a significant decrease in cured pigment levels at the end of the storage period (13th day). Analysis of residual NO₂^– in all treatment groups showed no detectable amounts. Endpoint temperature and addition of NO₂^– affected L* values: rolls cooked to the 75 °C endpoint had higher L* values. The additon of nitrite with the 75 °C endpoint temperature resulted in higher a* values. a* values also increased during the storage. The higher endpoint temperature (85 °C) resulted in lower a* values. Yellowness was not affected by final cooking temperature. Both the addition of NO₂^– and storage decreased b* values. The panel found no differences in pinkness intensity between the two levels of added nitrite (3 and 5 ppm). Sensory pinkness intensity in nitrite-added samples increased with increasing storage.     

Changes in iron,zinc and chelating agents during traditional African processing of maize: Effect of iron contamination on bioaccessibility

The effect of the different unit operations of processing traditionally used to produce four maize foods commonly consumed in Africa on the nutritional composition of the products was investigated, using Benin as a study context. The impact of the processes on lipid, fibre, phytate, iron and zinc contents varied with the process. The lowest IP₆/Fe and IP₆/Zn molar ratios, the indices used to assess Fe and Zn bioavailability were obtained in mawè, a fermented dough. Analysis of maize products highlighted a significant increase in iron content after milling, as a result of contamination by the equipment used. Evaluation of iron bioaccessibility by in vitro enzymatic digestion followed by dialysis revealed that the iron contamination, followed by lactic acid fermentation, led to a considerable increase in bioaccessible iron content. Extrinsic iron supplied to food products by the milling equipment could play a role in iron intake in developing countries.     

Effects of storage temperature and time on the biogenic amine content and microflora in Korean turbid rice wine,Makgeolli

We examined biogenic amine (BA) content and the diversity of lactic acid bacteria (LAB) population in Korean rice wine, Makgeolli, stored at 4 and 20 °C. Among 8 BAs examined by HPLC, only putrescine was detected in low levels during 30 days of storage at 4 °C. However, at 20 °C, several BAs were detected and total BA concentration increased during storage. The numbers of LAB in 4 °C Makgeolli remained constant while those in 20 °C Makgeolli were markedly changed. Denaturing gradient gel electrophoresis (DGGE) analysis shows the major LAB population in 4 °C Makgeolli to be Pediococcus acidilactici while that in 20 °C Makgeolli to be Lactobacillus plantarum, which has been known to produce BAs. The present study suggests that if Makgeolli is stored at an improper temperature, the diversity of LAB populations and BA formation can be markedly increased. Thus, low temperature storage and transport of the products are required to maintain a BA-free state.     

The effect of dietary starch on the digestion by sheep of cell wall monosaccharide residues in maize silage

The digestibility of individual cell wall monosaccharide residues from maize silage (MS) and from maize silage + concentrate (MS+con) diets, was examined in sheep equipped with rumen and duodenal cannulas. Dry matter digestibility was 73.8 and 86.6% in the MS and MS+con treatments, respectively. The overall digestibility of cell walls (CW) and CW monosaccharide residues was not depressed in the MS+con treatment. The values for total CW, CW glucose, CW uronic acid and for total xylose were 68.3, 77.0, 71.6 and 65.2 for MS and 69.4, 80.3, 75.3 and 63.7 for MS+con, respectively. However, the digestion of CW and CW monosaccharide residues in the rumen of the MS+con sheep was reduced and the contribution of the lower tract to the digestion of the potentially digestible CW-sugar residues was in the range of 15 to 20%. Digestibility of the soluble uronic acid was adversely affected by the concentrate, its digestibility being reduced from 88.6% in the MS to 68.7% in the MS+con treatment. Based on compositional considerations, it is envisaged that the CW structural unit of the ensiled maize plant is made of cellulose fibres enveloped by a thin, poorly lignified and penetrable matrix. The degree of branching of the matrix polysaccharides is low compared with other forage plants. It is suggested that the above mentioned properties significantly contribute to the high quality of the ensiled maize plant.     

Response of storage molds to different initial moisture contents of maize (corn) stored at 25 °C, and effect on respiration rate and nutrient composition

Maize was stored for 2 months in chambers maintained at 25 °C to simulate conditions observed in the central part of the “Corn Belt” of the United States when the grain warms because of high summertime temperatures after a period of winter storage. Maize was brought to three moisture contents (m.c.) within the range typically observed in farm and commercial storage, and was inoculated to simulate the amount of storage mold contamination typical of this situation. Certain of the experimental units were packed in insulation so that heat could accumulate within the grain masses to simulate hot spots. The wettest grain heated rapidly and became semi-anaerobic. The hot grain then dried rapidly, with the amount of moisture loss influenced by the ratio of water vapor pressures inside and outside the grain. The hot grain cooled and became more aerobic over time. New infections by storage molds, disappearance of viable field molds, development of kernel damage, and changes in atmospheric gases within the grain masses were correlated with the grain moisture or temperature and the rate at which the moisture and temperature changed. The rate of increase in new kernel damage was as high as 3.3% per week. Both the rate of respiration and the estimated ratio of starch to fat consumed were associated with the mean grain m.c. during the trial, and the estimated ratio of starch to fat consumed was in the range of 2.2/1–2.6/1 in the grain containing 16.6–18.2% m.c. That both fat and starch were consumed calls into question loss estimates based on starch metabolism alone. The fat content of the grain decreased more than 10% in some experimental units, but increased less than 5% in others. The protein content generally increased as other grain constituents were consumed.     

Effects of diet and storage on fatty acid profile,micronutrients and quality of muscle from German Simmental bulls

This study evaluated the effect of diet on fatty acid profile, vitamins, trace elements, lipid peroxidation, and quality of longissimus muscle of German Simmental bulls. The effect of storage on fatty acid profile and vitamins was also included. A control group was fed concentrate including soybean, and maize silage/grass silage. Treatment group I (unrestricted) was fed concentrate including rapeseed, and grass silage. Treatment group II (restricted) was fed like treatment group I with a feed restriction period. The treatment diet was not effective to give similar daily live weight gain to the control diet, but it was successful in improving beef fatty acid composition without affecting tenderness and colour (under unrestricted conditions). There were no differences in vitamins and cooking loss, but selenium decreased in treatment groups. Stimulated lipid peroxidation, in samples taken immediately post-mortem, was higher in treatment groups. Polyunsaturated fatty acids decreased, saturated fatty acids and intramuscular fat increased after 14 days of storage while vitamins had no significant reduction.