Maize Kernel Samples Research Articles

The nutritional benefits of maize-soybean rotational systems in the North-Western Free State, South Africa

BackgroundMalnutrition is one of the major health concerns, particularly in the developing and under-developed world. In South Africa, maize is produced as a staple food and is the primary food for most of the country’s population. The North-Western Free State which forms part of the Nala municipality in the Lejweleputswa district of South Africa is a main producer of the country’s maize. However, the area is known for its sandy soil which contains little organic material, silt and clay. Maize in this area is normally grown in monoculture but with a focus on sustainable agriculture has recently incorporated soybean. As a means of fighting malnutrition, the objective of this study was to determine the influence that soybean incorporation as a rotation crop has on the nutritional value of maize.MethodsA trial was conducted on the farm Christinasrus in the North-Western Free State to compare the nutritional value of monoculture maize and maize in rotation with soybean over three consecutive seasons. Maize kernel samples were taken each season and its nutritional properties analyzed. Subsequent data were further analyzed using statistical analysis.ResultsResults showed that there was a seasonal effect on all nutritional properties with a general decrease in nutritional values in wetter years. Cropping systems had an effect on fibre content, with increased values observed in maize after soybean. In addition, there was a significant interaction between season and cropping systems on the total digestible nutritional value, with maize after soybean being more nutritious in wetter seasons.ConclusionResults suggest that maize in cropping systems with soybean has potential to be more nutritious while the soybean in the cropping system can act as a protein-rich companion, providing a more balanced diet for human consumption, thereby fighting malnutrition.

Characterization and Detection Classification of Moldy Corn Kernels Based on X-CT and Deep Learning

Moldy corn produces aflatoxin and gibberellin, which can have adverse effects on human health if consumed. Mold is a significant factor that affects the safe storage of corn. If not detected and controlled in a timely manner, it will result in substantial food losses. Understanding the infection patterns of mold on corn kernels and the changing characteristics of the internal structure of corn kernels after infection is crucial for guiding innovation and optimizing detection methods for moldy corn. This knowledge also helps maintain corn storage and ensure food safety. This study was based on X-ray tomography technology to non-destructively detect changes in the structural characteristics of moldy corn kernels. It used image processing technology and model reconstruction algorithms to obtain the 3D model of the embryo, pores and cracks, endosperm and seed coat, and kernels of moldy corn kernels; qualitative analysis of the characteristic changes of two-dimensional slice grayscale images and 3D models of moldy corn kernels; and quantitative analysis of changes in the volume parameters of corn kernels, embryos, endosperm, and seed coats as a whole. It explored the detection method of moldy corn kernels based on a combination of X-ray tomography technology and deep learning algorithms. The analysis concluded that mold infection in maize begins in the embryo and gradually spreads and that mold damage to the tissue structure of maize kernels is irregular in nature. The overall volume parameter changes of corn kernels, embryos, endosperm, and seed coats in the four stages of 0 d, 5 d, 10 d, and 15 d showed a trend of first increasing and then decreasing. The ResNet50 model was enhanced for detecting mold on maize kernels, achieving an accuracy of over 93% in identifying mold features in sliced images of maize kernels. This advancement enabled the non-destructive detection and classification of the degree of mold in maize kernel samples. This article studies the characterization of the characteristic changes of moldy corn kernels and the detection of mildew, which will provide certain help for optimizing the monitoring of corn kernel mildew and the development of rapid detection equipment.

Smartphone-based chemiluminescence detection of aflatoxin B1 via labelled and label-free dual sensing systems

To develop a sensing platform for onsite determination of AFB1 in foodstuffs, we developed smartphone-based chemiluminescence detection of AFB1 via labelled and label-free dual modes. The labelled mode was characteristic of double streptavidin–biotin mediated signal amplification, obtaining limit of detection (LOD) of 0.04 ng/mL in the linear range of 1–100 ng/mL. To reduce the complexity in the labelled system, a label-free mode based on both split aptamer and split DNAzyme was fabricated. A satisfactory LOD of 0.33 ng/mL was generated in the linear range of 1–100 ng/mL. Both labelled and label-free sensing systems achieved outstanding recovery rate in AFB1-spiked maize and peanut kernel samples. Finally, two systems were successfully integrated into smartphone-based portable device based on custom-made components and android application, achieving comparable AFB1 detection ability to a commercial microplate reader. Our systems hold huge potential for AFB1 onsite detection in food supply chain.

Uticaj različitih pesticida i napada kukuruznog plamenca na sadržaj fitinskog fosfora u zrnu kukuruza

This work aimed to evaluate changes in phytic phosphorus content as the response of three maize hybrids (ZP 457, ZP 5601, and ZP 606) to different pesticide treatments for European Corn Borer (ECB) attacks and, as well as the correlation between damage caused by ECB attack and Pphy content. In the experimental field, maize ears were sampled and dried at a moisture content of 14% for the determination of changes in phytic phosphorus content in the grain. The content of phytic phosphorus was determined using UV / VIS spectrophotometry. Observed results showed the highest content of phytic phosphorus for untreated control for all tested hybrids, compared to pesticide treatments. The content of Pphy in the tested maize kernel samples ranged from 2.12 to 3.40 mg g-1. A significant positive correlation between attacks of larvae and Pphy content could indicate activation of its antioxidative function as a response to damage caused by ECB attack.

Feature Wavelength Selection Based on the Combination of Image and Spectrum for Aflatoxin B1 Concentration Classification in Single Maize Kernels

Aflatoxin B1 (AFB1) is a very strong carcinogen, maize kernels are easily infected by this toxin during storage. Rapid and accurate identification of AFB1 is of great significance to ensure food safety. In this study, a novel method for classification of AFB1 in single maize kernels was developed. Four groups of maize kernel samples with different AFB1 concentrations (10, 20, 50, and 100 ppb) were prepared by artificial inoculation of toxin. In addition, one group of maize kernel samples without AFB1 were prepared as control, each group with 70 samples. The visible and short wave near-infrared (Vis-SWNIR) region (500–1000 nm) and long wave near-infrared (LWNIR) region (1000–2000 nm) hyperspectral images of all samples were obtained respectively, and the hyperspectral images in 500–2000 nm range was obtained after spectral pretreatment and fusion. Kennard-Stone algorithm was used to divide the samples into calibration set or prediction set. Competitive adaptive reweighted sampling (CARS) and successive projections algorithm (SPA) were used to roughly select the characteristic wavelengths of the calibration set samples, and 25 and 26 effective wavelengths were obtained respectively. Based on the roughly selected wavelengths, a method of fine selection of the characteristic wavelengths was proposed by using the gray-value difference of image (GDI), and a few number of characteristic wavelengths were further selected. Under the LDA classification model, 10 characteristic wavelengths were selected to test the prediction set and the independent verification samples, and the ideal result were obtained with an accuracy of 94.46% and 91.11%, respectively. This study provides a new approach for AFB1 concentration classification of single maize kernels.

Rasprostranjenost Penicillium metabolita u kukuruzu gajenim u Srbiji

Maize can be contaminated with a wide range of fungal secondary metabolites that decrease the quality and safety of maize and maize-derived products. The increase of natural fungal metabolites occurrence in maize, influenced by climate changes, is recognized as a significant issue in recent years. Therefore, the main aim of this study was to investigate the influence of weather conditions on the natural occurrence of Penicillium spp. metabolites in maize kernel samples. The survey was conducted for two maize vegetation seasons 2016 and 2017. In total 458 maize samples were analyzed by liquid chromatography-tandem mass spectrometry method. The samples originated from the Autonomous Province of Vojvodina, and regions of Bačka, Srem, and Banat. Among 45 Penicillium metabolites investigated 16 and 18 were detected in samples from 2016 and 2017, respectively. The most commonly occurring Penicillium metabolite in both years was oxaline, which was detected in more than 90% of analyzed samples. Questiomycin A, 7hydroxypestalotin, pestalotin, and mycophenolic acid were also very frequently detected Penicillium metabolites. This is one of the unique studies in the Republic of Serbia, as well as in this part of Europe, investigating the occurrence of a great number of Penicillium metabolites in maize samples.

Rasprostranjenost Penicillium metabolita u kukuruzu gajenim u Srbiji

Maize can be contaminated with a wide range of fungal secondary metabolites that decrease the quality and safety of maize and maize-derived products. The increase of natural fungal metabolites occurrence in maize, influenced by climate changes, is recognized as a significant issue in recent years. Therefore, the main aim of this study was to investigate the influence of weather conditions on the natural occurrence of Penicillium spp. metabolites in maize kernel samples. The survey was conducted for two maize vegetation seasons 2016 and 2017. In total 458 maize samples were analyzed by liquid chromatography-tandem mass spectrometry method. The samples originated from the Autonomous Province of Vojvodina, and regions of Bačka, Srem, and Banat. Among 45 Penicillium metabolites investigated 16 and 18 were detected in samples from 2016 and 2017, respectively. The most commonly occurring Penicillium metabolite in both years was oxaline, which was detected in more than 90% of analyzed samples. Questiomycin A, 7hydroxypestalotin, pestalotin, and mycophenolic acid were also very frequently detected Penicillium metabolites. This is one of the unique studies in the Republic of Serbia, as well as in this part of Europe, investigating the occurrence of a great number of Penicillium metabolites in maize samples.

Study on mycotoxin contamination of maize kernels in Spain

Mycotoxins are secondary metabolites produced mainly by fungal species belonging to the genera Fusarium, Aspergillus and Penicillium and belong to the most relevant contaminants of food and feed. Cereals are the main source of mycotoxins in the diet. The most prominent mycotoxins are aflatoxins B1, B2, G1 and G2 (AFB1, AFB2, AFG1 and AFG2), fumonisins B1 and B2 (FB1 and FB2), ochratoxin A (OTA), zearalenone (ZEA), deoxynivalenol (DON), 3- and 15-acetyl-deoxynivalenol (3- and 15-ADON), and T-2 and HT-2 toxins. Maximum levels allowed in food are very different depending on mycotoxin and food type, consumer susceptibility and current legislation in each country. Among cereals, maize and its derivatives deserve special attention. The present study was designed to investigate the occurrence of these mycotoxins in Spanish maize kernels collected in different regions for a five-year period (2015–2019) using a multi-mycotoxin UPLC-MS/MS method. Ninety-eight samples of maize kernels collected in 26 Spanish grain stores were ground to fine powder, extracted with acetonitrile-water-formic acid (80:19:1, v/v/v), centrifuged and analyzed by UPLC-ESI-MS/MS using matrix-matched calibration. The method was validated and mean recovery rates were 83–103.4% and mean relative standard deviations ranged from 4.1 to 8.5%. FB1, FB2, DON, 3-ADON, ZEA, AFB1, AFB2, AFG2, T-2 and HT-2 toxins were detected at levels higher than their respective limits of quantification in 71.4%, 56.2%, 31.6%, 5.02%, 24.5%, 9.2%, 9.2%, 2%, 5.1% and 5.1% of maize kernel samples, respectively. OTA was not detected. Among the positive samples, 20.4%, 5.1%, 3%, and 3% had levels exceeding the European Union permissible limits for FB1+FB2, ZEA, AFB1, and total aflatoxins, respectively. Co-occurrence of various mycotoxins (two to seven) in the same sample at quantifiable levels was observed in 33.5% of samples being the association of FB1, FB2 and DON the most frequent, followed by the presence of FB1, FB2, ZEA and DON.

Fungal contamination and aflatoxin content of maize, moringa and peanut foods from rural subsistence farms in South Haiti

Mycotoxins are toxic, low molecular weight compounds produced by fungi. Among them, aflatoxins are the most carcinogenic and they mainly impact on rural communities of developing countries. The present study supplies data on mycobiota and aflatoxin contamination in the most common food products consumed in Haiti. The study concerns analyses performed on 49 samples of meals and seeds collected in South Haiti and tested for fungal occurrence and aflatoxin content by HPLC-DAD technique. The results revealed that three main fungal genera affected Haitian food products: Aspergillus spp. (Section Flavi and Nigri), followed by Penicillium spp. and Fusarium spp. Aflatoxin was present in more than half of the samples of maize (Zea mays L.) kernels (55%), maize meal (57%) and moringa (Moringa oleifera Lam.) seeds (64%), and in 25% of peanut (Arachis hypogaea L.) samples. The tested food products were mostly contaminated by aflatoxin B1 (AFB1) followed by aflatoxin B2 (AFB2), while no aflatoxins type G were detected. The total concentration of aflatoxins in the positive samples was 228 μg/kg on average, i.e., fifty-seven and eleven times higher than the maximum levels allowed in Europe and USA, respectively. Both the presence of aflatoxigenic fungi and aflatoxin contamination in maize kernels seemed to be related to agricultural practices, such as weed control, irrigation and growing cycle length. These findings suggest that the Haitian population is strongly exposed to aflatoxin risk. This risk could be reduced by exploiting simple and accessible farming strategies for minimizing mycotoxin contamination, at least for maize.

Deteriorative changes in maize kernels due to Aspergillus flavus Link. and Fusarium verticillioides (Sacc.) Nirenberg

The study aimed at measuring changes in chemical composition of maize kernels due to Aspergillus flavus Link. and Fusarium verticillioides (Sacc.) Nirenberg infection. The samples of maize kernels were incubated at 28 °C for 7, 14, 21, and 28 days. The samples were analysed for mycotoxin, moisture, crude fat, crude protein, crude ash, and crude fibre. Maize kernels inoculated with A. flavus and F. verticillioides exhibited a significant decrease in crude fat. Aflatoxin B1 (AFB1) contamination increased in maize kernels inoculated with A. flavus, and fumonisin B1 (FB1) in kernels inoculated with F. verticillioides. Crude ash and crude fibre content showed no changes. Incubation time significantly affected AFB1 and FB1 contamination levels, moisture, crude fat, and crude protein contents. AFB1 and FB1 contamination were significantly correlated with crude fat degradation. The tested strains had similar deteriorative effects on maize kernels. The significant changes in the proximate composition were only observed in maize kernels with mycotoxin contamination above the regulatory limit of 10 µg kg−1, thus not fit for human consumption.

Isolation, Molecular Identification and Mycotoxin Profile of Fusarium Species Isolated from Maize Kernels in Iran.

Fusarium species are among the most important fungal pathogens of maize, where they cause severe reduction of yield and accumulation of a wide range of harmful mycotoxins in the kernels. In order to identify the Fusarium species and their mycotoxin profiles associated to maize ear rot and kernel contamination in Iran, a wide sampling was carried out from field in ten major maize-producing provinces in Iran, during 2015 and 2016. From 182 samples of maize kernels, 551 strains were isolated and identified as belonging to Fusarium genus. Among the 234 representative strains identified at species level by translation elongation factor (EF-1α) sequences, the main Fusarium species were F. verticillioides and F. proliferatum, together representing 90% of the Iranian Fusarium population, and, to a lesser extent, F. incarnatum equiseti species complex (FIESC), F. thapsinum and F. redolens. Fumonisin (FBs) production by F. verticillioides and F. proliferatum representative strains was analysed, showing that all strains produced FB1. None of F. verticillioides strains produced FB2 nor FB3, while both FB2 and FB3 were produced only by F. proliferatum. Total mean of FBs production by F. verticillioides was higher than F. proliferatum. The occurrence of different Fusarium species on Iranian maize is reason of great concern because of the toxigenic risk associated to these species. Moreover, the diversity of the species identified increases the toxigenic risk associated to Fusarium contaminated maize kernels, because of the high possibility that a multi-toxin contamination can occur with harmful consequences on human and animal health.

Impacts of climatic conditions on aflatoxin B1 and fumonisins contamination of maize kernels and their co-occurrence

Agroecological and climatic conditions in Serbia greatly affected the development of toxigenic fungi and occurrence of mycotoxins in the maize. The presence of fungal toxigenic Aspergillus and Fusarium species and levels of aflatoxin B1 (AFB1) and sum of fumonisins B1, B2 and B3 (FBs) were established in 127 maize kernel samples harvested during 2012 (37 samples) and 2013 (90 samples). The periods of silking and grain filling of the maize in 2012 in comparison to 2013 were characterised with extremely dry spells, with high temperatures and low precipitation sums. The mean incidences of A. flavus and F. verticillioides were 50.4 and 11.7% in 2012 and 18.9 and 33.4% in 2013, respectively. According to the regulations of the World Health Organisation, unacceptable levels of AFB1 (>20 ?g kg-1) and FBs (>2000 ?g kg-1) were established in the 30.6 and 24.1% samples of 2012 and 16.7 and 40% maize kernel samples of 2013, respectively. It can be concluded that high temperatures and low precipitation sums in 2012 favoured the development of A. flavus affecting the high level of AFB1 , in comparison with F. verticillioides and the production of FBs. There was no positive correlation between the incidences of A. flavus and F. verticillioides, while a statistically significant positive correlation has been found between AFB1 and FBs levels, in both investigated years (2012-2013). This indicates that the mycotoxin production depended more on weather conditions than on the distribution of corresponding toxigenic fungal species.

Natural occurrence of fumonisins B1 and B2 in maize from eight provinces of China in 2014

ABSTRACTA total of 249 maize kernel samples from 8 maize-producing provinces of China were collected after the harvest season in 2014. All samples were analysed using high-performance liquid chromatography. The incidences of FBs (FB1 + FB2) from Guizhou, Hebei, Inner Mongolia, Shanxi, Chongqing, Liaoning, Heilongjiang, and Henan provinces were 71.4%, 73.8%, 28.0%, 52.6%, 85.0%, 87.5%, 38.1%, and 100.0%, respectively. The average concentration of FBs was 817 µg kg−1 and the concentrations ranged from <6 to 15,252 µg kg−1. Among the 249 maize kernel samples, 28 samples exhibited higher levels as set by the Food and Drug Administration (2000 µg kg−1), whereas 12 samples exhibited higher levels as set by the European Commission (4000 µg kg−1). The average exposure to FBs (0.12 µg kg−1 body weight/day) is within the provisional maximum tolerable daily intake of 2.0 µg kg−1 body weight as set by the Joint FAO/WHO Expert Committee on Food Additives.

Development of a screening method for the monitoring of 38 genetically modified maize events in food and feed in South Korea

A multiplex PCR system was developed to trace GM maize events in food and feed. Genetic elements of 38 single GM maize events were investigated, and 10 screening targets were selected as follows: promoters [Cauliflower mosaic virus (CaMV) 35S, rice actin 1 gene (rAct1)], terminators [CaMV 35S, Agrobacterium nopaline synthase (nos), proteinase inhibitor II of potato (PinII), heat shock protein 17 of wheat (hsp17)] and structural genes [cry1A gene derived from Bacillus thuringiensis, phosphinothricin acetyltransferase gene derived from Streptomyces hygroscopicus (bar), and Streptomyces Viridochromogenes (pat), 5-enolpyruvulshikimate-3-phosphate synthase enzyme derived from Agrobacterium tumefaciens strain CP4 (cp4-epsps)]. These screening targets were combined in three individual multiplex PCR assays. The method specificity was confirmed by detecting the specific amplification of DNA derived from 16 different GM maize events. The limit of detection of the multiplex PCR system was tested using the certified reference materials of GM maize events with different GM % (w/w) and approximately 0.1%. To test the applicability of the developed screening method, 22 food samples containing maize as ingredients, and 36 maize kernels were analyzed. Various types of single and/or stacked GM events were found in 11 food and 20 maize kernel samples. These results demonstrate that the screening method developed may be useful for tracking GM maize events in food and feed.

Mycotoxins and related Fusarium species in preharvest maize ear rot in Poland

This work presents a survey on mycotoxins (seasons 2013 and 2014) and Fusarium species (seasons from 1985 to 2014) in maize ear rot in Poland. Twelve mycotoxins were identified in maize kernel samples exhibiting symptoms of Fusarium ear rot or rotten kernels at the harvest in two locations in Poland during the seasons 2013 and 2014. This is the first complex survey on the co-occurrence of four Fusarium mycotoxin groups in maize kernels: the group of the mycohormone zearalenone; the group of trichothecenes – deoxynivalenol and nivalenol; the group of fumonisins; and the group of cyclic hexadepsipeptides – beauvericin and enniatins; and in addition, moniliformin. Four Fusarium species were identified in preharvest maize ear rot in the 2013 and 2014 harvests namely:&lt;br /&gt; F. graminearum, F. poae, F. subglutinans and F. verticillioides. Since 1985, eleven Fusarium species have been identified in 13 investigation seasons. Apart from those mentioned above, F. avenaceum, F. cerealis, F. culmorum and&lt;br /&gt; F. sporotrichioides were observed with irregular frequencies, and three species, i.e. F. proliferatum, F. tricinctum and F. equiseti, were identified sporadically. A significant increase of F. verticillioides frequency and a decrease of F. subglutinans frequency and changes of mycotoxin profile have been observed in the two decades since 1995.

Natural occurrence of Fusarium species and fumonisin on maize grains in Ethiopia

Fusarium species causing maize kernel rot are major threats to maize production, due to reduction in yield as well as contamination of kernels by mycotoxins that poses a health risk to humans and animals. Two-hundred maize kernel samples, collected from 20 major maize growing areas in Ethiopia were analyzed for the identity, species composition and prevalence of Fusarium species and fumonisin contamination. On average, 38 % (range: 16 to 68 %) of maize kernels were found to be contaminated by different fungal species. Total of eleven Fusarium spp. were identified based on morphological characteristics and by sequencing the partial region of translation elongation factor 1-alpha (EF-1α) gene. Fusarium verticillioides was the dominant species associated with maize kernels (42 %), followed by F. graminearum species complex (22.5 %) and F. pseudoanthophilium (13.4 %). The species composition and prevalence of Fusarium species differed among the areas investigated. Fusarium species composition was as many as eight and as few as four in some growing area. The majority of the maize samples (77 %) were found positive for fumonisin, with concentrations ranging from 25 μg kg−1 to 4500 μg kg−1 (mean: 348 μg kg−1 and median: 258 μg kg−1). Slight variation in fumonisin concentration was also observed among areas. Overall results indicate widespread occurrence of several Fusarium species and contamination by fumonisin mycotoxins. These findings are useful for intervention measures to reduce the impact of the main fungal species and their associated mycotoxins, by creating awareness and implementation of good agricultural practices.

Fusarium species identification and fumonisin production in maize kernels from Shandong Province, China, from 2012 to 2014

ABSTRACTA total of 225 maize kernel samples were collected from Shandong Province in China from 2012 to 2014 and analysed for contamination with Fusarium spp. and fumonisins (FBs) using molecular methods and high-performance liquid chromatography with fluorescence detection. The results showed that the average incidences of Fusarium spp. in 2012, 2013 and 2014 were 23.3%, 37.1% and 36.5%, respectively, Fusarium verticillioides being the predominant species. In 2012, the average contamination level of FBs was 3071 ng g−1, which was higher than that in 2014 (2913 ng g−1) and 2013 (2072 ng g−1). Of all samples, 13% and 19% had FB contamination levels higher than 2000 and 4000 ng g−1, which are the maximum limits as set by the Food and Drug Administration of the United States and the European Commission, respectively. Therefore, efforts should be taken to minimise the potential risk of FBs to the health of humans and animals.

Aflatoxins, Fumonisins and Zearalenone Contamination of Maize in the Southeastern and Central Highlands Provinces of Vietnam

A survey of the contamination of maize with aflatoxins, fumonisins and zearalenone was carried out in the Southeastern and Central Highland provinces in Vietnam. Four provinces were chosen for sampling maize: Dong Nai (22), Binh Phuoc (25), Dak Lak (30) and Dak Nong (20). Aflatoxin B1 (AFB1), B2 (AFB2), G1 (AFG1), G2 (AFG2), fumonisin B1 (FB1), fumonisin B2 (FB2) and zearalenone (ZEA) were analysed by HPLC in 97 maize kernel samples. Fumonisins were the most common toxins found in all samples (67%), followed by aflatoxins (55.7%) and zearalenone (27.8%). The incidence of aflatoxin positive samples (61.7%) in the Southeastern provinces was higher than in the Central Highlands (50%), while fumonisins and zearalenone incidences were higher in the Central Highlands. The mean level of fumonisin B1 in samples from the Central Highlands provinces (1757 µg/kg) was significantly greater (p &lt; 0.05) than in the Southeastern provinces (740 µg/kg). Importantly, the percentage of positive samples (about 70%) that had over 20 µg/kg (ppb) aflatoxin was very high. Moreover, many samples (53%) contained more than one mycotoxin and this result highlights the difficulty of diagnosing mycotoxicoses in the field and the need for ongoing research to reduce the occurrence of mycotoxins in Vietnamese maize.

In-silico and in-vitro evaluation of the potential of maize kernels to inhibit trypsin activity

Abstract A study has been conducted in order to evaluate the potential of maize kernels to inhibit trypsin activity in-silico and in-vitro. Assessment of published proteomic data revealed at least one specific trypsin inhibiting peptide within the Zea mays proteome with significant homology to proteins in other grain species but not legumes. Subsequently, a total of 12 maize kernel samples from two countries (Germany and Austria) were screened for their native trypsin inhibitor activity (TIA). The average TIA was 1.27 ± 0.33 mg/g dry matter (DM), ranging between 0.56 and 1.87 mg/g DM, and was no longer detectable after autoclaving (125 °C, 250 kPa, 1 h). Moreover, the degree of inhibition seemed to correlate positively with the crude protein content (r = +0.68*). The trypsin inhibiting effect declined through stepwise addition of exogenous trypsin, highlighting its specific suicidal mode of action. The optimal temperature for denaturation of the inhibitor pool was 82 ± 1 °C. Our results provide, to our knowledge for the first time, information about the trypsin inhibiting potential of maize kernels in-vitro. Furthermore, we identified several significant homologies between a maize bound trypsin inhibitor and peptides which are abundant in the proteomes of other grain species.

Mycobiota and mycotoxins in freshly harvested and stored maize

The incidence of mycobiota and mycotoxin levels were investigated in the freshly harvested maize kernel samples from October 2014 and in the samples of stored maize kernels from February 2015. Toxigenic fungal species (moulds) were isolated, cultivated and identified on agar plates according to standard mycological methods, while mycotoxins were detected by enzymelinked immuno-sorbent assay (ELISA). Mycological analyses of kernels showed the presence of toxigenic species from genera Aspergillus, Fusarium and Penicillium. Among the Aspergillus species, Aspergillus flavus was identified with higher incidence in the stored kernels (10.25%), than in freshly harvested kernels (3.67%) whereas A. parasiticus was the predominant species in the freshly harvested kernels (4.17%) compared to the stored kernels (0%). From the genus Fusarium three species were identified: F. graminearum, F. subglutinans and F. verticillioides, with the incidence of 1.08%, 8% and 25.75%, respectively in freshly harvested kernels and the incidence of 2.50%, 7.10% and 29.75%, respectively in the stored kernels. Species from genus Penicillium had higher incidence in freshly harvested kernels (14.25%) than in the stored kernels (9%). In addition, tested samples of harvested and stored maize kernels were 100% positive with aflatoxin B1 (AFB1), deoxynivalenol (DON) and total fumonisins B1, B2 and B3 (FBs). The mean levels of AFB1, DON and FBs were 2.77 ?g kg-1, 117.83 ?g kg-1, and 3700.84 ?g kg-1, respectively in the freshly harvested kernels and a mean levels of 2.16 ?g kg-1, 2034.40 ?g kg-1, and 5976.50 ?g kg-1, respectively in the stored maize kernels. In the freshly harvested maize kernel samples, statistically significant (P ? 0.05) positive correlations of kernel moisture content with the incidence of Penicillium spp. (r = 0.47), and levels of AFB1 (r = 0.46) and FBs (r = 0.47), and between the incidence of Penicillium spp. and level of AFB1 (r = 0.53) were established. In the stored maize kernel samples, statistically significant (P ? 0.05) positive correlations were found between the incidence of F. subglutinans and level of FBs (r = 0.50) and between levels AFB1 and FBs (r = 0.52). A highly significant (P ? 0.01) positive correlation was established between the incidence of F. verticillioides and level of FBs (r = 0.64) in freshly harvested maize kernel samples. These results indicate that the incidence of toxigenic fungi and levels of mycotoxins, in particular DON and FBs, were higher in the stored maize kernel samples than in freshly harvested maize kernels. Therefore, to prevent the development of toxigenic fungi and mycotoxins accumulation in post-harvest period it is necessary to thoroughly dry maize and keep it in hygienic food storages.