Screening and HPLC methods for carotenoids in sweetpotato, cassava and maize for plant breeding trials

Analytical methods for sweetpotato, cassava and maize were developed. In orange and salmon-fleshed sweetpotatoes, (all-E)-β-carotene predominated and results of spectrophotometric screening and HPLC quantification did not differ significantly. In yellow-fleshed sweetpotato and cassava, however, spectrophotometric screening overestimated the HPLC values because of the presence of several minor carotenoids. Aside from (all-E)-β-carotene, Z-isomers were present in cassava in appreciable amounts. For both crops, extraction with acetone or tetrahydrofuran:methanol (1:1), using a mortar and pestle or a Polytron homogenizer, gave equivalent results. Rehydration of dry maize at room temperature for 30 min or at 85 °C for 5, 10 or 15 min gave equivalent results. Concentrations obtained with the C18 and C30 columns did not differ significantly for zeaxanthin, lutein, β-cryptoxanthin and β-carotene in the all-E-configuration, but their Z-isomers were difficult to locate in the chromatogram obtained with the C30 column. Extraction with tetrahydrofuran:methanol (1:1) gave significantly lower results for zeaxanthin and lutein.     

Antinutritional effects of the chitin-binding lectin from Microgramma vacciniifolia rhizome (MvRL) on Sitophilus zeamais

Sitophilus zeamais Motsch. (Coleoptera: Curculionidae) is one of the most common and destructive storage pests in the world and its control depends mostly on the utilization of synthetic pesticides. The hazards of synthetic chemicals to people and the environment, together with the development of resistance by the insects, stimulate the investigation of alternative methods. In the present study, we determined the effects of the ingestion of artificial diet containing the Microgramma vacciniifolia rhizome lectin (MvRL) on survival, feeding and nutrition of S. zeamais adults. MvRL was incorporated into the artificial diets at concentrations ranging from 10 to 130 mg/g. Mortality rate, ingested food and variation in the weight of the insects were determined after 7 days. In addition, the in vitro effects of MvRL on the activity of insect digestive enzymes were investigated. MvRL did not increase the mortality rates but disrupted the nutritional status of the insects since the biomass variation and efficiency in conversion of ingested food were negative. The lectin was able to inhibit in vitro β-glucosidase and α-amylase activities. In conclusion, MvRL showed anti-nutritional properties on S. zeamais adults, which may be due interference with digestive enzymes. MvRL may be useful as an additive or synergistic agent for reduced pest fitness by affecting the food conversion into biomass.     

Detecting corn tassels using computer vision and support vector machines

An automated solution for maize detasseling is very important for maize growers who want to reduce production costs. Quality assurance of maize requires constantly monitoring production fields to ensure that only hybrid seed is produced. To achieve this cross-pollination, tassels of female plants have to be removed for ensuring all the pollen for producing the seed crop comes from the male rows. This removal process is called detasseling. Computer vision methods could help positioning the cutting locations of tassels to achieve a more precise detasseling process in a row. In this study, a computer vision algorithm was developed to detect cutting locations of corn tassels in natural outdoor maize canopy using conventional color images and computer vision with a minimum number of false positives. Proposed algorithm used color informations with a support vector classifier for image binarization. A number of morphological operations were implemented to determine potential tassel locations. Shape and texture features were used to reduce false positives. A hierarchical clustering method was utilized to merge multiple detections for the same tassel and to determine the final locations of tassels. Proposed algorithm performed with a correct detection rate of 81.6% for the test set. Detection of maize tassels in natural canopy images is a quite difficult task due to various backgrounds, different illuminations, occlusions, shadowed regions, and color similarities. The results of the study indicated that detecting cut location of corn tassels is feasible using regular color images.     

The influence of climate conditions on the occurrence of deoxynivalenol in maize harvested in Serbia during 2013–2015

The objective of this study was to investigate the influence of climate conditions on deoxynivalenol (DON) content in 1800 maize samples collected from main maize growing regions in Serbia during a period of three years.DON concentration was determined by validated direct competitive Enzyme Linked Immunosorbent Assay (ELISA) method.Presence of DON in maize samples from 2013, 2014 and 2015 years was detected in 2.5%, 96.0% and 15.5% of samples in the concentration range of 260.1–1388 μg/kg, 260.4–9050 μg/kg and 252.3–6280 μg/kg, respectively.The obtained results indicate that different weather conditions recorded in examined years had a significant influence on DON occurrence in maize. Extremely rainy weather conditions in maize growing season 2014 were favourable for DON production and even 292 (48.3%) samples were unsuitable for human consumption, since DON concentrations were greater than 1750 μg/kg. However, lack of rainfall and higher air temperatures during the years 2013 and 2015 contributed to lower contamination frequency of DON.These findings confirmed that maize should be continuously monitored in order to protect human and animal population against the risk of DON contamination. Furthermore, monitoring of DON occurrence in maize from Serbia is required in order to collect data which is needed for establishing a Serbian as well as European database.     

DETERMINATION OF MOISTURE CONTENT IN MAIZE EARS

ABSTRACT

The paper seeks to establish a suitable oven drying standard for whole maize ears. The temperature/time combination of 130°C for 38 hours recommended for unmilled maize kernels (ISO 6540 end BS 4317) was taken as the starting point. The temperature was not varied, but the effects of time and shelling on the maize ear and its components were investigated. It was found that the oven drying rate for maize ears was very similar to that of the kernels, due to the small fraction of moisture in the cob and its rapid diffusion. ISO 6540 and BS 4317 standards for unmilled maize kernels are therefore also recommended for whole maize ears.     

Fumonisins and their masked forms in maize products

In recent years many papers on masked mycotoxins in maize-based products appeared, including reports on fumonisins capable to form non-covalent bonds with food macro constituents. Such so-called “hidden fumonisins” are frequently present in food at quantities higher than the free forms. The aim of this work was to assess levels of free and total (free + hidden) fumonisins (B₁, B₂ and B₃) in 88 maize products available on the Polish retail market. Isotope dilution ion trap mass spectrometery coupled to a high performance liquid chromatography was used. 57% of all tested samples contained free fumonisins at concentrations above our limit of quantification LOQ (mean 390 ± 676 μg/kg). More than 77% of the samples contained free + hidden fumonisins at concentrations above LOQ (mean 574 ± 1177 μg/kg). The highest mean fumonisins concentrations 1006 ± 1131 μg/kg, 1651 ± 2317 μg/kg, respectively for free and free + hidden forms were observed in the group of maize snacks. The lowest fumonisin concentrations were found in maize-based starch concentrate products. None of the tested products within that group had free fumonisins concentrations above LOQ, while mean concentration of free + hidden fumonisins was as low as 82 ± 42 μg/kg. In thermally processed products like corn flakes and various snacks the hidden-to-free fumonisin concentration ratio was higher than in unprocessed products like flour, groats or raw popcorn grains.     

Anaerobic digestion of maize focusing on variety,harvest time and pretreatment

The methane potential of six varieties of fresh maize (whole plant) harvested at three different times and of maize silage (whole plant) in two particle size distributions was experimentally determined in batch assays. Fresh maize gave the highest methane yield/hectare at late harvest (6270 m³ CH₄ (10⁴ m²)⁻¹). The methane yield/wet weight (WW) increased from 80 (early harvest) to 137 m³ CH₄ (t WW)⁻¹ (late harvest). Maize harvested at different times, or different varieties of maize had similar specific methane production/volatile solids content (m³ CH₄ (kg VS)⁻¹). The measured yield m³ CH₄ (kg VS)⁻¹ was 84% of the theoretical methane potential. The estimated ethanol yield was between 2.5 and 3.5 t ethanol (10⁴ m²)⁻¹. The energy yield was 62 and 19–22 MWh (10⁴ m²)⁻¹ if fresh maize (whole plant) is used for methane or ethanol production respectively. Reducing the particle size of maize silage to an average size of approximately 2 mm increased the methane yield m³ CH₄ (kg VS)⁻¹ by approximately 10%.     

Evaluation of methane production from maize silage by harvest of different plant portions

Biogas production is mainly based on the anaerobic digestion of cereals silages and maize silage is the most utilized. Regarding biogas production, the most important portion of the plant is the ear. The corn ear, due to high starch content, is characterized by a higher biogas production compared to the silage of the whole plant.In this paper, we present the results of experimental field tests carried out in Northern Italy that aim to evaluate the anaerobic methane potential (BMP) of different portions of ensiled maize hybrids. The BMP production is evaluated considering the possibility of harvesting and ensiling: the whole plant; the plant cut at 75 cm of height; the ear only; the plant without the ear. For the different solutions, the results are reported as specific BMP and as average biogas production achievable per hectare. The methane production by harvesting and ensiling the whole plant (10,212 and 10,605 m³ ha⁻¹, for maize class 600 and 700, respectively) is higher than the ones achievable by the other plant portions (7961 and 7707 m³ ha⁻¹, from the ear; 9523 and 9784 m³ ha⁻¹, from the plant cut at 75 cm; 3328 and 3554 m³ ha⁻¹, from the plant without the ear, for maize class 600 and 700, respectively). The harvest of the whole plant, although it is the most productive solution, could not be the best solution under an economic and environmental point of view. Harvesting only the ear can be interesting considering the new Italian subsidy framework and for the biogas plants fed by biomass transported over long distances.     

Comparison of Fatty Acid Profile of Specialty Maize to Normal Maize

Increasing utilization of specialty maize prompted us to evaluate its fatty acid profile. For this purpose maize germplasm, classified as low oil normal maize (group 1), high oil normal maize (group 2), quality protein maize (QPM) (group 3) and sweet corn (group 4) was evaluated for oil, starch, protein and fatty acid composition mainly palmitic, stearic, oleic and linoleic acid. High oil content was observed in sweet corn samples which might be result of shriveled grain texture because of an increased embryo to kernel ratio. Individual fatty acids showed wide differences among different groups. A slightly higher amount of palmitic acid was reported in specialty maize as compared to normal maize. In contrast, stearic acid content was significantly low in high oil normal maize (56 %), QPM (36.2 %) and sweet corn (28.4 %) in comparison to low oil normal maize. Although no significant differences were observed for oleic acid between low oil normal and high oil normal maize, but sweet corn samples showed significantly reduced oleic acid compared to low oil normal maize. However, the most important observation was the higher content of linoleic acid in specialty maize (groups 2, 3 and 4) as compared to low oil normal maize. Further, the ratio of MUFA/PUFA was also discussed. It was concluded that specialty maize possesses a better oil quality in comparison to low oil normal maize.