Effects of drying temperature and genotype on morphology and technological, thermal, and pasting properties of corn starch

Effect of maturity on the drying characteristics of lotus seed and molecular structure, gelation and digestive properties of its starch

Maturity and drying treatment are important factors affecting the processing characteristics of lotus seeds and its starch. This study aimed to investigate the effect of maturity (from low to high-M-1, M-2, M-3, M-4) on far-infrared drying kinetics of lotus seeds, and on the variation of structure, gelation and digestive properties of lotus seed starch (LSS) before and after drying. As the maturity increased, the drying time reduced from 5.8 to 1.0 h. The reduction of drying time was correlated with the decrease of initial moisture content, the increase of water freedom and the destruction of tissue structure during ripening. The increased maturity and drying process altered the multiscale structure of LSS, including an increase in amylose content, disruption of the short-range structure, and a decrease in relative crystallinity and molecular weight. The viscosity, pasting temperature and enthalpy of LSS decreased during ripening, and drying treatment caused the further decrease. The digestibility of LSS increased during ripening and drying. Lotus seeds at M-4 would be optimal for obtaining shorter drying time, lower pasting temperature and enthalpy, and higher digestibility. This study provided theoretical guidance for achieving effective drying process and screening LSS with suitable processing properties through maturity sorting.

Effect of microwave-assisted hot air drying on drying kinetics, water migration, dielectric properties, and microstructure of corn

This study investigates the effectiveness of microwave-assisted hot air drying (MAHD) on corn drying process, water migration, dielectric properties, microstructure, and quality attributes. The research compares MAHD with conventional hot air drying (HAD), employing various microwave powers (1.2-3.6 kW) and hot air temperatures (35-55 °C). The results demonstrate that MAHD significantly reduces the drying time (by 30.95-64.29%) compared to HAD. Two-term model accurately describes the drying kinetics of corn. Microwave facilitated the transformation and more uniform distribution of water within the corn, observed through LF-NMR/MRI. Additionally, MAHD was effective in preserving the color and carotenoids, while reducing fat acidity, indicating better quality retention. Microstructure analysis revealed that MAHD increases microporosity and cracks in corn, which correlates with the observed enhancement in drying efficiency. These findings underscore the potential of MAHD as a superior method for drying corn, offering benefits in terms of reduced drying time and improved quality preservation.

Insight into the mechanism of digestibility inhibition by interaction between corn starch with different gelatinization degree and water extractable arabinoxylan

On the basis of revealing the interaction mechanism between corn starch (CS) and water-extractable arabinoxylan (WEAX) with high/low molecular weight (H-WEAX, L-WEAX), the degree of gelatinization (DG) on structural behaviors and in vitro digestibility of CS-WEAX complexes (CS/H, CS/L) was evaluated. With the increased DG from 50 % to 95 %, the water adsorption capacity of CS/L was increased 64 %, 58 %, 47 %, which were higher than that of CS/H (39 %, 54 %, 33 %). The gelatinization of starch was inhibited by WEAX, resulting in the enhancement of crystallinity, short-range ordered structure and molecular size of CS-WEAX complexes. Stronger interaction was detected in CS/L than with CS/H as proved by the increased hydrogen bonds and electrostatic force. Complexes exhibited higher resistant starch content (RS) at diverse DG, especially for CS/L. Notability, RS content of samples with 50 % DG were increased from 27.72 % to 32.89 % (CS/H), 36.96 % (CS/L). Except for the reduction of gelatinization degree by adding WEAX, the other possible mechanisms of retarding digestibility were explained as the small steric hindrance of L-WEAX promoted encapsulation of starch granules, limiting enzyme accessibility. Additionally, the fragmentation of CS granules with high DG promoted the movement of H-WEAX, reducing the difference in digestibility compared to CS/L.

Hot air-assisted radio frequency drying of corn kernels: the effect on structure and functionality properties of corn starch

Hot air (HA) drying caused quality damage of grains with long treatment time. Radio frequency (RF) heating as an emerging technology was applied to improve drying quality of cereals effectively. The effects of HA-RF drying (50 °C, 70 °C, 90 °C) of corn kernels on the morphology, structure, and physicochemical properties of starch were investigated and compared with HA drying. The surface of treated starch became rough, along with fragments and pores. Drying treatments increased the amylose content from 10.59 % to 23.88 % and the residual protein content of starch from 0.58 % to 1.23 %, and reduced the crystallinity from 31.95 % to 17.15 % and short-range order structures of starch from 0.918 to 0.868. The change of structures in turn resulted in the increase of pasting viscosity, gelatinization temperature, storage modulus and loss modulus. Furthermore, the HA-RF dried starch displayed stronger thermal stability, higher gelatinization degree and better gelation properties than the HA-treated starch at the same temperature. The data proved that the synergistic effects of HA and RF were more effective in modulating the starch structure and improving the functional characteristics of corn starch. This paper would like to provide potential reference for better application of HA-RF technologies to corn.

Evaluation of Quality Properties of Brown Tigernut (Cyperus esculentus L.) Tubers from Six Major Growing Regions of China: A New Source of Vegetable Oil and Starch

Tigernut has been recognized as a promising resource for edible oil and starch. However, the research on the quality characteristics of tigernut from different regions is lagging behind, which limits the application of tigernut in food industry. Tigernut tubers were obtained from six major growing regions in China, and the physicochemical properties of their main components, oil and starch, were characterized. Tigernut tubers from Baoshan contained the most oil (30.12%), which contained the most β-carotene (130.4 µg/100 g oil) due to high average annual temperature. Gas chromatography analysis and fingerprint analysis results indicated that tigernut oil (TNO) consists of seven fatty acids, of which oleic acid is the major component. Changchun TNO contained the least total tocopherols (6.04 mg/100 g oil) due to low average annual temperature. Tigernut tubers from Chifeng (CF) contained the most starch (34.85%) due to the large diurnal temperature range. Xingtai starch contained the most amylose (28.4%). Shijiazhuang starch showed the highest crystallinity (19.5%). Anyang starch had the highest pasting temperature (76.0°C). CF starch demonstrated superior freeze-thaw stability (syneresis: 50%) due to low mean annual precipitation. The results could be further applied to support tigernut industries and relevant researchers that looks for geographical origin discrimination and improvements on tigernut quality, with unique physicochemical and technological properties.

Effect of Aspergillus flavus contamination on the fungal community succession, mycotoxin production and storage quality of maize kernels at various temperatures

Aspergillus flavus, a notorious saprobe and opportunistic plant pathogen, alters mycotoxin contamination and biochemical components in maize kernels during processing and storage, thereby reducing the possibilities of maize end use and compromising food safety. This study explored changes in mycotoxin production, fungal community succession and biochemical components in maize kernels stored at 20, 25 and 30 °C, exposed to A. flavus. Results showed that aflatoxin B1 concentration increased over time, reaching 4.88 μg/kg at 20 °C, 167.23 μg/kg at 25 °C and 349.64 μg/kg at 30 °C after 15 days of storage, whereas the zearalenone production was characterized by an increase followed by a decrease. Correspondingly, the number of molds gradually increased and reached a stable stage after 10 days. High-throughput sequencing of the internal transcribed spacer (ITS) revealed that Eurotium dominated the fungal communities, with A. flavus reaching maximum abundance in maize kernels stored at 30 °C for 15 days. Correlation analysis indicated that the relative abundance of A. flavus was significantly negatively correlated with the content of zein and moisture (P < 0.05). Moreover, the wet milling process of maize effectively eliminated the concentration of aflatoxin B1 and zearalenone from the starch. Pasting temperature and setback value of starch decreased while peak viscosity, final viscosity and breakdown value increased with storage. These findings indicate that interactions between the epiphytic fungal community and A. flavus at elevated storage temperatures aggravate both maize quality deterioration and mycotoxin contamination. Furthermore, they have a discernible impact on the pasting properties of starch. This insight informs strategies to control fungal infections during maize processing and storage.

Effects of corn drying and storage conditions on flour, starch, feed, and ethanol production: a review

The objective was to review the effects of the drying and storage conditions of corn on the physical-chemical quality in the processing of starch and flour, in the production of animal feed, and in the industrialization of ethanol. Initially, the review presented an overview of the post-harvest stages of corn grains, highlighting drying and storage. The main drying and storage methods used for corn grains were presented. Among the drying conditions, the air temperature was the main factor that affected the properties of starch, flour, feed, and ethanol produced from corn. It was verified that the corn grains submitted to drying at temperatures below 60 °C obtained better results in the industry. In storage, in addition to the storage time, factors such as temperature and moisture content of the grains affected the physical-chemical quality of the processed products. In this stage, the moisture content below 14% and the storage temperature below 25 °C conserved the physical-chemical quality of the grains and obtained better processing results. Further studies are needed to assess the effects of the drying and storage conditions of corn on the properties of flour, starch, animal feed, and, mainly, ethanol production.

Graphical abstract

Andean purple maize to produce extruded breakfast cereals: impact on techno-functional properties and sensory acceptance

BACKGROUND

Andean purple maize (APM) is an ancient crop widely used as a natural coloring in traditional Peruvian cuisine. However, it has been little explored within the food industry. The present study assessed how APM impacts on techno-functional properties and sensory acceptance of breakfast cereals. Extruded samples formulated with 100, 75, 50, and 25% APM, and complemented with yellow corn grits (YCG), were analyzed for their techno-functional and sensory properties.

RESULTS

Increases in bulk density, as well as reduction in the expantion and porosity were observated for extrudates containing ≥ 50% APM, accompanied by an increase in purple color intensity. Increase in milk absorption index, reduction in milk solubility index and decrease in cereal hardness with increase in APM were also observed. Despite this, APM extented the cereal bowl-life. High sensory scores of overall liking (6) and color (7) were obtained for extruded formulations containing ≥ 50% APM and low values for extrudates with 25% APM. Aroma, flavor, and texture scores did not present significant differences.

CONCLUSION

APM is an ingredient with the potential to be used to produce breakfast cereals since it improves their techno-functional characteristics and sensory acceptance, at the same time, it leads to the production of healthy, nutritious, and sustainable food. © 2022 Society of Chemical Industry.

Effects of drying temperature of corn from the center and extremities of the corncob on drying parameters, protein and starch properties, and carotenoid profile

The corn grains from the extremities of corncob are known to have a spherical shape and the grains from the center of corncob have higher length and lower thickness. It is understood that these differences in grain dimensions can affect post-harvest processes and the properties of the grains. Therefore, the objective of this study was to evaluate the effects of drying temperature (60, 80, and 100 °C) of corn from the center and extremities of corncob on drying parameters, protein and starch properties, and carotenoid profile. At 60 °C, the drying rate and effective moisture diffusivity of corn from the center and extremities of the corncob did not differ. However, at 80 and 100 °C these parameters were higher in the corn from the center. Corncob part and separation did not significantly affect corn pasting properties. However, they caused significant changes in the properties of the grain proteins, mainly the reduction of the solubility and inactivation of the lipase enzyme, and the reduction of the lutein and β-carotene contents in the grains from the center and separated after drying. The results of this research show the need to evaluate the effects of these drying conditions during grain storage. In addition, the implementation of an industrial separation step and/or the development of new corn cultivars with more homogeneous grains should be studied.

A Novel Starch from Talisia floresii Standl Seeds: Characterization of Its Physicochemical, Structural and Thermal Properties

Colok seed (Talisia floresii Standl) represents 80% of the total fruit weight and is obtained from trees that grow mainly in Yucatan Peninsula. The aim of this work was the physicochemical characterization from colok starch seeds as an alternative to conventional sources and to identify its characteristics for potential applications in different industrial sectors. Starch yield was 42.1% with low levels of lipids, ashes and fibers. The amylose content was 33.6 ± 1.15%. The gelatinization temperature was 85 ± 0.25 °C. Color analysis resulted in a starch with an intermediate luminosity, reflecting a dark color. Finally, in morphology, starch granule exhibited an average size of 18.7 μm, spherical, uniform and without fractures. Overall results demonstrated that isolated colok starch can be used in food products that require high processing temperatures, such as sauces, cookies, noodles, bread and food packages.

Preparation and characterization of low oil absorption corn starch by ultrasonic combined with freeze–thaw treatment

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Combined ultrasonic and freeze–thaw pretreatment significantly reduced oil absorption of corn starch.

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The combined treatment increased the density of corn starch granules.

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The combined treatment increased the short-range order of cornstarch.

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Modified starch could be used in low-fat fried food processing industry.

This study investigated the effects of ultrasonic, freeze–thaw, and combined pretreatments on corn starch oil absorption. Low-field nuclear magnetic resonance (LF NMR) was used to study the oil absorption changes after frying of corn starch (CS) subjected to different treatments. The structural characteristics of samples were evaluated using various techniques. Scanning electron microscopy, contact angle, and particle size analysis showed that corn starch subjected to combined ultrasonic and freeze–thaw treatment generated larger, coarser particles with a denser structure. Furthermore, X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry showed that combined treatment improved the order and thermal stability of CS molecules, thereby inhibiting oil absorption during frying. The results showed that combined ultrasonic and freeze–thaw pretreatment significantly reduced the oil absorption of corn starch before and after frying.

Mathematical modeling and multivariate analysis applied earliest soybean harvest associated drying and storage conditions and influences on physicochemical grain quality

Anticipating the harvest period of soybean crops can impact on the post-harvest processes. This study aimed to evaluate early soybean harvest associated drying and storage conditions on the physicochemical soybean quality using of mathematical modeling and multivariate analysis. The soybeans were harvested with a moisture content of 18 and 23% (d.b.) and subjected to drying in a continuous dryer at 80, 100, and 120 °C. The drying kinetics and volumetric shrinkage modeling were evaluated. Posteriorly, the soybean was stored at different packages and temperatures for 8 months to evaluate the physicochemical properties. After standardizing the variables, the data were submitted to cluster analysis. For this, we use Euclidean distance and Ward's hierarchical method. Then defining the groups, we constructed a graph containing the dispersion of the values of the variables and their respective Pearson correlations for each group. The mathematical models proved suitable to describe the drying kinetics. Besides, the effective diffusivity obtained was 4.9 × 10-10 m2 s-1 promoting a volumetric shrinkage of the grains and influencing the reduction of physicochemical quality. It was observed that soybean harvested at 23% moisture, dried at 80 °C, and stored at a temperature below 23 °C maintained its oil content (25.89%), crude protein (35.69%), and lipid acidity (5.54 mL). In addition, it is to note that these correlations' magnitude was substantially more remarkable for the treatments allocated to the G2 group. Furthermore, the electrical conductivity was negatively correlated with all the physicochemical variables evaluated. Besides this, the correlation between crude protein and oil yield was positive and of high magnitude, regardless of the group formed. In conclusion, the early harvest of soybeans reduced losses in the field and increased the grain flow on the storage units. The low-temperature drying and the use of packaging technology close to environmental temperatures conserved the grain quality.

Biomass utilization and production of biofuels from carbon neutral materials

The availability of organic matters in vast quantities from the agricultural/industrial practices has long been a significant environmental challenge. These wastes have created global issues in increasing the levels of BOD or COD in water as well as in soil or air segments. Such wastes can be converted into bioenergy using a specific conversion platform in conjunction with the appropriate utilization of the methods such as anaerobic digestion, secondary waste treatment, or efficient hydrolytic breakdown as these can promote bioenergy production to mitigate the environmental issues. By the proper utilization of waste organics and by adopting innovative approaches, one can develop bioenergy processes to meet the energy needs of the society. Waste organic matters from plant origins or other agro-sources, biopolymers, or complex organic matters (cellulose, hemicelluloses, non-consumable starches or proteins) can be used as cheap raw carbon resources to produce biofuels or biogases to fulfill the ever increasing energy demands. Attempts have been made for bioenergy production by biosynthesizing, methanol, n-butanol, ethanol, algal biodiesel, and biohydrogen using different types of organic matters via biotechnological/chemical routes to meet the world's energy need by producing least amount of toxic gases (reduction up to 20-70% in concentration) in order to promote sustainable green environmental growth. This review emphasizes on the nature of available wastes, different strategies for its breakdown or hydrolysis, efficient microbial systems. Some representative examples of biomasses source that are used for bioenergy production by providing critical information are discussed. Furthermore, bioenergy production from the plant-based organic matters and environmental issues are also discussed. Advanced biofuels from the organic matters are discussed with efficient microbial and chemical processes for the promotion of biofuel production from the utilization of plant biomasses.