A two-dimensional symmetric heat transfer model and a fluid rotation model were established to study beer pasteurization process through the COMSOL Multiphysics software. Two heating modes, including closed-loop heating (CLH) and open-loop heating (OLH), were considered. There was a significant natural convection phenomenon in both heating systems. However, the natural convection became weaker with a gradual increase in the heating temperature of the beer. The maximum fluid velocity (FV) in CLH and OLH modes was 69.34 and 43.74 mm/s, respectively. After heating at 333.13 K for 20 min, the minimum and maximum pasteurization unit (PU) values in CLH were 55 and 59, respectively, while the corresponding values for OLH were 30 and 55, respectively. The pasteurization effect under the CLH mode was better than the OLH one. The heat transfer was also affected by fluid flow (laminar and turbulence) patterns. The PU value was nonlinearly related to the FV. The optimal FV can be obtained at ∼50 mm/s.
Hot air drying is a commonly used technology in the preservation of red radish. This study was designed to investigate the correlations among total polyphenol content, total flavonoid content, antioxidant activities and polyphenol compounds in hot air dried red radish via chemometric analysis. UHPLC-QqQ-MS/MS analysis detected nine non-anthocyanin polyphenols and one anthocyanin in fresh and dried red radish samples, and found that hot air drying at 80 °C caused an increase in the p-coumaric acid and ferulic acid content of the red radish. The integral effect of hot air drying on the polyphenol profile of red radish was analyzed by principle component analysis, while sparse partial least squares-discriminant analysis showed that hot air drying induced changes mainly in the contents of poncirin, naringenin, phloetin and cyanidin-3-glucoside. These polyphenol degradations occurred as non-spontaneous and endothermic reactions during the hot air drying process, following first-order reaction kinetics.
In recent years, there has been a growing interest in the use of agricultural biomass for fermentation purposes; however, efficient strategies to counter lignocellulose inhibition are warranted to enhance xylitol production performance. Dilute-acid hydrolysis has been studied to selectively release a significant portion of xylose from hemicellulose, while leaving cellulose and lignin intact. The formation of inhibitory compounds, however, could jeopardise the overall performance during fermentation to produce xylitol. In this study, the fermentability of nitric acid-hydrolysed kenaf stem was substantially improved, through either adaptive evolution of the recombinant Escherichia coli BL21 (DE3) or removal of fermentation inhibitors by detoxification with activated carbon. Both methods were compared to evaluate the superiority in fermentative performance. In the fermentation with detoxified hemicellulosic hydrolysate, the non-adapted strain produced the highest xylitol concentration of up to 6.8 g/L, with 61.5% xylose consumption. The yields of xylitol production involving detoxification were successfully enhanced by 22.6% and by 35.7% compared to those involving adaptive evolution and raw hydrolysate, respectively. The results reported herein suggest that the utilization of detoxified kenaf stem hydrolysate could be advantageous.
The effects of weak oscillating magnetic fields (OMFs ≤7 mT at 50 Hz) on freezing were studied in three systems of different complexity. To do so, ferric chloride solutions, lactate dehydrogenase (LDH), and minced hake muscle experimentally infected with Anisakis L3 were frozen with and without OMF application. OMFs did not affect freezing kinetics of either ferric chloride solutions or minced hake muscle. LDH activity, Anisakis mortality, and water-holding capacity of the hake muscle after thawing were not affected by OMF either. Further studies are needed to evaluate the effectiveness of stronger OMFs in a wider frequency range.
Precise classification of seeds is important for agriculture. Due to the slight physical and chemical difference between different types of wheat and high correlation between bands of images, it is easy to fall into the local optimum when selecting the characteristic band of using the spectral average only. In this paper, in order to solve this problem, a new variable fusion strategy was proposed based on successive projection algorithm and the variable importance in projection algorithm to obtain a comprehensive and representative variable feature for higher classification accuracy, within spectral mean and spectral standard deviation, so the 25 feature bands obtained are classified by support vector machine, and the classification accuracy rate reached 83.3%. It indicates that the new fusion strategy can mine the effective features of hyperspectral data better to improve the accuracy of the model and it can provide a theoretical basis for the hyperspectral classification of tiny kernels.
A selenium-chelating corn oligopeptide (Se-COP) with high protein and low molecular weight was prepared as a selenium supplement. We utilized infrared (IR), ultraviolet (UV), and circular dichroism (CD) spectroscopy, 1-anilinonaphthalene-8-sulfonate (ANS)-binding fluorescence spectra, and isothermal titration calorimetry (ITC) to analyze and describe Se-COP and its reactions. It was concluded that the chelation reaction was a spontaneous process driven by enthalpy and entropy, with ΔH=3.79 × 104 ± 4075 cal/mol, ΔS = 146 cal/mol, ΔG = –23356.30 ± 126.94 cal/mol, binding constant Ka = 1.18 × 104 ± 855 M–1, and binding site number n = 0.13 ± 0.0126, and described as coordination bonds forming and hydrophobic interaction, as well as protein conformational changes including secondary and tertiary hydrophobic structure. Se-COP had strong antioxidant capacity, and mass spectrometry (MS) was used to identify the antioxidant peptide fragment, which was characterized as LLPPY and quantified at 428.95 ng/mg. This study indicated that Se-COP prepared by chelation may be a Se supplement with antioxidant capacity that can be applied in functional foods or ingredients.
The aims of this study included evaluation of copper-binding capacity (CBC) and amino acid composition of salmon by-product proteolysate and its peptide fractions, optimization of hydrolysis condition, and identification of copper-binding peptides from the proteolysate. The result was that under the ideal hydrolysis (Neutrase, temperature of 45 °C, pH 7, enzyme:substrate (E:S) proportion of 72.24 U/g protein and hydrolysis time of 8.02 h), the proteolysate had the indispensable amino acid content at approximately 38.7% and also displayed the maximal CBC of 15163.6 µg Cu2+/g protein. Besides, four peptide fractions of 10–30 kDa, 3–10 kDa, 1–3 kDa, and <1 kDa were recovered using ultrafiltration, among which the <1 kDa fraction had the highest CBC of 10852.00 ± 895.06 µgCu2+/g protein. A copper-binding peptide, Phe-Ile-Asp-Asp-Asp-Ala-Phe-Ile-Arg (1110 Da), was identified from this fraction using tandem mass spectrometry (MS/MS). As a whole, the proteolysate/peptides could be used for copper enhancement that could shield human body from copper inadequacy disorders.
Visible/Near-infrared (Vis/NIR) spectroscopy at a range of 450–1000 nm was used to predict the values of three qualitative variables (starch, reducing sugar, and moisture content) on 200 potato tubers from 2 potato genotypes (‘Agria’ and ‘Clone 397009–8’) stored in both traditional and cold storages. After spectroscopy measurements, these variables were measured using reference methods. Then, Partial Least Square (PLS) models were developed. To evaluate developed models, Root Mean Square Error of calibration and cross validation (RMSEC and RMSECV), as well as coefficient of determination for calibration and cross validation (R2C and R2CV), and Residual Predictive Deviation (RPD) were used. The best prediction belonged to reducing sugar with statistical values of R2C = 0.99, R2CV = 0.98, RMSEC = 0.029, RMSECV = 0.037, and RPD = 7.57 in ‘Clone’ genotype stored under cold storage. The weakest prediction was related to moisture content with statistical values of R2C = 0.93, R2CV = 0.92, RMSEC = 0.268, RMSECV = 0.279, and RPD = 6.45 in stored ‘Clone’ genotypes under cold storage. Results of the study showed that, Vis/NIR spectroscopy as a non-destructive, fast, and reliable technique can be used for prediction of inner compositions of stored potatoes.
Alginate, a heteropolysaccharide extracted from brown algae Laminaria digitata, has non-toxic status and good physical and chemical properties, was used in this study for encapsulation of the cyanobacterium Arthrospira platensis. Results indicated that adding A. platensis to alginate beads increased the level of mineral elements: magnesium by 55–60 mg/kg, iron by 38–40 mg/kg, and iodine by 88–107 μg/kg, as compared to respective control samples without microalgae addition. Adding A. platensis within alginate beads resulted in an increased antioxidative potential and consequent higher inhibition of the radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) by 15–25% compared to the respective control alginate beads. Finally, the content of beta-carotene in alginate beads fortified with A. platensis biomass amounts on average to 51 μg/g. Due to their health-promoting potential, alginate beads enriched with A. platensis biomass can, therefore, be used as a functional ingredient in the nutraceutical sector.