Volume 16, Issue 4 -

The stress relaxation, creep-recovery, temperature, and frequency sweep tests were performed within the linear viscoelastic region by using a dynamic mechanical analyzer to investigate the viscoelastic characteristic of oat grain. The result showed that 5-element Maxwell and Burgers model were able to describe viscoelastic behaviors better. The relaxation stress decreased with the increasing moisture content from 6.79 to 23.35%, while the creep strain increased as well as the final percentage recovery decreased from 58.61 to 32.50%. In frequency sweep, storage modulus increased with the increasing frequency. In temperature sweep, there was a clear turning point in storage modulus, loss modulus, and tan delta curves with increasing temperature. The turning value of 167.47, 147.44, 134.27, 132.41, 110.28, and 92.62 °C detected in the tan delta were regarded as the best glass transition temperatures. This temperature was found to be lower than gelatinization heating temperature and decrease with the increase of moisture content. The crystalline structure of oat exhibited a typical A-type pattern and corresponding crystallinity increased from 22.03 to 31.86% with increasing moisture content. The scanning electron microscopy (SEM) micrograph of oat section was found that the size and adhesive effect of starch granules increased due to hydration.

The objective of the present study was to predict the inactivation trends of acid-adapted foodborne pathogens in tomato juice by ohmic heating through a numerical analysis method. The mathematical model based on finite element method (FEM) was used to simulate the multiphysics phenomena including electric heating, heat transfer, fluid dynamics, and pathogen inactivation. A cold spot was observed in the corner part of the ohmic heating chamber, where some pathogens survived even though all pathogens were inactivated elsewhere. Challenges of this study were how to reflect the increased resistance of pathogen by acid-adaptation. After simulation, we verified that inactivation level of acid-adapted foodborne pathogens by 25 V rms /cm ohmic heating (1 kHz), predicted with the developed mathematical model, had no significant differences with experimental results ( p  > 0.05). Therefore, the mathematical approaches described in the present study will help juice processors determine the processing conditions necessary to ensure microbial safety at the cold point of a rectangular type batch ohmic heater.

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 × 10 4  ± 4075 cal/mol, ΔS = 146 cal/mol, ΔG = –23356.30 ± 126.94 cal/mol, binding constant K a  = 1.18 × 10 4  ± 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 Cu 2+ /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 µgCu 2+ /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.

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.

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 ( R 2 C and R 2 CV ), and Residual Predictive Deviation (RPD) were used. The best prediction belonged to reducing sugar with statistical values of R 2 C = 0.99, R 2 CV = 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 R 2 C = 0.93, R 2 CV = 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.

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.

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.