Kinetic modelling of ascorbic and dehydroascorbic acids concentrations in a model solution at different temperatures and oxygen contents

Formulations of selected Energy beverages promote pro-oxidant effects of ascorbic acid and long-term stability of hydrogen peroxide

Recently, autoxidation mediated by ascorbic acid (AA) and other ingredients, has been implicated in generation of hydrogen peroxide (H₂O₂) in so-called Energy beverages. Here, we report the use of cyclic voltammetry and the FOX assay to monitor at short and long incubation times, respectively, the production and stability of H₂O₂ generated by AA and redox-active ingredients. Levels of H₂O₂ in Energy drinks (36.5 ± 4.0 µM at 4 °C and 64.2 ± 7.6 µM at 20 °C) were found to be stable or increased (p < 0.05) upon vessel opening. A predictive model for the production of H₂O₂ as a function of AA concentration, temperature and incubation time, and depending on ingredients present, indicated that H₂O₂ peaked at 91-726 µM after 1 day and declined to ∼ 42-60 µM (4 °C) or zero after ∼10 days. The research supports that levels of H₂O₂ in beverages containing anti-oxidant mixtures and dissolved oxygen should be monitored and formulations modified to avoid AA autoxidation.

Preparation and characterization of electrospun nanofibers-based facial mask containing hyaluronic acid as a moisturizing component and huangshui polysaccharide as an antioxidant component

A novel nanofiber material incorporating hyaluronic acid (HA), crude huangshui polysaccharide (cHSP) and polyvinyl alcohol (PVA) were prepared to obtain dry facial masks (PVA/HA/cHSP) via electrospinning. The facial mask was characterized by scanning electron microscopy (SEM), water absorption and retention evaluation, in vitro release study, DPPH and hydroxyl free radical scavenging measurements, red blood cell hemolysis and chick embryo chorioallantoic membrane assay. The results suggested that the fiber mask was densely homogeneous, uniform and well distributed with a diameter <260 nm. Meanwhile, the water absorption rate was >300 %, DPPH and hydroxyl free radical half-inhibitory concentrations of cHSP aqueous solution scavenging were 0.2781 and 1.029 mg/mL, respectively. The PVA/HA/cHSP could retain the antioxidant capacity of cHSP, possessing simultaneous excellent moisture retention and oxidation resistance. Importantly, the mucous membrane irritation experiment indicated that it was mild and safe.

Application and Effects of Ohmic-Vacuum Combination Heating on the Quality Factors of Tomato Paste

Ohmic-vacuum combination heating is a common method used in the food industry as a concentration process. In the present study, an OH-VC combination heating system was developed for producing tomato paste at temperatures of 70, 80, and 90 °C and pressure of 0.3, 0.5, and 0.7 bar and electric field of 1.82, 2.73, and 3.64 V/cm using a central composite design. The effects of heating conditions on the quality and sensory evaluation of tomato paste were also evaluated. Each combination of temperature, pressure, and the electric field was quantified for specific energy consumption, energy efficiency, and productivity. A decrease of 35.08% in the amount of acid ascorbic and lycopene content 19.01%, using conventional heating compared to ohmic-vacuum heating under optimized conditions, was attained. The results also highlighted an increase in the amount of HMF (69.79%) and PME (24.33%) using conventional heating compared to ohmic-vacuum heating under optimized conditions. Ascorbic acid, lycopene, titratable acidity, productivity, energy efficiency was higher than conventional heating; on the other hand, HMF, PME, pH, SEC were lower than conventional heating at the applied OH-VC process. No significant effects between OH-VC and conventional heating on the TSS were observed. In addition, OH-VC heating was highly efficient in the inhibition of bacterial growth. Further, a minor effect on the sensory properties of tomato paste with OH-VC heating compared to the conventional treatment. The obtained results indicate a strong potential for an OH-VC combination heating system as a rapid-heating, high-efficiency alternative for saving electrical energy consumption and preserving nutritional value.

Effect of Alternative Preservation Steps and Storage on Vitamin C Stability in Fruit and Vegetable Products: Critical Review and Kinetic Modelling Approaches

Vitamin C, a water-soluble compound, is a natural antioxidant in many plant-based products, possessing important nutritional benefits for human health. During fruit and vegetable processing, this bioactive compound is prone to various modes of degradation, with temperature and oxygen being recognised as the main factors responsible for this nutritional loss. Consequently, Vitamin C is frequently used as an index of the overall quality deterioration of such products during processing and post-processing storage and handling. Traditional preservation methods, such as thermal processing, drying and freezing, are often linked to a substantial Vitamin C loss. As an alternative, novel techniques or a combination of various preservation steps ("hurdles") have been extensively investigated in the recent literature aiming at maximising Vitamin C retention throughout the whole product lifecycle, from farm to fork. In such an integrated approach, it is important to separately study the effect of each preservation step and mathematically describe the impact of the prevailing factors on Vitamin C stability, so as to be able to optimise the processing/storage phase. In this context, alternative mathematical approaches have been applied, including more sophisticated ones that incorporate parameter uncertainties, with the ultimate goal of providing more realistic predictions.

Reaction pathways and factors influencing nonenzymatic browning in shelf-stable fruit juices during storage

The occurrence of nonenzymaticbrowning in fruit juices during storage is a major quality defect. It negatively affects consumer acceptance and consumption behavior and determines the shelf-life of these products. Although nonenzymatic browning of fruit juices has been the subject of research for a long time, the exact mechanism of the nonenzymatic browning reactions is not yet completely understood. This review paper aims to give an overview of the compounds and reactions playing a key role in nonenzymatic browning during the storage of fruit juices. The chemistry of the plausible reactions and their relative importance will be discussed. To better understand nonenzymatic browning, factors affecting these reactions will be reviewed and several strategies and methods to evaluate color changes and browning will be discussed. Nonenzymatic browning involves three main reactions: ascorbic acid degradation, acid-catalyzed sugar degradation, and Maillard-associated reactions. The most important NEB pathway depends on the matrix. Nonenzymatic browning is affected by many factors, such as the juice composition, the pH, the oxygen availability (packaging material), and the storage conditions. Nonenzymatic browning can thus be considered as a complex problem. To characterize color changes and browning and obtain insight into the browning mechanism of fruit juices, food scientists applied several approaches and strategies. These included the use of model systems with/without the addition of labeled compound and real systems as well as advanced analytical methods.

The effects of reaction parameters on the non-enzymatic browning reaction between l-ascorbic acid and glycine

The non-enzymatic browning (NEB) reaction between l-ascorbic acid (ASA) and glycine (Gly), including the effects of temperature (110–150 °C), time (10–150 min) and pH (4.5, 6.8, 8.0 and 9.5) on the formation of un-colored intermediate products (UIPs), browning products (BPs) and volatile products (VPs), were investigated. The results showed that pH had a remarkable effect on the reaction. The characteristics of zero-order kinetics for the formation of UIPs and BPs were discussed, and the corresponding activation energy (E a ) was also calculated. When the pH was 4.5, the E a for the formation of UIPs was approximate 53.76 kJ/mol and less than that at other pH values; while the E a for BPs formation was approximate 94.06 kJ/mol and much higher than that at other pH values. The results suggested that an acidic environment facilitated the generation of UIPs, but did not remarkably promote the formation of BPs. The possible reaction pathway between ASA and Gly was proposed according to the experimental results.

Insight into non-enzymatic browning of shelf-stable orange juice during storage: A fractionation and kinetic approach

BACKGROUND

Non-enzymatic browning (NEB) is the main quality defect in shelf-stable orange juice and other fruit juices during storage. Previous studies on NEB focused solely on the soluble fraction of orange juice, regardless of the fact that both soluble and insoluble fractions turn brown during extended storage. Clear evidence of the relative contribution of both fractions to NEB is currently lacking in the literature. This study investigated the contribution of the soluble and insoluble fractions of orange juice, which were obtained by centrifugation and ethanol precipitation, to NEB during storage. Changes in different NEB-related attributes, such as ascorbic acid (AA) degradation, and the browning index (BI), were quantified and kinetically modeled.

RESULTS

Evaluation of color during storage showed that the orange juice and the soluble compound-containing fractions turned brown whereas the insoluble fractions did not. The soluble compound-containing fractions showed exactly the same browning behavior with storage as the plain orange juice. Based on the kinetic parameters obtained, the degradation of AA, the hydrolysis of sucrose, the increase in the glucose and fructose content, and the formation of furfural and 5-hydroxymethylfurfural during storage were similar for the plain orange juice and the soluble compound-containing fractions.

CONCLUSION

This work provided evidence that the soluble fraction of orange juice plays the major role in NEB, unlike the insoluble fraction, which seems to make no contribution. Results from this work also demonstrate the potential use of the soluble fraction as an orange-juice-based model system of reduced complexity that can be used for the further investigation of NEB processes. © 2020 Society of Chemical Industry.

Changes in the Soluble and Insoluble Compounds of Shelf-Stable Orange Juice in Relation to Non-Enzymatic Browning during Storage

For the first time in literature, this study revealed the participation of polymeric components of orange juice cloud and pulp (such as proteins, arabinogalactan proteins, or protein-pectin complexes) during nonenzymatic browning. In a quest to better understand the nonenzymatic browning of shelf-stable orange juice during storage, the juice was fractionated into different fractions depending on the solubility in water/ethanol and the obtained fractions were characterized. The results showed that brown compounds that were formed during storage of orange juice were distributed over water insoluble (pulp), ethanol insoluble (cloud), and ethanol soluble (serum) fractions. In the ethanol insoluble fraction, the brown compounds are hypothesized to be associated with proteins, arabinogalactan proteins, and/or protein-pectin complexes of this fraction without significantly changing their molecular weight distributions, monosaccharide compositions, and protein contents. The changes in the ethanol soluble fraction including ascorbic acid degradation, acid-catalyzed hydrolysis of sucrose, and formation of furfural and 5-hydroxymethylfurfural were highly correlated to the browning development of the juice during storage.