[Improved Indophenol Titration Method for Ascorbic Acid Using a Dropper and Electronic Balance: Enhanced Convenience and Efficiency].

The analysis of ascorbic acid using the 2,6-dichloroindophenol (DCIP) titration method is a well-established technique, but requires the skilled handling of a burette for accurate measurements. In the present study, we propose a modified DCIP titrimetric method that replaces the burette with a dropper and employs an electronic balance to measure the titrated amount by weight. The dropper used can be flexibly selected, allowing for a wide range of drop sizes, from large to very small. This modification offers several advantages, including lower skill requirements, a 43% reduction in the analysis time, a 50% decrease in sample/reagent consumption, and the ability to prepare DCIP standard solutions tailored to the concentration of ascorbic acid in the sample being analyzed. Our analysis of several food samples using this improved method showed that inherent issues of the DCIP method, such as determining the titration end point, could not be resolved. Nevertheless, the improved titration method remains more convenient and adaptable than the original approach using a burette, enabling quick and accurate analysis, especially for unskilled analysts.

Aerogel doped by sulfur-functionalized graphene oxide with convenient separability for efficient patulin removal from apple juice.

Patulin (PAT) contaminant causes severe food safety issue throughout apple industry. Although adsorption is the feasible approach to remove PAT, the limited adsorption capacity and separation difficulty of most adsorbent is the major drawback that remains to be overcome. Here GO-SH doped aerogel was prepared and used for removal PAT from apple juice. The intrinsic porous of the aerogel and abundant active sites including -COOH, -NH2 and -SH offered the PAT adsorption capacity of 24.75 µg/mg that superior to most reported adsorbents. Furthermore, it could reduce 89 ± 1.23% PAT in real apple juice without juice quality deterioration and cytotoxicity. Importantly, the aerogel with good mechanical strength and structure stability could endure the complex juice solution so that there was no any residue after convenient separation of the aerogel, which proved that the proposed aerogel was a promising adsorbent to be applied to apple juice industry for PAT removal.

Highly efficient and cost-effective removal of patulin from apple juice by surface engineering of diatomite with sulfur-functionalized graphene oxide.

Patulin (PAT) contamination of apple juice leads to a serious food safety issue. Developing an excellent adsorbent to efficiently remove PAT is more desirable. Herein, a cost-effective and efficient adsorbent (GO-SH/diatomite) with abundant active sites was successfully fabricated via surface engineering of diatomite with sulfur-functionalized graphene oxide (GO-SH) nanosheets, which exhibited excellent selective adsorption capacity toward PAT. The adsorption behavior, adsorption mechanism, stability and cytotoxicity were investigated by systematic studies. The adsorption results showed that its maximum adsorption capacity was 10.68 µg/mg. Moreover, attributed to the specific interaction between PAT and thiol group, more than 90% of PAT was removed from apple juice without any juice quality deterioration. Importantly, the risk of food safety issue of apple juice caused by residual GO-SH/diatomite was negligible due to the properties of easy removal and excellent biocompatibility, which guaranteed its potential application in apple juice industry for PAT removal.

Patulin removal from apple juice using a novel cysteine-functionalized metal-organic framework adsorbent.

Patulin (PAT) is one of the most common toxic contaminants of apple juice, which causes severe food safety issues throughout the apple industry. In order to remove PAT efficiently, a metal-organic framework-based adsorbent (UiO-66(NH2)@Au-Cys) was successfully synthesized and used for PAT removal from juice-pH simulation solution and real apple juice. Batch adsorption experiments were systematically performed to study the adsorption behavior for PAT. The results showed that adsorption process could be well described by the Pseudo-second order model and Freundlich isotherm model. The maximum adsorption capacity (4.38 µg/mg) was 10 times higher than the microbe-based biosorbents. Thermodynamic investigation demonstrated that adsorption process was spontaneous and endothermic. Furthermore, no marked cytotoxicity on NIH 3T3 cell lines was observed when the concentration of the adsorbent was lower than 10 µg/mL. Therefore, UiO-66(NH2)@Au-Cys is a potential adsorbent for PAT removal from apple juice with little quality changes.

Model development for non-destructive determination of rind biochemical properties of 'Marsh' grapefruit using visible to near-infrared spectroscopy and chemometrics.

Rind biochemical properties play major roles in defence mechanisms against the incidence of rind physiological disorders of citrus fruit during cold storage. Hence, multivariate calibration models were developed to rapidly and non-destructively determine rind biochemical properties of citrus fruit from visible to near-infrared (Vis/NIR) spectra acquired by Vis/NIR spectroscopy using partial least square regression algorithm. To achieve optimum models for determination of each rind biochemical property, several mathematical pre-processing methods were explored, including no pre-treatment. However, special emphases were given to the best model statistics in terms of coefficient of determination (R2) and residual predictive deviation (RPD). Models were performed by critical examination of different wavelength ranges (visible, near-infrared and full regions) and combinations of fruit harvested from different production regions and acquired before (week 0) and after (week 9) cold storage. Results obtained showed excellent models for determining parameters such as sucrose (R2 = 0.99 and RPD = 11.42), total flavonoids (R2 = 0.99 and RPD = 12.37), and chlorophyll b (R2 = 0.97 and RPD = 5.67). This study reported the first application of Vis/NIR and chemometrics in determining the rind biochemical properties of 'Marsh' grapefruit rapidly and non-destructively.

Antioxidant properties of selected fruit cultivars grown in Sri Lanka.

Extracts of twenty locally available Sri Lankan fruits were analysed for 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, ferrous reducing antioxidant power (FRAP), total phenolic content (TPC), total flavonoid content (TFC) and vitamin C content. The results showed that gooseberry (Phyllanthus emblica 'local') exhibited the highest DPPH scavenging activity (111.25mg ascorbic acid equivalent antioxidant capacity (AEAC)/g), FRAP (1022.05µmol FeSO4/g), TPC (915.7mg gallic acid equivalents (GAE)/100g), TFC (873.2mg catechin equivalents (CE)/100g) and vitamin C (136.8mg ascorbic acid equivalents (AAE)/100g), respectively. Sugar apple (Annona squamosa 'local') and star fruit (Averrhoa carambola 'Honey Sweet') obtained the second and third highest antioxidant activities in terms of rankings of FRAP, DPPH activities, TPC, TFC and vitamin C content. Strong correlation between vitamin C, TPC and TFC with FRAP and DPPH showed their contribution to antioxidant capacity. Among the selected fruits, underutilized fruit cultivar gooseberry showed the highest overall antioxidant potential.

Disturbance of brain energy and redox homeostasis provoked by sulfite and thiosulfate: potential pathomechanisms involved in the neuropathology of sulfite oxidase deficiency.

Sulfite oxidase (SO) deficiency is biochemically characterized by tissue accumulation and high urinary excretion of sulfite, thiosulfate and S-sulfocysteine. Affected patients present severe neurological symptoms and cortical atrophy, whose pathophysiology is still poorly established. Therefore, in the present work we investigated the in vitro effects of sulfite and thiosulfate on important parameters of energy metabolism in the brain of young rats. We verified that sulfite moderately inhibited the activity of complex IV, whereas thiosulfate did not alter any of the activities of the respiratory chain complexes. It was also found that sulfite and thiosulfate markedly reduced the activity of total creatine kinase (CK) and its mitochondrial and cytosolic isoforms, suggesting that these metabolites impair brain cellular energy buffering and transfer. In contrast, the activity of synaptic Na(+),K(+)-ATPase was not altered by sulfite or thiosulfate. We also observed that the inhibitory effect of sulfite and thiosulfate on CK activity was prevented by melatonin, reduced glutathione and the combination of both antioxidants, as well as by the nitric oxide synthase N(ω)-nitro-l-arginine methyl ester, indicating the involvement of reactive oxygen and nitrogen species in these effects. Sulfite and thiosulfate also increased 2',7'-dichlorofluorescin oxidation and hydrogen peroxide production and decreased the activity of the redox sensor aconitase enzyme, reinforcing a role for oxidative damage in the effects elicited by these metabolites. It may be presumed that the disturbance of cellular energy and redox homeostasis provoked by sulfite and thiosulfate contributes to the neurological symptoms and abnormalities found in patients affected by SO deficiency.

Expression of Pisum sativum PsAO3 gene, which encodes an aldehyde oxidase utilizing abscisic aldehyde, is induced under progressively but not rapidly imposed drought stress.

Aldehyde oxidase (AO; EC 1.2.3.1) catalyzes the final step of abscisic acid (ABA) biosynthesis, which is the oxidation of abscisic aldehyde (ABAld) to ABA. Gene expression analyses indicate that the stress-induced Pisum sativum PsAOγ isoform, which effectively uses ABAld as a substrate, is encoded by the PsAO3 gene. PsAO3 was heterologously expressed in Pichia pastoris and the recombinant PsAO3 protein revealed substrate preferences highly similar to the native PsAOγ protein present in the pea leaves and roots. Both proteins prefer indole-3-aldehyde and naphthaldehyde as substrates, although high activities against abscisic aldehyde and citral were also observed. The Km values of PsAO3 for naphthaldehyde and abscisic aldehyde (4.6 and 5.1 µM, respectively) were the lowest among the substrates tested. PsAO3 activity was almost completely inhibited by potassium cyanide, diphenyleneiodonium, and methanol. Rapidly imposed drought stress did not increase the level of PsAO3 mRNA or activity of any AO isoform, although an enhanced ABA accumulation and induction of PsNCED2 and -3 (9-cis-epoxycarotenoid dioxygenase; EC 1.13.11.51) expression, both in the pea roots and leaves, was observed. During a progressively induced drought, the level of PsAO3 transcript and PsAOγ activity increased significantly in the roots and leaves, whereas ABA accumulation occurred only in the leaves where it was accompanied by induction of the PsNCED3 expression. Therefore, we suppose that next to NCED, also AO (mainly PsAOγ) might be involved in regulation of the drought-induced ABA synthesis. However, while the "constitutive activity" of PsAOγ is sufficient for the fast generation of ABA under rapid drought stress, the enhanced PsAOγ activity is required for the progressive and long-term ABA accumulation in the leaves under progressive drought stress.

Enzymatic characterization of an active NDH complex from Thermosynechococcus elongatus.

Although type-1 NAD(P)H dehydrogenase (NDH) complex subunit constituents and physiological functions have been reported in plants and cyanobacteria, the biochemical properties of this enzyme are not clear. We used chromatographic isolation to purify and characterize a NADPH-active NDH from the cyanobacterium Thermosynechococcus elongatus. Ferredoxin (Fd) and ferredoxin-NADP(+) oxidoreductase (FNR) were co-eluted with NDH, implying the electron donation from NADPH to NDH via the interaction with FNR. We investigated the enzymatic properties of the complex. Furthermore, the activity is competitively inhibited by rotenone, suggesting that it possesses a quinone binding site, similar to mitochondria complex I.