Non-thermal plasma effects on the lipoxygenase enzyme activity, aroma and phenolic profiles of olive oil

Refining quinoa storage stability through microwave-induced structural alterations and activity suppression of key enzymes

This study investigated the effects of microwave on preserving the quality of quinoa during storage. Quinoa treated with 9W/60s exhibited a significant decrease in fatty acid values compared to hot air treatment. Microwave effectively delayed lipid oxidation during quinoa storage by suppressing the increase in peroxide values. MDA gradually accumulated from peroxides during storage, reaching its peak at 0.423 μmol/L in the second week. Microwave disrupted the original hydrogen bonds in lipase, causing the unwinding of the α-helix and resulting in the loss of its regular structure. Microwave reduced the stability of the β-sheet structure in lipoxygenase, breaking the natural secondary structure composition. The observed fluorescence and UV spectra features were similar, indicating that microwave alter the peptide chain of the enzyme's skeletal structure, increasing the exposure of hydrophobic chromophores. These results indicated the potential of microwave to enhance the stability of quinoa during storage.

Elucidation of heavy metal content, phenolic profiles, and antioxidant activities of kale (Brassica oleracea L. var. acephala) and arugula (Brassica eruca L.) grown in urban gardens in Istanbul

This study was conducted to evaluate the effect of two distances: close (0-10 m) and far (60 m) from the heavy traffic roadside, at three different cultivation sites (MS: Mevlanakapi-Silivrikapi, SB: Silivrikapi-Belgradkapi, and BY: Belgradkapi-Yedikule kapi) along the road line. First, the phenolic compounds, antioxidant activity, and physicochemical properties in kale and arugula vegetables were examined. Second, heavy metal concentrations in vegetables, soil, and irrigated water were investigated. In both vegetables, the highest total phenolic content was detected in samples obtained from far distance in SB site (3880.3 mg/kg) for kale and in BY site (1459.9 mg/kg) for arugula, whereas the lowest content was found at the close distance in MS site for both kale (448.5 mg/kg) and arugula (586.4 mg/kg). The antioxidant activity values [mg Trolox/kg (dw)] ranged from 366.74 to 586.10 and 2349.00 to 3757.4 for kale and from 520.00 to 945.60 and 3323.00 to 5814.70 for arugula in 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) and 2,2-diphenyl-1-picrylhydrazyl methods, respectively. The levels of Cd and Hg in kale and arugula and Fe content in arugula exceeded FAO/WHO permissible limits, making them unsafe for human consumption. Meanwhile, the Pb content in kale and arugula and Fe content in kale were observed to be within acceptable limits set by FAO/WHO. In the irrigated water, the Pb value was below the permissible limit, whereas the Cd value was above it and no Hg and Fe were detected. In the soil samples, the Pb and Fe values were below the limit, whereas the Cd and Hg values were higher.

Novel insight into the evolution of volatile compounds during dynamic freeze-drying of Ziziphus jujuba cv. Huizao based on GC-MS combined with multivariate data analysis

To understand the evolution of aroma in jujubes during dynamic freeze drying (FD), the relationship between aroma compounds, precursors, and related enzyme activities were analyzed. Fifty-three volatiles were identified during FD processing. After FD, the total aroma contents were increased from 11,004 to 14,603 μg/kg, ketones content was significantly decreased by 54.11 %, resulted in the loss of creamy note in freeze-dried jujube (FDJ). Through the network analysis, serine, glycine, proline, valine, cysteine, arginine, glutamic acid, lysine and leucine had the significant correlation with pyrazines, dominated the roasty note of FDJ. Linoleic acid, α-linolenic acid and oleic acid with lipoxygenase had important effects on the increase of esters (from 412 to 9,486 μg/kg), contributed fruity and sweet notes of FDJ. Besides, through the Mantel test, the influence degree of factors on the formation of FDJ aroma was ranked as temperature > enzyme activity > fatty acids > amino acids.

Effect of Flavoring with Rosemary, Lemon and Orange on the Quality, Composition and Biological Properties of Olive Oil: Comparative Study of Extraction Processes

The goal of this work was to investigate the impact of the flavoring of some aromatic plants/spices, including rosemary (R), lemon (L) and orange (O) at the concentration of 5% and 35% (w/w) added by 2 methods (conventional maceration and direct flavoring), on quality attributes, chemical changes and oxidative stability of extra virgin olive oil (EVOO). Six flavored oils were obtained (EVOO + O, O + O, EVOO + R, O + R, EVOO + L and O + L). The physicochemical parameters (water content, refractive index, acidity and peroxide value, extinction coefficient, fatty acids, volatile aroma profiles, Rancimat test, phenols and pigments composition) of the flavored oils were investigated. Based on the results obtained, it was observed that flavoring with a conventional process provided increased oxidative stability to the flavored oils, especially with rosemary (19.38 ± 0.26 h), compared to that of unflavored oil. The volatile profiles of the different flavored oils revealed the presence of 34 compounds with the dominance of Limonene. The fatty acid composition showed an abundance of mono-unsaturated fatty acids followed by poly-unsaturated ones. Moreover, a high antioxidant activity, a significant peripheral analgesic effect (77.7% of writhing inhibition) and an interesting gastroprotective action (96.59% of ulcer inhibition) have been observed for the rosemary-flavored oil. Indeed, the flavored olive oils of this study could be used as new functional foods, leading to new customers and further markets.

EFFECTS OF COLD PLASMA ON CHLOROPHYLLS, CAROTENOIDS, ANTHOCYANINS, AND BETALAINS

Plasma is considered by several researchers to be the fourth state of matter. Cold plasma has been highlighted as an alternative to thermal treatments because heat induces less degradation of thermolabile bioactive compounds, such as natural pigments. In this review, we provide a compilation of the current information about the effects of cold plasma on natural pigments, such as the changes caused by plasma to the molecules of chlorophylls, carotenoids, anthocyanins, and betalains. As a result of the literature review, it is noted that can degrade cell membrane and promote damage to pigment storage sites; thereby releasing pigments and increasing their content in the extracellular space. However, the reactive species contained in the cold plasma can cause degradation of the pigments. Cold plasma is a promising technology for extracting pigments; however, case-by-case optimization of the extraction process is required.

Reduction of pesticide residues in Chrysanthemum morifolium by nonthermal plasma-activated water and impact on its quality

This study investigated the efficiency of plasma-activated water (PAW) on the reduction of pesticides, namely, metribuzin and metobromuron, and the effect of PAW treatment on the quality of fresh chrysanthemums. The reduction efficiencies reached 74.3% for metribuzin and 38.2% for metobromuron after 240 s of PAW treatment. Compared with reverse osmosis (RO) water, PAW achieved significantly higher pesticide reductions because of its higher acidity, enhanced oxidizing ability, and increased formation of reactive species. Moreover, when compared with metobromuron, metribuzin was reduced more efficiently irrespective of the RO water or PAW treatments because of its higher water solubility, lower log octanol-water partition coefficient, and more oxidizable chemical structure. Additionally, the PAW treatment did not cause adverse changes to the chrysanthemums' color, total flavonoid content, radical scavenging, or metal chelating activities, but it did cause a slight decrease in the chrysanthemums' aroma compounds and total reducing power. This study successfully demonstrated the effectiveness of PAW for reducing pesticides in herbal flowers like chrysanthemums and reveals PAW's promising potential to treat foods with non-smooth surfaces.

Effects of ultrasound, heat, ascorbic acid and CaCl2 treatments on color enhancement and flavor changes of freeze-dried carrots during the storage period

Discoloration and unpleasant flavor were observed in freeze-dried carrots (FDC) during shelf life. This study aimed to investigate the effects of thermal/non-thermal pre-treatments and storage temperatures on the color and flavor of FDC during the 120-day storage. Results showed that terpenes and sulfur-containing organics were the main volatiles sensitive to the 60 °C treatment (p < 0.05). Nonenzymatic browning of FDC happened during storage, which was significantly positively related to moisture content (r = 0.63) and water activity (r = 0.84), while negatively correlated with total carotenoid content (TCC, r = -0.62). However, redness (29.66%), chroma (16.59%) and TCC (3.40%) of FDC at 120-day (25 °C) was effectively improved after the combination treatment of ultrasound (40 kHz, 100 W, 10 min) and ascorbic acid (2%, w/v)-CaCl₂ (1%, w/v) solution (UAA-CaCl₂), showing that carrots pre-treated with UAA-CaCl₂ and preserved at 25 °C facilitated the FDC storage.

Discoloration investigations of freeze-dried carrot cylinders from physical structure and color-related chemical compositions

BACKGROUND

High carotenoid content always lead to a yellower/redder color in carrots, while a puzzling phenomenon still exists that freeze-dried carrots (FDC) have a higher carotenoid content but a lighter color compared with thermal-dried carrots. It seems that carotenoid is not the only main factor affecting sample color. Hence the discoloration characteristics of freeze-dried carrots were comprehensively analyzed from physical structure and color-related chemical composition profile.

RESULTS

Outcomes of low-field nuclear magnetic resonance and scanning electron microscopy showed that sublimation of immobilized water preserved the intact porous structure of FDC, which kept the volume shrinkage below 30% and led to less accumulations of color-related compositions. Besides, results of correlation and principal component analysis-X model proved that lutein and caffeic acid mainly affected a* value (r = 0.917) and b* value (r = 0.836) of FDC, respectively. Moreover, lipoxygenase indirectly affected sample color by degrading carotenoids, and the lutein content loss for fresh and blanching FDC was 41.56% and 47.14%, respectively.

CONCLUSIONS

The discoloration of FDC was significantly affected by both physical structure and color-related chemical compositions. © 2021 Society of Chemical Industry.