Structural Variations of Broccoli Polyphenolics and Their Antioxidant Capacity as a Function of Growing Temperature

Polyphenolics in plants exist in free, soluble-bound, and insoluble-bound structural forms. The concentration of these structural forms depends on the plant's developmental stage, tissue type, soil water availability, and food preparation methods. In this study, for the first time, the effects of growth temperature (RT-room temperature-23 °C day/18 °C night, HT-high temperature-38 °C day/33 °C night, LT-low temperature-12 °C day/7 °C night) on variations of polyphenolic structural forms-free, soluble-bound (esterified and glycosylated), and insoluble-bound-in broccoli (Brassica oleracea L. convar. botrytis (L.) Alef. var. cymosa Duch.) microgreens were investigated. Using spectrophotometric, RP-HPLC, and statistical analyses, it was found that the highest amount of total phenolics (TP) in broccoli microgreens was present in the esterified form, regardless of the temperature at which they were grown (63.21 ± 3.49 mg GAE/g dw in RT, 65.55 ± 8.33 mg GAE/g dw in HT, 77.44 ± 7.82 mg GAE/g dw in LT). LT significantly increased the amount of free (from 13.30 ± 2.22 mg GAE/g dw in RT to 18.33 ± 3.85 mg GAE/g dw) and esterified soluble TP (from 63.21 ± 3.49 mg GAE/g dw in RT to 77.44 ± 7.82 mg GAE/g dw), while HT significantly increased the amount of TP glycosylated forms (from 14.85 ± 1.45 mg GAE/g dw in RT to 17.84 ± 1.20 mg GAE/g dw). LT also enhanced free and esterified forms of total flavonoids, tannins, hydroxycinnamic acids, and flavonols. HT, on the other hand, increased glycosylated forms of TP, flavonoids, tannins, hydroxycinnamic acids, flavonols, and phenolic acids, and decreased insoluble-bound tannins. According to the ABTS method, HT induced antioxidant potential of free and glycosylated forms, while LT increased antioxidant capacity of free forms only. According to the FRAP method, LT increased antioxidant potential of free and esterified polyphenolic forms. Also, based on ABTS and FRAP assays, esterified polyphenolics showed significantly higher antioxidant capacity than any other form. Principal component analysis showed that structural form had a greater impact than temperature. Hierarchical clustering showed that RT-, HT- and LT-broccoli microgreens were most similar in their glycosylated polyphenolics, but differed the most in esterified forms, which were also the most distinct overall. In conclusion, HT and LT induced specific shifts in the structural forms of broccoli polyphenolics and their antioxidant capacity. Based on the results, we recommend applying LT to increase the amount of free and esterified polyphenolics in broccoli microgreens, while HT may be used to enhance glycosylated forms.

Use of different protein and antioxidant sources in couscous production to improve chemical and functional properties

In this study, it was aimed to improve couscous chemical and functional properties by replacing wheat flour used in traditional couscous production with pea and mung bean flours as different protein sources at the rate of 20% and with ginger and turmeric powders as antioxidant sources at the rate of 1%, 2%, and 3%. Sixteen different couscous formulations were produced. In those couscous samples, some chemical contents (moisture, ash, protein, fat, and phytic acid), bioactive contents (2,2-diphenyl-1-picrylhydrazyl radical, ferric reducing antioxidant power assay and ion reducing antioxidant capacity antioxidant activities and total phenolic content), color (L*, a*, and b*), firmness and cooking properties were determined. The use of pea and mung bean flour decreased the L* value of the samples, while turmeric increased the yellowness values. In addition, the weight increase and firmness values of couscous decreased with the use of leguminous flours and antioxidant sources. The use of peas and mung beans significantly increased the amount of ash, protein, and phytic acid values compared to the control. The antioxidant activity value of ion-reducing antioxidant activity capacity increased by 7 and 5 times, and the total phenolic contents increased approximately 2 times, respectively, in the samples with the substitution of 3% turmeric and pea and mung bean flour. Pea flour and mung bean flour provided a significant increase in the amounts of Ca, Mg, K, and Zn. The combination of pea flour with 3% turmeric powder resulted in couscous with superior nutritional and functional properties.

xAgrotriticum spp.: Quality properties of a potential perennial cereal candidate for sustainable agriculture

Perennial crop species have gained greater importance with regard to agricultural sustainability because of the ecological concerns related to annual crops. This study aimed to determine some of the primary quality traits of xAgrotriticum grains, a potential perennial wheat genotype, in comparison to the annual bread wheat variety Fineway. The antioxidant activity of xAgrotriticum was 2.79-, 1.38-, and 2.35-fold higher than that of bread wheat according to the 2,2-diphenyl-1picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and cupric ion reducing antioxidant capacity (CURPAC) methods, respectively. The free, bound, and total phenolic contents in xAgrotriticum were 1.34-, 1.59-, and 1.54-fold higher than those in bread wheat. The protein content (19.58 %) of xAgrotriticum was 1.48-fold higher than that of bread wheat. Essential amino acids constituted 28.65 % of the total amino acids in xAgrotriticum and 30.38 % in Fineway. Interestingly, methionine and tryptophan were present in xAgrotriticum although both were below the detection limits in wheat. However, compared with wheat, the arginine content of xAgrotriticum was 18-fold higher with glycine and tyrosine both 8-fold more abundant. xAgrotriticum has significantly richer iron, zinc, and copper contents; 1.31-, 1.74-, and 2.02-fold, respectively, than wheat. xAgrotriticum may offer potential for direct use as a foodstuff or raw material due to its nutritional elements, in addition to its potential as a genitor in hybridisation programs to improve the nutritional values of annual wheat and its prenniality which is considered one of the primary necessities for more sustainable agriculture.

Drying Behavior of Bulgur and Its Effect on Phytochemical Content

The objective of this study was to determine the influence of two types of dryers (hot air oven and vacuum dryer) and the yellow berry percentage (1.75%, 36.25%, 43.25%) on the drying process and phytochemical content of bulgur. Results showed that the Midilli model successfully described the moisture diffusion during drying at 60 °C in all bulgur samples, where an increase in yellow berry percentage generated an increase in moisture content. Effective diffusion coefficient (Deff) increased significantly (p ≤ 0.05) from 7.05 × 10−11 to 7.82 × 10−11 (m2.s−1) and from 7.73 × 10−11 to 7.82 × 10−11 (m2.s−1) for the hot air oven and vacuum dryer, respectively. However, it decreased significantly with a decrease of yellow berry percentage. It was concluded that the vacuum dryer provided faster and more effective drying than the hot air oven. Total polyphenol (TPC), total flavonoid (TFC), and yellow pigment contents (YPC) of bulgur were investigated. TPC ranged between 0.54 and 0.64 (mg GAE/g dm); TFC varied from 0.48 to 0.61 (mg QE/g dm). The YPC was found to be between 0.066 and 0.079 (mg ß-carotene/100g dm). Yellow berry percentage positively and significantly affected the TPC, TFC, and YPC contents due to the hard separation of the outer layers from the starchy grain during the debranning step.

Available technologies on improving the stability of polyphenols in food processing

Polyphenols are the most important phytochemicals in our diets and have received great attention due to their broad benefits for human health by suppressing oxidative stress and playing a protective role in preventing different pathologies such as cardiovascular disease, cancer, diabetes, and obesity. The stability of polyphenols depends on their environments of processing and storage, such as pH and temperature. A wide range of technologies has been developed to stabilize polyphenols during processing. This review will provide an overview of the stability of polyphenols in relation to their structure, the factors impacting the stability of polyphenols, the new products deriving from unstable polyphenols, and the effect of a series of technologies for the stabilization of polyphenols, such as chemical modification, nanotechnology, lyophilization, encapsulation, cold plasma treatment, polyphenol–protein interaction, and emulsion as a means of improving stability. Finally, the effects of cooking and storage on the stability of polyphenols were discussed.