LEE- Gıda Mühendisliği-Doktora
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ÖgeEffects of novel food processing techniques on bioaccessibility and transepithelial transport of cranberrybush polyphenols(Graduate School, 2021-08-06) Özkan, Gülay ; Çapanoğlu Güven, Esra ; 506142507 ; Food EngineeringPhenolic compounds, which are present in a wide variety of foods such as fruits, vegetables, flowers and leaf of plants, exhibit a variety of beneficial effects including antimicrobial, antioxidant, antidiabetic, diuretic, hypoglycemic, cough reliever, antiinflammatory and antiviral activities as well as prevention of cardiovascular, pancreas, liver and kidney diseases. However, most of the polyphenols have poor water solubility, chemical instability in gastrointestinal tract and, thus, a reduced bioavailability. Therefore, a wide variety of attempts have been investigated to improve the solubility, stability, bioaccessibility and bioavailability of phenolic compounds. Considering the above, a research framework to study the effects of novel processing techniques on the antioxidant capacity, bioaccessibility and bioavailability of cranberrybush polyphenols has been developed. The objectives of this Ph.D. thesis were (i) to determine the effects of novel non-thermal food processing on cranberrybush polyphenols and vitamin C; (ii) to investigate the effects of non-thermal food processing and food matrix on bioaccessibility and transepithelial transportation of bioactive compounds, in particular chlorogenic acid, from cranberrybush (Viburnum opulus) using combined in vitro gastrointestinal digestion/Caco-2 cell culture model; (iii) to obtain an effective Supercritical Anti-Solvent (SAS) coprecipitation of quercetin or rutin with polyvinylpyrrolidone (PVP), enhancing the dissolution rate, and, therefore, improving the bioavailability of these natural antioxidant compounds; (iv) to determine the effects of SAS processing and food models on the antioxidant capacity, bioaccessibility and transport dynamics of flavonol-loaded microparticles by using combined in vitro gastrointestinal digestion/Caco-2 cell culture model. To achieve these goals, four different experiments (Chapters 3-6) were conducted. Firstly, effects of high pressure processing (HPP) and pulsed electric field (PEF) treatments on physicochemical properties, bioactive compounds, antioxidant capacities and polyphenol oxidase activities of cranberrybush purée samples were evaluated (Chapter 3). Following that, non-thermal treated cranberrybush purée samples as well as cranberrybush juice/water, bovine or almond milk blends were subjected to combined in vitro gastrointestinal digestion/Caco-2 cell culture (Chapter 4). In line with the outcomes of previous chapter, in order to increase the bioavailability of some phenolic compounds that could not be absorbed across the gut epithelium after transport experiments with cranberrybush samples, the micronization of two flavonoids, quercetin and rutin, and their coprecipitation with PVP were studied by using SAS processing to increase their solubility and enhance their stability during gastrointestinal tract (Chapter 5). Finally, SAS-processed flavonoids in different simulated food models were exposed to combined in vitro gastrointestinal digestion/Caco-2 cell culture in order to investigate their transport dynamics (Chapter 6). In Chapter 1, research framework and objectives of this Ph.D. thesis are introduced. Following that, in Chapter 2, comprehensive reviews on the antioxidant properties, bioaccessibility and bioavailability of polyphenols are presented, with a specific focus on the application of novel processing techniques. Initially, a critical evaluation of the effects of novel non-thermal food processing technologies on the beverage antioxidants have been provided. Then, the studies about microencapsulation methods for food antioxidants regarding principles, advantages, drawbacks and applications have been reviewed. Afterwards, effects of encapsulation on the bioaccessibility and bioavailability of phenolic compounds were discussed. Lastly, in vitro and in vivo approaches on interactions of phenolics with food matrix were described. In Chapter 3, the effects of high pressure processing (HPP; 200-600 MPa for 5 or 15 min) and pulsed electric field treatment (PEF; 3 kV/cm, 5-15 kJ/kg) on physicochemical properties (conductivity, pH and total soluble solids content), bioactive compounds (vitamin C, total phenolic, total flavonoid, total anthocyanin and chlorogenic acid contents), antioxidant capacities (DPPH and CUPRAC assays) and polyphenol oxidase activity of cranberrybush purée samples were evaluated. Results showed that conductivity increased significantly after PEF (15 kJ/kg) treatment. PEF and HPP treatments resulted with a better retention of bioactive compounds (increase in the total phenolic content in the range of ~4 – 11% and ~10 – 14% and total flavonoid content in the range of ~1 – 5% and ~6 – 8% after HPP and PEF, respectively) and antioxidant capacity compared to untreated sample. HPP reduced residual enzyme activity of PPO comparatively better than PEF. Besides, cranberrybush polyphenols were identified along with their detected accurate mass, molecular formula, error in ppm (between the mass found and the accurate mass < 10 ppm) of each phytochemical, as well as the MS/MS fragment ions. UPLC–QTOF–MS/MS analysis of cranberrybush led to the identification of flavan-3-ols (catechin, epicatechin, epi(catechin) hexoside), proanthocyanidins (procyanidin dimer, procyanidin trimer, procyanidin dimer monoglycoside), flavonols (quercetin, quercetin-deoxyhexose, quercetin-3-O-glucoside, quercetin pentoside hexoside, rutin, isorhamnetin-3-O-rutinoside), flavone (diosmetin-rhamnosylglucoside), phenolic acids (caffeic acid, chlorogenic acid, coumaric acid, p-coumaroyl-quinic acid) as well as anthocyanins (cyanidin-3-glucoside, cyanidin-3-rutinoside and cyanidin-3-xylosyl-rutinoside). In conclusion, high retention of bioactive compounds was achieved, with a potential extraction of vitamin C, phenolics, flavonoids and anthocyanins in cranberrybush purées after HPP and PEF treatments at selected processing intensities. In Chapter 4, effects of food matrix and non-thermal food processing on bioaccessibility and transport dynamics of cranberrybush phenolics, in particular chlorogenic acid, in a combined in vitro gastrointestinal digestion/Caco-2 cell culture model were studied. Results showed that PEF treatment at 15 kJ/kg specific energy input resulted in a higher recovery of total flavonoid content (TFC; increase of 3.9% ± 1.1%, p < 0.0001), chlorogenic acid content (increase of 29.9% ± 5.9%, p < 0.001) and antioxidant capacity after gastrointestinal digestion. The present study also demonstrates that untreated and treated samples display comparable transport across the epithelial cell layer. Besides, addition of milk matrix have a positive effect on the stability and transportation of chlorogenic acid. JM increased the transport efficiency of chlorogenic acid by 3.5% ± 0.8% (p < 0.0001), while JA increased the transport of chlorogenic acid by 3.3% ± 0.5% (p < 0.001) in comparison with JW blend. The in vitro gastrointestinal digestion/Caco-2 cell culture method applied in this chapter was used in the succeeding chapter (Chapter 6). In Chapter 5, micronization of two flavonoids, quercetin and rutin, and their coprecipitation with polyvinylpyrrolidone were studied by using the SAS process. In particular, optimum conditions in terms of operating pressure, type of the solvent, total solute concentration and polymer/active ratio for the formation of spherical composite microparticles were determined. Morphology, mean size and size distribution of the particles were analyzed and discussed. The effectiveness of the process was also verified through entrapment efficiency and dissolution tests. Overall, amorphous microparticles were produced with total solute concentrations greater than 20 mg/mL. Furthermore, release studies confirmed the improvement of the flavonoids dissolution rates: 10 and 3.19 times faster dissolution rates were achieved with PVP/quercetin and PVP/rutin microparticles rather than those of unprocessed quercetin and rutin, respectively. Besides, the high entrapment efficiencies, up to 99.8%, were achieved for quercetin and rutin coprecipitates by using DMSO, which was the solvent chosen to coprecipitate the flavonoid compounds with PVP by the SAS process. Consequently, the characteristics of the powders could allow to use of these quercetin and rutin loaded microparticles in pharmaceutical and nutraceutical applications due to their high antioxidant and anticancer benefits for, in which the flavonoid compounds have high stability and bioavailability. In Chapter 6, effects of SAS processing on bioaccessibility and transepithelial transportation of quercetin and rutin were investigated by using a recognized combined gastrointestinal digestion/cell-based assay. Moreover, aqueous hydrophilic and acidic conditions were simulated to analyze food-related factors that could have an impact on the transport of these compounds across the gut epithelium. SAS processing improved the recovery of the quercetin (94 and 13 times in hydrophilic and acidic conditions, respectively) and rutin (7 and 2 times in hydrophilic and acidic conditions, respectively) after in vitro digestion. Besides, transepithelial transportation of PVP/quercetin and PVP/rutin microparticles were found to be much higher rather than unprocessed quercetin and rutin. Finally, in Chapter 7, based on the outcomes of the previous chapters, the general discussions and conclusions on the antioxidant properties, bioaccessibility and bioavailability of polyphenols were presented. The status and main outcomes of this thesis were discussed under the headings of fate of the polyphenols after application of novel non-thermal food processing techniques, effects of encapsulation on the food phenolics and interactions of phenolics and food matrix. During the discussion on the effects of encapsulation on the food phenolics, important factors to be considered during encapsulation, advantages and drawbacks of these techniques, their impacts on the antioxidant properties, bioaccessibility and bioavailability of phenolic substances were discussed. Besides, while referring to the interactions with food matrix, special attention has been paid to comparison of the different in vitro and in vivo digestion models.