Effect of Different Drying Methods on the Microwave Extraction of Phenolic Components and Antioxidant Activity of Highbush Blueberry Leaves

In the last few decades, researchers have found blueberry leaves to be an interesting source of different phenolic compounds, and drying is an important part of their postharvest and sample preparation processes. In the current study, blueberry leaves were dried using microwave-assisted hot air drying or hot air drying alone at 45, 60, and 75°C to 10–15% wet basis. Corresponding drying characteristics were determined by fitting the moisture ratio obtained in each case with eight theoretical and semitheoretical models for hot air and microwave drying stages. It was observed that best fitting drying models for blueberry leaves depended not only on the nature of the biomaterial but also on the method of drying and the temperature of drying. Phenolic content, monomeric anthocyanin content, and the corresponding antioxidant activity in terms of 2,2-diphenyl-1-picrylhydrazyl (DPPH) inhibition activity and ferric reducing ability of plasma (FRAP) activity were evaluated for the leaf extract obtained following microwave extraction of the dried samples obtained using the above-mentioned drying methods and were compared to the corresponding bioactive compositional characteristics of freeze-dried blueberry leaves. It was observed that the freeze-dried sample had the highest content of total phenolics and total monomeric anthocyanins along with high antioxidant activity. Furthermore, extracts obtained from the microwave-dried leaf samples obtained with a drying temperature of 60°C had highest total phenolic content and highest total monomeric anthocyanin content among all other drying methods and the extract had an antioxidant activity similar to the freeze-dried blueberry leaf samples, implying that microwave drying at 60°C is a potential alternative to freeze drying for preservation of the phenolic components and antioxidant activity of dried blueberry leaves.     

Analysis of Phenolic Compounds and Antioxidant Activity in Wild Blackberry Fruits

Twenty three different wild blackberry fruit samples were assessed regarding their phenolic profiles and contents (by LC/MS quadrupole time-of-flight (QTOF) and antioxidant activity (ferric reducing ability of plasma (FRAP) and 2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS)) by two different extraction methods. Thirty four phenolic compounds were detected (8 anthocyanins, 15 flavonols, 3 hydroxycinnamic acids, 6 ellagic acid derivatives and 2 flavones). In samples, where pressurized liquid extraction (PLE) was used for extraction, a greater increase in yields of phenolic compounds was observed, especially in ellagic acid derivatives (max. 59%), flavonols (max. 44%) and anthocyanins (max. 29%), than after extraction by the ultrasonic technique extraction (UAE) method. The content of phenolic compounds was significantly correlated with the antioxidant activity of the analyzed samples. Principal component analysis (PCA) revealed that the PLE method was more suitable for the quantitative extraction of flavonols, while the UAE method was for hydroxycinnamic acids.     

Antioxidant activity of red wine phenolic extracts towards oxidation of corn oil

The antioxidant activity of Xinomavro red wine phenolic extracts in corn oil stripped of tocopherols was evaluated. One wine extract, at 100 mg/L total phenolics, rich in phenolic acids and flavonols, inhibited the oxidation of corn oil stripped of tocopherols to a greater extent than butylated hydroxyanisole, at 200 mg/L. Moreover, another extract, at 100 mg/L total phenolics, rich in flavanols, flavonols and tyrosol, also exhibited high inhibitory action. The present results indicate that some red wine phenolics – such as phenolic acids, flavonols or flavanols – may be strong antioxidants in corn oil.     

Pulsed Electric Field Pretreatment for Osmotic Dehydration of Apple Tissue: Experimental and Mathematical Modeling Studies

The aim of this study was to analyze the influence of pulsed electric field pretreatment (PEF) on the osmotic dehydration of apple tissue. Osmotic dehydration was carried out in sucrose solution at 40°C and 100 rpm in a water-bath shaker. PEF pretreatment was performed using varying field strength of 5 and 10 kV/cm and 10 and 50 pulses. On the basis of electric conductivity measurement, the cell disintegration index was calculated. The course of osmotic dehydration was described by means of water loss, solid gain, weight reduction, and water content changes. Moreover, the course of the process was described by different mathematical models that are commonly used in the literature. PEF application before osmotic dehydration significantly increased water loss after 60 minutes of the process. In turn, no significant differences were found in the case of solid gain. The highest osmotic dehydration efficiency ratio (WL/SG) was noticed for samples treated by PEF at the electric field strength of 5 kV/cm and 10 pulses. The statistical analysis of mathematical modeling of the process showed the equations utilized generally exhibit a good fit to the experimental data.     

The Role of Processing Conditions on the Color and Antioxidant Retention of Jet Tube Fluidized Bed–Dried Blueberries

Jet tube fluidized bed drying was investigated as a means of rapidly generating shelf-stable and high-quality sweetened and nonsweetened blueberries. Sugar-infused and noninfused scarified Rabbiteye blueberries (Vaccinium ashei ‘Brightwell’) were dried at 99, 107, and 116°C. Prior scarification of the blueberry surface aided in decreasing the drying time. Increased lightness (L*) values were most notable at higher drying temperatures for sugar-infused blueberries, suggesting loss of pigments. Total monomeric anthocyanins level, initially 7.65 mg cyanidin-3-O-glucoside equivalents (C3G eq)/g extract, decreased as drying temperature increased and ranged between 4.07 down to 1.51 mg C3G eq/g extract for dried blueberries. The total phenolics content increased with drying for noninfused blueberries, with highest levels of 31.6 mg gallic acid equivalents (GAE)/g extract for samples dried at 107°C. With the exception of sugar-infused berries dried at 107 and 116°C, the dried blueberries maintained or demonstrated slightly increased hydrophilic oxygen radical absorbance capacity (H-ORAC_FL) values, indicating that their antioxidant capacity was retained upon drying. Blueberries dried at 107°C possessed the greatest preference scores and best retention of blueberry flavor and required a relatively short drying time.     

Mass Transfer during Osmotic Dehydration in a Multicomponent Solution Rich in Grape Phenolics with Antioxidant Activity

Osmotic dehydration has been assessed as an operation for obtaining solid foodstuffs supplemented with grape phenolics. However, mass transfer in multicomponent osmotic solutions during OD needs to be described appropriately if the infusion of target solutes, in this case phenolics with antioxidant activity, is to be better controlled. The effective diffusion coefficients of moisture, total phenolics, and the major individual phenolics of low-molecular-weight (caftaric acid, coutaric acid, caffeic acid, coumaric acid, ferulic acid, and rutin) were evaluated during the OD of a model food with a concentrated red grape must. An increase in the concentration of soluble solids above 50° Brix decreased the level of penetration of phenolics in the model food.     

Mass Transfer during Osmotic Dehydration in a Multicomponent Solution Rich in Grape Phenolics with Antioxidant Activity

Osmotic dehydration has been assessed as an operation for obtaining solid foodstuffs supplemented with grape phenolics. However, mass transfer in multicomponent osmotic solutions during OD needs to be described appropriately if the infusion of target solutes, in this case phenolics with antioxidant activity, is to be better controlled. The effective diffusion coefficients of moisture, total phenolics, and the major individual phenolics of low-molecular-weight (caftaric acid, coutaric acid, caffeic acid, coumaric acid, ferulic acid, and rutin) were evaluated during the OD of a model food with a concentrated red grape must. An increase in the concentration of soluble solids above 50° Brix decreased the level of penetration of phenolics in the model food.     

Effects of pretreatments on properties of microwave-vacuum drying of sweet potato slices

Abstract

Pretreatments of blanching (BL); osmotic dehydration at 35°Brix of sucrose (OD); ultrasound in distilled water (UD), and ultrasound-assisted osmotic dehydration (UO) were carried out for microwave-vacuum drying (MVD) orange- and purple-flesh sweet potato slices, and effects on their properties were investigated in this study. UO had improvements effects on water loss, solid gain, and relaxation time of the samples compared to other pretreatments. Low-field nuclear magnetic resonance results offered a view of water state concerning the effects of different pretreatments on sweet potato. UD treatment following by BL showed a long relaxation time corresponding to the weaker degree of bound hydrogen proton or the greater freedom degree of hydrogen comparing to other pretreated samples. Differential scanning calorimetry parameters appeared to be sensitive to pretreatments by increased Tg value compared to blanched sample. The value of Tg shows that it does not depend only of the water content but also on the experimental conditions (pretreatments). The dried sweet potato exhibited amorphous structures as evidenced by the X-ray diffractograms due to the BL treatment and MVD. Concentration of total phenolics and anthocyanins were high in purple sweet potatoes, whereas content of vitamin C and total carotenoid were high in orange ones. Application of UO is suitable for retention of bioactive compound and stability of MVD sweet potato slices.     

Phenolic Contents and Compositions in Skins of Red Wine Grape Cultivars among Various Genetic Backgrounds and Originations

In order to analyze and compare the phenolic characteristics of red wine grapes with diverse genetic backgrounds, skin phenolics among 21 different cultivars belonging to Vitis vinifera L., East Asian and North American Vitis species and hybrids, as well as 2 varieties of muscadine grapes were estimated by HPLC-MS/MS. There were 45 anthocyanins, 28 flavonols, 8 flavan-3-ols, 9 cinnamic acids, 5 benzoic acids, 5 ellagic acids and 2 stilbenes detected in all the samples. Total contents of each phenolic type varied significantly among the different grape cultivars investigated. There was also a large variability in the phenolic compositions of different grape groups. The differences in anthocyanin composition were obvious between V. vinifera and non-V. vinifera grapes and also between the grapes originating from Eurasia and North America. Quercetin-3-glucuronide and quercetin-3-glucoside were marker flavonol compounds for Euvitis grape skins. Flavan-3-ol monomers were dominant in the skins of muscadine and non-V. amurensis East Asian grapes, whereas polymers were more common in V. vinifera and North American grapes. The muscadine grapes were very rich in flavonols, flavan-3-ols and ellagic acids. Via principal component analysis, these grape cultivars were clustered into three groups according to their characteristic phenolic content and composition.     

Effect of maturity on phenolics (phenolic acids and flavonoids) profile of strawberry cultivars and mulberry species from pakistan

In this study, we investigated how the extent of ripeness affects the yield of extract, total phenolics, total flavonoids, individual flavonols and phenolic acids in strawberry and mulberry cultivars from Pakistan. In strawberry, the yield of extract (%), total phenolics (TPC) and total flavonoids (TFC) ranged from 8.5-53.3%, 491-1884 mg gallic acid equivalents (GAE)/100 g DW and 83-327 mg catechin equivalents (CE)/100 g DW, respectively. For the different species of mulberry the yield of extract (%), total phenolics and total flavonoids of 6.9-54.0%, 201-2287 mg GAE/100 g DW and 110-1021 mg CE/100 g DW, respectively, varied significantly as fruit maturity progressed. The amounts of individual flavonols and phenolic acid in selected berry fruits were analyzed by RP-HPLC. Among the flavonols, the content of myricetin was found to be high in Morus alba (88 mg/100 g DW), the amount of quercetin as high in Morus laevigata (145 mg/100 g DW) while kaempferol was highest in the Korona strawberry (98 mg/100 g DW) at fully ripened stage. Of the six phenolic acids detected, p-hydroxybenzoic and p-coumaric acid were the major compounds in the strawberry. M. laevigata and M. nigra contained p-coumaric acid and vanillic acid while M. macroura and M. alba contained p-hydroxy-benzoic acid and chlorogenic acid as the major phenolic acids. Overall, a trend to an increase in the percentage of extraction yield, TPC, TFC, flavonols and phenolic acids was observed as maturity progressed from un-ripened to fully-ripened stages.     

Antioxidant activity of grape extracts in a lecithin liposome system

Extracts of 14 different grapes were tested for their antioxidant activities in a copper-catalyzed lecithin liposome oxidation assay and analyzed for their phenolic components by high-performance liquid chromatography (HPLC). The total phenolic contents of the grape extracts varied from 176 to 1236 mg gallic acid equivalents (GAE)/L. Extracts of red wine grape varieties contained higher concentrations of phenolics than other varieties. When compared at the same 20 μM GAE basis, the grape extracts inhibited formation of conjugated diene hydroperoxides by 25.1 to 67.9%, and hexanal formation by 49.3 to 97.8%. Extracts of red table grape varieties Red Globe and Emperor and white wine grape varieties Chardonnay and Sauvignon Blanc gave the highest antioxidant activities. The relative percentage inhibition of conjugated dienes and hexanal correlated with total phenols (r=0.86 and 0.89). HPLC analyses showed that anthocyanins were the most abundant phenolic compounds in extracts of red grapes, and flavonols were most abundant in extracts of white grapes.     

Ultrasound-Assisted Osmotic Dehydration of Strawberries: Effect of Pretreatment Time and Ultrasonic Frequency

Pretreatment of fruits prior to drying has shown success in reducing drying time and costs. In this work, ultrasound-assisted osmotic dehydration has been implemented as a method to increase water diffusivity and reduce drying time in strawberries. Strawberry halves were immersed in distilled water and in two different concentrations of sucrose solutions while pretreatment time and ultrasonic frequency levels were varied to determine their effect on drying time, water loss, and soluble solids gain. A microscopic analysis was carried out to evaluate the formation of microchannels and other changes to the fruit tissue structure. Greater sucrose concentration used in ultrasound-assisted osmotic dehydration resulted in greater water loss with greatest loss observed for the strawberry halves pretreated for 45 min in a 50% w/w sucrose solution. The pretreatment carried out for 30 min employing an osmotic solution of 50% w/w of sucrose resulted in the highest drying rate among the pretreatments. Osmotic dehydration used alone during pretreatment increased total processing time, whereas osmotic dehydration combined with ultrasonic energy during pretreatment reduced total processing time and increased effective water diffusivity. Cell distortion and breakdown were observed not only in pretreatments employing ultrasound-assisted osmotic dehydration but in conventional osmotic dehydration. Formation of microchannels through ultrasonic application and effects of osmotic pressure differential were considered to be largely responsible for reducing drying time for strawberry halves.     

Effect of microwave-vacuum,ultrasonication, and freezing on mass transfer kinetics and diffusivity during osmotic dehydration of cranberries

The objectives of this study were (i) to evaluate moisture loss (ML), solids gain (SG), moisture loss rate (d(ML)/dt), solids gain rate (d(SG)/dt), effective moisture diffusivity (D_eM), and effective solids diffusivity (D_eS) during osmotic dehydration (OD), ultrasound-assisted osmotic dehydration (UA-OD), and osmotic dehydration of whole cranberries, preceded by microwave-vacuum pretreatment (MV?+?OD) or freezing/thawing treatment (F?+?OD ) and (ii) to use a mathematical model to predict moisture content ML_∞ and solids content SG_∞ in equilibrium state and the distribution of moisture and sucrose in whole cranberries during dehydration. Microwave-vacuum and OD treatments produced cranberries with the highest values of ML and SG (39.7 and 8.4?g 100?g?fresh?fruit^?1, respectively), d(ML)/dt and d(SG)/dt (76.9 and 8.5?h^?1, respectively), D_eM and D_eS (6.1 and 3.7?×?10^?10?m²?s^?1, respectively). Azuara’s and Peleg’s models adequately described the OD kinetics of whole cranberries in terms of ML and SG. The results indicate that the equilibrium values of ML_∞ and SG_∞ were not reached under the conditions specified in the present study.     

Identification of phenolic compounds and antioxidant activity of guava dehydrated by different drying methods

Abstract

The influence of different drying techniques on guava was investigated, including phenolic components and antioxidant activities. Through drying processes, total phenolic content (TPC) increased and formation of small molecular phenolic acids (multi-methoxy benzoic acid and sinapic acid) was promoted. UPLC-ESI-QTOF-MS determination showed flavanol compounds, hydrolyzable tannins, ellagic acid conjugates and cinnamic acid derivatives were four predominant phenolics of guava. Drying treatments caused degradation of catechin and its derivatives. Contrarily, drying treatments contributed to higher contents of procyanidin trimers. Moreover, thermal drying treatments led to degradation of macromolecular tannins and formation of smaller molecular tannins and ellagic acid conjugates, while simultaneously reduced the stabilities of most intrinsic ellagic acid conjugates. Furthermore, drying processes increased the yield of cinnamic acid dihexose, probably generating from lignin or phenolics–carbohydrate complex. Freeze drying and hot air drying showed better performance on retention of TPC and enhancement of antioxidant activity (AA).     

Bioactive Compounds and Antioxidant Activity in Different Types of Berries

Berries, especially members of several families, such as Rosaceae (strawberry, raspberry, blackberry), and Ericaceae (blueberry, cranberry), belong to the best dietary sources of bioactive compounds (BAC). They have delicious taste and flavor, have economic importance, and because of the antioxidant properties of BAC, they are of great interest also for nutritionists and food technologists due to the opportunity to use BAC as functional foods ingredients. The bioactive compounds in berries contain mainly phenolic compounds (phenolic acids, flavonoids, such as anthocyanins and flavonols, and tannins) and ascorbic acid. These compounds, either individually or combined, are responsible for various health benefits of berries, such as prevention of inflammation disorders, cardiovascular diseases, or protective effects to lower the risk of various cancers. In this review bioactive compounds of commonly consumed berries are described, as well as the factors influencing their antioxidant capacity and their health benefits.     

Effect of agronomic practices and drying techniques on nutritional and quality parameters of onions (Allium cepa L.)

The effects of four drying treatments (freeze-drying, hot air drying, oven drying, and vacuum oven drying) on the bioactive compounds (total phenolics, total flavonoids, and quercetins), color, and antioxidant capacity of organic and nonorganic onions of two varieties (Red Baron and Hyfort) subjected to two agronomic treatments (OSOP and CSCP) were investigated. The average final dry weight of the samples was 9.82?±?0.41%. After drying, there was a significant increase in total phenolics, total flavonoids, total quercetin, and antioxidant capacity in comparison with fresh onion samples, which suggested that drying can improve the extractability of phenols and accordingly the antioxidant activity of onions. Different drying techniques also resulted in different fractions of individual quercetins. Dried organic onions had higher levels of bioactive compounds and antioxidant capacity than dried nonorganic onions for a same variety. The highest antioxidant capacity displayed by freeze-dried and hot-air-dried organic Red Baron onion is in agreement with their higher phenolic and flavonoid contents compared to all other samples.     

Effect of In Vitro Gastrointestinal Digestion on Amino Acids,Polyphenols and Antioxidant Capacity of Tamarillo Yoghurts

Laird’s Large tamarillo powder is high in protein (10%) essential amino acids (EAAs), gamma-aminobutyric acid (GABA) and polyphenols (0.6% phenolics plus anthocyanins) and fibre 25%. This study aimed to investigate, using a standardized static in vitro digestion model, the stability of amino acids and antioxidant capacity of polyphenols in yoghurt fortified with 5, 10 and 15% tamarillo powder either before (PRE) or after (POS) fermentation. Compared to plain yoghurt, the fruit polyphenols (rutinosides and glycosides) were retained and substantial increases in FEAAs (free essential amino acids), total phenolic content (TPC) and antioxidant activity were observed particularly at the end of intestinal phase of digestion. Together with SDS-PAGE results, peptides and proteins in tamarillo yoghurts were more easily digested and therefore may be better absorbed in the small intestine compared to the control. TPC and antioxidant activity of fortified yoghurts increased significantly after in vitro digestion. Relatively high bioaccessibilty of chlorogenic acid and kaempferol-3-rutinoside in digested PRE samples was observed. The results suggest that the yoghurt matrix might protect some compounds from degradation, increasing bioaccessibility and in the small intestine allow increased absorption and utilization possible. Fortification would deliver intact polyphenols and fibre to the large intestine and improve gut health. Further research of acceptability, shelf life, and then trials for health effects should be implemented.     

Ultrasound-assisted osmotic process on quality of microwave vacuum drying sweet potato

The effects of pretreatment before microwave vacuum drying (MVD) on texture, color, expansion, rehydration, drying rate, microstructure, sensory evaluation, and other properties of sweet potato were investigated in this study. The pretreatment consisted in five processing conditions, using blanching; osmotic dehydration at 35°Brix of sucrose (OD); ultrasound in distilled water (US); ultrasound in distilled water before osmotic dehydration (US?+?OD), and ultrasound-assisted osmotic dehydration (USOD). Pretreatments of sweet potato before MVD have shown success in reducing drying time with US treatment relatively more effective regarding drying time than other treatments. Compared with other treatments, US showed the highest rehydration ratio values. The osmotic group pretreatment exhibited a pronounced effect on water loss and solid gain, improved the color, aroma, and taste of dried sweet potato, whereas sucrose impregnation resulted in a hard texture observed with OD sample. USOD samples had a higher expansion ratio, lower hardness and color difference values, appeared less cell damaged, and recorded better overall quality than the other samples. There was a slight difference between USOD and US?+?OD samples. Combining osmotic dehydration with ultrasound as a pretreatment can significantly accelerate the heat transfer rate, reducing the dried time accordingly and increasing energy efficiency.     

Convective-intermittent drying of cherries preceded by ultrasonic assisted osmotic dehydration

This paper presents the results of experimental studies on convective drying of cherries (Prunus cerasus L.) in stationary and intermittent conditions, previously pretreated with ultrasonic assisted osmotic dehydration. The effect of a stepwise changing air temperature and osmotic pretreatment on drying kinetics and the biomaterial quality were investigated. The main aim of the studies was to find the possibly best drying conditions, by which the drying time was shortened and the product quality degradation was minimized. Except drying kinetics and total color and water activity changes, the effect of osmotic pretreatment expressed by such parameters as the Solid Gain and the Water Loss were examined. It was proved that intermittent drying of cherries preceded by ultrasonic assisted osmotic dehydration contributes to shorter drying time, better color preservation and smaller water activity.     

Correlation between antioxidant activity and bioactive compounds of açaí (Euterpe oleracea Mart) comercial pulps

The purpose of this work was to analyze commercial a?aí pulp and to correlate the contribution of vitamin C, total carotenoids and phenolic compounds with the antioxidant activity of there products besides the examination of the standard related to the quality of the obtained products. Analysis were made with regard to pH, acidity total, soluble solids, sugars, color, water activity, vitamin C, total anthocyanins, total carotenoids, antioxidant activity and phenolic compounds. All parameters analyzed showed significative difference among the marks not added with preservatives and sucrose. The a?aí fruit can be considered a fair source of vitamin C and good source of natural antioxidants. In regard to the correlation with the antioxidant activity only the total anthocyanins and the total carotenoids presented positive and significative correlation.