Effect of different drying methods on drying characteristics,colour, total phenolic content and antioxidant capacity of Goldenberry (Physalis peruviana L.)

In this study, the effects of convective, microwave and microwave–convective drying methods on the drying characteristics, colour, total phenolic content and antioxidant capacity of goldenberry fruits were investigated. To select the most appropriate thin‐layer drying model for drying treatments, nine mathematical drying models were fitted to the experimental data. Based on the statistical tests used for evaluation, the Midilli et al. and Wang and Singh models were considered the best models to describe the drying behaviours of goldenberry fruits in all drying methods. The colour values (L*, a* and b*) of fresh fruit were decreased by drying. Compared with the fresh sample, the dried samples exhibited a 64–75% and 65–75% decrease in total phenolic content and antioxidant capacity, respectively. Among the different drying treatments, the values closest to those of fresh samples with respect to colour values, total phenolic content and antioxidant capacity were achieved with the 160 W microwave drying method.     

Colour,phenolic content and antioxidant capacity of some fruits dehydrated by a combination of different methods

The objective of this study was to improve product quality of dehydrated fruits (apple, pear, papaya, mango) using combined drying techniques. This involved investigation of bioactivity, colour, and sensory assessment on colour of the dried products as well as the retention of the bio-active ingredients. The attributes of quality were compared in regard to the quality of dehydrated samples obtained from continuous heat pump (HP) drying technique. It was found that for apple, pear and mango the total colour change (ΔE) of samples dried using continuous heat pump (HP) or heat pump vacuum-microwave (HP/VM) methods was lower than of samples dried by other combined methods. However, for papaya, the lowest colour change exhibited by samples dried using hot air–cold air (HHC) method and the highest colour change was found for heat pump (HP) dehydrated samples. Sensory evaluation revealed that dehydrated pear with higher total colour change (ΔE) is more desirable because of its golden yellow appearance. In most cases the highest phenol content was found from fruits dried by HP/VM method. Judging from the quality findings on two important areas namely colour and bioactivity, it was found that combined drying method consisted of HP pre-drying followed by VM finish drying gave the best results for most dehydrated fruits studied in this work as the fruits contain first group of polyphenol compounds, which preferably requires low temperature followed by rapid drying strategy.     

Evaluation of antioxidant capacity and total phenolic content of different fractions of selected microalgae

In order to identify new sources of safe and inexpensive antioxidants, the antioxidant capacity and total phenolic content of different fractions of 23 microalgae were evaluated, using Trolox equivalent antioxidant capacity assay and the Folin–Ciocalteu method, respectively. The microalgae were extracted using hexane, ethyl acetate and water by a three-step sequential extraction procedure. Most of these microalgae were evaluated for the first time for their antioxidant activities. It was found that the microalgae Synechococcus sp. FACHB 283, Chlamydomonas nivalis and Nostoc ellipsosporum CCAP 1453/17 possessed the highest antioxidant capacities and thus could be potential rich sources of natural antioxidants. In addition, the correlation coefficients between the antioxidant capacities and the phenolic contents were very small in hexane (R² = 0.0075), ethyl acetate (R² = 0.5851) and water (R² = 0.3599) fractions. Thus, phenolic compounds were not a major contributor to the antioxidant capacities of these microalgae. This was very different from many other plant species like fruits, vegetables and medicinal plants. The microalgae could contain different antioxidant compounds from other plants.     

不同品种蓝莓酚类物质组成特征及抗氧化能力比较分析

以高丛、矮丛、兔眼蓝莓为研究对象,比较了其总酚、花色苷、原花色素、单体酚以及抗氧化力差异。超高效液相色谱检测结果表明,绿原酸为3种蓝莓中含量最多的酚酸;表没食子儿茶素是高丛蓝莓和兔眼蓝莓含量最丰富的黄烷醇,表儿茶素没食酸酯则是矮丛蓝莓含量最高的黄烷醇;在3种蓝莓中含量最高的黄酮醇均为芦丁;矮丛蓝莓单体酚总量显著高于高丛蓝莓和兔眼蓝莓。抗氧化分析结果则表明,无论从DPPH、ABTS还是FRAP测定结果来看,矮丛蓝莓均具有最强的抗氧化能力。相关性分析结果表明,3种蓝莓总酚、总花色苷和原花色素含量均与抗氧化能力存在明显的正相关性。     

Relationship between antioxidant capacity and total phenolic content of red,rosé and white wines

Phenolic compounds are one of the most important quality parameters of wines, since they contribute to wine organoleptic characteristics such as colour, astringency, and bitterness. Furthermore, several studies have pointed out that many show biological properties of interest, related to their antioxidant capacity. This antioxidant activity has been thoroughly studied and a wide variety of methods have been developed to evaluate it.     

Effect of temperature and air velocity on drying kinetics, antioxidant capacity, total phenolic content, colour, texture and microstructure of apple (var. Granny Smith) slices

The aim of this work was to study the effect of temperature and air velocity on the drying kinetics and quality attributes of apple (var. Granny Smith) slices during drying. Experiments were conducted at 40, 60 and 80 °C, as well as at air velocities of 0.5, 1.0 and 1.5 m s⁻¹. Effective moisture diffusivity increased with temperature and air velocity, reaching a value of 15.30 × 10⁻⁹ m² s⁻¹ at maximum temperature and air velocity under study. The rehydration ratio changed with varying both air velocity and temperature indicating tissue damage due to processing. The colour difference, ΔE, showed the best results at 80 °C. The DPPH-radical scavenging activity at 40 °C and 0.5 m s⁻¹ showed the highest antioxidant activity, closest to that of the fresh sample. Although ΔE decreased with temperature, antioxidant activity barely varied and even increased at high air velocities, revealing an antioxidant capacity of the browning products. The total phenolics decreased with temperature, but at high air velocity retardation of thermal degradation was observed. Firmness was also determined and explained using glass transition concept and microstructure analysis.     

Evaluation of the phenolic content,antioxidant activity and colour of Slovenian honey

Honey samples from the seven most common honey types in Slovenia were screened for total phenolic content by the modified Folin–Ciocalteu method, for potential antioxidant activity using the ferric reducing antioxidant power (FRAP) assay and by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method for antiradical activity. In addition the colour characteristics of honey samples were analysed. The results of the study showed that total phenolic content, antioxidant activity and colour parameters differ widely among different honey types. Phenolic content expressed as gallic acid equivalent ranged from 44.8 mg/kg in acacia honey to 241.4 mg/kg in fir honey. Antioxidant activity was the lowest in the brightest acacia and lime honeys and the highest in darker honeys, namely fir, spruce and forest. The colour of the Slovenian honeys, analysed in this study was very variable and ranged from pale yellow to dark brown. Correlations between the parameters analysed were found to be statistically significant (p < 0.05).     

Effect of air-drying temperature on physico-chemical properties,antioxidant capacity,colour and total phenolic content of red pepper (Capsicum annuum, L. var. Hungarian)

Red pepper has been recognised as an excellent source of antioxidants, being rich in ascorbic acid and other phytochemicals. Drying conditions, particularly temperature, leads to pepper modifications that can cause quality degradation. In this work, the effects of process temperatures between 50 and 90 °C on physico-chemical properties, rehydration, colour, texture, vitamin C, antioxidant capacity and total phenolics during the drying of red pepper were studied. The rehydration ratio decreased with temperature and the maximum water holding capacity was achieved at 50 °C. Both vitamin C content and the total phenolic content decreased as air-drying temperature decreased. The radical scavenging activity showed higher antioxidant activity at high temperatures (i.e. 80 and 90 °C) rather than at low temperatures (i.e. 50, 60 and 70 °C). Chromatic parameters (L*, a*, b*, C* and H°), non-enzymatic browning compounds and extractable colour were affected by drying temperature, which contributed to the discolouring of pepper during this process.     

Geographical discrimination of honeys through antioxidant capacity,mineral content and colour

The assessment of geographical origin of honey is economically important for producers and consumers as every region may present particular quality characteristics. In this study, honeys from the seven different regions of Buenos Aires province (Argentina) were characterised by their antioxidant capacity (DPPH, FRAP), total phenolic content (TPC), mineral composition, colour and ash. Honeys showed significant differences among their antioxidant capacity (DPPH), ash, colour and mineral content (P ≤ 0.05). Besides, a good antioxidant activity and low amounts of Cu and Zn (<1.0–1.5 and 0.7–1.8 mg kg^?1, respectively) were found in the samples. Significant Pearson's correlations (P ≤ 0.05) among the different parameters were found. Moreover, the linear discriminant analysis allowed the classification of honeys in their original groups with a prediction success of 98%. The present results suggest that honeys could be correctly classified by their geographical origin through their TPC, colour, ash and mineral concentrations.     

Drying kinetics,physico‐chemical properties,antioxidant activity and phenolic composition of foam‐mat dried germinated rice bean (Vigna umbellata) hydrolysate

This research was aimed to study physico‐chemical properties and antioxidant activities of foam‐mat dried germinated rice bean (Vigna umbellata) hydrolysate. Germination led to an increase in released phenolic content and antioxidant activity (DPPH radical scavenging activity and FRAP) of rice bean hydrolysate. The hydrolysate obtained from germinated rice bean (GRB) and non‐germinated rice beans (NGRBs) was foam‐mat dried at 60 and 70 °C. Semi‐theoretical and empirical model could suitably describe the drying characteristic of foamed bean hydrolysate. Total phenolic content and antioxidant activities of foam‐mat dried samples decreased with increasing air‐drying temperature (P ≤ 0.05). Gallic acid, catechol and epicatechin were major phenolic compounds in foam‐mat dried samples prepared from both GRB and NGRB. The higher phenolic content and antioxidant activities were found in foam‐mat dried hydrolysate of GRB. Electron spin resonance spectrometry revealed that foam‐mat dried rice bean hydrolysate showed a strong ability to scavenge free radicals, especially carbon‐centred radicals.     

桑椹中酚类物质极性分布及抗氧化活性评价

采用超声波辅助,用不同极性的溶剂提取红果2号桑椹,测定并分析各提取浸膏的酚类含量,自由基清除能力、抗脂质过氧化能力、总还原力和DNA保护潜力。研究结果表明,乙醇提取物浸膏(absolute ethanol extracts of fruit,FAE)的酚类含量最高,为3.65 mg GAE/g dw,且总还原力和羟基自由基(·OH)清除力最强(P0.05);乙酸乙酯提取物浸膏(ethyl acetate extracts of fruit,FEE)的DPPH自由基(DPPH·)清除力(0.71mg/m L)和抗脂质过氧化能力最强;水提取物浸膏(water extracts of fruit,FWE)的ABTS自由基(ABTS+·)清除力最强(3.52 mg/m L),且能有效保护DNA不被损伤;石油醚提取物浸膏(petroleum ether extracts of fruit,FPE)酚类含量最低,且4种活性均最弱。基于实验结果,红果2号桑椹具有作为功能性保健品(天然抗氧化剂)的巨大潜力。     

Effect of different rehydration temperatures on the moisture,content of phenolic compounds,antioxidant capacity and textural properties of edible Irish brown seaweed

The effect of temperature (20, 40, 60, 80 and 100 °C) on the rehydration kinetics and phytochemical constituents of dried edible Irish brown seaweed, Himanthalia elongata, were studied. The moisture content of fresh and dried seaweed was 4.07 and 0.07 g water/g dry basis, representing a 98.1% reduction in water content. All rehydration moisture curves had a clear exponential tendency, and it was observed that the rehydration time decreased when temperature was increased. Although restoration of the product to its original moisture content was achieved, rehydration resulted in losses in phytochemical content. Moisture equilibrium was achieved fastest at 100 °C (40 min) with losses of 83.2 and 93% in the total phenol and total flavonoid contents, respectively. The moisture content was fitted to empirical kinetic models; Weibull, Peleg’s, first-order and exponential association. Activation energies of 4.03, 4.28 and 3.90 kJ/mol were obtained for the parameters of Peleg’s, first-order and exponential models, respectively.     

Antioxidant capacity and total phenolic content of selected plants from Turkey

A total of 28 different plants from different regions of Çanakkale, Turkey, were investigated for their antioxidant capacity and total phenol contents to find new potential sources of natural antioxidants. The antioxidant capacity of methanolic extracts prepared from various parts of plants was evaluated by both trolox equivalent antioxidant capacity (TEAC) and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assays, while the total phenolics were determined using the Folin‐Ciocalteu method. The TEAC values of plant extracts ranged in a large scale from 1472.36 to 17.61 μmol of trolox equivalents per g dry weight (dw), and EC₅₀ values (concentration at which 50% radical scavenging occurred) varied from 0.174 to 42.475 mg dw of plant, while the total phenol content of plant extracts ranged between 117.20 and 1.27 mg of gallic acid equivalents per g dw. There was a positive linear correlation between the TEAC and total phenols of plant materials (r = 0.916). The extracts of Hypericum perforatum, Arbutus andrachne and Paliurus spina‐christii showed higher antioxidant activities (both TEAC and DPPH assays). However, there was no clear relationship between TEAC and EC₅₀ values (r = 0.477) of plant extracts.     

Factors influencing antioxidant activities and total phenolic content of guava leaf extract

The aim of this study is to investigate the influence of certain factors on the yield, antioxidant activity (AA) and total phenolic content (TPC) of guava leaf extract. The effects of pretreatment of leaf sample prior to extract, extraction method, and the leaf age were investigated. Folin-Ciocalteau was used to determine the TPC. Trolox equivalent antioxidant capacity (TEAC) and equilibrium concentration (EC) were used for evaluation of AA. Results indicated that ultrasonication is the most suitable method for guava leaf extraction as it yielded the extract with the significantly highest TPC and AA. Blanching followed by ice water cooling (BCD) was suggested for the pretreatment process of guava leaves. The study of leaf maturity demonstrated that the highest activity was from the young leaves. Hot water was the best solvent to extract the active principles. The extract of BCD pretreated young leaves, extracted by hot water exhibited the highest TPC and AA with the TEAC and EC values of 24.30 ± 0.50 and 20.41 ± 0.67 mM/mg, respectively. These values are 1.88 and 8.72 times higher than the synthetic antioxidant butylated hydroxy toluene (BHT) and 1.75 and 1.21 times higher than vitamin E, respectively. It was concluded that pretreatment and drying process, method of extraction and leaf maturity played important roles on the bioactive compounds and their antioxidant power of guava leaf extract.     

Organic acids,antioxidant capacity,phenolic content and lipid characterisation of Georgia-grown underutilized fruit crops

Four underutilized Georgia-grown fruit crops, namely loquat (Eriobotrya japonica), mayhaw (Crataegus sp.), fig (Ficus carica), and pawpaw (Asimina triloba), and their leaves were analysed for total polyphenols by Folin–Ciocalteau method, and antioxidant capacity by ferric-reducing antioxidant power (FRAP) and Trolox-equivalent antioxidant capacity (TEAC) assays. Organic acids and phenolic compounds were identified by RP-HPLC. For lipid profile, fruits were separated into two fractions – seed and fruit (i.e., without seed); lipid was extracted using the Folch method and analysed for fatty acids, phytosterols, tocopherols, and phospholipids. The major organic acid identified in all samples was malic acid (177–1918 mg/100 g FW). The predominant phenolic acids in all the fruits were gallic (1.5–6.4 mg/100 g FW) and ellagic (0.2–33.8 mg/100 g FW), and the most abundant flavonoid was catechin (12.2–37.8 mg/100 g FW). Total lipid content varied from 0.1% in mayhaw fruit to 21.5% in pawpaw seed. Linoleic acid was the predominant fatty acid in all of the samples (28.2–55.7%).     

Total phenolic and total flavonoid content,antioxidant activity and sensory evaluation of pseudocereal breads

The aim of the study was to investigate the effect of adding (in two different doses 15% and 30%) pseudocereal (buckwheat, amaranth and quinoa) flour on the antioxidant properties and sensory value of breads. Buckwheat flour had the highest phenolic content (7.25 ± 0.23 mg/g dw). The content of total flavonoids in flours was about 2–4 fold higher when compared to breads. The addition of buckwheat flour to wheat bread, particularly in higher dose, was more effective in enhancing antioxidant activity, as evaluated by means of FRAP and DPPH, which increased by 2.36 fold, and 3.64 fold respectively, in comparison with other pseudocereal flours (amaranth, quinoa), which caused, in higher doses, the changes of above parameters within the ranges 1.20–1.79 fold, and 0.60–1.71 fold. Analysis of sensory results of breads showed that addition of buckwheat flour to the dough might improve subjective properties of bread and increase acceptable quality attributes such as taste, colour or odour. All these observations suggest that addition of buckwheat flour into bread can improve antioxidant as well as sensory properties of bread. Bread fortified with pseudocereal flours, and especially with buckwheat flour, may be placed on the market as a functional food.     

Drying kinetics and thermal degradation of phenolic compounds and anthocyanins in pomegranate arils dried under vacuum conditions

The effects of temperature and pretreatment on drying kinetics and thermal degradation of phytonutrients present in pomegranate arils were investigated. The arils were divided into two groups, and half of the samples were pretreated by dipping into 80 °C hot water for 2 min. The drying process was conducted in the vacuum drier at the temperatures of 55, 65 and 75 °C. The fastest drying was completed at 75 °C after pretreatment of the samples. The highest anthocyanin–phenolic compound contents and antioxidant capacity were detected in the arils dried at 55 °C. Seven thin‐layer drying models were used to predict drying curves, and Arrhenius and Eyring–Polanyi models were employed to predict phytonutrient degradation kinetics. Activation energy for drying was 24.26 kJ mol^?1 for pretreated samples and 31.54 kJ mol^?1 for untreated samples. Effective moisture diffusivities were ranged from 1.43 × 10^?9 to 6.03 × 10^?9 m² s^?1.     

Influence of winemaking techniques on the resveratrol content, total phenolic content and antioxidant potential of red wines

In this paper, the influence of winemaking techniques and cultivars on the resveratrol content, total phenolic content and antioxidant potential of red wines was studied. Wines were made from the cultivars Merlot, Cabernet Sauvignon, Pinot Noir and Prokupac. Applied winemaking technologies included thermovinification and separation of must from pomace. The analysis of trans- and cis-resveratrol in wines was performed by HPLC, while the total phenolic content and antioxidant potential was determined by spectrophotometric methods. The total resveratrol content in analysed samples ranged from 0.35 to 4.85 mg/l; Merlot wines had the highest average resveratrol content, while the lowest was found for native cultivar Prokupac. Although the resveratrol content depended on grape variety, correlation between the winemaking technology applied and the resveratrol level in wines was not observed. The total phenolic content (TPC) varied from 544.4 to 1410.4 mg/l expressed as gallic acid equivalents, and the antioxidant potential, assayed by DPPH in terms of SC₅₀ (mean scavenging concentration), ranged from 0.58 to 2.91 μl/ml. Obtained results showed that thermovinificated wine samples had higher amount of phenolic compounds. Significant negative correlation was observed (p < 0.05) between the total phenolic content and SC₅₀, but there was no significant correlation (p > 0.05) between the resveratrol content and SC₅₀ or TPC. This study could contribute to the establishment of optimal conditions for producing red wines which contain more beneficial phenolic compounds.     

Correlation of tocopherol,tocotrienol, γ-oryzanol and total polyphenol content in rice bran with different antioxidant capacity assays

The relationship between antioxidant capacity and levels of various antioxidants in rice bran and brown rice powder was evaluated. Three different varieties of Venezuelan rice, namely, Cimarrón, Zeta 15 and FONAIAP-1, were studied using ferric reducing antioxidant power (FRAP), 2,2′-azinobis-3-ethylbenzotiazoline-6-sulphonic acid (ABTS), and oxygen radical absorbance capacity (ORAC) to measure antioxidant capacity. The results showed that rice varieties contained different levels and combinations of total polyphenols, γ-oryzanol, α- and γ-tocopherols and α-, γ- and δ-tocotrienols. Compared to brown rice powder, rice bran contained most of the antioxidants and had correspondingly higher values of antioxidant capacity. Principal components analysis and multiple regression on the data indicate that FRAP was sensitive to polyphenols and total tocotrienols, while ORAC was sensitive to polyphenols and total tocopherols. ABTS was the least sensitive of all assays tested. Thus, results from antioxidant capacity assays must be interpreted with caution particularly in complex systems and that further study is necessary to define more precisely the nature of the relevant chemical reactions.