Removal of phenolic compounds in pomegranate juices using ultrafiltration and laccase‐ultrafiltration combinations

Phenolic compounds of fruit juices are responsible for haze and sediment formation as well as for color, bitterness and astringency. The influence of ultrafiltration (UF) and laccase‐UF combination was investigated on phenolic contents of pomegranate juices and on filtration output. Laccase‐treated and then ultrafiltered pomegranate juices have shown a rapid increase in their color, when compared to only ultrafiltered (control) samples. Kinetic parameters of laccase were also determined. During the oxidation period, the changes occurring in pomegranate juices were estimated from phenolic contents, color and anthocyanin measurements. Results have shown that laccase oxidation produced a significant decrease in phenolic content of pomegranate juices while juice color the increased. However, in recent literatures, the possibility to remove polyphenols in apple juices was reported. We decided in this study that laccase treatment can not be applied due to the loss of natural red color and unwanted dark brownish color formation in pomegranate juice.     

Changes of phenolic compounds and antioxidant capacity in cocoa beans processing

A number of studies have shown that the consumption of cocoa and chocolate products has positive health effects on humans. The object of this research was to monitor changes of total and individual phenolics and antioxidant capacity during the cocoa bean manufacturing. The loss of cocoa phenolics and their antioxidant activity vary with the degree of technological process. The process of roasting and cocoa nib alkalisation had the major influence on phenolic compounds as well as on antioxidant capacity. The roasting treatment resulted in 14% loss of the total phenolics content, while alkalisation resulted in 64% loss of total phenolics content. Procyanidins B1 and B2 as well as (?)‐epigallocatechin were the unstable components, while caffeic acid derivate showed the greatest stability in all technological process. Furthermore, PCA showed that phenolic contents, antioxidant capacity and non‐fat cocoa solids parts of the samples were classified in groups according technological conditions.     

The effect of some processing variables on non-coloured phenolic compounds in port wines

The non-coloured phenolic fraction of fortified port wines was studied. Trials using several mash-extraction techniques which may be used during port wine making were evaluated for their effectiveness by measuring qualitative and quantitative differences in phenolics. Total phenolic compounds measured by spectrophotometry and HPLC analysis were compared, and the greater values obtained using spectrophotometry are attributable to the contribution of anthocyanins and non-phenolic UV-absorbing compounds. Quantitative and qualitative differences in composition were observed depending on the extraction mode. The greatest total phenolic content was found in port wine made by traditional foot treading, while early addition of extra alcohol to the mash had a neutral or negative effect on the yield of phenolic compounds.     

The effect of some processing variables on non-coloured phenolic compounds in port wines

 The non-coloured phenolic fraction of fortified port wines was studied. Trials using several mash-extraction techniques which may be used during port wine making were evaluated for their effectiveness by measuring qualitative and quantitative differences in phenolics. Total phenolic compounds measured by spectrophotometry and HPLC analysis were compared, and the greater values obtained using spectrophotometry are attributable to the contribution of anthocyanins and non-phenolic UV-absorbing compounds. Quantitative and qualitative differences in composition were observed depending on the extraction mode. The greatest total phenolic content was found in port wine made by traditional foot treading, while early addition of extra alcohol to the mash had a neutral or negative effect on the yield of phenolic compounds. Received: 20 March 1997     

Oxidative stabilization of cold‐pressed sunflower oil using phenolic compounds of the same seeds

It is known that sunflower seeds are rich in phenols, constituting approximately 1–3 g per 100 g of seeds. The principal phenol is chlorogenic acid (CGA), followed by caffeic acid (CA) and lower quantities of several other compounds. On the contrary, it is known that phenols are present only in trace amounts in cold‐pressed sunflower seed oils. In this study, the possibility of improving the oxidative stability of cold‐pressed sunflower oil is evaluated using phenolic substances constitutive of seeds. Phenols, extracted from two different dehulled sunflower seed samples, were identified, measured and added to a cold‐pressed sunflower oil and compared with butylated hydroxyanisole (BHA), pure CGA and pure CA. Raw phenolic extract (RPE) was composed of CGA exclusively, whereas CA was present only in traces in its free form was not present. On the contrary, hydrolysable phenol acids (HPAs) were constituted prevalently from CA, released by CGA alkaline hydrolysis. The stabilization effect on oil oxidation at 110 °C was evaluated as 41% and 118% for RPE and HPAs respectively with respect to the control. At 30 °C, no significant differences were recorded between the two seed extracts. Their antioxidant effect was lower than that at 110 °C and evaluated to be, on average 13%. In comparison with BHA, at 30 °C, both seed extracts were more effective than this synthetic phenol; at 110 °C, the antioxidant effect of RPE and BHA was similar, whereas HPA was significantly more effective than BHA. In conclusion, this study demonstrates that the phenols present in sunflower seeds can be considered natural antioxidants suitable for stabilizing the oxidation of cold‐pressed sunflower oil, at both low and high temperatures. Copyright © 2003 Society of Chemical Industry     

Alterations of phenolic compounds in red raspberry juice induced by high-hydrostatic-pressure and high-temperature short-time processing

Most studies on health-promoting attributes of red raspberries have been conducted using extracts or freeze-dried powders instead of commercially processed products. This work aimed to trace the alterations of phenolic compounds in HHP- and HTST-treated juices. In total, 151 phenolic compounds were identified: 13 and 26 differential phenolics were discriminated in HHP- and HTST-treated juices, respectively. The alterations of phenolic compounds could be related to the increased oxidative stress derived from the indirect oxidation and thermal degradation. HTST processing promoted the release of free phenolic acids from their conjugated forms, while HHP processing could maximize the flavonol glycosides. Furthermore, morin was observed with a 7400-fold increase in HTST-treated juice, indicating the potential use for juice authenticity. Generally, HHP processing showed less impact on phenolic profiles in comparison with HTST processing. These findings provide novel insights into the impacts of sterilization processes on phenolic compounds in red raspberries.     

Comparison of aromatic and phenolic compounds in cherry wines with different cherry cultivars by HS‐SPME‐GC‐MS and HPLC

To compare the influence of cultivars on the production of aroma compounds and polyphenols, eight cherry varieties (six sweet and two sour) were fermented into cherry wines, and their compositions were analysed. Results showed that by headspace solid microextraction coupled to gas chromatography–mass spectrometry (HS‐SPME‐GC‐MS), a total of twenty‐first aromatic compounds, mostly consisting of esters, acids, terpenoids and C₁₃‐norisoprenoids, were identified, and eleven polyphenols including five anthocyanins and six phenolic acids were quantified using HPLC. May Duck and Early Richmond wines contained significantly higher levels of phenolic acids (>42 mg L^?1) that were associated with high contents of chlorogenic and neochlorogenic acids and also relatively high amounts of octanoic acid and β‐damascenone (odour activity values ≥1000). Hongdeng, Zhifuhong and Bing wines were characterised by higher concentrations of anthocyanins (>41 mg L^?1) and also relatively higher levels of isopentyl acetate. Lapins and Governer Wcod wines were distinguished by lower concentrations of polyphenols and relatively higher contents of ethyl 3‐methylbutanoate.     

The influence of various phenolic compounds on scavenging activity assessed by an enzymatic method

The effect of pure monomeric and dimeric procyanidins on superoxide anion radicals (O₂°⁻) was studied with an enzymatic method and their IC₅₀ was determined. A comparative study of the results suggested that the antiradical potential of these phenolic compounds closely depends on their stereochemical structure. Modification of the chiral carbon, C₃ involved in the oxidation mechanism induces differences in the scavenging action of (+)‐catechin (2R : 3S) or (−)‐epicatechin (2R : 3R). The stereochemical conformation of the interflavan linkage (axial or pseudo) according to the chemical nature of dimeric procyanidin units also influences the radical oxidation mechanism. The nature of the interflavan linkage between the two units in dimeric procyanidins (C₄–C₈ or C₄–C₆ linkage) is an important factor responsible for effectiveness of the behaviour polyphenols towards O₂°⁻. The extraction of oligomeric procyanidins in grape seeds enabled us to study the effect of polymerisation and galloylation on their scavenging activities. The results clearly showed that the molecular scavenging mechanism of these molecules is closely connected with their spatial conformation. © 1999 Society of Chemical Industry     

Multivariate analysis for the safety assessment of genetically modified rices in the anti‐nutrients and phenolic compounds

A safety assessment of genetically modified (GM) rice Agb0102 (resveratrol synthesis) and Agb0103 (drought‐tolerant) were conducted by comparing with their non‐GM comparators. Phytic acid, trypsin inhibitors and phenolic acids of the rices were analysed to identify the biological equivalences and the impacts of the environment. The analytical tools were principal component analysis (PCA), Pearson's correlation analysis and hierarchical clustering analysis (HCA). The PCA results of phytic acid and trypsin inhibitors revealed no clear separation among rices due to breeding conditions, environmental conditions or among various cultivars. The total, bound, free and ester forms of phenolic acids were not separated in the environmental conditions and different cultivars. The HCA analysis showed strong relationship between GM rice and non‐GM rice. The concentrations of anti‐nutrient and phenolic compounds of the GM rices were not different from those of non‐GM comparators and that various chemometric tools were useful to describe the separation of GM and non‐GM groups.     

In vitro inhibition of α‐chymotryptic activity by phenolic compounds

α‐Chymotrypsin was modified by covalent attachment of selected phenolic and related compounds (caffeic acid, chlorogenic acid, ferulic acid, gallic acid, quinic acid, m‐/o‐/p‐dihydroxybenzene and p‐benzoquinone) at pH 9. The derivatives formed were characterised in terms of their activity and selected physicochemical properties. In vitro experiments showed that the proteolytic digestion of food proteins with α‐chymotrypsin derivatives was adversely affected. This decrease depended on the reactivity of the phenolic and related substances tested as well as on the kind of substrate applied. The derivatisation was accompanied by a reduction in the amount of free lysine and tryptophan residues. Moreover, the solubility of the derivatives decreased over a broad pH range, with a parallel increase in the hydrophobicity. The isoelectric point was shifted to a lower pH value, and formation of high‐molecular‐weight fractions was documented by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE). © 2001 Society of Chemical Industry     

Biological evaluation and quantitative analysis of antioxidant compounds in pulps of the Amazonian fruits bacuri (Platonia insignis Mart.), ingá (Inga edulis Mart.), and uchi (Sacoglottis uchi Huber) by UHPLC‐ESI‐MS/MS

Bacuri, ingá, and uchi are Amazon fruits consumed specially in the North region of Brazil. Due to their large consumption and the lack of knowledge regarding its chemical composition, these fruits were studied in relation to their Antioxidant chemical constitution. The total phenolic content ranged from 3.86 ± 0.47 to 33.38 ± 1.51 mg GAE/100 g, and the total flavonoid content ranged from 1.75 ± 0.22 to 19.44 ± 0.87 mg QUERE/100 g, where the contents showed a significant correlation with DPPH and ABTS antioxidant assays. Thus, UHPLC‐MS/MS was applied do quantify selected compounds, been citric acid the most abundant for all fruits. Furthermore, samples were screened for their α‐glycosidase and lipase inhibitory effects, in addition to their antimicrobial potentials. Bacuri showed the highest antioxidant and α‐glycosidase inhibitory capacity (IC₅₀ 15.20 μg/mL), whereas uchi and its main metabolite bergenin displayed moderate antimicrobial activities. The results shed light into the potentials of Amazonian fruit sources.

Practical applications

Plant phenolics are essential components of functional foods, due to their antioxidant and enzyme inhibition activities, which are directly linked to several diseases prevention. This is the first study about the quantification of antioxidant compounds in the Amazonian fruits: bacuri, ingá, and uchi. Although they are quite consumed in the North region of Brazil, there are no bio‐products made from them. This study aimed to elucidate the knowledge about the chemical composition and potentialities within these fruits with the practical purpose of highlighting them to future commercial applications. In addition, once we indicate their capabilities, we contribute with local populations in respect to the production of such fruits, which still is a family activity.     

Total phenolic compounds and antioxidant capacity of wheat graded flours by polishing method

The graded flour fractions, which were milled from whole wheat grain from outer to inner parts without removal of germ and bran, are rich in dietary fibers and minerals, the sources of nutrition for human beings. In this study, the whole waxy wheat was milled into five fractions using the gradual milling method and the phenolic contents and antioxidant capacity of these flours were investigated. The total phenolic and flavonoid contents of free and bound phenolic extracts gradually increased in the order from the inner to the outer fractions. The flours milled from the outer parts of grain contained significantly higher amount of phenolics and exhibited significantly higher antioxidant capacity than did the whole grain. Likewise, the inner flour fractions milled from mostly endosperm part had significantly higher amount of phenolics and exhibited significantly higher antioxidant capacity than did the white flour, which was milled by a conventional milling method. Thus, the graded flours from whole waxy wheat should be encouraged to be used for processing whole-grain foods to improve both qualities of end-use products and health benefits.