Dietmar R. Kammerer

Identification and quantification of phenolic compounds from pomegranate (Punica granatum L.) peel, mesocarp, aril and differently produced juices by HPLC-DAD–ESI/MSn

Phenolic compounds were extracted from pomegranate (Punica granatum L.) peel, mesocarp and arils. Extracts and juices were characterised by HPLC-DAD-ESI/MS(n). In total, 48 compounds were detected, among which 9 anthocyanins, 2 gallotannins, 22 ellagitannins, 2 gallagyl esters, 4 hydroxybenzoic acids, 7 hydroxycinnamic acids and 1 dihydroflavonol were identified based on their UV spectra and fragmentation patterns in collision-induced dissociation experiments. To the best of our knowledge, cyanidin-pentoside-hexoside, valoneic acid bilactone, brevifolin carboxylic acid, vanillic acid 4-glucoside and dihydrokaempferol-hexoside are reported for the first time in pomegranate fruits. Furthermore, punicalagin and pedunculagin I were isolated by preparative HPLC and used for quantification purposes. The ellagitannins were found to be the predominant phenolics in all samples investigated, among them punicalagin ranging from 11 to 20g per kilogram dry matter of mesocarp and peel as well as 4-565mg/L in the juices. The isolated compounds, extracts and juices were also assessed by the TEAC, FRAP and Folin-Ciocalteu assays revealing high correlation (R(2)=0.9995) of the TEAC and FRAP values, but also with total phenolic contents as determined by the Folin-Ciocalteu assay and by HPLC. Selection of raw materials, i.e. co-extraction of arils and peel, and pressure, respectively, markedly affected the profiles and contents of phenolics in the pomegranate juices, underlining the necessity to optimise these parameters for obtaining products with well-defined functional properties.

Influence of postharvest processing and storage on the content of phenolic acids and flavonoids in foods

The review is based on the evaluation of electronically collated data published between 2002 to June 2006. It is based on 325 references dealing with the following subclasses of phenolic compounds: hydroxycinnamic and hydroxybenzoic acids, chalcones, flavanones, flavones, flavonols, monomeric flavanols and anthocyanins. Only publications dealing directly with the effects of storage and postharvest processing on the phenolic acid and flavonoid contents of foods were considered. The expectation that the structural diversity even within each subgroup, and the number of different procedures and of different parameters would make finding homogenous tendencies unlikely, has, in most instances, been confirmed. By adding a database Excel table combined with a focused and unified evaluation, specific additional information was rendered accessible and concise. It holds true for most of the subclasses in question that the effect of storage and food processing on the polyphenol content is negligible in comparison to the differences between different varieties of plants. Variety dependence must always be considered, for all classes of compounds.

Betacyanins and phenolic compounds from Amaranthus spinosus L. and Boerhavia erecta L.

Stem bark extracts of Boerhavia erecta L. (erect spiderling) and Amaranthus spinosus L. (spiny amaranth), two wild growing weed plants used in traditional African medicine, were characterized with respect to their phenolic profile including the betalains. While the main betalains in A. spinosus were identified as amaranthine and isoamaranthine, the major betacyanins in B. erecta were betanin, isobetanin together with neobetanin. The latter showed higher betalain concentrations amounting to 186 mg/100 g, while the former contained 24 mg betacyanins in 100 g of the ground plant material. Extracts of A. spinosus were found to contain hydroxycinnamates, quercetin and kaempferol glycosides, whereas catechins, procyanidins and quercetin, kaempferol and isorhamnetin glycosides were detected in B. erecta. The amounts of these compounds ranged from 305 mg/100 g for A. spinosus to 329 mg/100 g for B. erecta.

Adsorption and Ion Exchange: Basic Principles and Their Application in Food Processing

A comprehensive overview of adsorption and ion exchange technology applied for food and nutraceutical production purposes is given in the present paper. Emanating from these fields of application, the main adsorbent and ion-exchange resin materials, their historical development, industrial production, and the main parameters characterizing these sorbents are covered. Furthermore, adsorption and ion exchange processes are detailed, also providing profound insights into kinetics, thermodynamics, and equilibrium model assumptions. In addition, the most important industrial adsorber and ion exchange processes making use of vessels and columns are summarized. Finally, an extensive overview of selected industrial applications of these technologies is provided, which is divided into general applications, food production applications, and the recovery of valuable bio- and technofunctional compounds from the byproducts of plant food processing, which may be used as natural food additives or for their potential health-beneficial effects in functional or enriched foods and nutraceuticals.

Thermal stability of anthocyanins and colourless phenolics in pomegranate (Punica granatum L.) juices and model solutions

The present study aimed at a systematic assessment of the factors influencing the anthocyanin (AC) stability and colour retention of pomegranate juices and less complex model solutions with particular focus on the effects of colourless phenolic copigments (CP). The thermal stability of ACs in three pomegranate juices obtained from isolated arils and the entire fruit with and without previous steaming, in model solutions with AC:CP ratios ranging from 1:0 to 1:4 (m/m), and in two purified extracts from pomegranate juices characterised by different phenolic profiles, respectively, was investigated upon heating at 60, 70, 80 and 90°C for 15 min to 5h. The thermal impact on the AC and CP contents, and the formation of 5-hydroxymethylfurfural (HMF) and AC degradation products were monitored using HPLC-DAD-MS(n). Total phenolic contents, antioxidant capacity and colour properties were determined spectrophotometrically. Heating at 90°C for 5h resulted in total AC losses ranging from 76% to 87% of the initial AC levels in the juices, 78% in both extracts as well as 57% and ∼78% in the model solutions, showing the best stability at an AC:CP ratio of 1:2 and in juices having the highest initial AC contents, respectively. In contrast, the AC stability was independent of total phenolic contents, and low and high molecular pomegranate matrix components (such as organic acids and sugars). Good correlation of the AC contents with red colour (a(∗)) was observed for all samples at elevated temperatures (70-90°C). The stability of putative health-promoting polyphenols of pomegranate juices was not markedly affected by the thermal treatment. Unexpectedly, the HMF contents only slightly increased upon forced heating. Therefore, the visual appearance does not adequately reflect the quality and storage stability of pomegranate juices.

The Content of Phenolic Compounds and Radical Scavenging Activity Varies with Carrot Origin and Root Color

The contents of phenolic compounds and radical scavenging activities were assessed in a carrot collection comprising 35 cultivars, landraces and breeding populations. The accessions originated from various world regions and they represented Eastern and Western carrot gene pools. In two-year field trial carrot roots of orange, red, yellow, white and purple color were cultivated, freeze-dried and analyzed for phenolic content by Folin-Ciocalteu assay and UV/Vis assay. Radical scavenging activity in the extracts was determined with a stable DPPH radical. Carrots developing purple roots possessed on average 9 times more phenolics than roots of other colors. Furthermore, they were rich in anthocyanins that caused very high antiradical activity. Red carrots showed higher antioxidant activity than orange, yellow and white carrots and in the season of lower rainfall they accumulated higher amounts of phenolic compounds. Carrots of Asian origin belonging to Eastern gene pool were more often purple or red and richer in phenolics and had higher antiradical activity than those from the Western gene pool with mainly orange roots.

Pilot-scale resin adsorption as a means to recover and fractionate apple polyphenols

The purification and fractionation of phenolic compounds from crude plant extracts using a food-grade acrylic adsorbent were studied at pilot-plant scale. A diluted apple juice concentrate served as a model phenolic solution for column adsorption and desorption trials. Phenolic concentrations were evaluated photometrically using the Folin-Ciocalteu assay and by HPLC-DAD. Recovery rates were significantly affected by increasing phenolic concentrations of the feed solutions applied to the column. In contrast, the flow rate during column loading hardly influenced adsorption efficiency, whereas the temperature and pH value were shown to be crucial parameters determining both total phenolic recovery rates and the adsorption behavior of individual polyphenols. As expected, the eluent composition had the greatest impact on the desorption characteristics of both total and individual phenolic compounds. HPLC analyses revealed significantly different elution profiles of individual polyphenols depending on lipophilicity. This technique allows fractionation of crude plant phenolic extracts, thus providing the opportunity to design the functional properties of the resulting phenolic fractions selectively, and the present study delivers valuable information with regard to the adjustment of individual process parameters.

Impact of pectin type on the storage stability of black currant (Ribes nigrum L.) anthocyanins in pectic model solutions

The effects of different pectins on the stabilisation of black currant anthocyanins in viscous model solutions at pH 3.0 were investigated. For this purpose, low esterified amidated (AM), low (LM) and high (HM) methoxylated citrus and apple pectins and a sugar beet pectin were added to a purified anthocyanin extract (ACN-E) and to an extract containing anthocyanins and non-anthocyanin phenolics (PP-E). Model systems were stored at 20±0.5°C in the dark. Anthocyanin contents were monitored by HPLC analysis over a period of 18 weeks, and half-life and destruction values were calculated. In all pectic model solutions anthocyanin stability was significantly improved compared to stability of the extracts without added pectins (blank). Best stabilisation was obtained with AM pectin, followed by LM and HM pectins. In model systems containing citrus pectins, anthocyanin stabilisation was better compared to that of apple pectins having similar degrees of esterification and amidation, respectively. This was primarily due to the strong interaction of delphinidin glycosides with the citrus pectins, whereas stabilisation of cyanidin derivatives was less important. Sugar beet pectin improved anthocyanin stability only to a limited extent. In the presence of non-anthocyanin phenolics (PP-E) the impact of the pectin source was even more pronounced than the effect of the pectin type. Addition of citrate to pectic systems accelerated anthocyanin decay. Stabilising effects of pectins were hardly noticeable when evaluating total phenolic content (TPC, Folin-Ciocalteu) and antioxidant capacity during storage. Highest TPC, TEAC- and FRAP values were observed in systems containing citrus pectin, which was in contrast to sugar beet pectin, where values fell below those of the blank after storage.

The influence of postharvest processing and storage of foodstuffs on the bioavailability of flavonoids and phenolic acids

Postharvest processing and storage not only influence the content and composition of flavonoids and phenolic acids in foodstuffs, thereby altering the amount of potentially bioavailable bioactive compounds, but can also modify their chemical form. Moreover, due to the intensive metabolism during absorption, the metabolites circulating in blood differ from the parent compounds found in food. Thus, it is difficult to predict potential in vivo effects of phenolic compounds merely by their contents in foodstuffs. Their specific bioavailability needs to be determined. This review considers studies regarding the bioavailability of flavonoids and phenolic acids from foodstuffs that meet the following criteria: providing actual concentrations of flavonoids and phenolic acids in blood plasma, body tissues, or urine, comparing differently stored or processed foods (excluding studies that use supplements or pure substances), and considering the high interindividual variability by repeated measurements in the same individuals. Only a few studies meet all of these criteria. In conclusion, processing and storage of food can have either positive or negative effects on the bioavailability of flavonoids and phenolic acids because these treatments may not only change the content, but also the chemical form of these compounds.

Heat Stability of Strawberry Anthocyanins in Model Solutions Containing Natural Copigments Extracted from Rose (Rosa damascena Mill.) Petals

Thermal degradation and color changes of purified strawberry anthocyanins in model solutions were studied upon heating at 85 degrees C by HPLC-DAD analyses and CIELCh measurements, respectively. The anthocyanin half-life values increased significantly due to the addition of rose (Rosa damascena Mill.) petal extracts enriched in natural copigments. Correspondingly, the color stability increased as the total color difference values were smaller for anthocyanins upon copigment addition, especially after extended heating. Furthermore, the stabilizing effect of rose petal polyphenols was compared with that of well-known copigments such as isolated kaempferol, quercetin, and sinapic acid. The purified rose petal extract was found to be a most effective anthocyanin-stabilizing agent at a molar pigment/copigment ratio of 1:2. The results obtained demonstrate that the addition of rose petal polyphenols slows the thermal degradation of strawberry anthocyanins, thus resulting in improved color retention without affecting the gustatory quality of the product.