Retention of aroma compounds by β-lactoglobulin in different conditions

This contribution to the study of the retention and the release of aroma compounds was conducted on model systems in the presence or absence of β-lactoglobulin. To know the interactions between the aroma compounds and this protein we studied the hydration of the protein and the effect of water activity on the sorption of the volatiles. It has been shown that water is necessary in the formation of aroma–protein interactions. The presence of β-lactoglobulin in aqueous solution increased the retention of the four aroma compounds considered. They modify the flux at the interface air–aqueous solution. These results could be applied in the technology of foods such as emulsions which could be stabilized with proteins, and particularly in dairy products which are generally flavored.     

Contribution of dynamic headspace GC–MS analysis of aroma compounds to authenticity testing of honey

The volatile profiles of 43 authentic honey samples of different botanical and geographical origins were obtained by means of gas chromatography–mass spectrometry. A qualitative analysis of the volatile compounds identified was performed in order to assess the marker compounds (if/when existing) for both botanical and geographical origin. The results seem to indicate the existence of certain marker compounds for the floral origins assessed (e.g. acacia, chestnut, eucalyptus, heather, lavender, lime, rape, rosemary and sunflower). Also such compounds for two geographical origins (e.g. Denmark and England) seem to exist and possible marker compounds could also be found for the honeys from The Netherlands, Spain and Portugal.     

By-products of plant food processing as a source of functional compounds — recent developments

There is a rapidly growing body of literature covering the role of plant secondary metabolites in food and their potential effects on human health. Furthermore, consumers are increasingly aware of diet related health problems, therefore demanding natural ingredients which are expected to be safe and health-promoting. By-products of plant food processing represent a major disposal problem for the industry concerned, but they are also promising sources of compounds which may be used because of their favourable technological or nutritional properties. The purpose of this review is to highlight the potential of selected by-products as a source of functional compounds.     

Ultrahigh pressure extraction of bioactive compounds from plants—A review

Extraction of bioactive compounds from plants is one of the most important research areas for pharmaceutical and food industries. Conventional extraction techniques are usually associated with longer extraction times, lower yields, more organic solvent consumption, and poor extraction efficiency. A novel extraction technique, ultrahigh pressure extraction, has been developed for the extraction of bioactive compounds from plants, in order to shorten the extraction time, decrease the solvent consumption, increase the extraction yields, and enhance the quality of extracts. The mild processing temperature of ultrahigh pressure extraction may lead to an enhanced extraction of thermolabile bioactive ingredients. A critical review is conducted to introduce the different aspects of ultrahigh pressure extraction of plants bioactive compounds, including principles and mechanisms, the important parameters influencing its performance, comparison of ultrahigh pressure extraction with other extraction techniques, advantages, and disadvantages. The future opportunities of ultrahigh pressure extraction are also discussed.     

Role of sepiolite in the release of active compounds from gelatin–egg white films

Nanosized material fillers are widely used to enhance certain properties of polymers. Moreover, the use of nanoclays as a delivery host in pharmaceutical fields has gained a great interest. Sepiolite was incorporated to gelatin–egg white films containing clove essential oil. The effect of the incorporation of both sepiolite and clove essential oil on the physical properties of the resultant films was evaluated. Special attention was given to the role of this nanoclay in the release of antioxidant and antimicrobial compounds from the film matrix. Sepiolite showed a reinforcement effect of Young’s modulus and tensile strength, meanwhile the clove essential oil had a certain plasticizing effect by increasing the elongation at break and water vapour permeability (WVP). When both compounds were added together, a noticeable loss of mechanical properties was observed, related to the loss of gelling capacity (G′), protein self-aggregation and α-helix structure decrease (FTIR). However, the WPV increased, probably due to the presence of cavities in the matrix observed by SEM. The incorporation of sepiolite in these films containing clove essential oil increased the release of both protein components and eugenol from the film matrix, leading to a controlled release of the antioxidant activity measured by ferric reducing ability and radical scavenging capacity, as well as a higher antimicrobial effect.     

Effect of γ-irradiaton on the volatile compounds of licorice (Glycyrrhiza uralensis Fischer)

The volatile compounds of non-irradiated and 1, 3, 5, 10 and 20 kGy γ-irradiated roots of licorice (Glycyrrhiza uralensis Fischer) were isolated by simultaneous distillation–extraction (SDE) technique and analyzed by gas chromatography-mass spectrometry (GC-MS). A total of 61 volatile compounds belonging to the chemical classes of acid (2), alcohol (16), aldehyde (8), ester (6), furan (2), hydrocarbon (14), ketone (10) and N-containing compounds (3) were identified in non-irradiated licorice. The prime volatile compound of licorice was 2-ethoxy-1-propanol, which makes up to 22.82% of the total composition. Over a dose of 1 kGy, another compound, benzaldehyde appeared, whereas other compounds, 3,5-dimethyl octane and phenethyl alcohol, disappeared at the dose of 20 kGy. Though the content of several volatile compounds increased after γ-irradiation, the content of major volatile compounds such as 4-terpineol, myrtenal, tetramethylpyrazine, hexanoic acid, azulene and p-cymene decreased. In comparison to non-irradiated licorice, 10 kGy dose of irradiation induced the maximum level of total yield of volatile compounds by 12%, but slightly decreased at 20 kGy. Therefore, the application of γ-irradiation is feasible without major qualitative and quantitative loss of volatile compounds when exposed at 10 kGy.     

Bioactive compounds and health benefits of exotic tropical red–black berries

Tropical countries produce a large amount of native and exotic fruit species which are potentially interested in the food industry. The nutritional and therapeutic values in this fruits are mainly due to the presence of bioactive compounds, especially polyphenols. The anthocyanins belong to the flavonoid family and represent a group of pigments responsible for most of the colors in fruits, leaves, flowers, stems and roots of plants. Several investigations have focused on the health benefits of consumption of red–black fruit, claiming these as natural sources of bioactive compounds with highly promising antioxidant and anti-inflammatory characteristics. Furthermore, the consumption of red–black berries brings a positive impact on several chronic conditions, such as obesity, diabetes, cancer, cardiovascular and neurodegenerative diseases. This article summarizes the foremost bioactive compounds and the health properties of exotic tropical red–black berries, specifically Euterpe oleracea, Eugenia uniflora, Myrciaria cauliflora, Myrciaria dubia, Syzygium cumini.     

Extraction of phenolic compounds from grapes and their pomace using β-cyclodextrin

Use of aqueous cyclodextrins (CD) for recovery of selected bioactive phenolic compounds from grapes and their pomace was evaluated. When α, β and γ forms of CD were compared, β-CD was the most effective in recovering stilbenes, flavonols, and flavan-3-ols from grape pomace. The maximum quantified phenolics were obtained from the powder and the slurry of grape pomace when extracted with 2.5% (w/v) aqueous β-CD solutions at 60 °C for 12–24 h. With β-CD, total quantified phenolics obtained from the dry powder were 123 mg/100 g (DW) while from the slurry, they were 35.8 mg/100 g (FW). Incorporation of β-CD to grape mash prior to pressing for juice enhanced the recovery of phenolics in juice. Incorporation of β-CD was more effective in recovering flavan-3-ols than flavonols. Aqueous CD can effectively be used in recovering phenolics from by-products of fruit processing and therefore for functional foods and nutraceutical applications.     

Discrimination of teas with different degrees of fermentation by SPME–GC analysis of the characteristic volatile flavour compounds

As tea is traded all over the world, it is necessary for both customs officers and business investigators to develop an easy and reliable method to discriminate teas from each other. A total of 56 kinds of various green, Oolong, and black teas were collected from different countries and markets, and their catechin contents and volatile flavour compounds (VFC) were compared by analyses, using HPLC and solid-phase microextraction–gas chromatograph (SPME–GC). It was found that neither total catechin nor individual catechin contents in green and Oolong teas were significantly different among the samples investigated, but the fermentation processes altered the profiles of tea VFC. Because many of the individual VFC did not change in response to the fermentation levels, several VFC in combination might be more reliable than a single compound to identify broader ranges of teas. A total concentration of five VFC, trans-2-hexenal, benzaldehyde, methyl-5-hepten-2-one, methyl salicylate, and indole, was shown to be able to discriminate clearly unfermented and fermented teas, while that of trans-2-hexenal and methyl salicylate together supplied an index to differentiate semi- and fully-fermented teas. In addition, the SPME–GC analysis was also able to distinguish real jasmine teas from fake jasmine teas based on the disappearance of some grassy/green odorants.     

Formation of discrete molecular size domains of melanoidins depending on the involvement of several α-dicarbonyl compounds: Part 2

The correlation of several α-dicarbonyl compounds with the melanoidin formation and their molecular size distribution was investigated. The results point out that α-dicarbonyl compounds, which were formed during the Maillard reaction, are not only the most important intermediates but also the direct precursors for carbohydrate-based melanoidins. Discrete molecular size domains are detected by size exclusion chromatography (SEC-DAD/RI), which were formed depending on the involvement of several α-dicarbonyls by thermal treatment of sucrose Maillard reaction solutions. By investigating sucrose Maillard reaction solutions spiked with methylglyoxal and 3-deoxyhexosulose carried on with direct melanoidin formation in aqueous solutions with α-dicarbonyls, molecular size domains of melanoidins could be connected for the first time with the reaction of several involved α-dicarbonyl compounds. High molecular size domains formed on the basis of methylglyoxal, whereas 3-deoxyhexosulose and d-glucosone promote lower molecular size domains. Concerning colour measurement methylglyoxal shows the highest browning activity followed by 3-deoxyhexosulose and d-glucosone. The reactivity of α-dicarbonyls and a correlated colour formation increase with rising alkaline pH-value. At a pH 5 the degradation and colour formation of α-dicarbonyl compounds is suppressed. The results provide new knowledge about colour formation in sucrose solutions. First part with the title, “Influence of α-dicarbonyl compounds to the molecular weight distribution of melanoidins in sucrose solutions: Part 1” was accepted in EFRT in January 2006. DOI: 10.1007/s00217-006-0277-1.     

Analysis of volatile compounds by GC–MS of a dry fermented sausage: chorizo de Pamplona

The profile of volatile compounds of a typical Spanish dry fermented sausage, chorizo de Pamplona, has been analyzed by GC–MS, using a simultaneous distillation-extraction (SDE) system. Qualitative and quantitative differences were found in the volatile profiles obtained in the five analyzed commercial brands. One hundred and ninety-three different substances were isolated, the group of acids being the most important from a quantitative point of view in all brands, accounting at least for the 60% of the total area. Aldehydes, basically from lipid oxidation, contributed between 7.72 and 13.97% to the total amount. Acids and aldehydes were the chemical families that showed the lowest variability among brands. In contrast, esters showed the highest coefficient of variation among brands (111%), followed by phenols (82%) and terpenes (76%). The variability observed in these three families could be attributed respectively to the different starter cultures, smoking process and spices employed in their production. Butylated hydroxytoluene (added as an antioxidant, E-321) was the third most abundant compound in three of the five brands.     

Iron binding characteristics of phenolic compounds: some tentative structure–activity relations

Two mechanisms are commonly proposed to explain the antioxidant role of phenolic compounds; these are metal chelation and/or free radical scavenging. However, the structural requirements for each may not be the same. This paper describes the determination of iron-binding efficiencies (in vitro) for a series of pure phenolics of known structure [gallic acid, tannic acid, catechin, epicatechin (EC), epicatechingallate (ECG), epigallocatechin (EGC), epigallocatechingallate (EGCG) and quercetin] and of tea beverages of known flavonoid composition. Iron-binding efficiency was measured as catechin equivalents or tannic acid equivalents using the two wavelength assay. High catechin equivalents require the presence of a 3′,4′ dihydroxy (catechol ) group on flavanoid ring B. In contrast, the presence of a 3′,4′,5′-trihydroxy (galloyl) group of ring B (epigallocatechin) or ring C (epicatechin gallate) was associated with reduced Fe-binding. The extent of Fe-binding was also found to be lower for quercetin than catechin, which is probably due to the presence of conjugation extending from the C4-keto group, via C2-3 to the 3′-OH group (rings B and C). For the polyphenols examined, catechin equivalents were inversely correlated with tannic acid equivalents and with antioxidant activity of flavonoids, as measured by the TEAC assay. Requirements for efficient iron-binding are discussed.     

Volatile compounds of the Hallabong (Citrus kiyomi × Citrus ponkan) blossom

The objective of this study was to identify and compare the volatile compounds of liquid essential oils and volatiles of headspace-solid phase microextraction (HSSPME) of the hallabong blossom. SPME is a sampling technique based on sorption of analytes into a polymeric material that coats a silica fiber. Two different fiber coatings tested to evaluate the extraction efficiencies of volatiles. The hallabong blossom exhibited 5 major volatile compounds: linalool (28.89–43.24%), limonene (0.39–23.06%), β-myrcene (0.38–16.67%), sabinene (1.37–11.42%), and 4-terpineol (1.26–6.12%). The amounts of identified compounds in the hallabong blossom were more abundant in carboxen/polydimethylsiloxane (CAR/PDMS) fiber than in PDMS fiber.     

Production of volatile compounds by Lactobacillus sakei from branched chain α-keto acids

Lactobacillus sakei belongs to the main flora of raw fermented sausages and is used as starter culture. Bacterial starter cultures can convert amino acids to α-keto acids by aminotransferases. These α-keto acids are the precursors of aroma active aldehydes, alcohols and carboxylic acids. In this study the formation of aldehydes, alcohols and carboxylic acids from leucine, isoleucine, valine and the corresponding α-keto acids are analysed in model fermentations with two different strains of L sakei. In the absence and upon addition of leucine, isoleucine and valine they produced 1 μg/ml 3-methylbutanoic, 0.2 μg/ml 2-methylbutanoic acid and 3 μg/ml 2-methylpropanoic acid, respectively. Upon addition of α-ketoisocaproic acid, α-keto-3-methyl-pentanoic acid or α-ketoisovaleric acid the amount of the corresponding carboxylic acid was increased to 40 μg/ml 3-methylbutanoic acid, 20 μg/ml 2-methylbutanoic acid and 35 μg/ml 2-methylpropanoic acid. The response patterns of the strains and amounts of carboxylic acids produced were similar. This behaviour was typical when compared with other strains of L. sakei and suggests general lack of transaminase activity and a limit in the transport of branched chain amino acids and their conversion to volatiles, some of which can contribute to the aroma of fermented sausages.     

Sucuk and pastırma: Microbiological changes and formation of volatile compounds

There is an increasing interest in traditional foods in Turkey like other countries. Sucuk, dry-fermented sausage, and past?rma, a type of dry-cured meat product, are traditional Turkish meat products that are widely consumed. Sucuk is air-dried and neither smoked nor ripened by mold. In spite of increasing use of starter culture in production of sucuk in the industry, traditionally produced sucuk is generally preferred by the consumers because of its sensory characteristics. Past?rma is traditionally processed under natural conditions where air temperature and relative humidity depend on climate and weather conditions. Past?rma differs from other raw cured meat products made from whole pieces of meat in terms of manufacturing process, ingredients, microbial properties and flavor. In this study, microbiological changes and formation of volatile compounds in sucuk and past?rma were reviewed.     

Influence of α-dicarbonyl compounds to the molecular weight distribution of melanoidins in sucrose solutions: part 1

The correlations between formation of melanoidins and the content of α-dicarbonyl compounds and colour formation were studied in Maillard reaction model sucrose solutions at high treating temperatures (130 °C) corresponding to the industrial sucrose processing. Molecular weight distribution was determined by gel permeation chromatography (GPC) and α-dicarbonyls as high reactive intermediates of the Maillard reaction were detected by RP-HPLC and GC/MS. Referring to formation of melanoidins, new knowledge could be gained. The investigations clearly point out, that individual α-dicarbonyls are involved in formation of specific molecular weight fractions. 3-Deoxyhexosulose (3-DH) and methylglyoxal are the important α-dicarbonyl compounds in thermal-treated sucrose solutions. A low molecular weight fraction with a molecular weight range of <5,800 g/mol preferably occurs when 3-DH is formed in high concentrations. The high increase in intensity of a low molecular weight fraction is combined with a strong colour formation. In contrast to 3-DH, methylglyoxal promotes the formation of high molecular weight fractions between 6,600 g/mol and approximately 17,000 g/mol. Furthermore, model solutions with a high intensity of high molecular weight fractions show an early colour formation during the starting period of the reaction. Indeed, this early browning is not as intensive as the colour formation caused by the low molecular weight fraction during the later stage of the browning reaction. Out of this, 3-DH can be regarded as the most important intermediate for an intensive colour formation in sucrose solutions.     

Cytotoxicity of α-dicarbonyl compounds submitted to in vitro simulated digestion process

α-Dicarbonyl compounds (α-DCs), such as glyoxal, methylglyoxal and 2,3-butanedione, are highly reactive substances occurring in thermally treated and fermented foods, that may react with amino and sulphydryl groups of side chains of proteins to form Maillard reaction end products, inducing a negative impact on the digestibility and on nutritional value of protein. In recent years the role of food derived α-DCs in gastroduodenal tract is under investigation to understand whether excess consumption of such dietary compounds might be a risk for human health. In this study the interactions between a mixture of glyoxal, methylglyoxal and 2,3-butanedione and the digestive enzymes (pepsin and pancreatin) were studied. The results showed that during gastroduodenal digestion α-DCs react with digestive enzymes to produce carbonylated proteins. Moreover, undigested and digested α-DC cytotoxicity against human cells, as well as their ability to inhibit the function of human enzymes responsible for DNA repair were shown.     

Identification of active compounds from Aurantii Immatri Pericarpium attenuating brain injury in a rat model of ischemia–reperfusion

Ischemic stroke is caused by brain injury due to prolonged ischemia by occlusion of cerebral arteries. In this study, we isolated active compounds from an ethanol extract of Aurantii Immatri Pericarpium (HY5356). We first showed by DNA fragmentation assay that HY5356 improved human hepatocellular carcinoma cells (HepG2) under hypoxic conditions by inhibiting apoptosis. When HY5356 was fractionated with dichloromethane (MC), ethyl acetate (EA) and n-butanol (BU), the MC fraction improved cell viability at the lowest concentration (100 μg/ml). Intraperitoneal injection of HY5356 (200 mg/kg) or the MC fraction (200 mg/kg) to rats prior to occlusion attenuated brain injury significantly in a rat model of ischemia–reperfusion. Adopting cell viability under hypoxic conditions as an activity screening system, we isolated nobiletin and tangeretin as active compounds. The results suggest that intake of Aurantii Immatri Pericarpium containing nobiletin and tangeretin as active compounds might be beneficial for preventing ischemic stroke.     

Development of volatile compounds during the manufacture of dry-cured "lacón," a Spanish traditional meat product

Volatile compounds were determined throughout the manufacture of dry-cured "lacón," a traditional dry-salted, and ripened meat product made in the north-west of Spain from the foreleg of the pig following a similar process to that of dry-cured ham. Volatiles were extracted by a purge-and-trap method and analyzed by gas chromatographic/mass spectrometry. One hundred and two volatile compounds were identified. In raw material, only 34 volatile compounds were found and at very low levels. The number of volatile compounds increased during processing. The substances identified belonged to several chemical classes: aldehydes (23), alcohols (9), ketones (15), hydrocarbons (37), esters (4), acids (3), furans (4), sulphur compounds (1), chloride compounds (1), and other compounds (4). Results indicated that the most abundant chemical family in flavor at the end of the manufacturing process was aldehydes, followed by hydrocarbons and ketones. Lipids were the most important precursor of flavor compounds of dry-cured "lacón."