H. De Pooter

Production of flavours by microorganisms

Abstract Flavours and fragrances are extremely important for the food, feed, cosmetic, chemical and pharmaceutical industries. Most available flavour compounds are now produced via chemical synthesis or extraction. Drawbacks of such chemical processes are the formation of undesirable racemic mixtures and the growing aversion of the consumer towards chemicals added to his food, cosmetics and other household products. This has caused flavour companies to direct their attention towards flavour compounds of biological origin, so called natural- or bio-flavours. Up to now, plants were also an important source of essential oils and flavours: however, active components are often present in minor quantities or in bound form or are only found in exotic plants, making isolation difficult and the flavour products expensive. Apart from plant cell and tissue culture techniques (which still need further development) a directly viable alternative route for flavour synthesis is based on microbial processes, i.e. fermentation (=de novo) and bioconversion of appropriate precursor-compounds. This review presents the current state of the art of bioflavour-synthesis, based on microorganisms (bacteria, fungi, yeasts) and their enzymes, with emphasis on currently commercialised processes. It also comments on regulatory aspects of biotechnological production of aroma-compounds. A comprehensive referenced literature survey of de novo fermentation and of bioconversion processes for flavour-compound synthesis concludes this review.

High-performance liquid chromatographic separation of naturally occurring esters of phenolic acids

Abstract High-performance liquid chromatographic (HPLC) data of cinnamic and benzoic acid derived phenols, esterified with quinic acid at the C (5) hydroxyl, and with glucose at the C (1) hydroxyl (β anomeric form), are presented for the first time. These naturally occurring compounds have been obtained synthetically. They are chromatographed on reversed-phase and on diol HPLC systems. The four chlorogenic acid isomers are also chromatographed on these columns.

Gas chromatographic separation and analysis of trimethylsilyl derivatives of some naturally occurring non-volatile phenolic compounds and related substances

Abstract The gas-liquid chromatographic (GLC) separation of a group of naturally occurring phenolic compounds embracing benzaldehyde, benzoic acid, cinnamaldehyde, cinnamic acid, coumarin, flavone and isoflavone and/or derivatives has been studied. By using N,N-bis(trimethylsilyl)trifluoroacetamide as a silylating agent, a glass column packed with Chromosorb W AW DMCS (80–100 mesh) coated with 1.5% SE-30 + 1.5% SE-52 and a temperature program about thirty-six of the above substances could be separated in a single run. Using preparative GLC, together with a new collecting device, it was found that the yield of trimethylsilyl (TMS) 14C-labelled p-coumaric or ferulic acid was 81 to 85%. After hydrolysis of the collected radioactive TMS compounds it was further shown, via thin-layer chromatography and autoradiography, that only labelled p-coumaric or ferulic acid were present, indicating that little decomposition had occurred during GLC. In addition, ultraviolet, infrared, proton magnetic resonance and mass spectrometry were employed for studying the structures and conditions of the collected TMS derivatives from kaempferol, pyrocatechol and a series of phenolic acids. All the above analyses confirmed that the compounds were not appreciably altered during GLC. It is further suggested that preliminary multiple elimination thin-layer chromatographic separation and purification of eventually unknown phenolic substances from plant extracts, in combination with the described GLC technique and the employed physical methods, will be of great value for quantitative analysis and structure determination.

Composition and variability of the branched-chain fatty acid fraction in the milk of goats and cows

Branched-chain fatty acids of the milk fat of goats were analyzed by high resolution gas chromatography-mass spectrometry. Iso- and anteiso-acids predominated, but a range of other monomethyl-branched components, mostly with methyl-substitution on carbons 4 and 6, was present. Analysis of the milk fat of cows revealed the presence of iso- and anteiso-fatty acid; other mono-methyl-substituted fatty acids, as found in the milk fat of the goat, were virtually absent. Only a trace amount of 6-methylhexadecanoate was detected. The difference between goats and cows in the effectiveness with which these animals metabolize propionyl-CoA and methylmalonyl-CoA is discussed.

N-feruloylglycyl-l-phenylalanine: A sequence in barley proteins

Abstract N -Feruloylglycyl- l -phenylalanine was obtained from barley globulins by partial hydrolysis with 4 N HCl. It was isolated by means of preparative and ‘multiple elimination’ TLC (METC) and further identified by TLC comparison with a synthetic sample. Additional proof for its identity was obtained by UV, fluorescence and IR spectroscopy and by the action of carboxypeptidase A. The possible role of N -feruloylglycine as a starter in protein biosynthesis in the barley seed is discussed.

The Essential Oils of Tanacetum vulgare L. and Tanacetum parthenium (L.) Schultz-Bip

Abstract The volatile fraction of T. parthenium is characterized by a high camphor (44%) and trans-chrysanthenyl acetate (23%) content. T. vulgare oils, obtained from specimens growing in the province of Eastern Flanders (Belgium), conformed to the infra-specific chemical variability; three chemical types were identified: i.e., the β-thujone, trans-chrysanthenyl acetate and camphor/β-thujone types. A small scale experiment confirmed the mosquito-repellent activity of T. vulgare, without allowing the identification of the active principle. However, the activity was much lower than that of diethyltoluamide containing commercial preparation.

Composition and Antimicrobial Activity of Otostegia fruticosa Forssk. Oil

ABSTRACT The hydrodistilled essential oil of fresh aerial parts of cultivated Otostegia fruticosa Forssk. was analyzed by GC/MS. Thirty-six compounds representing 98.8% of the oil were identified. The main components of the oil were thymol (43.7%), γ-terpinene (16.4%) and p-cymene (12.4%). The oil exhibited significant antimicrobial activity against Gram-positive and Gram-negative bacteria as well as fungal species.

Essential oils of Otacanthus

Abstract The taxa of Otacanthus were found to contain between 0.007 and 0.2% of essential oils, that consist of monoterpenoids and sesquiterpenoids. Their composition provided additional data for classification, especially of intermediate taxa that are difficult to classify on purely morphological grounds. Ten taxa of Otacanthus were found to contain essential oils ranging from 0.007 to 0.2% of fresh weight, that consisted of monoterpenoids and sesquiterpenoids. Their composition was submitted to principal component analysis and cluster analysis. This provided additional data for the classification of the taxa, especially for the position of intermediate taxa that are difficult to classify on purely morphological grounds.

Volatile Fractions of Chamaecyparis lawsoniana (A. Murray) Parl, and Chamaecyparis pisifera (Sieb. et Zucc.) Endl. var. filifera. Identification of Oplopanonyl Acetate

ABSTRACT The volatile fractions of Chamaecyparis lawsoniana and C. pisifera, although qualitatively analogous and fairly rich in lLnon jne, were differentiated from each other by the absence of δ-3-carene and bornyl acetate in the former, and a moderate δ-3-carene and bornyl acetate content in the latter. Both contained appreciable amounts of the acetate of the relatively rare sesquiterpenoid oplopanone, and the diterpene hybaene, both of which were identified by1 H-,13 C-NMR and mass spectrometry. No character impact compound could be identified in the oils.

Otacanthus Species: In Vitro Culture, Plant Propagation, and the Production of Essential Oil

The genus Otacanthus (family Scrophulariaceae) comprises six species that are distributed in east Brazil. They are half-shrubs with stems lignified at the basis, and opposite, lanceolate to obovate leaves; the inflorescence is a terminal spike of solitary flowers with a green calyx and blue to purple, bilabiate corolla with a white spot on the lower lip. All species possess ornamental value due to their showy flowers that last for several weeks, especially Otacanthus coeruleus Lind., which has the largest flowers (Fig. 1). This species originates from east Brazil, in the states Rio de Janeiro and Espirito Santo, where it is sometimes called incenso, which means incense. It is also found cultivated or naturalized in north Brazil and on the Mascarenes and Seychelles (Ronse 1993). It was cultivated as an ornamental in Belgium and France during the last century (Van Houtte 1862), and is now again being cultivated as a pot plant in several countries. It has also potential as a cut flower crop (Geertsen 1990).