Georges Lognay

Enrichment of anhydrous milk fat in polyunsaturated fatty acid residues from linseed and rapeseed oils through enzymatic interesterification

Lipozyme TL IM was used in a solvent-free batch and microaqueous system for enzymatic interesterification of anhydrous milkfat (AMF) with linseed oil (LO) in binary blends and with rapeseed oil (RO) in one ternary blend. The aim was to obtain and characterize physicochemically fats enriched with unsaturated C 18 fatty acids (oleic, linoleic, and, especially, linolenic acids) from natural vegetable oils. Binary blends of AMF/LO 100/0, 90/10, 80/20, 70/30, and 60/40 (w/w) were interesterified. The change in triacylglycerol (TAG) profiles showed that quasi-equilibrium conditions were reached after 4-6 h of reaction. Free fatty acid contents <1%. The decrease in solid fat content and in dropping point temperature obtained with increasing content of LO and interesterification resulted in good plastic properties for the products originating from the blends 70/30 and 60/40. This was confirmed by textural measurements. Melting profiles determined by differential scanning calorimetry showed complete disappearance of low-melting TAGs from LO and the formation of intermediary species with a lower melting temperature. Oxidative stability of the interesterified products was diminished with increasing LO content, resulting in low oxidation induction times. A ternary blend composed of AMF/RO/LO 70/20/10 gave satisfactory rheological and oxidative properties, fulfilling the requirements for a marketable spread and, moreover, offering increased potential health benefits due to the enriched content in polyunsaturated fatty acid residues.

Emission of alarm pheromone by non-preyed aphid colonies

The sesquiterpene (E)‐β‐farnesene (Eβf) is the primary component of the alarm pheromone of most aphid species. It is released in response to physical stress including attack by natural enemies and causes aphids to cease feeding and disperse. Eβf also acts as a kairomonal cue for aphid natural enemies. In this study, we collected the headspace volatiles released by aphid colonies of different sizes. Gas chromatography‐mass spectrometry analysis demonstrated the presence of Eβf in the absence of predator attack. A quadratic relationship was found between the released (E)‐β‐farnesene amounts and aphid colony size. Behavioural impact of aphid alarm pheromone towards Episyrphus balteatus female oviposition behaviour was also demonstrated in this work. These results highlight the primary role of the small but continuous release of aphid alarm pheromone in mechanisms of decision‐making by aphid predators during their foraging and egg‐laying behaviour.

Solid-state fermentation of xylanase from Penicillium canescens 10-10c in a multi-layer-packed bed reactor.

Xylanase is produced by Penicillium canescens 10–10c from soya oil cake in static conditions using solid-state fermentation. The impact of several parameters such as the nature and the size of inoculum, bed-loading, and aeration is evaluated during the fermentation process. Mycelial inoculum gives more production than conidial inoculum. Increasing the quantity of inoculum enhances slightly xylanase production. Forced aeration induces more sporulation of strain and reduces xylanase production. However, forced moistened air improves the production compared to production obtained with forced dry air. In addition, increasing bed-loading reduces the specific xylanase production likely due to the incapacity of the Penicillium strain to grow deeply in the fermented soya oil cake mass. Thus, the best cultivation conditions involve mycelial inoculum form, a bed loading of 1-cm height and passive aeration. The maximum xylanase activity is obtained after 7xa0days of fermentation and attains 10,200xa0U/g of soya oil cake. These levels are higher than those presented in the literature and, therefore, show all the potentialities of this stock and this technique for the production of xylanase.

Enzymatically prepared n-alkyl esters of glucuronic acid: the effect of freeze-drying conditions and hydrophobic chain length on thermal behavior.

In this work, some of the physicochemical properties of enzymatically prepared n-alkyl esters of glucuronic acid are presented. Two questions are addressed. The first concerns the influence of post-purification freeze-drying conditions on octyl glucuronate thermotropic behavior. Depending on the amount of water added before freeze-drying, the alpha/beta anomeric ratio determined by (1)H NMR is affected and differences are observed in DSC thermograms probably due to polymorphism. The second question concerns the effect of hydrophobic chain length on the thermal behavior. An increase of both transition temperature and transition enthalpy is observed by increasing the number of carbon atoms in the alkyl chain (C8<C10<C12<C14). This kind of results can provide relevant information for the processing and the practical use of these nonionic surfactants.

Chemical Characterization of Cuticular Extracts of Sitobion avenae (Hemiptera: Aphididae)

Abstract Data on the chemical composition of the aphid epicuticle are scarce and often incongruent depending on the methodological parameters of the extraction and chemical analysis. This study aims to provide a chemical characterization of the epicuticular lipids of the English grain aphid, Sitobion avenae (F.) (Hemiptera: Aphididae). First, our results showed that the adsorption chromatography on a silica gel column is suitable to separate the hydrocarbons from more polar constituents found in the extract (e.g., wax esters, alcohols, and aldehydes). Then, we showed that other compounds not detected in previous analysis are likely to be constituents of the extract. Through a transesterification reaction, we demonstrated that the extracts produced numerous fatty acid methyl esters that can come either from long chain wax esters or fatty acid parts of cuticular acylglycerols. The possible semiochemical value of the wax esters and other long chain compounds is discussed. This study opens new insight on the identification of host recognition chemical cues by the parasitoids.