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International audience; A fast and low-cost analytical method to determine the concentrations of carotenoids (β-carotene, lutein, and lycopene) from mixed standard solutions or from fruit extracts (kiwi fruits, tomato paste, pink grapefruit juice, kiwi-pineapple smoothie, and apricot nectar) was tested. The methodology was based on UV-Vis spectrophotometry and Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS). Results showed that relative concentrations of β-carotene, lutein, and lycopene in solvent were successfully determined by this technique with an error inferior to 6%. In real extracts, the procedure succeeded well in identifying the major carotenoid type of the fruit samples but also a more complex profile of a fruit mixture. The results also showed that accuracy of carotenoids determination by UV-Vis spectrophotometry-MCR-ALS in fruit extracts was conditioned by their spectral characteristics (III/II ratios and λmax), their relative proportion, and the extract purity.

African locust bean (Parkia biglobosa) is a legume widely spread in west Africa. The major consumed part is the seeds after processing in the so-called Soumbala in Ivory Coast. It is rich in proteins and lipids and used as a condiment to enhance sauce flavour. The seeds processing can be generalized as a first cooking to allow the dehulling of the seeds, a second cooking of the almond, an alkaline spontaneous fermentation of 2 to 3 days before final sun-drying. During fermentation, microorganisms belonging to the genus Bacillus are responsible of an extensive proteolysis (Odunfa et Adewuyi, 1985) and lipolysis (Ouoba et al. 2003). This gives the specific flavour to the product but may lead to toxic compounds such as biogenic amines. Biogenic amines accumulate by microbial decarboxylation of free amino acids and are thus susceptible to be present in fermented protein rich foods. They were reported in wine, cheese and fermented fish while they have not been studied yet in processed African locust bean seeds. The objective is to evaluate amino acids decarboxylation activities of Bacillus spp. isolates from Soumbala and biogenic amines content. Soumbala samples were collected among 6 producers in 3 regions of Ivory Coast. 52 Bacillus spp. strains were isolated and identified using API 50 CHB kits. Histidine, lysine, arginine, phenylalanine and ornithine decarboxylation activities and arginine dehydrogenase activities were determined in order to study their ability to produce histamine, cadaverine, phenylethylamine and putrescine. Soumbala samples were analysed for histamine, cadaverine, phenylethylamine and putrescine content. Bacillus spp. strains were identified as followed: B. subtilis (16); B. lentus (3), B. pumilus (1), Geobacillus stearothermophillus (5), B. megaterium (9), B. firmus (2), B. circulans (2), Brevibacillus non reactive (5), B. licheniformis (4), Aneurinibacillus aneuriniliticus (4), B. cereus (1). 16 strains did not show arginine deshydrogenase activities and histidine, lysine, ornithine, or phenylalanine decarboxylation activities. Biogenic amines content of Soumbala was in average 82 mg.kg-1 for histamine, 36 mg.kg-1 for cadaverine, 45 mg.kg-1 for putrescine and 272 mg.kg-1 for phenylethylamine, some samples reaching high levels. Strategies for the control of biogenic amines production in African locust bean fermented seeds are discussed.

Fibers are macronutrients naturally presents in fruits and vegetables and contribute to the nutritional quality of raw or processed food. During heat treatments, fibers, and particularly soluble fibers are subjected to degradations that impact the textural property of the dish but also its nutritional properties (composition and bioaccessibility of micronutrients). This study was aimed to understand the behavior of Jew's mallow soluble fibers (Corchorus olitorius) during the cooking process of a traditional Tunisian dish: Mloukhiya. A simplified recipe of Mloukhiya was made by mixing three main ingredients (dried powder of Corchorus olitorius, tomato paste and olive oil) and was submitted to a cooking treatment (150 min) with added water. Quantification of soluble fibers as well as methylation degree (ratio of methanol and uronic acids) were monitored at different cooking times along with viscosity and microstructure analyses by epifluorescence and confocal microscopy (Zeiss LSM 880). The chemical analysis showed a decrease (40%) of soluble fibers and a slightly increase of their degree of methoxylation was observed. We suggested that these polysaccharides also underwent a 0-eliminative depolymerization during cooking process. At initial time, the dish had a high viscosity and its structure was an "oil in water" emulsion stabilized by the presence of fibers. As a function of time, the viscosity substantially dropped, due to the depolymerization phenomenon. Microscopic observations by epifluorescence and confocal confirmed the destabilization of emulsion due to polysaccharides degradation with a coalescence of oil droplets (Image Jc software show a decrease of oil droplet percentage from 25 % to 15 % during the first hour of heating). These observations can be linked with a previous work showing the increase of bioaccessibility by better micellarization or better diffusion in oil of fat-soluble micronutrients during cooking1. By impacting soluble fibers chemical structure, heat processes modulates the microstructure of a complex emulsion from a vegetable-based dish and the extractability of fat-soluble micronutrients.

Calyces of Hibiscus sabdariffa are traditionally used to prepare a red beverage rich in anthocyanins (delphinidinand cyanidin-3-O-sambubioside) by decoction in water. These molecules are subjected to degradation during storage leading to a undesirable color intensity decay and change from red to brown in few months. The chemical origins of this quality loss have been already identified as scission and mainly condensation reactions leading to uncolored or brown polymers of anthocyanins (Sinela et al., 2016). Scission and condensed products are known to be instable and/or of various molecular weight. Their concentration is therefore very difficult to get unless numerous time- and money-consuming analysis. An alternative of getting mecanistic and kinetic insigth into anthocyanin degradation during processing or storage is the UV-VIS spectra analysis with chemometric tools. Indeed, UV-VIS spectra are easy to get, but may be complex to interpret as they result from the contribution of all molecules that absorb in this spectral region, which is the case of most of the polyphenols. The objective of this study is to use spectral deconvolution by mean of Multivariate Curve Resolution- Alternating Least Squares (MCR-ALS) on spectral evolution of Hibiscus sabdariffa extract obtained by soaking calyx powder in water at a ratio 1/9 (g/g) during one month of storage at 37°C. In this work, we propose a twosteps approach: a first deconvolution on two fractions of the extract, low molecular and high molecular weigth fractions obtained by size-exclusion chromatography and a MCR done on the spectrum of the whole extract. Absorbance from 250 to 700 nm (each 0.5 nm) was recorded on 10 samples at different storage times. MCRALS was carried out on the 10 spectra using a toolbox developped by Jaumot et al. (2005) on Matlab (The MathWorks, Inc., Natick, MA, USA) with a non negativity constraint algorithm. To improve the mathematical resolution and the chemical validity, the data set was augmented with pure spectra obtained with standards in solution. The results showed that the deconvolution made on the fractions obtained with size-exclusion chromatography was useful to extract qualitative information in the form of spectra of the low and high molecular weigth compounds. Three spectra were clearly identified as anthocyanin (with a spectral contribution equivalent to their relative concentration), chlorogenic acid, scission products (gallic and protocatechuic acids) and two spectra were attributed to condensed molecules (because of their absorbance in the brown region) and other colorless anthocyanin forms in equilibium (because of their peak in the UV region). The five spectra were used to improve the MCR-ALS applied to the whole extract. For this second step, the relative concentration of each specy was obtained. The anthocyanin evolution could be modeled by a first-order kinetic with a rate value consistent with litterature. Chlorogenic, gallic and protocatechiuc acids were found stable as expected. A significant evolution was evidenced for condensed molecules whose relative concentration increased by a 1.6-fold. To conclude, MCR results on Hibiscus sabdariffa extracts, fractionnated and not, were interesting since they could successfully represent the evolution trend of the different species in solution during storage: the anthocyanin but also their degradation products.

Intégration de la bioaccessibilité des vitamines liposolubles dans un système de profilage nutritionnel durant la préparation d’un plat traditionnel tunisien. Journées Francophones de Nutrition, JFN 2015