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Processing, such as fresh cutting and drying, is essential to enhance profitability; therefore, to limit waste and reduce losses in fruit production such as mangoes. Metabarcoding and microbial enumeration methods were utilized to explore the structure of mango microbiota, as well as their evolution after processing. Two mango ripening stages of cv. Cogshall were selected and processed into fresh-cut pieces or dried slices. Microbiological and physicochemical parameters were monitored during product storage, in order to assess the dynamics of quantitative and qualitative variations of the microbial flora. Proteobacteria was the dominant bacterial phylum of the mango surface and accounted for 73.16%, followed by Actinobacteria (10.16%), Bacteroidetes (7.82%) and Firmicutes (6.68%). Aureobasidium and Cladosporium were the only two genera shared between all types of samples (peel surface, dried slices and mango fresh-cut). However, the bacterial genera Lactobacillus and Pantoea were the most abundant in fresh-cut mango after 14 days of storage. Ascomycota was the dominant fungal phylum in the mango surface and accounted for 90.76% of the total number of detected sequences, followed by Basidiomycota (9.21%). In total, 866 microbial genera were associated with mango surface (562 bacterial and 304 fungal). Among detected yeast genera, Saccharomyces, Candida and Malassezia prevailed in mango flesh and were replaced by Wickerhamomyces after 14 days of storage. Alpha and beta diversity analyzes revealed differences in fungal and bacterial communities on fruit peel, in fresh-cut, dried slices, and during conservation (fresh-cut and dried slices). Mango processing (washing, peeling, cutting and drying) reduced the richness and the microbial diversity (bacterial and fungal) associated to the fruit, and drying limits the development of cultivable microorganisms during storage in comparison to fresh-cuts mangoes.

In a number of tropical countries, the expansion of cassava processing is tied to the development of small-scale, energy-efficient pneumatic dryers used to dry flour and starch. To facilitate this development, in this study a model of the pneumatic drying of starch particles was developed, to be fitted to measurements taken from large cassava processing factories. After that, numerical simulations were performed to analyse the effects of geometry and operating conditions on the energy efficiency and pipe length required to dry the product. The results clarified the influence of processing capacity, air inlet conditions and starch particle size, emphasizing that air velocity, as well as the dilution of the starch, should be minimised. In light of the findings described here, we offer guidelines for the design of efficient small-capacity flash dryers.

A 1D mechanistic model was developed to describe water, deformation, amylose transport and starch gelatinization inside rice grains during cooking. Four migrating species were considered: two water populations according to the state of the starch, soluble amylose and an insoluble solid phase network. Three coupled mass transport PDE were formulated assuming diffusional mass transport and using a Lagrangian-Eulerian framework. The model integrates the convective effect of a water flux on the transport of soluble amylose. Rice grain deformation was the result of both water-induced swelling and erosion of the surface of the solid phase, assuming a zero-order kinetic process. The model was adjusted on a milled Chil-bo rice cultivar steeped in excess water at 75 °C and 95 °C. After 30 min at 95 °C, which is the standard cooking time, water uptake, leaching of soluble amylose and the amount of eroded material were 3.15 kg kg−1 db, 5.0% and 15.5% (w/w) respectively. Using the predicted distribution of species within the grain, the model could help to control the texture of cooked rice. (Resume d'auteur)

An isothermal model of rice cooking process was developed that accounts for the impact of starch phase transition on water transfer and swelling, using an arbitrary Lagrangian–Eulerian framework. Two water populations were distinguished: water in native starch and excess water absorbed by starch since it starts to gelatinize. The model was solved by FEM. Water apparent diffusivities in native and gelatinized starch were 3.6 × 10 −10 and 2.8 × 10 −10 m 2 s −1 respectively. The model was validated on the Chil-Bo rice cultivar using experimental water uptake and microscopy measurements of the gelatinization front. At 50 °C, 75 °C and 95 °C, the volume gains were 0.3, 4.8 and 8.3 m 3 m −3 respectively. The model adequately reproduces swelling as its extent corresponds to the amount of water absorbed (±4% v/v). Both water and gelatinization profiles over time would be of tremendous benefit for the optimization of cooked rice properties such as texture.

A space-and-time dependent model describing the impact of heat transfer on insect survival rate was developed for analyzing the heat disinfestation process of dates. A 2D axial-symmetric domain was defined with five sub-domains: the bulk date pulp, a thin air layer and the date pit, a larva (located in the air layer) and eggs (on the date surface). The model included convective heating and microwave heating (915 MHz). Dielectric properties of the date pulp, egg and larvae were measured. The model predictions showed good agreement with experimental results in the case of the “biological model” (Ephestia kuehniella Zeller) in dates subjected to hot air treatment (70 °C). Sensitive analysis showed that the date size and water content greatly affected the heating time process, during hot air and microwave treatments. Moreover, regarding the eggs’ specific surface, it is advisable to combine convective hot air with microwave heating to induce egg mortality on the date surface.

Aims: To quantify and model the combined effects of temperature (T) (10–40°C), water activity (aw) (0·993–0·818) and CO2 concentration (9·4–55·1%, v/v) on the growth rate of Aspergillus niger and Alternaria alternata that cause spoilage during the storage and packaging of dates. Methods and Results: The effects of environmental factors were studied using the γ-concept. Cardinal models were used to quantify the effect of studied environmental factors on the growth rates. Firstly, the cardinal parameters were estimated independently from experiments carried out on potato dextrose agar using a monofactorial design. Secondly, model performance evaluation was conducted on pasteurized date paste. The boundary between growth and no-growth was predicted using a deterministic approach. Aspergillus niger displayed a faster growth rate and higher tolerance to low aw than Al. alternata, which in turn proved more resistant to CO2 concentration. Minimal cardinal parameters of T and aw were lower than those reported in the literature. Conclusions: The combination of the aw and CO2 effects significantly affected As. niger and Al. alternata growth. The γ-concept model overestimated growth rates, however, it is optimistic and provides somewhat conservative predictions. Significance and Impact of the Study: The developed model provides a decision support tool for the choice of the date fruit conservation mode (refrigeration, drying, modified atmospheric packaging or their combination) using T, aw and CO2 as environmental factors. (Resume d'auteur)

The effects of heat treatment on the survival of isolated Ephestia kuehniella Zeller larvae were examined. Larvae were treated in a specific device at a temperature range of 46 to 70 °C. Statistical analysis of the data demonstrated that the thermal survival kinetics was best represented by a 2-parameter Weibull model above 50 °C. The mortality of larvae only occurs beyond a critical temperature of 41.6 °C ± 2.5 °C. A 2D axial-symmetric model of heat transfer (convection, microwave at 915 MHz) was developed for cocoa bean and date palm. It was combined with the survival rate of larvae (Weibull model) and some z -values (from literature) are used for calculating a “food quality index” degradation kinetics. The intensive heating/convection process may not be adaptable for food products at low water activity due to high surface product temperatures. The use of microwave heating for date fruits and conventional hot air treatments for cocoa beans is recommended.

The effect of heat treatment on the survival of Ephestia kuehniella eggs was examined. Samples of 60 eggs were immersed in hot water at constant temperature in the 46–75 °C range for 5–1200 s. Following heat treatment and cooling, the eggs were stored at 24 ± 1 °C in a growth chamber for 7 days before survival evaluation. Statistical analysis of the data demonstrated that the thermal survival kinetics were best represented by a first-order reaction. The rate constant had an Arrhenius-type dependence over the 54–75 °C temperature range. Kinetic parameters were estimated by non-linear regression. The activation energy ( E a ) and rate constant ( k ref ) at the reference temperature ( T ref = 64.8 °C), were determined as 102.2 ± 6.2 kJ mol −1 and 0.061 ± 0.003 s −1 , respectively, over the 54–75 °C temperature range. A 0.01% survival rate was obtained after 50 s at 75 °C. The data at temperatures below 50 °C were not in accordance with those at higher temperatures. Above this temperature, mortality was likely due to physiological disorders, as noted on a DSC thermogram.

Water activity is the main criterion for characterizing the storage and drying behavior of biological products. As current standardized devices are expensive, a cheaper apparatus was designed and built. After preliminary tests, functional specifications were determined. This gravimetric device was tested and validated on microcrystalline cellulose and then used for the characterization of various tropical products. This operational equipment, easy to handle, robust, and four times cheaper than the reference apparatus, was able to obtain accurate sorption isotherms.

This paper describes the adaptation of a one-dimensional rice cooking model including water transfer, starch phase transitions and swelling to simulate both milled and brown Chu-cheong and Chil-bo rice cultivars cooked in excess water or in limited amounts of water. The pericarp was found to play a temperature-dependent role during steeping of brown rice. At 50 °C, surface mass-transfer resistance was identified whereas from 75 °C the pericarp ruptured. Despite pericarp rupturing, apparent water diffusion coefficients for brown rice (∼1.9 × 10 −10 m 2 s −1 ) were lower than for milled rice (∼3.3 × 10 −10 m 2 s −1 ). This was due to the mechanical constraining effect of pericarp with respect to water uptake. In the limited-water cooking mode, predicted water and gelatinization profiles of four selected cooking procedures explained the texture of cooked rice. Indeed, the highly hydrated gelatinized periphery of the cooked grain resulted in high “initial starchy coating” sensory scores whereas the uncooked core increased instrumental firmness.

A survey was carried out in Togo, Benin and Burkina Faso involving 140 respondents and three climatic zones. Ten typical types of dryers with batch operating and natural convection were inventoried. Analysis of the results showed that: (1) Traditional sun dryers were widely used everywhere from 1 to 4000 kg per cycle, costing ?0 to ?7.63 per m2 drying area. (2) Low power solar dryers were mostly used in the Sahel and Sudan-Sahel tropical climate, from 5 to 1000 kg, costing from ?9.11 to ?238.55 per m2 of tray. (3) Gas dryers were used in all climatic zones at around 100 kg per cycle, with a high drying power, costing from ?107.52 to ?181.75 per m2 of tray. The acquisition of dryers depended mostly on the distance between provider and user and on the means of dissemination. A thermo-economic analysis was carried out to determine which dryers were most successfully adopted. These dryers will be re-employed by the users when the investment and maintenance costs enable profit to be made from the drying operation. Two types of dryers met those conditions: the traditional simple sun dryer used by families and groups: a study of an application on maize showed costs of ?0.01/kg of evaporated water equal to 7% of daily capital gain; the Atesta gas dryer used by small and medium-sized enterprises: applied to pineapple, cost ?0.07/kg of evaporated water equal to 9% of daily capital gain. New criteria had to be added to all those listed from the literature in order to choose a dryer properly: characteristics of the product to be dried, product added value, local energy availability and cost, labour skills and availability, local material availability and user investment capacity. (Resume d'auteur)

The reduction of the post-harvest loses that reaches 50% in the developing countries constitutes a major stake for their development. Then, it is right to make more efficient the processes of stabilization and conservation of products. The drying constitutes of a more used process but the mistakes committed in the choice of dryer in a given context entail important losses of products. As an approach of solution to this problem, we conceived and realized a decision making tool. An industrial engineering procedure has been led to analyze drying activities. The tool is informed by a data base containing the features of tropical products, the climatic environment and the construction supplies for dryers. The technical solutions describing the types of dryers have been counted from a technological watch over and analyzed using industrial engineering tools. The choice of indicators permits to value and to compare the different technical solutions. The implementation of the decision making tool in Visual Basic with Microsoft Excel software permits, from the input data, to size the technical solutions, and calculate the value of the indicators for the each technical solutions and to compare them one with another. An ex post validation of the tool has been made from the functional specifications of a SMAI of drying of pineapple in Lome, Togo. The better choice recommended by these specifications is the use of ATESTA dryers. The choice corresponds to the dryer used by the SMAI satisfaction. The rough idea of the development expenses and profitability are near of the reality. Although this validation is partial, the tool seems to have from now on, a worthwhile applicative interest.

L’impact du blanchiment, de la decoupe et du sechage des tubercules d’ignames (Dioscorea rotundata, cultivar kokoro du Benin) sur la couleur de la pâte reconstituee a partir de la farine de cossettes broyees a ete etudie par modelisation couplee des transferts de chaleur et d’eau et de reaction de brunissement. Le modele de transferts utilisant les equations de Fourrier et de Fick permet une bonne description du sechage. Un modele cinetique de modification de la couleur en fonction de la temperature et de l’activite d’eau a ete developpe. Ses parametres ont ete identifies a partir d’experiences originales. Les modeles ont ete implementes sous COMSOL® en 2D. Les modifications de qualite predites par le modele couple correspondent aux observations de terrain des partenaires du projet. Il vaut mieux secher doucement a basse temperature que vite a haute temperature. Effect of blanching treatment, cutting and drying of yam tubers (Dioscorea rotundata, cultivar kokoro from Benin) on color of the thick paste prepared from flour was studied by coupled modelling of heat and water transfers and of browning reaction. The model of transfers using the equations of Fourrier and Fick gives a good representaiton of the drying kinetics. Dependence of colour modification to temperature and water activity was modelled. Parameters of the model were identified from original experiments. The models were implemented under COMSOL® in 2D. The modifications of quality predicted by the coupled model agree with the ground observations made by the partners of the project. It is better to dry gently at low temperature that quickly at high temperature.

La saison de recolte des mangues est courte et la production generalement abondante. Aussi est-il interessant de pouvoir valoriser ce fruit en le sechant, ce qui necessite la mise au point et la diffusion de procedes et d'equipements specifiques. Cet ouvrage est la synthese de travaux menes par une equipe pluridisciplinaire du Centre de cooperation internationale en recherche agronomique pour le developpement (Cirad) et de ses partenaires, avec les acteurs de la filiere de la mangue sechee au Burkina Faso, pays pionnier dans ce domaine. II presente les etapes de la transformation de la mangue, depuis l'approvisionnement en fruits jusqu'a la commercialisation du produit seche. L'analyse de chaque operation est detaillee: principes theoriques, equipements mis en oeuvre, bonnes pratiques d'utilisation et d'hygiene, gestion de la qualite, rendement "matiere" et consommation d'energie, besoin en main-d'oeuvre... Outre des fiches techniques, le lecteur trouvera dans ce guide le schema d'une unite de sechage de mangues, les plans de fabrication d'un sechoir ventile ainsi qu'un manuel de production utile pour preparer, suivre et faire le bilan d'une campagne de sechage. Ce guide s'adresse aux responsables de petites et moyennes entreprises qui souhaitent ameliorer les conditions de fonctionnement de leurs unites de production ainsi qu'aux entrepreneurs et porteurs de projets desireux de creer une unite de sechage de mangues. (Resume d'auteur)

The aim of this study is to model the stress building in a solid product which shrinks during drying, in order to choose the best drying parameters to avoid cracks formation. For this, a simulation model has been developed to predict the evolution of temperature and moisture content in the product, and consequently the shrinkage and the induced strain and stress. The studied case is an infinite cylinder of pasta, representing the case of spaghetti. For this, we need to know the mechanical behaviour of the studied product, which varies both with moisture X and temperature T. The experimental results are presented as an effective Young’s modulus Eeff=f(X,T). The simulation results evaluate the mechanical stress path followed at each location in the material, during all the drying process, and according to the chosen external drying conditions.

In this paper, we report on the water vapour desorption isotherms, at 25°C, of eleven date ( Phoenix dactylifera ) varieties, from different locations, collected at full ripeness: Mech-Degla, Deglet-Nour and Haloua (Algeria), Barhi, Fardd, Khadrawi, Khalass, Madjol, Rizaz (Saudi Arabia), Madjhoul (Israel) and Kentichi (Tunisia). The static gravimetric method was used, according to the COST 90 recommendations. The overall shape of the curves describing the water content as function of the water activity was typical of sugar-rich materials. Experimental data were analysed using the Guggenheim–Anderson–Brunauer (GAB) and Brunauer–Emmett–Teller (BET) models, through direct non-linear regression without any transformation of data. Both models correctly fit the whole set of data, for water activity ranking from 0.11 to 0.90, but the BET model was preferred since the values of its parameters were more realistic.