Mechanical approach for the evaluation of the crispiness of food granular products.

Crispiness of food products is a key parameter for consumer acceptance. Available methods to evaluate this attribute are subjective and have limitations. They are particularly difficult to implement when granular products are considered. The present study aims to provide a physical characterization of the crispiness of food granular products (gari and grinded corn flakes) based on the compression cycle modeling and the determination of the Py (yield pressure) parameter of the Heckel model. High Py values attributed to the brittle behavior, are indicative of product crispiness. Furthermore, Py parameter showed sensitivity to the plasticizing effect of water. This developed physical method was validated through sensory analysis and acoustic measurements which are both considered as reference methods for crispiness evaluation. The brittle/plastic behavior attributed to crispy/non crispy products respectively was confirmed through image analysis using X-ray microcomputed tomography. The latter made it possible to distinguish the brittle from the plastic behavior through the particle size distribution evolution. This work suggests that the Py value is a relevant indicator for the crispiness evaluation of granular products. This physical characterization is expected to contribute in food engineering as an alternative method for granular products crispiness in a simpler and a more objective way.

Role of dewatering and roasting parameters in the quality of handmade gari.

Gari is a common cassava precooked dried semolina in sub-Saharan Africa. Our study investigated the role of process parameters and mash water content on gari quality during traditional roasting stage. The statistical analysis for eight quality criteria revealed that gari quality is highly influenced by the process parameters adopted by the operators. To emphasise the twin impact of roasting parameters and mash water content, different mashes with varying water content were roasted leading to different adjustments of the roasting conditions according to the operators. When the variability of the water content becomes greater, a greater variability in the final quality of the obtained garis was observed between operators (lightness, swelling capacity, starch content, texture and colour). These results suggest that technological improvements to the gari process could be achieved by appropriate management of the roasting and dewatering parameters.

Identification of critical versus robust processing unit operations determining the physical and biochemical properties of cassava-based semolina (gari).

The gari-making process involves several unit operations (U.O.), some of which strongly influence the quality of the end product. Two contrasting process scales (laboratory-scale vs conventional) were compared in order to identify which U.O. were affected by the change of scale. U.O. that changed end-product characteristics depending on process scale were deemed critical; whereas U.O. that resulted in similar characteristics were deemed robust. The classification depended on quality attributes considered: rasping and roasting were critical for physical properties, in particular particle size which ranged from 0.44 to 0.89 mm between the two process scales; and robust for biochemical properties. In contrast, fermentation and pressing were critical for biochemical properties such as lactic acid content (0.93-1.88 g/100 g dry matter after pressing), which influences the perception of flavour, and robust for physical properties. This classification between critical and robust operations help quality control of gari, by pinpointing which U.O. control specific quality characteristics.

Organotins' fate in lagoon sewage system: dealkylation and sludge sorption/desorption.

Organotin compounds (OTs) have been widely used for their biocidal properties and as stabilizers in various industrial applications. Due to their high toxicity, organotins are subject to many studies regarding their behavior in wastewater treatment plant and aquatic environment. However, few studies are available regarding their behavior in lagoon sewage system, although such treatment is commonly used for sewage treatment in low-population areas. The present study aimed at studying the fate of organotins (monobutyltin (MBT), dibutyltin (DBT), and tributyltin (TBT)) in lagoon sewage system. Short-term experiments, carried out at lab scale, consisted in sampling sludge from aerobic stabilization ponds, and then quantifying sorption and desorption of the different organotin species, as well as their respective transformation, under defined operating conditions (e.g., tributyltin spike and dilution) simulating possible change in the surrounding environment of sludge in the lagoon. Results established that a very important percentage of the OTs was localized in the solid phase of the sludge (more than 98 %), whatever the operating conditions may be; however, transformation and locations of the three OT species differed according to the different conditions of sludge dilution, TBT spiking, and test duration. After dilution of lagoon sludge, TBT desorption from sludge was observed; it was supposed that dealkylation of TBT after desorption occurred rapidly and increased dissolved MBT and DBT in liquid phase; MBT sorbed subsequently on solid phase. The nature of the diluent (i.e., tap water or saline solution) appeared to slightly influence the sludge behavior. After TBT spiking, TBT was supposed to be rapidly sorbed but also transformed in DBT and MBT that would as well sorbed on the sludge, which explained the decrease of these species in the liquid phase. Tests aimed at studying long-term effect of TBT spiking demonstrated that the sorbed species could be remobilized and transformed after a dilution.

Impact of physicochemical environment on the super disintegrant functionality of cross-linked carboxymethyl sodium starch: insight on formulation precautions.

The aim of this work is to improve the understanding of the physicochemical mechanisms involved in the functionality of cross-linked carboxymethyl sodium starch (CCSS) as a tablet super disintegrant (SD). The behavior and properties of this SD (medium uptake, disintegration times, particle size, and rheology) was investigated in a wetting medium of different physicochemical properties. In particular, the relative permittivity (dielectric constant) of these media was intentionally modified for evaluating its effect on CCSS properties. Results showed different swelling behaviors of CCSS particles according to the relative permittivity of the tested media and allow to propose two underlying mechanisms that explain CCSS functionality. Both the intra-particular swelling and the inter-particular repulsion are affected by the relative permittivity of the media. Finally, disintegration test performed on tablets specially formulated with mannitol (used commonly as an excipient and known to modify relative permittivity) confirmed that the functionality of CCSS and therefore the disintegration of the tablet can be altered according to the mannitol content.

A contribution to the understanding of micro-pollutant sorption mechanisms in wastewater biological processes: case of the tributyltin.

Micro-pollutant fluxes distribution throughout the physical separation and biological units of wastewater treatment plants (WWTPs) are very dependent ofsorption phenomena. The understanding and the control of the sorption stage is thus essential for the optimization of micro-pollutant removal in WWTPs, and particularly in biological treatments where these mechanisms influence the bioavailability towards micro-organisms. If the influence of the micro-pollutant physicochemical characteristics (e.g. Kow, pKa) on their ability to sorb on biological media (i.e. sludge) has been demonstrated, it appears that some other parameters, like the biosorbent characteristics, have to been taken into account. The aim of this study is thus to correlate the capacities of sorption of an environmentally relevant substance (tributyltin), with a thorough characterization of different types of sludge. The characterization of three biological media (raw, sonicated and flocculated activated sludges) is proposed according to various characterization parameters related to biochemical composition, aggregate size, rheological behaviour etc. The results show first that, whatever the sludge characteristics may be, the sorption mechanisms are very rapid and that an equilibrium state is reached after a few minutes. The influence of the sludge characteristics, notably the floc size and the chemical oxygen demand partition between solid and colloidal fraction, on sorption efficiency is demonstrated. A Langmuir modelling allows giving the maximum sorption capacity, as well as the binding energy for the three studied sludges, according to their physicochemical characteristics.