Eco-friendly process combining acid-catalyst and thermomechanical pretreatment for improving enzymatic hydrolysis of hemp hurds.

The aim of this study was to investigate a pretreatment by combined H2SO4 acid-catalyst and thermomechanical process to improve hemicelluloses solubilization of hemp hurds and subsequently enzymatic hydrolysis extent of potentially fermentable sugars. It was found that the sugars released were gradually increased with treatment severity. Soluble sugars generated before enzymatic hydrolysis (R1) increased up to 2.23 g/L indicating that autohydrolysis reaction occurred during pretreatment. Consequently, the solubilization of hemicelluloses was correlated with combined severity factor (CS). As a result, increase of overall reducing sugars (ORS) from 23.4% (untreated) to 81.4% was observed at optimized conditions of steaming temperature of 165 °C for 30 min and acid loading of 62.9 g/kg DM (dry material) corresponding to CS = 1.2, with limited production of identified by-products: 0.035 g/L and 0.46 g/L (per 100 g DM) for furfural and HMF, respectively. Structural and physicochemical modifications of biomass were observed by FTIR, ABET and SEM.

Physicochemical and crystalline properties of standard maize starch hydrothermally treated by direct steaming.

The changes in physicochemical properties of standard maize starch (SMS) by three hydrothermal treatments; DV-HMT (Direct Vapor-Heat Moisture Treatment), RP-HMT (Reduced Pressurized-Heat Moisture Treatment) and DIC (instantaneous controlled pressure drop) were investigated at different processing conditions; steam pressure (SP) varied from 1 to 3bar during 20min. Starch was steamed by direct contact, whose interest was to intensify the heat transfer phenomenon but also the water transfer. The physicochemical changes of SMS depended on process conditions and their extent followed this order: DIC>RP-HMT>DV-HMT. All treatments significantly increased gelatinization temperatures and decreased the enthalpies, confirmed by loss of granules birefringence. From 2bar, the crystalline structure changed from A-type to Vh-type, revealing formation of amylose-lipid complexes during steaming. The results clearly showed that the particle size distribution depends on the melting extent of crystalline structure during treatment. At severe processing conditions the melted fraction increased and more complex aggregates of different sizes have been formed.

Risk assessment of heavy metals via consumption of vegetables collected from different supermarkets in La Rochelle, France.

In this study, a food survey was carried out with two purposes: (1) to investigate the levels of nickel (Ni), zinc (Zn), and copper (Cu) in various vegetables randomly collected in supermarkets of La Rochelle and (2) to assess the potential health risk for consumers by estimating the daily intake (EDI) and the target hazard quotient (THQ) for each heavy metal. The concentrations of Ni, Cu, and Zn in selected foodstuffs were detected within the following ranges: (3.2-9.6), (25.2-104.7), and (10.8-75.6) mg/kg (DW), respectively. Results showed that metals are more likely to accumulate in fruit vegetables (8.8, 63.8 and 47.8 mg/kg DW for Ni, Cu, and Zn, respectively), followed by leafy vegetables (6.5, 60.9 and 42.6 mg/kg DW for Ni, Cu, and Zn, respectively) and finally root vegetables (5.4, 40.0 and 27.3 mg/kg DW for Ni, Cu, and Zn, respectively). The levels of the metals match with those reported for similar vegetables from some other parts of the world. For all foodstuffs, EDI and THQ were below the threshold values for Cu (EDI 11.30; THQ 0.283) and Zn (EDI 6.86; THQ 0.023), while they exceeded the thresholds for Ni (EDI 20.71; THQ 1.035), indicating an obvious health risk over a life time of exposure.

Role of vacuum steps added before and after steaming treatment of maize starch. Impact on pasting, morphological and rheological properties.

Standard maize starch (SMS) was hydrothermally treated by three processes; DV-HMT (Direct Vapor-Heat Moisture Treatment), RP-HMT (Reduced-Pressurized Heat Moisture Treatment) and DIC (in French: Détente Instantanée Contrôlée, instantaneous controlled pressure drop). Impact of processes were studied in order to determine the role of added steps of vacuum before and after treatment of starch by live steam at different pressures (1, 1.5, 2, 2.5 and 3 bar) on morphological, pasting (Brabender) and rheological properties of SMS suspension. The three treatments tend to modify the physical properties of starch on the same way, but the extent of these modifications depends on the process and on the level presure applied. The intensity of modifications follows this order: DIC>RP-HMT>DV-HMT. This was attributed to the presence of the initial vacuum step (DIC and RP-HMT) which intensified the transfer phenomena and to the mechanical effect induced by the abrupt decompression towards vacuum (DIC) leading to weakness of starch granules. The treatments changed the shape and distribution size of granules. The sizes were shifted towards higher values after the treatment due both to the improvement of swelling capacity of granules and to the presence of agglomerates particles of different sizes as confirmed by scanning electron microscopy. The agglomerates glued together by gelatinized granules were favored by the direct contact of starch with steam during the treatments. The results showed for all treatments, a reduction of the consistency coefficient (k) and of the yield stress (τ0) of starch suspensions with increasing of process intensity. For severe conditions (3 bar), no difference between the treatments was observed; a complete fluidization of starch suspensions (the consistencies were too weak to be detected), τ0 vanished and the rheological behavior tended to a Newtonian type. Elastic modulus (G'), measured during gelation at 25°C, decreased dramatically (G'<1 Pa), that revealed the loss of rigidity and disappearance of granular integrity of starch.