Banana plantain functional properties evaluation during water cooking processes: a NIRS original assay and perspectives

Starch is the major component of edible banana at green stage of maturity, and is well-known to highly contribute to its functional properties. Among others, methods based on near-infrared spectroscopy (NIRS) have already been successfully applied to evaluate various native starch functional properties. In our study, an assay was carried out to try to differentiate the cooking behavior of 6 banana genotypes. Pulp cylinder accessions were cooked in boiling water, and also packed and vacuum sealed in heat-resistant pouches prior to similar cooking. At various time intervals, samples were removed from the water bath and dried at 40°C prior to milling to get stabilized flour samples. The physicochemical properties of the flours were then evaluated by reference methods (DSC, RVA, gravimetry, instrumental firmness).Based on physicochemical properties, a PCA showed that the first 3 components accounted for 84% of the variation. PC1 was positively related to RVA slope (Slope), firmness (F), hot paste viscosity (HPV), and pasting temperature (Ptemp), and negatively correlated to cooking ability (CA). A discussion will be proposed in regards to the wavelengths correlated to the different PCs on the potential structural justification of the phenomenon probably related to starch crystallinity. The factorial map (PCs1 x2) highlighted some crossed-effects of the cooking mode and varietal contribution, making possible to distinguish both processes and genotypes. Results of PLS modeling indicated that NIRS was accurate in predicting Ptemp, HPV, CA, slope, and F with good coefficients of determination (RSQ = 0.70-0.93).Surprisingly, near infrared spectra were able to predict properties measured on the freshly cooked material, although the NIR measurements were carried out on flours. Rapid predictive methods such as NIRS, applied on native or even cooked flour samples can contribute to routinely predict the cooking behavior of the banana starchy resources in breeding programs. (Texte intégral

High frequency ultrasonic devices for the evaluation of the viscosity of coconut water in a rapid and simple way

Coconut water is a well-known beverage under the tropics, but its popularity on the international market has recently been increasing. In fact, it has drawn the attention of manufacturers as a natural functional drink. In this context, and in order to reach the large volume expected by the international markets, one of the key processes is “coconut water concentration”. To optimize and control this unit operation, viscosity of the fluid is one of the most important physical/rheological parameter to be evaluated along with the soluble solid content (SSC in °Brix). Usually, the viscosity of a fluid is measured by rheometry. However, manipulations are time consuming and not suitable for online measurements of the visco-elastic flow properties. In this communication, we suggest two high frequency ultrasonic approaches dedicated to fluid viscosity estimation using both longitudinal or shear wave devices. At first, the investigation carried out using longitudinal waves will be presented. The relationship between longitudinal viscosity and SSC of the coconut water will be demonstrated, prior to the discussion on the relationship between longitudinal viscosity (novel in food rheology) and shear viscosity. Later on, the use of a shear ultrasonic reflectometry approach will be suggested. Thanks to an enhanced experimental device, the direct estimation of the shear viscosity with ultrasound will be compared to shear viscosity by rheometry. A discussion will be proposed for the measurement of viscosity and SSC during concentration using longitudinal or shear ultrasonic waves, on the one hand, for on-line process control on pipelines and, on the other hand, for off-line portable devices (suggestion of a new device coupled to refractometers). These solutions could be applied to any other viscous fluid in the food industry. (Texte intégral

Functional properties of a promissory Dioscorea trifida waxy starch for food innovation

Starches with low amylose contents generally exhibit good gel clarity, high swelling power and RVA peak viscosity, large breakdown, and high resistance to retrogradation during gel storage, as compared to some other starches with higher amylose contents. The demand of the food processing industry for new low amylose or even waxy starchy ingredients for the improvement of the quality of end-use products is considerable. Thereby, the objective of this work is to characterize the functional properties of starches isolated from three Dioscorea trifida genotypes (white, purple and black) cultivated in the Venezuelan Amazon. The investigation of the Dioscorea trifida starches revealed very low amylose contents in the three genotypes. DSC and amperometric amylose determinations of the starches fluctuated from 1.4 to 3.6% and 2.2 to 5.9%, respectively, whereas a commercial Dioscorea trifida starch exhibited an amylose content of 8.7% and 9.5%, respectively. All starch granules were large, triangular or shell-shaped, and exhibited a monomodal particle size distribution from 24.5 to 35.5 ?m. Onset gelatinization temperatures varied from 69.1 to 73.4 °C, and quite high gelatinization enthalpies were recorded in the 22.5 to 25.3 J g-1 range. All starches X-ray diffractograms exhibited B-type patterns. The degrees of crystallinity varied from 24% to 40%. The highest crystallinity was found for the starches exhibiting the highest amylose content. At 90°C, solubility and swelling power varied from 2.1 to 4.4% and 20.5 to 37.0%, respectively. Gel clarity was quite variable from 22.4 to 79.2% and a 5% starch suspension induced a high viscosity between 1420 and 2250 cP using RVA. This discovery could present some industrial potential for the food industry. (Résumé d'auteur