Qualité des pommes de terre : nouvelles méthodes d'évaluation calibrées sur l'analyse sensorielle

Quality of potatoes : new assessment methods calibrated by means of sensory analysis [frying index]. For the potato sector, raw material quality became an important criterium because it determines the type of use and the transformation ability of the tubers. It is now primordial to be able to identify the quality level of a share by reliable and objective methods. The qualitative criteria of potatoes are for the most estimated via sensory tests. During this survey, we measured several texture descriptors (desintegration, flouriness, granulation), the flesh colour, the after-cooking blackening susceptibility, the taste intensity and the after-frying coloration of the samples. In order to get rid of the human subjectivity, we studied the potentialities of near infrared spectrometry (NIRS) and of image analysis to predict or to measure these sensory behaviours. We observed high correlation between real values and values predicted by NIRS models, mainly for texture descriptors and flesh colour. Frying index prediction by NIRS is acceptable, but less precise than its measurement by image analysis

Concentration of nutrient solution in the hydroponic production of potato minitubers Concentração da solução nutritiva na produção hidropônica de minitubérculos de batata

The effect of the nutrient solution concentration on potato plant growth and minituber yield were determined in a sand closed hydroponic system. Minitubers and micropropagated plantlets of the cv. 'Macaca' were used. Treatments were five nutrient solution concentrations at electrical conductivities (EC) of 1.0 (T1), 2.2 (T2), 3.4 (T3), 4.7 (T4) and 5.8dS m-1 (T5). The split plot randomised experimental design was used with three replications. Plants from minitubers produced higher fresh and mean weight of minitubers, shoot dry mass and leaf area index than the micropropagated ones. However, higher dry mass of minitubers was found with micropropagated plantlets compared to minitubers. The concentration of the nutrient solution did not affect minituber number. Increasing the nutrient solution concentration decreased total and minituber dry mass production of micropropagated plantlets and plant growth and minituber production of minituber-originated plants. Low concentration of nutrient solution at an EC of about 1.0dS m-1 can be used in the hydroponic production of potato minitubers of both micropropagated and minituber-originated plants.<br>Neste trabalho foi determinado o efeito da concentração da solução nutritiva no crescimento e na produtividade de minitubérculos de batata em um sistema hidropônico fechado empregando areia como substrato. Plântulas micropropagadas e minitubérculos foram plantados em 24 de março de 2004. Os tratamentos foram cinco soluções nutritivas com condutividades elétricas (CE) de 1,0 (T1), 2,2 (T2), 3,4 (T3), 4,7 (T4) e 5,8dS m-1 (T5). O experimento foi conduzido em parcelas subdivididas no delineamento inteiramente casualizado com três repetições. Plantas originadas de minitubérculos produziram mais massa fresca total e média de minitubérculos, massa seca da parte aérea e maior índice de área foliar que plantas micropropagadas. Entretanto, maior massa seca dos minitubérculos foi obtida em plantas micropropagadas. A concentração da solução nutritiva não afetou o número de minitubérculos. O aumento da CE reduziu a massa seca total e dos minitubérculos de plantas micropropagadas e decresceu linearmente o crescimento e a produtividade de minitubérculos de plantas oriundas de minitubérculos. Concentrações baixas de solução nutritiva com valores da ordem de 1,0dS m-1 podem ser empregadas na produção de minitubérculos de batata a partir de plântulas micropropagadas e minitubérculos