A comparative study of the physicochemical properties of starches from root, tuber and cereal crops

Some properties of starches from cassava, potato and sweet potato were compared with cereal starches from maize, wheat, millet and sorghum. The aim was to determine the properties of tuber and root crop starches and compare them with cereal starches in addition to unravelling the potential of commonly grown sorghum and millet climate resilient crops as cheap and sustainable sources of starch. Significant variations were observed for amylose content and solution properties of starches, where blue values for amylose ranged from 0.355 in potato to 0.476 in cassava, but were averagely low in cereal starches. Amylose leaching increased with temperature with the highest value (0.432) in cassava at 80°C compared with cereal starches (average 0.361). Starch amylosis increased with time of hydrolysis and was highest (>16%) for millet and sorghum and least for potato (<8.5% average). Average swelling power at 80°C was high for cassava (8.58 g/g) and potato (8.44 g/g) compared with sweet potato (6.88 g/g) and low among cereal starches (5.17 g/g). Similarly, starch solubility was low in potato (0.77 g/g) and sweet potato (0.577 g/g) compared with cassava (1.23 g/g). The paste clarity was also high for cassava (48.32%) and potato (42.16%) and least for sweet potato derived starches (23.22%) and all the cereal starches (14.97%). These properties demonstrate the untapped potential of cassava and tuber based starches for use in food and non-food applications previously dominated by cereal starches.Key words: Tuber starch, root crop starches, cereal starches, amylose, amylosis

Estimates for heritability and consumer-validation of a penetrometer method for phenotyping softness of cooked cassava roots

Although breeders have made significant progress in the genetic improvement of cassava ( Manihot esculenta Crantz) for agronomic traits, lack of information on heritability and limited testing of high-throughput phenotyping methods are major limitations to improving root quality traits, such as softness after cooking, which rank high among Ugandan consumers. The objectives of this study were to determine heritability for softness of cooked cassava roots, and quantify the relationship between penetrometer and consumer testing methods for phenotyping softness of cassava roots. Softness defined as the maximum force (N) needed to penetrate cooked root samples using a penetrometer, was evaluated at four cooking time intervals: 15, 30, 45, and 60 min on 268 cassava genotypes. Estimates of broad-sense heritability (repeatability) ranged from 0.17 to 0.37, with the highest value observed at 45 min of cooking time interval. In the second study involving 135 cassava consumers from Kibaale district in Uganda, penetrometer measurements of cooked roots from six cassava varieties were found to be in strong agreement (r2 = 0.91; P-value = 0.003) with ordinal scores of root softness from consumer testing. These results suggest that: (a) softness of cooked cassava roots is a trait amenable for evaluation and selection; and (b) a penetrometer can readily be used for assessment of cooked root softness. These findings form the basis for operationalising the routine assessment of root softness in cassava breeding trials, an output that will enhance ongoing efforts to breed for desired end-user root quality traits.Les s\ue9lectionneurs ont fait des progr\ue8s consid\ue9rables dans l\u2019am\ue9lioration g\ue9n\ue9tique des caract\ue8res agronomiques du manioc ( Manihot esculenta Crantz). Cependant un manque de m\ue9thodes de ph\ue9notypage haut-d\ue9bit adapt\ue9es aux caract\ue8res de qualit\ue9s tel que la fermet\ue9 de la racine apr\ue8s cuisson, essentiel pour les consommateurs Ougandais. Cette \ue9tude ambitionne a) de determiner l\u2019h\ue9ritabilit\ue9 de la fermete de racine cuite b) de quantifier la relation entre l \ue9valuation de la fermet\ue9 de racine cuite au p\ue9n\ue9trom\ue8tre et un panel consommateurs. Cette \ue9valuation a \ue9t\ue9 realisee a quatre intervals de temps: 15, 30, 45 et 60 minutes sur 268 genotypes de manioc. Pour d\ue9finir l\u2019h\ue9ritabilit\ue9 de la fermet\ue9 de la racine, celle ci a \ue9t\ue9 d\ue9finie par la force maximum (N) n\ue9cessaire pour p\ue9n\ue9trer des \ue9chantillons de racines incluant diff\ue8rent temps de cuisson (15, 30, 45, and 60 min) a l\u2019aide d\u2019un p\ue9n\ue9trom\ue8tre. L\u2019h\ue9ritabilit\ue9 au sens large (ou r\ue9p\ue9tabilit\ue9) observ\ue9e varie de 0.17 a 0.37, la valeur la plus \ue9lev\ue9 \ue9tant observ\ue9e pour un temps de cuisson de 45 minutes. Dans une seconde \ue9tude impliquant 135 consommateurs du district de Kibaale (Ouest de l\u2019Ouganda), les mesures au p\ue9n\ue9trom\ue8tre de racines cuites de six vari\ue9t\ue9s ont confirm\ue9es la forte correlation (r2 = 0.91; P-value = 0.003) avec les valeurs ordinales de fermet\ue9 de racine du panel consommateur. Les r\ue9sultats de cette \ue9tude indiquent que cette m\ue9thodologie de ph\ue9notypage est a) utile pour l\u2019 \ue9valuation de la fermet\ue9 sur des racines cuites en selection et b) d\ue9montre que l\u2019usage du p\ue9n\ue9trom\ue8tre est efficace pour celle ci. Ces r\ue9sultats offrent aux s\ue9lectionneurs une methode d\u2019 \ue9valuation de routine de la qualite de racine pour les essais experimentaux. Ceux ci contribueront aux efforts actuels pour l\u2019am\ue9lioration des caract\ue8res qualit\ue9s chers aux consommateurs

Development and validation of near-infrared spectroscopy procedures for prediction of cassava root dry matter and amylose contents in Ugandan cassava germplasm

Background Cassava utilization for food and/or industrial products depends on inherent properties of root dry matter content (DMC) and the starch fraction of amylose content (AC). Accordingly, in this study, NIRS models were developed to aid breeding and selection of DMC and AC as critical industrial traits taking care of root sample preparation and cassava germplasm diversity available in Uganda. Results Upon undertaking calibrations and cross-validations, best models were adopted for validation. DMC in calibration samples ranged from 20 to 45g kg^-1 while for amylose content it ranged from 14 to 33g kg^-1. In the validation set average DMC was 29.5g kg^-1 while for the amylose content it was 24.64g kg^-1. For DMC, Modified Partial least square (MPLS) regression model had regression coefficients (R2) of 0.98 and 0.96 respectively, in the calibration and validation set. These were also associated with low bias (-0.018) and ratio of performance deviation that ranged from 4.7 to 5.0. In addition, standard error of prediction values ranged from 0.9g kg^-1 to 1.06g kg^-1. For AC, the regression coefficient was 0.91 for the calibration set and 0.94 for the validation set. A bias equivalent to -0.03 and ratio of performance deviation of 4.23 were observed. Conclusions These findings confirm the robustness of NIRS in estimation of dry matter content and amylose content in cassava roots and thus justify its use in routine cassava breeding operations