Dominique Dufour

On-line automated monitoring and control systems for CO2 and O2 in aerobic and anaerobic solid-state fermentations

Abstract Two systems for monitoring and control of gases from solid-state cultures have been developed. The first involves on-line automated monitoring of CO 2 and O 2 concentration in exhaust gases from eight fermenters or eight gas sampling ports in a large fermenter. It proved to be efficient in obtaining information on the physiological state and respiration rate of the culture in a real-time process. Furthermore, the specific growth rate (μ) can be estimated reliably by gas measurements in aerobic cultures. The second system is for automated control of exit gases from aerobic solid-state fermentations. It permitted elimination of biomass and temperature gradients in a large fermenter due to the maintenance of culture under non-limiting conditions on oxygen. These two systems have applicability in aerobic and anaerobic solid-state processes and were found to be reliable in a number of fermentation experiments as well as optimization of solid-state fermentation. To our knowledge no earlier report of such versatile and reliable on-line automated monitoring/control systems has appeared.

Characterization of heat and mass transfer during deep-fat frying and its effect on cassava chip quality

Abstract Heat and mass transfer in thin slices of fresh cassava ( Manihot esculenta Crantz) were studied. The frying process was described as two stages involving inner vaporization of mainly high available water, which can be transported inside the material, at temperature around the boiling point and inner vaporization of “bound” water at higher temperature depending on water desorption equilibrium. During the first stage, drying rate was controlled by the serial association of both diffusive and convective thermal resistances. During the second stage, temperature gradients decreased and the core temperature followed the corresponding boiling curve (water desorption curve against boiling temperature). Oil uptake depended on the thermal history of the product, characterized by its final water content. Apparent elasticity modulus and color changes were similar for a same final water content. Boiling curves and core temperature measurement are therefore proposed as a means of predicting the development of chip quality during frying.

Comparison of pasting and gel stabilities of waxy and normal starches from potato, maize, and rice with those of a novel waxy cassava starch under thermal, chemical, and mechanical stress.

Functional properties of normal and waxy starches from maize, rice, potato, and cassava as well as the modified waxy maize starch COLFLO 67 were compared. The main objective of this study is to position the recently discovered spontaneous mutation for amylose-free cassava starch in relation to the other starches with well-known characteristics. Paste clarity, wavelength of maximum absorption (lambda(max)), pasting properties, swelling power, solubility, and dispersed volume fraction measurements and gel stability (acid and alkaline resistance, shear, refrigeration, and freeze/thaw stability) were evaluated in the different types and sources of starch included in this study. lambda(max) in the waxy cassava starch was reduced considerably in comparison with that of normal cassava starch (535 vs 592 nm). RVA peak viscosity of waxy cassava starch was larger than in normal cassava starch (1119 vs 937 cP) and assumed a position intermediate between the waxy potato and maize starches. Acid, alkaline, and shear stability of waxy cassava starch were similar to normal cassava except for alkaline pH, at which it showed a low effect. Gels from normal root and tuber starches after refrigeration and freeze/thaw had lower syneresis than cereal starches. Gels from waxy starches (except for potato) did not present any syneresis after 5 weeks of storage at 4 degrees C. Waxy cassava starch was the only one not showing any syneresis after 5 weeks of storage at -20 degrees C. Natural waxy cassava starch is, therefore, a promising ingredient to formulate refrigerated or frozen food.

The effect of pre-harvest pruning of cassava upon root deterioration and quality characteristics

One of the major constraints of cassava as a crop is its perishability. Physiological deterioration, parenchymal blue–black vascular streaking, often starts within 24 h after harvest. This paper presents the results of a detailed study of the effects of pre-harvest pruning upon post-harvest physiological deterioration (PPD) and some other quality characteristics. Six cultivars, grown at CIAT (Centro International de Agricultura Tropical), with varying intrinsic susceptibility to PPD, were assessed at pruning–harvest intervals of 0, 2, 4, 6, 8, 10, 15, 20, 25, 28 and 39 days. After harvesting, the roots were analysed. For the unpruned plants a low susceptibility was found to coincide with a low dry matter content and a high sugar content. After pruning, the susceptibility for all cultivars was drastically reduced, reaching a minimum of around 25% of the original value for a pruning–harvest interval of up to 25 days. Beyond this interval the plants slowly develop new leaf canopy, normal assimilation sets in again and the starch content increases. Analysis of the cassava roots revealed a relationship between the combined sugar and starch contents and the interval duration, and that sugar and starch contents were inversely related to each other. The sugar content increased with the interval period, probably as a result of starch hydrolysis. Other properties such as the contents of dry matter, cyanogen, scopoletin, amylose and reducing sugars and the starch pasting properties were not affected by pruning to a comparable, interval-dependent, extent. It is concluded that the sugar content, ie the sugar/starch ratio, of cassava roots is positively related to their resistance to post-harvest physiological deterioration. © 2000 Society of Chemical Industry

Differentiation between Cooking Bananas and Dessert Bananas. 1. Morphological and Compositional Characterization of Cultivated Colombian Musaceae (Musa sp.) in Relation to Consumer Preferences

The morphological, physical, and chemical characteristics of 23 unripe cultivated varieties of Colombian Musaceae were assessed. Fresh pulp dry matter helped to discriminate the following consumption subgroups: FHIA dessert hybrids (hydes: 24.6%) < dessert bananas (des: 29.4%) < nonplantain cooking bananas (cook: 32.0%) < FHIA cooking hybrids (hycook: 34.2%) < plantains (pl: 41.1%). Banana flour starch content on dry basis (db) varied from 74.2 to 88.2% among the varieties, with: pl: 86.5% > cook and hycook: 84% > des: 81.9% > hydes: 79.7% (p <or= 0.01). Flour pH varied in the range 4.8 to 6.2, with the highest pH for the plantain subgroup (5.6), which also had lower titratable acidity than those of the cooking banana and FHIA groups with 7.9, 13.6, and 15.6 mEq H(+)/100 g db, respectively (p <or= 0.05). pl and hycook presented the highest glucose and fructose contents at 0.8% and 1.5% (p <or= 0.05). No significant differences were observed between the groups in proteins (3.2%), total soluble sugars (1.7%), and crude fibers (3%). pl had lower ash, calcium, and magnesium contents (2.7%; 8.4 and 90.7 mg/100 g db) than des (3.2%; 9.3 and 117.9 mg/100 g db) and hydes (3.9%; 23.7 and 125 mg/100 g db) (p <or= 0.05). pl and des had significantly lower peel percentages (38%) than the other subgroups (42-45%). The principal components analysis (PCA) highlights the strong relationship between some of the varietal characteristics and the consumption pattern, which is especially marked for the plantain subgroup in relation to stakeholder and the consumer preferences.

Development of waxy cassava with different biological and physico-chemical characteristics of starches for industrial applications

The quality of cassava starch, an important trait in cassava breeding programs, determines its applications in various industries. For example, development of waxy (having a low level of amylose) cassava is in demand. Amylose is synthesized by granule‐bound starch synthase I (GBSSI) in plants, and therefore, down‐regulation of GBSSI expression in cassava might lead to reduced amylose content. We produced 63 transgenic cassava plant lines that express hair‐pin dsRNAs homologous to the cassava GBSSI conserved region under the control of the vascular‐specific promoter p54/1.0 from cassava (p54/1.0::GBSSI‐RNAi) or cauliflower mosaic virus (CaMV) 35S (35S::GBSSI‐RNAi). After the screening storage roots and starch granules from field‐grown plants with iodine staining, the waxy phenotype was discovered: p54/1.0::GBSSI‐RNAi line A8 and 35S::GBSSI‐RNAi lines B9, B10, and B23. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis showed that there was no detectable GBSSI protein in the starch granules of plants with the waxy phenotype. Further, the amylose content of transgenic starches was significantly reduced (<5%) compared with the level in starch granules from the wild‐type (about 25%). The inner structure of the waxy starch granules differed from that of the untransformed ones, as revealed by transmission electron microscopy analysis as well as morphological changes in the iodine–starch complex. Endothermic enthalpy was reduced in waxy cassava starches, according to differential scanning calorimeter analysis. Except B9, all waxy starches displayed the A‐type X‐ray diffraction pattern. Amylogram patterns of the waxy cassava starches were analyzed using a rapid viscosity analyzer and found to have increased values for clarity, peak viscosity, gel breakdown, and swelling index. Setback, consistency, and solubility were notably reduced. Therefore, waxy cassava with novel starch in its storage roots was produced using the biotechnological approach, promoting its industrial utilization. Biotechnol. Bioeng. 2011; 108:1925–1935.

Prediction of carotenoids, cyanide and dry matter contents in fresh cassava root using NIRS and Hunter color techniques

Efforts are currently underway to improve carotenoids content in cassava roots through conventional breeding as a strategy to reduce vitamin A deficiency. However, only few samples can be quantified each day for total carotenoids (TCC) and β-carotene (TBC) contents, limiting the gains from breeding. A database with >3000 samples was used to evaluate the potential of NIRS and chromameter devices to predict root quality traits. Maximum TTC and TBC were up to 25.5 and 16.6 μg/g (fresh weight basis), respectively. NIRS predictions were highly satisfactory for dry matter content (DMC, R(2): 0.96), TCC (R(2): 0.92) and TBC (R(2): 0.93). NIRS could also distinguish roots with high or low cyanogenic potential (R(2): 0.86). Hunter color parameters could also be used for predictions, but with lower accuracy than NIRS. NIRS or chromameter improve selection protocols, allowing faster gains from breeding. Results also demonstrate that TBC and DMC can be improved simultaneously (required for the adoption of biofortified cassava).

Differentiation between Cooking Bananas and Dessert Bananas. 2. Thermal and Functional Characterization of Cultivated Colombian Musaceae (Musa sp.)

The starch and flour thermal and functional characteristics of 23 cultivated varieties of bananas in Colombia were assessed. Onset temperature for gelatinization of starches measured by differential scanning calorimetry (DSC) varied from 59.7 to 67.8 degrees C, thereby significantly differentiating dessert bananas (63.2 degrees C) from nonplantain cooking bananas (65.7 degrees C) from FHIA hybrids (66.6 degrees C) and plantains (67.1 degrees C). FHIA hybrids are significantly discriminated from dessert banana landraces but not from the cooking group. The starch amylose contents varied from 15.4 to 24.9%; most dessert banana starch amylose contents were below 19%, whereas in cooking banana starches the contents were over 21%. Flour functional properties were assessed by Rapid ViscoAnalyser (RVA) using silver nitrate as alpha-amylase inhibitor. The flour pasting temperature was relevant to differentiate dessert bananas (69.5 degrees C) from FHIA dessert hybrids and nonplantain cooking bananas (72.8 degrees C) from cooking hybrids and plantains (75.8 degrees C). Among other criteria, the cooking ability also helped to differentiate dessert bananas and FHIA hybrids from cooking bananas. A close relation between cultivar genotypes and uses with the thermal and pasting properties were revealed.

Kinetics of moisture loss and fat absorption during frying for different varieties of plantain

This study compares the behaviour of four varieties of green plantain at their initial stage of maturity during the frying process. A variety traditionally used for the manufacture of thin plantain chips (Dominico Harton commun) and three other varieties found in Latin America (Bouroukou, Bluggoe and FHIA 21) were used. The varieties were characterised by measuring initial moisture content, total sugar content, reducing sugar content, starch content and apparent density. Moisture loss and fat uptake kinetics during frying were assessed at different temperatures (145, 165 and 185°C). With all four varieties, the time required to produce a final moisture content of 40 g kg−1 (wb) was about 90 s at 165°C and 185°C. Use of a lower temperature (145°C) extended the processing time to 150 s. On the other hand, temperature had very little effect on fat content, which proved to be essentially determined by the variety of plantain. Fat content for final water content levels of 40 g kg−1 (wb) ranged from 300 g kg−1 (wb) for Bouroukou to 450 g kg−1 (wb) for Bluggoe regardless of the processing temperature. © 1999 Society of Chemical Industry

Peach palm (Bactris gasipaes) in tropical Latin America: implications for biodiversity conservation, natural resource management and human nutrition

Peach palm (Bactris gasipaes) is a multi-purpose palm tree native to tropical Latin America, which is predominantly cultivated by smallholders in agroforestry systems. The fruits are rich in starch and contribute importantly to food security and the cash income of farmers who cultivate them. Complex value chains have emerged that link producers to consumers, but irregular product quality and market chain inequalities undermine the economic well-being of producers and retailers. Peach palm is genetically diverse, but screening for traits of commercial and nutritional interest is required to enhance the use of its genetic resources. Alliances between public organizations and private enterprises are needed to realize the potential for processing novel products from peach palm, especially in the pharmaceutical and cosmetic sectors. The diverse challenges that emerge at different stages of production, processing and marketing require participatory research that directly involves stakeholders from the beginning.