Sunee Chotineeranat

Processing of cassava waste for improved biomass utilization

Cassava (Manihot esculenta Crantz) pulp is the solid waste produced as a consequence of starch production. This pulp contains a high starch content (50–60% dry basis), causing an environmental problem with disposal. In order to recover this starch, physical or biological treatment of the material must be employed. Pulp was treated either by sonication or incubation with a multi-enzyme mixture of cellulase and pectinase. Both methods were found to improve efficiency of starch extraction by disrupting the complex structure of polysaccharides associated with and entrapping starch granules. In the enzymatic treatment, the content of cellulase and pectinase for high efficiency of starch extraction determined as the yield of liberated starch was investigated using Response Surface Methodology. Use of either cellulase or pectinase alone failed to effectively improve starch extraction. Cellulase concentration seemed to have a greater effect on efficiency of starch yield than pectinase concentration. Treatment of pulp with 15 Novo cellulase units (NCU) of cellulase and 122.5 polygalacturonase (PG) units of pectinase per g dry pulp for 60 min resulted in 40% starch recovery. Quality characteristics of the liberated starch, including paste viscosity (measured by Rapid Visco Analysis) and thermal properties (measured by Differential Scanning Calorimetry) were comparable to a primary starch obtained by root extraction. Susceptibility of the liberated starch to α-amylase was inferior to that of a primary starch. Cellulase and pectinase, however, increased α-amylase susceptibility of the starch remaining in the pulp.

Impact of water stress on yield and quality of cassava starch

Abstract Cassava ( Manihot esculenta Crantz) is an important source of industrial raw materials. Products obtained from cassava include chip/pellets for animal feed and starch. Important for major industrial uses are the amount and quality of starch obtained from this crop. Production efficiency, including yield and quality of starch, from cassava is markedly influenced by environmental conditions, especially water stress during early plant development and immediately before root harvest. In early plant development plants deprived of water for the first 6 months were characterized by a lower yield of starch compared to plants without water stress (starch yields of six varieties including Rayong 1, Rayong 5, Rayong 60, Rayong 90, Kasetsart 50 and CMR 33-57-81 were 0.1–0.2 and 5.0–8.7 t/ha for water-stressed and without water-stressed plants). Furthermore, starch from plants deprived of water for the first 6 months of growth, was functionally different to that laid-down under optimum growing conditions. Plants responded to subsequent rainfall and after 2 months contained significant amounts of starch, though this amount was less than was expected. Despite the fact that water-stressed plants responded to the availability of water by producing starch, most functional properties remained different. The portfolio of changes was sufficient as regards the starch of lower quality. Most effected were the hydration properties. Starch granules despite being smaller (mean size and distribution) than expected were morphologically normal. A second drought period further influenced some of the starch properties, but the sustained influence of the early drought seemed to dominate the response of the plants starch metabolism. All varieties were similarly affected.

Edible canna (Canna edulis) as a complementary starch source to cassava for the starch industry

Abstract Edible canna (Canna edulis Ker) as an alternative starch source was evaluated on the basis of genetic characteristics, agronomic traits and starch properties. Four canna varieties indigenous to Thailand were examined including Thai-green, Japanese-green, Thai-purple and Chinese-purple and compared with cassava (Manihot esculenta Crantz). Using the Random Amplified Polymorphic DNA (RAPD) technique employing ten 10-base primers, four primers implied that at least three types of canna including Thai-green, Japanese-green and Thai/Chinese-purple existed and corresponded to plant characteristics as identified by flower, stem, leaf and rhizome colors. Despite genetic diversification, starch properties were not variable. All four varieties produced 30.4–38.4 tonne/ha of rhizomes with starch content about 13% (wet basis). Starch yields of canna (4.1–4.9 tonnes/ha) were comparatively lower than cassava (6.5 tonnes/ha). The starches were characterized by giant granules (10–80 μm), and compared with cassava starch pastes had a higher peak viscosity (930–1060 BU for canna starches and 815 BU for cassava starch), occurring at a higher temperature. Pastes of canna starch were more stable and when cooled, viscosity increased to 1800 BU. Gelatinized pastes of canna starches also rapidly formed good gels on cooling. It is evident that edible canna provides starches with very attractive properties and totally different from cassava and is the greatest promise for the new base starch to be employed complementarily with cassava starch.

The influence of time and conditions of harvest on the functional behaviour of cassava starch: a proton NMR relaxation study

The extent of irrigation of crops in the field not only affects crop yield but also the functionality of the harvested product. This irrigation effect severely affects the processing response of starch harvested from Cassava and leads to industrial quality control problems. In this paper we show how the NMR transverse proton relaxation spectrum is a sensitive probe of the effect of irrigation on cassava starch functionality. The results suggest that increased irrigation results in a looser packing of the amylose and amylopectin chains in the cassava starch granule that facilitates their plasticization and gelatinization.

Effect of calcium ions on ethanol production from molasses by Saccharomyces cerevisiae

One of the most widely used feedstocks for potable or biofuel ethanol fermentation is blackstrap molasses, a byproduct of cane sugar production. Inconsistent quality of molasses frequently found in industrial production, however, makes ethanol production much less efficient and cost-ineffective. Besides fermentable sugars (sucrose, glucose and fructose) present in molasses, calcium is also found in the range of 10–20% of the total carbonated ash (15% by weight). In the sugar process, calcium is usually applied as lime, CaO, during defecation, which sometimes results in over-liming if juice quality is poor. In this study, the role of calcium residues (0–0.72% w/v of Ca2+ in the form of calcium chloride) on fermentation efficiency of yeast was evaluated using model solutions of sucrose, glucose and fructose (20% w/v). The results suggest a detrimental effect of calcium ions on yeast performance which was concentration dependent. A slight decrease in fermentation rates and ethanol yields was evident when calcium was present at 0.18% w/v Ca2+ in all sugar solutions. This effect was more pronounced when calcium ion concentration increased. At 0.72% w/v of Ca2+, the rates of fermentation and ethanol yields of all sugars were considerably decreased (the ethanol yields decreased by 14–25% relative to the control sample, i.e. no calcium ion added). At a very high concentration of Ca2+ (2.16% w/v), yeast fermentation of sucrose was almost absolutely inhibited. This might be, in part, due to the inhibition effect of invertase enzyme for conversion of sucrose to invert sugars, a limiting step in ethanol fermentation of sucrose by yeast. The pretreatment of molasses by acid prior to fermentation was then introduced to remove calcium which improved the fermentation efficiency.

An Improved Dewatering Performance in Cassava Starch Process by a Pressure Filter

As part of an ongoing study to improve the cassava starch manufacturing process, a potential improvement to the dewatering stage was explored. Two types of starch dewatering were compared, a pressure filter and a conventional centrifuge. Performance with respect to the dewatering efficiency of the starch slurry, implied by the filtration rate and percentage of dry solids in circulation, was measured for a pressure filter and a conventional centrifuge. For the pressure filter, effect of different filter cloths, feed time and pressing time were evaluated. At all filtering conditions, the pressure filter provided improved dewatering efficiency. The filtration rate significantly increased from 162 to 226 g m -2 s -1 and starch loss, to the circulation, notably decreased from 15 to 0.15%. Improvement in processing-efficiency did not sacrifice starch quality. Granule morphology and functional properties, such as paste viscosity, water adsorption, and solubility characteristics remained unchanged. One notable exception was that chemical compounds and microorganisms appeared to he more readily absorbed to the granule surface. The pressure filter not only improved dewatering efficiency but also minimized production cost due to a lower starch cake moisture, which requires less energy consumption for subsequent drying.