Modeling of starch gelatinization during cooking of cassava (Manihot esculenta Crantz)

There is a great variability in cooking time and final texture among cassava cultivars and one factor in determining these characteristics is the age of roots at harvest. Final texture after cooking is an important attribute for the acceptability of cassava and starch gelatinization has a role in softening the tissue. Two cassava cultivars at two different harvest maturities were cooked at 90 °C and at boiling water temperature (98 °C) and the extent of gelatinization was determined using an iodine colorimetric method. A generalized model for starch gelatinization, considering temperature and cooking time as continuous variables and age at harvest as qualitative variable, was used to model the cooking process and applied for each cultivar. At 90 °C IAPAR-19 Pioneira reached maximum gelatinization in 32 min for the 12 month old sample and 88 min for the 25 month old sample, while double the time was needed for Catarina Amarela. At 98 °C Pioneira gelatinized in 12 min for the 12 month and 32 min for the 25 month old sample while Catarina Amarela needed 28 and 56 min. Calculated activation energy for starch gelatinization was 122.3±5.2 and 98.6±4.7 kJ/mol for cultivar IAPAR-19 Pioneira and Catarina Amarela, respectively.     

Changes in some chemical constituents during the fermentation of cassava tubers (Manihot esculenta, Crantz)

Cassava tuber, Manihot esculenta, Crantz, was processed, after five days of fermentation, into ‘gari’ and ‘lafun’. The pH fell from 6·5 to 4·3 in the former. Titratable acidity increased during the course of fermentation. No cyanide residue was detected in gari by fluorimetry although low cyanide levels were detected in some samples of lafun. Thin layer chromatography (TLC) of extracts from gari confirmed the absence of cyanogenetic glycosides.     

Infestation of dried cassava (Manihot esculenta Crantz) by Prostephanus truncatus (Horn( (Coleoptera: Bostrichidae)

Stored dried cassava is known to become heavily infested by Prostephanus truncatus (Horn). A field study was undertaken in Tanzania to determine the extent of losses that this pest could cause in fermented and unfermented dried cassava roots stored over a period of about 4 months. In fermented roots, the mean weight loss (±SD) rose to 73.6 ± 25.9% over this period compared with 52.3 ± 12.0% in unfermented roots. At each time interval that roots were examined, the weight loss in fermented roots was significantly higher. Subsequent laboratory studies, undertaken to identify some of the factors responsible for this difference between the two types of cassava comprised (1) a determination of the length of larval and pupal development at 27°C and 50 or 70% r.h., (2) adult preference for the two types, and (3) their susceptibility to adult boring. P. truncatus developed at a similar rate in both fermented and unfermented roots, but the adults appeared to prefer the fermented cassava possibly because it was easier to bore into. This was certainly one factor making fermented roots more susceptible to damage by adults. It is concluded that although P. truncatus caused lower weight loss in the unfermented compared with the fermented roots, both were so heavily damaged that it is not worth recommending the storage of one rather than the other. The role of cassava as an intermediate host for P. truncatus is discussed and consideration is given to the need to control the beetle in cassava in order to reduce cross-infestation to maize.     

Textural changes during cooking of cassava (Manihot esculenta Crantz) roots

Consumer acceptability of cassava food products depends mostly on the final texture of the cooked tissue. The age of the roots at harvest seems to be an important factor in determining the final texture. Two cassava cultivars harvested at 8, 17 and 30 months after planting were used for texture loss determination by a puncture test after cooking at constant boiling water temperature. Kinetic data were analysed using fractional conversion. The raw tissue showed decreasing or constant peak yield force values as the root aged. There was a gradual first‐order softening during cooking, with decreasing rate constant as the root aged. Copyright © 2004 Society of Chemical Industry     

Fresh cut ‘Tommy Atkins’ mango pre-treated with citric acid and coated with cassava (Manihot esculenta Crantz) starch or sodium alginate

This work aimed to evaluate quality parameters of ‘Tommy Atkins’ mango slices pre-treated with citric acid and cassava starch or sodium alginate edible coatings, with or without glycerol. Samples only treated with citric acid were also evaluated. Mango slices dipped in sanitising solution were used as control. Colour parameters, mechanical properties, weight loss and respiration rate were analysed during 15 days at 5 °C. Cassava starch coating, with or without glycerol, provided higher stress at failure and lightness values than control sample throughout storage (p ≤ 0.05). The citric acid promoted colour preservation, but increased significantly samples weight loss during storage. Sodium alginate coatings did not maintain quality characteristics, showing stress at failure and lightness values lower than control after 15 days. All coatings reduced respiration rate, but citric acid dipping and cassava starch coating without glycerol treatments were more effective, reaching values around 41% lower, when compared to control sample.

Industrial Relevance

Fresh-cut mangoes are appreciated world-wide for its exotic flavour and nutritional composition. However, their shelf life is limited by changes in colour, texture, appearance and microbial growth. The edible coatings act as gas and water vapour barrier, extending the storage time of fresh-cut fruit and vegetables. Thus, cassava starch and alginate are alternatives to preserve minimally processed mangoes, maintaining the quality parameters of fresh fruit. This work is useful for the minimal processing industry in order to increase shelf life of fresh-cut mangoes, which can be considered an alternative to fast food and other ready-to-eat products, attending the demand for healthy and convenient foodstuffs.     

Screening of Starch Quality Traits in Cassava (Manihot esculenta Crantz)

Cassava (Manihot esculenta Crantz) is one of the most important sources of starch in the tropics. There is limited and contradictory information regarding cassava starch characteristics. The International Center for Tropical Agriculture (CIAT) holds in trust FAO's cassava germplasm collection. Starches from 3272 landraces (including 12 wild relatives) and 772 improved clones were extracted and analyzed over a period of several years. In most cases only one starch sample per genotype was analyzed. Average cyanogenic potential was 327 ppm but considerably higher in the landraces (340 ppm) than in improved clones (267 ppm). Average total and reducing sugars were slightly higher in improved clones (4.06 and 1.56%, respectively) than in landraces (3.68 and 1.25%, respectively). Amylose content was similar in both types of germplasm with an average of 20.7%. Average pasting temperature was 65.3°C. Maximum viscosity was 777.5 mPa s, breakdown was 298.1 mPa s, consistency was 155.8 mPa s and setback was ‐144.5 mPa s. The large sample of starches analyzed provides very robust information regarding the actual characteristics of cassava starch.     

Physicochemical characteristics of starches and flours from cassava varieties having different cooked root textures

Starches and flours from 12 cassava varieties having differences in cooked root texture - mealy, firm and mealy & firm - were investigated, with a particular focus on aspects of physicochemical characteristics. It was found that chemical composition (protein, lipid, fiber, ash), pasting properties, firmness of gel, thermal properties, morphology and granular size distribution and crystalline pattern of starches from the 12 varieties were not significantly different. On the contrary, cassava flours which consisted of both starch and non-starch components exhibited wider variations in these properties, especially pasting properties and firmness of gel, than the starches. All flour samples had lower paste viscosities than their corresponding starches. Pasting temperatures of flours were in a range of 70-74 ^°C, which was higher than those of starches (67-70 ^°C). Fluctuation in the values of pasting parameters of flours among the varieties was associated with the variations in the chemical composition and α-amylase activity, i.e. paste viscosity and setback were positively correlated to starch content and negatively correlated to α-amylase activity, while protein, lipid and fiber did not show correlation with pasting parameters. Cassava starches from all varieties, except the F-18 variety, had higher firmness of gels than their corresponding flours. Firmness values (except the F-18 variety) of starches were in a range of 149-207 g, whereas those of flours were 75-163 g. Firmness of flour gels was negatively correlated to lipid and fiber content, while strong positive correlation was found with the amylase activity.     

Changes in activities of cell wall degrading enzymes during fermentation of cassava (Manihot esculenta Crantz) with citrobacter freundii

The cell wall degrading enzymes polygalacturonase (EC 3.2.1.15),pectinase (EC 3.1.1.11), cellulose (EC 3.2.1.4) and xylanase (EC 3.2.1.8), as well as α-amylase (EC 3.2.1.1) and phosphorylase (EC 2.4.1.1), were monitored during fermentation of cassava (Manihot esculenta Crantz) with Citrobacter freundii. All the enzymes were detected in cassava at the start. During fermentation, initial decreases in polygalacturonase, cellulase and xylanase were followed by increases which peaked as the tissue softened. There were significant (P<0.05) increases in pectinase, xylanase, cellulase, polygalacturonase and phosphorylase in inoculated cassava and the fermentation medium relative to controls (uninoculated cassava and medium) during the softening period. The control cassava did not ferment, indicating that the textural changes in inoculated cassava were due to enzymes secreted by C freundii. Studies on the effect of enzyme inhibition on fermentation showed that the pectic enzymes and cellulase were of primary importance and that inhibition of α-amylase and phosphorylase had no effect on the process.     

Changes in the ultrastructure and texture of prawn muscle (Macrobrachuim rosenbergii) during cold storage

Changes in the ultrastructure and proteolytic activity of prawn muscle were determined during storage at 5 °C, in order to better understand changes in physical and sensory texture measurements. Progressive deterioration of myofibril structure was observed during refrigeration of prawn for 14 d. The loss of density and order in Z-line alignment was first detected after 3 d of storage. Progressive disruption of Z-line, I-bands and M-lines was observed after 4-6 d of storage. Muscle degradation included pronounced disruption of the mitochondria as revealed by swollen cristae, loss of cristae material, and membrane breakage. Along with ultrastructural changes, decreased shear force values and mean textures scores were measured. An initial shear force value of 18.21 N/g decreased to 14.50, 12.46, and 10.79 N/g on days 3, 6, and 14, respectively. Mean texture scores indicated that prawn muscle maintained firm texture during 0-3 d of storage, and became soft during 4-6 d of storage. After 6 d of storage, the prawn texture was very soft. Increased deterioration of the muscle ultrastructure coincided with the increase of proteolytic microorganisms and salt soluble muscle proteins found by Sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It is concluded that the weakening of the ultrastructure is related to proteolytic activity and results in a more soft texture in prawns.     

Synthesis and Characterization of low DS Succinate Derivatives of Cassava (Manihot esculenta Crantz) Starch

Succinylation of cassava starch was carried out in aqueous medium to prepare derivatives with low degree of substitution (DS) and the physicochemical properties of the products were determined. A response surface design was used for the experiment with three levels of each of the three variables viz., concentration of succinic anhydride, reaction time and pH of the reaction medium. The reaction was followed in terms of the DS of the products and reaction efficiency (RE). The degree of substitution of the derivatives varied from 0.001 to 0.022 and reaction efficiency from 2.2 to 46.8%. The DS and RE showed an adequate fit to a second order polynomial model of the variables used. Succinylation brought about increase in the swelling volume, peak viscosity and paste clarity of the starch. However, the pasting temperature and solubility did not show any significant change. The in‐vitro α‐amylase digestibility of the succinylated derivatives decreased in comparison to that of native starch and this decrease correlated with a corresponding increase in DS.     

Microwave‐Assisted Synthesis and Characterization of Succinate Derivatives of Cassava (Manihot esculenta Crantz) Starch

The use of microwave heating to prepare very rapidly cassava starch succinates with high viscosity is described. A response surface design was used for the experiment and different factors affecting the succinylation of cassava starch, including concentration of succinic anhydride, reaction time, temperature and moisture content of the medium were investigated. The degrees of substitution of the modified starches increased with an increase in reaction time and were in the range 0.007 – 0.051. The products exhibited higher viscosity, lower pasting temperature, enhanced water binding capacity and reduced swelling and paste clarity than unmodified cassava starch. The results of this study indicated that succinylation of starch can be achieved in shorter reaction times, which offers a benefit to laboratories and industries involved in developing newer and more versatile uses for cassava starch.     

Effects of freezing/thawing on the microstructure and the texture of smoked Atlantic salmon (Salmo salar)

The changes in microstructure and texture during smoking of fresh and frozen/thawed Atlantic salmon was studied in fish from three different origins; ocean-ranched Atlantic salmon (Salmo salar) from Iceland and two groups of farmed Atlantic salmon from northern and western Norway. The muscle fibers from the frozen and thawed fish shrank, and the extracellular space increased compared to the fresh muscle. The muscle fibers from salmon fillets with smaller fiber diameter shrank to a less extent than fibers from salmon material with a larger fiber diameter. After smoking the space between the fibers and the fiber shrinkage increased to a higher extent in the muscle from the salmon that were frozen prior to smoking than muscle smoked from fresh salmon. The initial cross-sectional area of the fibers was not found to be related to the yield during smoking.     

Effects of cultivar and harvesting conditions (age,season) on the texture and taste of boiled cassava roots

Age of plant and environmental conditions during growing may affect texture (friability) and taste of boiled cassava roots. We investigated the quality of boiled roots of seven cultivars harvested at 10, 12 and 14 months in three different seasons.     

Water uptake and its impact on the texture of lentils (Lens culinaris)

Water uptake behavior of three cultivars of lentils (Boomer, French-green and Nugget) was studied at three different hydration temperature regimes (room temperature, 50 °C and 85 °C). Boomer had the highest amount of water uptake capacity (74.60 g water/100 g of seeds) at room temperature (20 °C) which can be linked with its pore properties. French-green lentils imbibed the largest amount of water at elevated soaking temperatures (50 °C and 85 °C) and can be attributed to its higher seed surface area to volume ratio, high protein content and relatively thinner seed coat. Water uptake at elevated temperatures (50 °C and 85 °C) were predicted by a two parameter Mitscherlich model (R² > 0.99, χ² < 0.5) within 1.36–3.07% average absolute error. At room temperature, only the water uptake of Boomer was reasonably predicted by this model. The texture (hardness) of the soaked lentils was found to be related the amount of water uptake and soaking temperature used rather than seed size or seed mass alone. The hardness values of Boomer, French-green and Nugget at 85 °C after 75 min soaking were reduced to 5.66%, 3.53% and 6.77%, respectively compared to their respective initial seed hardness values. The water uptake capacity of the aged Boomer was found to be significantly reduced compared to the fresh seeds (p < 0.01) while French-green and Nugget do not exhibit significant change (p < 0.05). During 72 h of germination, hardness of all lentil cultivars showed a typical pattern which decreased in the first 24 h followed by an increase compared to the hydrated seeds. A peak hardness value was obtained within 36–48 h before finally declining in all types of lentils. Structural changes within the cotyledon, such as depletion of starch granules, new nuclei formation and development of tissues in vascular bundles and rupture of the seed coat were observed during germination.     

Effect of canning process on texture of Faba beans (Vicia Faba)

The effects of different treatments such as traditional cooking, sterilizing at different time–temperature combinations and the addition of different brines on instrumental texture were evaluated. Previously, a comparison of different texture-measuring devices and optimisation of instrumental texture analysis were carried out. The results showed that all the texture-measuring devices used differentiated perfectly among the different products tested. Regarding heat treatments assayed, different sterilization treatments affected skin texture but had no significant effect when whole grain was considered. Finally, the addition of chelation agents to the brine did not affect the textural parameters but the commercial quality related to the production of Faba beans under a “Geographical Indication” had an important effect on the firmness of both the pericarp and whole seed and on pectin content.     

Effects of different salting and smoking processes on the microstructure, the texture and yield of Atlantic salmon (Salmo salar) fillets

The effect of different conditions during the salting and smoking process on the microstructure and the texture of salmon fillets was studied in interaction with different raw salmon material; ocean-ranched Atlantic salmon (Salmo salar) from Iceland and two groups of farmed Atlantic salmon (Salmo salar) from Norway, one from Northern Norway and one from Western Norway. The ocean-ranched salmon was found to have significantly smaller fiber diameters and higher shear force compared to the farmed fish. The cross-sectional area of the muscle fibers decreased during the salting and smoking process. Small differences were noted in the cross-sectional area between smoked fillets processed by different salting and smoking methods. However, the cross-sectional area of fibers in dry salted fish fillets from the farmed groups were significantly smaller than in the brine salted fillets, as the fibers shrunk more during dry salting than brine salting. The force required to shear the smoked fillets was significantly higher than for the unprocessed fillets, but was not found to be related to the different salting and smoking processes. Yield during smoking was not related to the initial cross-sectional area or the shear force of the unprocessed muscle.     

Carrot texture degradation kinetics and pectin changes during thermal versus high-pressure/high-temperature processing: A comparative study

Texture degradation kinetics of carrots during traditional thermal and novel high-pressure/high-temperature (HP/HT) processing were compared. Carrots were thermally (0.1 MPa) or HP/HT (600 MPa) treated in a temperature range from 95 to 110 °C. The residual texture (hardness) was determined using a texture analyzer. Kinetic parameters were estimated using a fractional-conversion model. In comparison to the thermal treatments, the HP/HT treatments resulted in a 10-fold slower texture degradation. The retarded texture loss was accompanied by a significantly lower degree of methyl-esterification (DM) of the cell wall pectin. Additionally, the effect of lowering the DM (by applying an HP pretreatment) and adding exogenous calcium ions prior to the HP/HT treatment on the texture of carrots was investigated. It was observed that this combined pretreatment resulted in a notably harder texture of HP/HT-treated carrots. However, a similar outcome was obtained by HP/HT treating carrots directly in a calcium chloride solution without preceding DM reduction and calcium soak. Excluding a separate pretreatment step will lead to time savings and a lower cost. This study demonstrated that HP/HT processing has great potential, concerning texture preservation of processed fruits and vegetables.     

An evaluation of edible red seaweed (Chondrus crispus) components and their modification during the cooking process

In this study, phycobiliproteins, carotenoids (β-carotene and lutein), volatile compounds and antioxidant activity were determined in dried, hydrated, boiled and steamed Chondrus crispus seaweed.