Degree Of Cooking Research Articles

Impact of the degree of cooking on starch digestibility of rice – An in vitro study

The impact of cooking degree on the starch digestibility of a non-waxy, cooked rice was examined through a simulated gastro-small intestinal in vitro digestion model. The starch hydrolysis of both non-homogenised and homogenised cooked rice samples during simulated digestion was also compared in order to examine the impact of grain structure on starch digestibility. Polished rice grains were cooked in boiling water for 10min (partially cooked) and 20min (fully cooked) to obtain samples of different cooking degree. No significant differences in the equilibrium starch hydrolysis (%) were observed among the partially and fully cooked grains, although significant differences were observed among the uncooked and cooked samples. The equilibrium starch hydrolysis (%) of homogenised rice was higher than its non-homogenised counterpart. These results showed that rice starch digestibility should not be affected by the cooking degrees related to starch gelatinisation, but was influenced by the modification/destruction of the grain structure during mechanical processing.

Effect of chemical composition and thermal properties on the cooking quality of common beans (Phaseolus vulgaris)

The relationship between chemical composition and thermal properties as it affects the degree of cooking in six varieties of common beans was investigated. The degree of cooking (DC) and the hardness of cooked beans were estimated by differential scanning calorimetry (DSC) and texture analysis, respectively. The total protein of bean seeds varied between 19.7 and 23.6%. However, the fractions of albumin, glutelin, and globulin showed significant differences among varieties. The amylose content varied from 18.4 to 36.0%. The first endothermic peak was associated with inactivated enzymatic activity, denaturation of low-protein fractions, and starch gelatinization, while the second endothermic peak was associated with the denaturation of heat-resistant protein fractions. The high values of minerals and chemical composition among bean varieties affected thermal behavior and was associated with greater hardness and a lower degree of cooking.

Effects of extrusion conditions on physical and nutritional properties of extruded whole grain red sorghum (sorghum spp)

In order to analyze the effects of extrusion temperature (T: 164, 182, 200 °C) and grits moisture content (g/100 g sample) (%M: 14, 16.5, 19) on textural and physicochemical properties of red sorghum extrudates, whole grain flour was extruded according to a factorial experimental design. The higher values for specific mechanical energy consumption (1006.98 J/g) and expansion (3.36) were obtained at 164 °C–14%M and for sensorial hardness at 164 °C–19%M. While for specific volume, the highest value (10.41 cm3/g) was obtained at 200 °C–14%M. Water solubility and water absorption were directly related with T and inversely with M. Microscopic observation of the samples indicates that the greatest cooking degree was obtained at 200 °C–4%M and the lowest at 164 °C–19%M. Extrusion at 182 °C–14%M allows obtaining an expanded product with good properties. Proximal composition did not show statistically significant differences with raw sample. Extruded sample showed a 25.4% reduction of available lysine and a 31% increase in protein digestibility.

Sensory Factors of Some Cassava Traditional Dishes: Foufou, Placali, Attiéké and Boiled

Ivorian traditional dishes, Placali, Attieke, Foufou and Boiled cassava were prepared from improved cassava varieties CM (52), I88/00158, IM84 and TMS4 (2) 1425 and control variety Bonoua 2 in “Centre National de Recherche Agronomique, Abidjan, Cote d’Ivoire”. The sensory factors (color, smell, taste, degree of cooking) of these five cassava varieties are determined. And it appeared that the different cassava varieties studied were suitable for the preparation of these dishes

Effect of steam cooking on the residual enzymatic activity of potatoes cv. Agria

The aim of this work was to study the influence of steam cooking on pectin methylesterase (PME) and endogenous α- and β-amylase activities in different tissues (cortex and pith) of raw and heat-treated potatoes cv. Agria. Three different cooking temperatures were chosen (55, 70 and 85 °C). For each cooking trial, time-temperature profiles were recorded and the degree of cooking was expressed in terms of cooking factor. Steam cooking contributed to significantly activate PME at 55 °C and to reduce its activity at the final processing temperature (85 °C), with the highest amount in the cortex (0.3745 ± 0.0007 µmol galacturonic acid (GA) g(-1) fresh weight (FW) min(-1) ) compared with the pith (0.2617 ± 0.0012 µmol GA g(-1) FW min(-1) ). The presence of heat-labile and heat-stable isoforms of PME in the considered potato tissues was also assumed. Heat treatment by steam resulted in a significant decrease in endogenous α- and β-amylase activities in both tissues compared with the raw potato, though without complete deactivation. Starch-degrading enzymes were also found to be differently distributed in the raw tuber. Steam cooking affected in different ways the assessed residual enzymatic activity in the considered tissues of potatoes cv. Agria. Further research is needed to confirm the results obtained.

Kinetics of thermal softening of cassava tubers and rheological modeling of the starch

Cassava or tapioca (Manihot esculenta Crantz) tubers having high amount of carbohydrate are utilized after boiling or processing into starch and flour. Textural properties of raw and cooked tubers depend on variety, maturity, growing environment, physico-chemical and starch properties. Starch is used in food preparations as gelling and thickening agent, stabilizer and texture modifier. This study aims at analyzing and modeling the textural, dynamic rheological and gelatinization properties of selected cassava varieties. The thermal softening behavior was analyzed by linear regression and fractional conversion techniques, rheological properties of the gelated starch by Maxwell and power law models. The varieties were classified based on their physico-chemical, texture profile, rheological and gelatinization properties by multivariate analysis. The textural, rheological and gelatinization properties were significantly affected by the varieties (p < 0.05). Thermal softening of tubers was modeled by dual mechanism first order kinetic model with rate constant values ranging from 0.081 to 0.105min(-1). Linear regression models with extremely good fit were obtained to explain the relationship between the degree of cooking and relative firmness. The dynamic spectra of the gelated starch showed the characteristics of concentrated biopolymer dispersion and described using Maxwell and power law model. The results showed that textural, rheological and gelatinization properties varied considerably among the varieties and besides the physico-chemical properties, interaction between them and structural make up of the tuber parenchyma had a great influence on cooking quality and rheological properties.

Control of Porosity and Expansion in Starch Extrusion by Monitoring Pressure at Die Outlet

Pore structure of starch extrudates is an important area of study in the food industry. Usually, changes in porosity also results in variations in skeletal material due to influence from degree of cook and type of cook (e.g., pure gelatinization vs. mechanical degradation). However, changing the pressure differential across the extruder die face provides a method by which expansion is controlled without influencing the skeletal material. Results from this study have shown that the volume fraction porosity can be varied from 0.23 to 0.53 with negligible effect on skeletal density. The expansion control method does not control pore sizes with distributions and means having an element of randomness. However, average pore wall thickness is linearly related to the pressure differential across the die face with a reduced pressure differential giving increased pore wall thickness and vice versa. Thus, controlled expansion can be used to produce products/samples that have the same skeletal material but different average pore wall thickness and total porosity.

Thermal treatments to partially pre‐cook and improve the shelf‐life of whole pearl millet flour

AbstractBACKGROUND: Pearl millet flour is highly susceptible to rancidity during storage. Urbanization has created a demand for pearl millet flour with longer shelf‐life and short cooking time. To try to prevent rancidity and pre‐cook the flour, pearl millet grain was subjected to the thermal treatments of toasting, boiling, and toasting then boiling.RESULTS: Fat acidity of flour from the untreated grain increased from 0.11 to 3.73 g KOH kg−1 during three months' storage, whereas the wet thermally treated samples showed no significant increase (P &gt; 0.05). Peroxide and conjugated diene values of wet thermally treated samples increased substantially, whereas those of flour from untreated grain did not, indicating less formation of rancid final oxidation products in the wet thermally treated samples. Starch degree of cook of the wet thermally treated samples was two times higher than the other treatments. Descriptive sensory evaluation revealed that porridges of flour from untreated grain were associated with hydrolytic rancidity, whereas those of flours from thermally treated grains were not. Consumers showed a preference for the porridges prepared from flour of boiled as well as toasted grain.CONCLUSION: Thermal treatments can be applied to extend whole pearl millet flour shelf‐life, and the treatment of boiling can be used to produce pearl millet flour that cooks more quickly. Copyright © 2008 Society of Chemical Industry

Magnetic resonance measurements of French fries to determine spatially resolved oil and water content

Deep-fat frying is a popular cooking method, particularly for potato based snack products. While fats and oils are known to add unique flavour, texture and overall palatability to foods, the absorption and distribution of oil is not well established. This work examines the absorption of oil in fried potato products with a range of nuclear magnetic resonance and magnetic resonance imaging techniques. We investigate the oil and water contents in French fries based upon the distribution of relaxation times. Relaxation times from different oil and water environments overlap precluding a simple analysis. We develop several techniques for isolating the oil signal from the water signal, and present images mapping the oil absorption as a function of the degree of cooking. Lastly, we present an image derived T 2 map. Spatially resolving the relaxation times permits quantification of the oil and water contributions in the crust and in the core.

Texture analysis of raw and cooked tubers of short‐duration lines of cassava by multivariate and fractional conversion techniques

AbstractBACKGROUND: Cassava tubers are mainly consumed after boiling in water. Their cooking quality depends on the variety, maturity, growing conditions and physicochemical and starch properties. In this study the textural and gelatinisation characteristics of ten short‐duration lines of cassava were assessed. Textural changes due to cooking were modelled by fractional conversion techniques and correlated with gelatinisation and physicochemical properties by principal component analysis.RESULTS: There was a significant variation (P &lt; 0.05) in the textural properties of tubers and the thermal and pasting properties of flours among varieties. The degree of cooking and relative firmness of tubers were modelled by a linear equation. The thermal softening behaviour was modelled by a dual‐mechanism first‐order kinetic model with rate constant values ranging from 0.106 to 0.190 min−1. About 69.21% of the total variation in texture profile, gelatinisation and physicochemical parameters could be explained by the first three principal components.CONCLUSION: The results indicated that the textural and gelatinisation properties varied considerably among different varieties. However, the interaction between the components of the tubers and the structural make‐up of the tuber tissues played a more important role than the physicochemical and functional properties. Copyright © 2008 Society of Chemical Industry

In-line colour monitoring during food extrusion: Sensitivity and correlation with product colour

Abstract During food extrusion the degree of cooking and the quantity of expensive colorants used, both influence colour and the aesthetic appeal of the product. Thus, the use of a fiber optic equipped spectrophotometer for colour monitoring inside the extruder holds great potential for product characterization and effective quality control. However, this approach presents two difficulties: (1) inadequate sensitivity of the spectrophotometer to dark colours; and (2) the need to correlate the colour monitored inside the extruder (in-line) with that of the final product (off-line). In this paper, a method of spectrophotometer calibration, termed the “virtual white reference”, is shown to overcome the sensitivity and reproducibility problems related to dark-colour measurements. In addition, to predict the final-product colour based on in-line measurements, different artificial neural networks were tested. A multilayer feedforward network with three hidden neurons provided an acceptable correlation between the in-line and off-line colour measurements.

Effect of the Extrusion on Functional Properties and Mineral Dialyzability from Phaseolus Vulgaris Bean Flour

The effects of extrusion conditions on cooking degree, flour dispersion viscosity and mineral potential availability of extruded bean flour were studied. Phaseolus vulgaris beans of the agronomic cultivar "Flor de mayo" were ground and dehulled to obtain grits and then extruded at different temperatures (140, 160 and 180 degrees C) and moisture contents (17, 20 and 23%), according to a bifactorial experimental design. Degree of cooking was estimated by water solubility (WS) and specific mechanical energy (SME). The effect of variables on WS and SME were analysed by surface response methodology. Flour dispersion viscosity and mineral availability (estimated by in vitro dialyzability), were also evaluated on selected samples. Results showed that, within the ranges of the variables used for this study, only the effect of temperature was significant on the degree of cooking. No direct correlation was observed between water solubility and SME, although a maximum value of WS corresponded to a range of SME values of 400-500 J/g was observed. Dispersion viscosity decreases as WS increases, so if high calorie density is desired, for instance in order to produce a cream soup formula, bean grits should be extruded at high temperature and as low moisture as possible, in our case 180 degrees C and 17% moisture. On the other hand, the effects of extrusion variables on iron and zinc dialyzability were not much affected.

Measuring Flow Velocity and Uniformity in a Model Batch Digester Using Electrical Resistance Tomography

AbstractThe literature shows that the extent of delignification in batch digesters varies as a function of chip location in the vessel. This non‐uniformity may be exacerbated by a number of factors but is commonly attributed to poor and/or non‐uniform liquor flow through the reactor (which causes poor chemical and heat distribution to the chip mass during the cook). Electrical resistance tomography (ERT) was used to evaluate the uniformity of liquor flow in a laboratory model digester under scaled industrial conditions (a 1:15 geometrically scaled vessel, a vessel to particle diameter ratio of 93:1 to minimize wall effects, and close approximation of liquor superficial velocity and pore Reynolds number). Local interstitial flow velocities were measured using pixel‐pixel cross correlation techniques. It was possible to create uniform zones in the digester, but a stagnation point was observed in the centre of the vessel at the screen level. This point coincides with the location of highest kappa numbers (lowest degree of cooking) reported in industrial tests.

Eliminating Cross Cultural Variations in Consumer Perceptions of Cooked Beef Steaks

Tourism and the food service industries have become major interdependent industries in many countries. This paper focuses on the differing expectations and perceptions of domestic and international consumers within the food service industry and, in particularly, the extent of cooking (degree of doneness) of their beef steak meals. The results of a random survey of 1430 participants in Sydney, Australia and Tokyo, Japan showed how cross-cultural perceptions differ between consumers and accordingly provided a method to eliminate the variation in expectations. This concept could be universally applied to all beef steak food service outlets striving to improve their customer satisfaction.

Nonlinear inferential multi-rate control of Kappa number at multiple locations in a continuous pulp digester

The continuous pulp digester represents a large-scale, distributed parameter system. Control of the spatial profile of degree of cooking, characterized by the Kappa number, rather than its endpoint value can effectively control properties that are dependent on the history of cooking. However, profile control of such large-scale distributed parameter systems throws up new challenges in estimation and control. We design a nonlinear model predictive controller using a multi-rate extended Kalman filter to infer and control discrete points along the Kappa number profile. Both, the plant and controller models are based on first principles. The design is tested for significant mismatches in parameters, initial state errors, and stochastic disturbances in the entering wood composition.

IDENTIFICATION OF RESIDENCE TIMES IN CONVENTIONAL CONTINUOUS KRAFT COOKING

Industrial kraft cooking process producing both softwood and hardwood pulp was studied. Residence times of chips in the conventional continuous digester were modelled based on volume fractions of chips. The volume fractions were modelled as a function of a real-time modelled cooking degree profile of chips in the digester. Control of continuous cooking process can be improved by the more accurate information about the residence times.

Effects of extrusion conditions and structural characteristics on melt viscosity of starchy materials

The effects of several factors, like screw rpm, die restriction ( l/ r) and moisture, together with corn endosperm hardness and rice amylose content, on melt viscosity, were analyzed using a Brabender single screw extruder. Bagley’s method was utilized to estimate melt viscosity at the die and to obtain rheological models. Relationships among different responses such as mass output, die pressure, specific mechanical energy consumption, melt viscosity and degree of cooking were discussed. All responses analyzed were found to be dependent on both extrusion conditions and material structural characteristics. Very low values of the exponent of the viscosity power law model “ n” were found, particularly at low moisture. This fact is explained on the basis that to get different value pairs of mass output and pressure, rpm has to be changed and, as rpm increases, structural damage (degree of cooking) also increases, which in turn produces a reduction in pressure. It was concluded that “Bagley’s method” should not be used to estimate melt viscosity in cases where pressure and mass output pairs of data obtained do not correspond to samples differing excessively in degree of cooking.

Determination of the cooking degree for bulgur production using amylose/iodine, centre cutting and light scattering methods

In the present study, the amylose/iodine and light scattering methods were used to determine the cooking degree based on starch gelatinization for the production of bulgur as alternative to traditionally used centre cutting method. Cooking operation was carried out at boiling temperature (97 °C) using Triticum durum wheat for 130 min. The cooking degree was controlled using the three methods and the deformation degree of the intact wheat kernels. It was found that the gelatinization values obtained from the amylose/iodine method were higher than the others up to reaching 100% cooking degree. The results for the cutting method were same with the light scattering method. The optimum cooking time was determined as 40 min. Excess cooking caused significant deformation on the intact wheat kernel during the cooking operation. Both alternative methods i.e. amylose/iodine and light scattering can be used to the control of cooking system. In addition, the light scattering method can be preferred in the automation having bulgur production systems.

Meat intake, cooking-related mutagens and risk of colorectal adenoma in a sigmoidoscopy-based case-control study

Reported habits of red meat consumption, particularly red meat that has been cooked to the degree termed 'well-done', is a positive risk factor for colorectal cancer. Under high, pyrolytic temperatures, heterocyclic amines (HCA) and benzo[a]pyrene (BP) molecules can form inside and on the surface of red meat, respectively. These compounds are precursors that are metabolically converted to compounds known to act as mutagens and carcinogens in animal models, yet their role in human colorectal carcinogenesis remains to be clarified. We investigated whether intake of these compounds is associated with risk of colorectal adenoma in the context of a polyp-screening study conducted in Southern California. Using a database of individual HCAs and BP in meats of various types and subjected to specified methods and degrees of cooking, we estimated nanogram consumption of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, 2-amino-3,4,8-trimethylimidazo[4,5-f] quinoxaline, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline and benzo[a]pyrene (BP). We observed a 6% increased risk of large (>1 cm) adenoma per 10 ng/day consumption of BP [OR = 1.06 (95% CI, 1.00-1.12), P (trend) = 0.04]. A major source of BP is red meat exposed to a naked flame, as occurs during the barbecuing process. Consistent with this finding an incremental increase of 10 g of barbecued red meat per day was associated with a 29% increased risk of large adenoma [OR = 1.29 (95% CI, 1.02-1.63), P (trend) = 0.04]. Individuals in the top quintile of barbecued red meat intake were at increased risk of large adenoma [OR = 1.90 (95% CI, 1.04-3.45)], compared with never consuming barbecued red meat. The consumption of oven-broiled red meat was inversely related to adenoma risk compared with non-consumers [OR = 0.49 (95% CI, 0.28-0.85)]. We did not identify any association with consumption of individual HCAs and colorectal adenoma risk. These results support the hypothesis that BP contributes to colorectal carcinogenesis.

NUTRITIONAL COMPOSITION AND SENSORY PROFILE OF MICROWAVE AND CONVENTIONALLY COOKED VEGETABLES

Vegetables are either consumed in the raw or cooked form. While in the raw state, most of the nutrients are retained, whereas any degree of cooking generally results in partial loss of nutrients and considerable changes in its sensory characteristics. This study is aimed at comparing the effect of different cooking methods namely, conventional (boiling), pressure cooking, and microwave cooking on the nutritional and sensory parameters of selected vegetables. The results confirm that cooking time, or water uptake, was dependent on the type of vegetable rather than the cooking method. Moisture content of ladies finger was significantly decreased (P≤ 0.01) after cooking. Proximate composition and minerals (namely, calcium, iron and phosphorus) did not vary to a significant extent due to different cooking methods. Pressure cooking caused a greater loss in ascorbic acid content of capsicum. Sensory analysis showed that color and appearance were the two attributes which were significantly impacted by varying cooking methods. Capsicum and carrot cooked in microwave oven scored higher for these attributes.