Min Cooking Research Articles

Some aspects of the production of dry Dackere, a granular starchy food from corn

The overall effect of urbanisation on food consumption pattern is a gradual shift from cheaper, traditionally prepared, perishable food to more easy to make, processed foods with extended shelf life. In Africa, where maize is the most important staple food consumed daily in the form of Fufu, alternative ways of using corn flour are being more and more requested. In an attempt to develop a stable food commodity from corn flour, a study of the indigenous food Dackere, a granular starchy product was made. The method consisted of a follow up of the production in a Fulani settlement, production trials in a pilot plant and scaling up of the process. Drying was used as a method of conservation of the product and treatments for re-hydration of died Dackere proposed. Indigenous Dackere is made from fine corn flour mixed with water 1:0.75 (kg flour:water) and rolled to form granules of 2–6 mm diameter. They are steam-cooked for 20 min. The resulting product, cream in colour with a typical scent of cooked corn is consumed in boiled, fermented milk or with stew. Production trials at the pilot plant revealed that 60–65% of water was needed for proper mixing and rolling for granule formation in a batch process, and cooking time of 15 min was enough for complete gelatinisation of the starch. For the scale up of the process, a batch production with up to 5 kg of flour was possible with 5 min mixing time in a robot mixer and 15 min cooking time. Less than 4 h drying under the sun was required or 1 h at 60 °C in a cabin dryer. The resulting product is self-stable and could be stored for a year. For its re-hydration, heating in boiling water for 10 min in proportions of 1:2 granules/water (w/w) yielded cooked Dackere of acceptable quality as suggested by the taste panel analysis.

Effect of storage on the selected properties of macaroni enriched with wheat germ

Macaroni was produced from semolina blended with 15% raw and microwaved wheat germ and stored at room temperature. Samples were analyzed for sensory attributes, cooking quality, color and compressibility during storage. Effect of cooking time (10, 20, 30 min) on cooking quality of macaroni was also studied. Results indicated that protein content of macaroni increased up to 17% with wheat germ addition, as expected. Addition of raw and microwaved wheat germ increased cooking losses and volume of cooked macaroni but reduced weight after cooking. Increasing cooking time significantly increased cooked weight and cooking loss, as well as volume, acidity and compressibility of macaroni samples. However, after 20 min cooking, a decrease in volume of cooked macaroni was observed. No significant effect of storing was found on the measured parameters except acidity. Acidity of enriched samples showed a significant increase during storage. Supplementing durum semolina with raw and microwaved wheat germ provided macaroni with similar results to durum macaroni in compressibility. Enriched macaroni samples were more red and less yellow in color compared to the control sample. In taste panel evaluation, panelists showed the same preference in texture and overall score for both types of macaroni.

Evaluation of the oiling off property of cheese with computer vision: Influence of cooking conditions and sample dimensions

Image-related parameters including the difference/ratio of luminance features and percentage oil area (POA) were examined under different cooking conditions to investigate if they could be used as oiling off indexes of cheese in a computer vision method. POA was most suitable because, in addition to its high correlation with the fat leakage obtained from the traditional oil ring test, the information regarding the oiling off property of cheese provided by POA was in good accordance with observation. Free oil formation of both Cheddar and Mozzarella cheeses occurred rapidly during the initial stage of cooking, followed by a notable decrease afterwards. For the Cheddar cheese, obvious oiling off was observed at all temperatures from 70 to 200 °C, while the maximum oiling off occurred at 160 °C. Little free oil was formed for the Mozzarella cheese below 100 °C and the highest value of POA was observed at 130 °C. The oiling off property of cheese was significantly influenced by sample dimensions. Regardless of sample dimensions, the maximum oiling off of Cheddar cheese occurred at 1 min of cooking and little free oil was observed after cooking for 4 min. As the side length of cheese slices increased from 25 to 70 mm, the increase in POA after 1 min cooking can be described by a square polynomial. Free oil formation was limited for Mozzarella cheese in spite of a wide range of heating temperature and sample dimensions applied.

Rumen fermentation patterns and nutrient digestion in lambs fed cottonseed meal supplemental diets

Twenty crossbred 3–4-month-old male lambs of uniform body weight were used to assess the effect of raw and processed cottonseed ( Gossypium) meals (CSM) on nutrient utilisation and rumen fermentation patterns. Lambs were assigned to five dietary treatments in a completely randomised design and fed isonitrogenous and isocaloric concentrate mixtures containing 30% deoiled groundnut cake (DGNC) (control), 40% of either raw, 45 min cooked, 1% calcium hydroxide (Ca(OH) 2) or iron (1 part free gossypol (FG):0.3 parts iron) treated CSM. The concentrate mixtures were fed to meet 80% of crude protein requirements ( NRC, 1985) with ad libitum access to chopped maize hay ( Zea mays). A metabolic trial of 6 days duration was conducted after 135 days of feeding, and rumen liquor was collected for 2 days at its end. Incorporation of 40% raw CSM resulted in reductions ( P<0.01) in the digestibility of dry matter and organic matter in comparison to control fed lambs. Cooking and Ca(OH) 2 treatment of CSM improved digestibilities of these nutrients, to levels comparable to those in control fed lambs. The ether extract ( P<0.05) and energy ( P<0.01) digestibilities in lambs fed Ca(OH) 2 treated CSM were higher compared to those lambs fed raw CSM diets. Acid detergent fibre and cellulose digestibilities were lower ( P<0.05) on cooked and iron treated CSM fed lambs. Retention of nitrogen and energy did not differ among diets. The digestible and metabolisable energy content of the Ca(OH) 2 treated CSM incorporated diet was higher ( P<0.01) than the other CSM containing diets, but similar to DGNC containing ration. Rumen pH and total volatile fatty acid concentration was similar among diets, but NH 3–N was lower ( P<0.05) on the cooked CSM diets versus the control. Feeding of lambs with raw CSM amounting to 17.9% of total dry matter intake (i.e. 303 mg FG intake per day) adversely affected utilisation of nutrients and rumen fermentation. This depression was alleviated to the greatest extent by 45 min cooking and 1% calcium hydroxide treatment. Iron treatment of CSM had little overall benefit.

Transfer of heat and moisture during microwave baking of potatoes

AbstractMicrowave baking of potatoes comprised two phases. In the first phase the internal temperature of the potatoes rose to approximately 100 °C with little loss of water vapour. The uniformity of internal heating during this phase was assessed by identifying gelatinised starch. Starch gelatinisation began near the outer surface after 1.5 min of cooking and was complete by 2.5 min. During the second cooking phase the thermal energy absorbed was used to evaporate water. When immersion in boiling water was substituted for this second phase of microwave cooking, it took significantly longer for the internal texture to soften adequately for the potatoes to be considered cooked. This suggests that microwave cooking influences texture independently of the thermal profile of the cooking process. Damage by escaping steam is suggested as a mechanism.© 2002 Society of Chemical Industry

Acetone Pulping of Wheat Straw. Influence of the Cooking and Beating Conditions on the Resulting Paper Sheets

This paper reports on the influence of independent variables in the pulping of wheat straw [viz., cooking temperature (140−180 °C), time (60−120 min), and acetone concentration (40−80%)] and of the number of PFI beating revolutions (0−1750) to which the pulp is subjected, on the yield and Shopper−Riegler index of the pulp, and on the breaking length, stretch, burst index, and tear index of the resulting paper sheets. By using a central composite factorial design, equations that relate each dependent variable to the different independent variables were obtained that reproduced the experimental results for the dependent variables with errors of less than 25%. Ensuring the optimal Shopper−Riegler index for the pulp (29.53 °SR), and also the optimal stretch (2.37%) and burst index (2.63 kN/g) for the paper sheets, entails using a 180 °C temperature and 1750 number of PFI beating revolutions. The use of these conditions in conjunction with a 40% acetone concentration and a 60 min cooking time allows one to save solvent in the recovering and recycling steps and also to increase production. The values thus obtained for the breaking length and tear index differ by less than 12% and 29% from their optimum levels (5781 and 4.72 mN·m2/g, respectively).

Texture and Microstructure of Steam Cooked, Vacuum Packed Potatoes

ABSTRACTUniaxial compression tests combined with light microscopy and scanning electron microscopy were used to study textural properties of vacuum packed, steam cooked (VPS‐cooked) potato tubers. Comparisons were made with conventionally water cooked tubers for cooking intervals of 0–60 min. In the VPS‐cooked potatoes the gelatinized starch formed dense clusters. In contrast, water cooked cells were filled with gelatinized starch. The textural attributes declined with increased cooking time, faster for water cooked potatoes than for VPS‐cooked. After &gt;30 min cooking, firmness of VPS‐cooked potatoes increased, while cell separation and disintegration of tissue made the water cooked tubers less firm. Textural properties and cell structure were directly affected by processing conditions.

Mechanism of cyanogen reduction in cassava roots during cooking

The cyanogen elimination profile during cooking of cassava roots was investigated and correlated with the changes in cyanogenic β-glucosidase (GLase) activity monitored at close intervals in the cook water and root. Cyanogenic β-glucosidase (GLase) activity was detected in the cook water within 5 min of starting cooking. Whilst significant decrease in the GLase activity was noticed in cook water and root within 15 and 10 min, respectively, for varieties M4 and H165, H1687 GLase activity decreased tremendously only at 20 and 15 min in the cook water and root, respectively. There was no GLase activity in cook water after the 30 min pre-boiling phase while GLase activity was present in the roots even after 60 min of cooking. The decrease in GLase activity at 15–20 min pre-boiling phase led to accumulation of cyanogens in cook water. The cyanogen fractions (glucosidic and non-glucosidic) increased significantly with cooking in the cook water in the case of varieties M4 and H165 while their levels were almost static throughout the post-boiling phase for H1687. The amount of HCN escaping through steam did not bear a direct relationship with the initial cyanogen content in cassava roots. Although free cyanogen is highly volatile, all of it does not escape through steam and a certain quantity appears to be stabilised in the cook water. ©1997 SCI

Effect of tempering and end moisture content on the quality of micronized lentils

The use of micronization (infrared treatment) on grain legumes tempered with water has potential for reducing cooking times. Using Laird lentils, the effects of tempering conditions and moisture content following micronization were evaluated in terms of color, chemical properties and texture after 15 min cooking. The texture of cooked lentils softened as tempering moisture increased. This was related to increasing starch gelatinization and decreasing protein solubility during micronization. Changes in the pectic substances did not appear to influence texture. The reduction in hardness indicates that shorter cooking times are required for samples micronized under high moisture conditions. Lentil color changed slightly under these high moisture conditions as evidenced by the Hunterlab readings.

Pressure Pretreatment of Vegetables for Controlling the Hardness before Cooking.

The effects of pressure pretreatment before cooking on the hardness of vegetables were studied.The vegetables used here were Japanese radish, carrot, burdock and potato. The hardness of the samples which had been treated at 50-500MPa for 0-120min at room temperature before cooking at 99.5°C was evaluated. The ratio of hardness of the pretreated vegetables to that of the untreated ones, called hardness, increased substantially with the magnitude and the retention time of applied pressure. The relative hardness of vegetables pretreated at 400MPa for 120min was in the range of 2-3 after 30min cooking. The period of optimum cooking time for the desirable hardness of vegetables was prolonged twice by the pressure pretreatment. This phenomenon, the suppression of softening in the cooking process, depended mainly on the time after reaching the prescribed pressure and little on whether the pressure was retained for a long time or released immediately after the short-time application. The replaceability of the standing time after release of pressure and the retention time during pressurization indicates that the loss of intra- and intercellular water molecules and ions, induced by the membrane collapse due to pressure, proceeds at almost the same rate under atmospheric pressure as at high pressure. This suggests that the loss of water plays an important role in determining the pressureinduced hardening. This work also shows that pressure pretreatment at room temperature can be used to avoid the overcooking of vegetables instead of preheating.

The influence of process variables and inoculum composition on the sensory quality of kinema

Kinema, a traditional food condiment, is produced in homes in a crude manner. The natural fermentation of soybeans usually produces an acceptable product. However, inconsistencies in the final product and spoilage do often occur. In order to standardize the production with quality consistency, the traditional process conditions were optimized by sensory evaluation. Thinly perforated polythene bag as a wrapping material, 10-15 min cooking in 0·7 kg cm -2 steam pressure and 48 h fermentation at 37°C were optimum for kinema making. The influence of micro-organisms, isolated from commercial kinema, was also studied. Organoleptically, the monoculture fermentation of soybeans by Bacillus subtilis produced the best quality kinema. Any microbial combination with this bacterium had significantly adverse effect on fermentation and consequent scoring. The monoculture fermentations by other micro-organisms could not produce kinema, suggesting B. subtilis as the sole fermenting organism for this product. Consumers' preference trials showed that the kinema produced under optimum conditions was more acceptable than even the best scored market samples.

A new modified pulping process alternative to sulphate method ?Alkali-Sulfite-Antraquinone-Ethanol (ASAE)?

In this study, ASAM method was modified by the use of ethanol instead of methanol. This new organosolv pulping method is referred to as ASAE. Brutia pine (Pinus brutia Ten.) was chosen as raw material in cooking because of its wide-spread usage in Turkish sulphate mills. 28 cooks were made by changing the cooking conditions systematically to achieve the most effective cooking parameters for yield and physical properties of ASAE pulps. Also, a control sulphate cook was made. After statistical evaluations of the data optimum pulping conditions were determined to be 20% Na2SO3 with 50% ethanol ratios and 150 min cooking time at maximal temperature. It was found that ASAE pulps had higher yield, viscosity, brigthness and strength properties than sulphate control pulps with the exception of breaking length. Furthermore bad-odour problems were absent during the blowing and washing process in the laboratory trials.

Folate retention in dried legumes after different methods of meal preparation

Twenty-five different samples of legumes were analyzed for total folate. A composite sample of each legume was prepared and assigned to usual cooking time categories, 20, 90 and 150 min. Within each cooking time the legumes were pretreated with a quick soak (brought to a boil and held for 2 min, covered and left to soak for 1 h) and a long soak method (soaked in water overnight for 16 h). The average folate retention in legumes cooked for 20 and 90 min differed significantly ( p ≤ 0·05). The mean retention for folate in legumes in the 20 min cooking category was 60% without presoak, 18% for quick soak versus 35% for long soak, and for 90 min cooking 31% for quick soak versus 42% for long soak. There was no significant difference ( P > 0·05) in folate retention between quick (41%) and long soak (44%) pretreatment for legumes in the 150 min cooking category. The results indicate that presoak treatment can affect folate retention in meal prepared from legumes.

Influence of cooking on benzo(a)pyrene content in smoked sausages

The changes in benzo(a)pyrene (BaP) content of smoked sausages were monitored during 1 h cooking. During this time, the BaP content decreased from 4·80 to 1·87 μg/kg. The maximum drop in BaP content was reached in the first 20 min of cooking. Two factors affected the course of BaP changes, viz. water-holding capacity and the fat content. After excluding these factors, there was a high correlation coefficient of 0·996 between time of cooking and BaP content, which confirmed an inverse relationship between the decrease in BaP content and time of cooking. The BaP decrease was directly proportional to the decrease of fat content during cooking, when the relatively high BaP content of 7·71 μg/kg was found in the cooked-out fat.

Short communication: Effect of pre‐soaking on the rate of thermal softening of soybeans

SummaryWhole soybeans and dehulled soybean cotyledons were soaked in water at ambient temperature for 0, 8 and 12h then cooked in boiling water at atmospheric pressure for up to 6h. In every case there was an initial rapid rate of softening followed by progressively slower softening until, after about 3h, there was little change in firmness. The kinetics of softening of every sample was consistent with the two substrate theory of thermal softening. The firmness ranking in descending order after 15 min cooking was no soak, whole beans &gt; 12h, soak cotyledons &gt; no soak, cotyledons &gt; 8h soak, whole beans &gt; 12h soak, whole beans. This ranking was maintained for the entire cooking period. For whole beans the soaked samples were less firm than the unsoaked samples while for the cotyledons the soaked samples were more firm than the unsoaked. This reversal in behaviour may be caused by the seed coat (skin) retarding the imbibition of water in the whole beans thus delaying the onset of enzyme activity in the bean tissue.

Effect of cooking time on mutagen formation in smoke, crust and pan residue from pan-broiled pork

The effect of cooking time on mutagenic activity in crust, pan residue and smoke from pan-broiled pork patties was studied in the Ames Salmonella mutagenicity test system. The effect on mutagenicity of reheating the cooked patties and of keeping them warm was also studied. The meat was broiled at 200°C for various times between 2 and 10 min. Broiled meat was reheated up to 5 times at 200°C, each time to a centre temperature of 70°C. Reheating was also performed in a microwave oven for 2 min and in an electric oven at 200°C for 10 min. In addition, broiled patties were kept warm at 60°C in an incubator for up to 9 hr. The mutagenic activity increased rapidly in all fractions except the volatile phase over the first 6 min of cooking, after which time only a slight increase was seen. At cooking times below 4 min no mutagenic activity was detected in the smoke. Reheating or keeping the meat warm for up to 9 hr had very little effect on the mutagenic activity of the meat. Reversed-phase high-performance liquid chromatography mutagenicity profiles of the aerosol, crust and pan-residue extracts showed no major qualitative differences in samples cooked at different times. It is concluded that during pan broiling at 200°C the major part of the mutagenic activity is formed during the first 6 min of cooking. Reheating the meat or keeping it warm does not significantly affect the mutagenic activity. No major additional mutagens are formed during continued heating for up to 25 min.

EFFECT OF BLANCHING AND SULFITE TREATMENT ON THE QUALITY OF FROZEN CAULIFLOWER

ABSTRACTThe influence of blanching time and post‐blanching sulfite treatment on the sensory quality and texture of frozen cauliflower were assessed after storage at ‐18°C for up to one year. The treated cauliflower florets, sealed in polyethylene bags, were placed in waxed paperboard cartons and frozen in a contact plate freezer at ‐35°C. Samples blanched for 3 min and dipped in a solution containing 1000ppm of SO2 for 5 min gave a significantly (p&lt;0.05) superior product even when stored for one year. The residual SO2 content of 50 ppm found in these stored samples disappeared after a 3 min cooking in boiling water. Cauliflower texture was influenced by blanching time but the textural differences of blanched samples diminished following freezing and storage. After a 3 min cooking, the texture of all thawed samples were comparable to that of fresh cauliflower cooked for 10–12 min.

Residual peroxidase activity as influenced by blanching, SO2 treatment and freezing of cauliflowers

AbstractThe influence of blanching time and SO2 treatment on the residual peroxidase activity and its implication for the sensory quality of frozen cauliflowers were assessed after storage for up to one year at −18°C. The treated cauliflowers, sealed in polythene bags, were placed in waxed paperboard cartons and frozen in a contact plate freezer at −35°C. The sensory quality of frozen stored cauliflowers related well to their residual peroxidase activity, which was sensitive to the SO2 treatment. Blanched cauliflowers following a brief dip in a metabisulphite solution prior to freezing gave a significantly (P&lt;0.05) superior product even when stored for one year. The residual peroxidase activity, which ranged from 1 to 5.5% in the blanched samples, was below 1 % in the SO 2‐treated samples, and the SO2 content of50 ppm found in these stored samples disappeared after 3 min cooking in boiling water.

A Histological Basis for ‘Hard‐To‐Cook’ Phenomenon in Red Gram (Cajanus cajan) Cultivars

ABSTRACTSections of cotyledons (dhals) and leached starch granules in red gram (Cajanus cajan), were examined microscopically. The average expansion ratios of good cooking (GCD) and poor cooking (PCD) dhals were 1.8 and 1.4 for cotyledons, 2.4 and 2.0 for cells at 30 min cooking, and 6.5 and 5.5 for starch granules at 6 min cooking, respectively. Cells and starch granules of GCD dispersed freely and quickly into the medium while those of PCD tended to disperse slowly and remain in clusters. The variation in expansion, separation and clustering properties of cells and starch granules during cooking caused cookability differences of red gram cultivars.

Specific factors affecting lead uptake by food from cooking water

AbstractFollowing earlier work, detailed studies have been carried out on the lead uptake of individual foods from soft and hard water containing various amounts of lead. Experiments have also been made to determine whether solutions of lead nitrate in distilled water simulate the behaviour of water containing naturally present lead. The effect of length of cooking time, weight/volume ratio and salt addition have been studied, as well as the depostion of lead on to cooking vessels. In general, green vegetables, carrots, rice and spaghetti were found to take up more lead than do other foods. The difference in uptake observed between hard and soft waters varied according to the particular food being studied. Uptake from lead nitrate solutions showed a very similar pattern to uptake from hard water containing naturally present lead. Equilibrium was reached after only 5 min cooking for cabbage and spaghetti. Varying the solid/volume ratio for cabbage affected the uptake of lead from water, but the addition of sodium chloride or sodium bicarbonate had little effect on lead uptake. There was no sign of saturation in uptake of lead by cabbage from solutions of 11 mg litre−1 lead as lead nitrate. Deposition of lead occurred on both aluminium and glass saucepans, and cleaning was more effective in removing lead from glass saucepans. Results obtained from the analysis of diets in a small population at Ayr confirmed those obtained previously by laboratory experiments.