Evaluation of Water-soluble Vitamins and Optimum Cooking Time of Fresh Edible Portions of Elephant Grass (Pennisetum purpureum L. Schumach) Shoot

Fresh edible inner tender stem (matrix) and base of domesticated elephant grass shoot were evaluated for water-soluble vitamins B₁, B₂, B₃, B₆ and vitamin C. The B-vitamins were determined using high performance liquid chromatographic (HPLC) technique, while vitamin C was evaluated using 2, 6 dichlorophenolindophenol (DCIP) titration method. The optimum blanching time of the matrix was also determined. Samples were water-blanched from 0 to 16 min at intervals of 2 min. Optimum cooking time was determined to be the time at which vitamin C showed maximum retention after the intervals of blanching. Vitamins B₁, B₂, B₃, B₆ and C concentrations (mg/100 g fresh weight) in the samples were respectively 1.23 mg/100 g, 4.37 mg/100 g, 12.35 mg/100 g, 2.40 mg/100 g and 17.23 mg/100 g in the matrix and 0.86 mg/100 g, 3.72 mg/100 g, 6.40 mg/100 g, 1.59 mg/100 g and 18.30 mg/100 g in the base. The amounts of the B-vitamins in 100 g portion of the samples adequately satisfy the RDAs for the respective B-vitamins for normal healthy adults. The matrix was significantly higher (p < 0.05) than the base in vitamins B₁, B₃ and B₆. The matrix showed an optimum blanching time of 10 min. This was considered the optimum cooking time required to avoid significant loss of vitamin C and other heat-labile nutrients in elephant grass matrix.     

Acid and moisture uptake in steamed and boiled sweet potatoes and associated structural changes during in vitro gastric digestion

Orange-fleshed sweet potatoes are a good source of phytochemicals. For these nutrients to be absorbed, they must be released from the food matrix as a result of physical and chemical breakdown. A key factor in food breakdown is gastric acid diffusion into the matrix, and its influence on structural changes. Cooking treatment may influence mass transport properties and structural changes of foods during digestion. The objective of this study was to determine the acid and moisture uptake into sweet potatoes and its influence on macro- and micro-structures during in vitro gastric digestion as a result of varying cooking treatments. Sweet potatoes were cut into cubes and cooked (boiled or steamed) for different times. In vitro oral and gastric digestions were simulated in a shaking water bath at 37 °C. Acidity, moisture content, and solid loss were measured after 9 digestion times (15 to 240 min). Hardness of individual cubes and microstructure (light microscopy) were completed before and after digestion. Effective diffusivity of acid and moisture into the cubes was estimated using MATLAB. Cooking method, cooking severity, and digestion time significantly influenced moisture uptake (p < 0.0001). Acid uptake was significantly influenced by digestion time (p < 0.0001). The change of softening after digestion was influenced by cooking method and severity (p < 0.05). Effective diffusivity of acid ranged from 0.03 × 10^− 10 (mild steamed) to 11.40 × 10^− 10 m²/s (severely boiled). Percent texture decrease after digestion from the initial hardness ranged from 16% (severely steamed) to 34% (mild boiled). Textural changes were related to cell wall breakdown and starch degradation. In general, mass transport properties and macro- and microstructural changes were influenced by cooking treatment and gastric digestion. The link between food cooking and behavior during digestion is crucial in determining optimal food processing and cooking methods for specific food functional properties.     

Influence of cooking conditions on cooking loss and tenderness of raw and marinated chicken breast meat

The influence of different cooking treatments on tenderness and cooking loss, as main quality characteristics of chicken breast meat, was investigated. Industrial skinless chicken breast meat samples were designated as raw and marinated and cooked in the oven by hot air and hot air-steam mixture at 130, 150 and 170 °C, for 4, 8 and 12 min. Cooking losses were evaluated by weight changes before and after cooking, and tenderness changes were determined on cooked samples by measuring shear force using instrumental texture analysis. Results showed that marination, followed by air-steam cooking is the best combination to obtain the most tender chicken breast slices. The time and temperature of cooking showed similar effects on cooking loss and tenderness: short cooking time (4 min) and temperatures of 130–150 °C resulted in lower cooking losses and best meat tenderness, in both not marinated and marinated meat. Statistically significant correlations between tenderness and cooking loss indicated that the cooking loss correlated better with cooking time than with cooking temperature. An opposite phenomenon was observed for meat tenderness.     

Effects of parboiling,storage and cooking on the levels of tocopherols,tocotrienols and γ-oryzanol in brown rice (Oryza sativa L.)

Vitamin E and γ-oryzanol display a wide range of biological activities including hypocholesterolemic, anti-inflammatory and antioxidant activities. Although white rice is far more popular worldwide, consumption of brown rice is increasing, partially on account of the presence of bioactive compounds; however, the effects of parboiling, storage and cooking on them are not well-characterized. The effects of parboiling and a 6-month storage period on the contents of vitamin E and γ-oryzanol in three brown rice cultivars grown in three different locations in Brazil were investigated. Also, their levels in branded non-parboiled and parboiled brown rice were monitored before and after cooking. Vitamin E homologues and γ-oryzanol were separated by RP-HPLC equipped with PDA and fluorescence detectors. The average levels of total tocols and γ-oryzanol in the raw brown rice cultivars studied were 25 and 188 mg/kg, respectively. Of the vitamin E homologues, γ-tocotrienol contributed with 74% of total tocols, followed by α-tocopherol, α-tocotrienol and γ-tocopherol in minor quantities. The combined processes, parboiling, storage and cooking, led to an approximate 90% reduction in tocols and only γ-tocotrienol was detectable after any of the processes. Parboiling followed by storage resulted in an approximate 40% loss of γ-oryzanol. Cooking had almost no further effect over γ-oryzanol levels in parboiled rice previously stored for 6 months.     

Effect of cooking on the composition of beans (Phaseolus vulgaris L.) and chickpeas (Cicer arietinum L.)

The effect of cooking on levels of nutrients and anti-nutritional factors in beans and chickpeas was investigated. Significant (p < 0.05) variation existed among the beans and chickpeas with respect to their crude protein, starch, soluble dietary fiber (SDF), insoluble dietary fiber (IDF), total dietary fiber (TDF), resistant starch (RS), trypsin inhibitor activity (TIA), mineral, phytic acid, tannin, sucrose and oligosaccharide (raffinose, stachyose and verbascose) contents. Cooking beans and chickpeas in water significantly increased protein, starch, SDF, IDF, TDF, Mn and P contents (on a dry weight basis), whereas reduced ash, K, Mg, TIA, tannin, sucrose and oligosaccharide contents were observed. Colored beans (black, cranberry, dark red kidney, pinto and small red bean) contained tannins, whereas little tannin in white-colored beans (great northern and white pea bean) and chickpeas (Desi and Kabuli type) was detected.     

Stability and release properties of double-emulsions stabilised by caseinate–dextran conjugates

The subject of the present paper was to investigate the possibility of stabilising water-in-oil-in-water emulsions (W/O/W) by using sodium caseinate (SC)–dextran (Dex) conjugates in order to influence the release of vitamin B₁₂ from the inner water phase (W₁) to the outer aqueous phase (W₂).To prepare the conjugate the SC was combined with Dex (M_r 250,000 or 500,000 g/mol) and incubated at 60 °C and a humidity of 79% for 8 h.The double emulsions, with encapsulated vitamin B₁₂, were prepared using a two-step emulsification technique. Whereas different amounts of polyglycerin polyricinoleate (PGPR, E476) were the hydrophobic emulsifier, the conjugate and the SC alone were used as the hydrophilic emulsifiers. The investigations comprised the determination of the particle size distribution of the W/O/W emulsion and measurement of the amount of vitamin B₁₂ migration from W₁- to the W₂-phase during the second stage of emulsion preparation and after heating or pH changing of emulsion.The water-containing oil droplets of the W/O/W emulsions were smaller and distributed more narrowly using SC–Dex conjugate as emulsifier instead of pure protein. Under acidic conditions, the conjugate-containing emulsions were more coalescence stable than the emulsions with SC, and the vitamin B₁₂ release from the inner W₁-phase was significantly decreased.     

Induced changes in bioactive compounds of kailan-hybrid broccoli after innovative processing and storage

The glucosinolates, sulforaphane, vitamin C and lutein content after several industrial cooking methods on the new kailan-hybrid broccoli and their changes during storage for 45 days at 4 °C were studied. Boiling and sous vide induced the highest glucosinolate loss (80%), while low pressure (LP) steaming, microwaving (MW) and sous vide-MW showed the lowest (40%) loss. Glucoraphanin was the most thermostable glucosinolate. Throughout their commercial life, microwaved and grilled samples showed a decrease in total glucosinolates. Generally, myrosinase activity was completely inhibited after cooking with undetected sulforaphane contents. The initial total vitamin C dropped by up to 58% after cooking and progressively decreased during storage, with sous vide-MW (92%) and microwaving (21%) showing the highest and lowest decrements, respectively. LP steaming and microwaving were the best industrial cooking methods for maintaining the glucosinolate and vitamin C contents, and enhancing up to 7.5-fold the initial lutein content.     

Distribution of ergosterol in different tissues of mushrooms and its effect on the conversion of ergosterol to vitamin D2 by UV irradiation

Analysis of ergosterol content in different tissues of Shiitake mushrooms showed a significant difference (p < 0.01) in its distribution. Thus, the conversion of ergosterol in whole mushrooms to vitamin D₂, by exposure to UV irradiation, was significantly affected (p < 0.01) by the orientation of the mushroom tissues to the UV. The highest ergosterol content was found in button mushrooms (7.80 ± 0.35 mg/g DM) while the lowest was in enoki mushrooms (0.68 ± 0.14 mg/g DM). The conversion of ergosterol to vitamin D₂ was about four times higher when gills were exposed to UV-A irradiation than when the outer caps were exposed to the same. The lowest conversion to vitamin D₂ (12.5 ± 0.28 μg/g DM) was observed for button mushrooms while the highest value (45.1 ± 3.07 μg/g DM) was observed for oyster mushrooms. The optimum moisture content of mushrooms for this conversion was around 78% on a wet basis and the temperature was around 35 °C.     

Nutrients and antinutritional factors in faba beans as affected by processing

 The influence on the nutrients content (soluble sugars, starch, dietary fibre and calcium) and antinutritional factors (α-galactosides and phytic acid) of faba beans (Vicia faba, L. major) of soaking in different solutions (distilled water, citric acid, and sodium bicarbonate solutions), cooking the presoaked seeds, dry-heating and germination have been studied. Soaking brought about a decrease in starch, sucrose, fructose, α-galactoside, dietary fibre and calcium content. Glucose was detected in soaked faba beans and soaking did not modify the phytic acid content. Cooking the presoaked faba beans produced a slight decrease in starch, and caused a general drop in α-galactosides, dietary fibre, calcium and phytic acid, with the exception of seeds presoaked in sodium bicarbonate in which cooking did not cause any appreciable changes in comparison with the unprocessed faba beans. Germination caused a sharp reduction in α-galactoside and phytic acid content after 6 days, whilst starch and dietary fibre decreased slightly. Calcium, however, enjoyed a slight increment during germination which was related to the decrease in the content of hemicellulose and phytic acid. Dry-heating caused a noticeable reduction in all the nutrients and antinutritional factors investigated. Of all the treatments studied, germination appears to be the best processing method to obtain nutritive faba bean flour, since it caused a minor decrease in starch content (15% loss), the largest α-galactoside and phytic acid removal (94% and 45%, respectively) and provided an appreciable amount of dietary fibre. Received: 21 December 1997 / Revised version: 19 February 1998     

Effects of different objective functions on optimal decision variables: a study using modified complex method to optimize hamburger cooking

Hamburger patties are prepared from ground beef and cooked to obtain a safe product before consumption. Cooking process eliminates microbial hazards and results in certain quality changes (e.g., cooking loss, textural changes). All these changes can be used as an objective function to achieve an optimum cooking process, but their effects on decision variable (e.g. process temperature profiles) of the optimization should be known. The use of different objective functions (minimization of cooking losses, hardness, chewiness, and shear to work) was compared to see their effects on plate temperature profiles for double-sided contact cooking. Modified Complex Method was applied as the optimization procedure. Lower and higher limits of grill temperatures (177–220°C) were explicit constraints while lethality and temperature at the patties center (F₀⩾15 s; T_c⩾71°C) were implicit constraints. The objective functions and implicit constraints were determined using a previously developed numerical heat transfer simulation model. Constant temperature profiles (decision variables) for different objective functions at different processing times (121 and 130 s) were determined. Same decision variables were found regarding the different objective functions (198.3°C and 184.1°C) for the given processing times.     

Modeling of rice hydration using finite elements

Great effort has been devoted towards developing models that describe cooking processes. A difficulty towards developing such models arises from the fact that during cooking, the physical properties and quite often sample geometry are time dependent. In this work a finite element model describing cooking of rice and water uptake using a Fickian diffusion model was developed, assuming axisymmetric conditions. Effective diffusivity was considered a function of moisture content. The numerical model compared favorably with experimental results. The value of the effective water diffusivity was estimated to be in the order of 7 × 10⁻¹⁰ m²/s, by minimizing the error between experimental and numerically predicted results.The effect of grain size on the cooking was also investigated using the model. Cooking time, i.e. the time to reach about 70% moisture content (wet basis), appeared to be a strong function of the initial size distribution.     

Application of simultaneous combination of microwave and steam cooking to improve nutritional quality of cooked purple sweet potatoes and saving time

The influence of simultaneous combination of microwave and steam cooking on contents of specific phytochemicals, carbohydrate and antioxidant activity of purple sweet potatoes (PSPs) was investigated, and compared to those of individual steaming and microwaving. Results showed that the contents of phytochemicals including total phenolics, flavonoids and anthocyanins and phenolic acids except caffeic acid increased after cooking to different extent depending on cooking methods. The PSPs cooked by simultaneous combination of microwave (500 W) and steam (1700 W) for 12 min (M₅₀₀-S₁₇₀₀-12) contained the highest of total phenolics, flavonoids, phenolic acids and anthocyanins. Simultaneous combination of microwave and steaming resulted in higher content of soluble sugar in PSPs. PSPs cooked by M₅₀₀-S₁₇₀₀-12 showed the highest antioxidant activity, which was well accordance with higher contents of phytochemicals. The findings suggest that appropriate simultaneous combination of microwave and steaming could better preserve active phytochemicals in PSPs, but significantly shorten cooking time compared with individual steaming.Industrial relevanceSimultaneous combination of microwave and steam cooking is a new technology for cooking food. However, the information about the effects of simultaneous combination of microwave and steam cooking on quality of food is limited. The present findings showed that the appropriate combination of microwave and steam cooking could significantly decrease the cooking time and improve nutrition value of cooked PSPs. This research is not only of importance for understanding the changes of food composition during different heating process, but also has important practical significance for choosing a scientific cooking methods and developing new type of cooking utensils which can better satisfy current consumers' needs.     

Alleviation of the adverse effect of cooking on sorghum protein digestibility through fermentation in traditional African porridges

Cooking sorghum is well known to reduce its protein digestibility. In southern Africa fermented sorghum porridges are commonly consumed. Knowledge is lacking as to how their preparation affects sorghum protein digestibility. Five sorghum varieties of varied origin were fermented using traditional semi-solid state fermentation. In vitro protein digestibility and a new index, in vitro insoluble protein digestibility, were measured. Both increased during fermentation, generally within the first day, coinciding with a strong decrease in pH. The increase in insoluble protein digestibility suggests fermentation causes structural changes in the sorghum storage proteins (prolamins and glutelins), making them more accessible to pepsin attack. Wet cooking during porridge-making greatly reduced protein digestibility. Combining fermentation with cooking, either fermenting then cooking or cooking then fermenting, significantly improved protein digestibility over wet cooking alone. Thus natural fermentation, as applied in traditional African porridge preparation is an effective method of improving the protein digestibility of cooked sorghum.     

Preliminary investigations on the effects of ageing and cooking on the Raman spectra of porcine longissimus dorsi

The influence of ageing and cooking on the Raman spectrum of porcine longissimus dorsi was investigated. The rich information contained in the Raman spectrum was highlighted, with numerous changes attributed to changes in the environment and conformations of the myofibrillar proteins.Predictions equations for shear force and cooking loss were developed from the Raman spectra of both raw and cooked pork. Good correlations and standard errors of prediction were obtained for both WB shear force and cooking loss, with the raw and the cooked samples showing almost identical results R² = 0.77, root mean standard error of prediction (RMSEP)% of mean = 12% for shear force; R² = 0.71, RMSEP% of mean = 10% for cooking loss. The Raman spectra were also able to predict the extent of cooking that occurred within the pork (R²_val = 0.94, RMSEP% of range = 5.5%).Raman spectroscopy has considerable potential as a method for non-destructive and rapid determination of pork quality parameters such as tenderness. Raman spectroscopy may provide a means of determining changes during cooking and the extent to which foods have been cooked.     

Effect of soaking,germination, cooking and fermentation on antinutritional factors in cowpeas

The present work deals with the study of efficacy of some treatments, namely soaking (in water and bicarbonate solution( ordinary and pressure cooking, germination and fermentation in reducing or removal of antinutritional factors usually present in cowpeas (protease inhibitors, tannins, phytic acid and flatus‐producing oligosaccharides (raffinose and stachyose). The results showed that long‐time soaking (16 h) in bicarbonate solution caused remarkable reduction in the antinutritional factors. Pressure cooking was more effective than ordinary. Cooking pregerminated cowpeas was most effective. Fermentation completely removed trypsin inhibitor, oligosaccharides and reduced remarkably phytic acid. However, tannins noticeably increased.     

Effect of soaking,germination, cooking and fermentation on antinutritional factors in cowpeas

The present work deals with the study of efficacy of some treatments, namely soaking (in water and bicarbonate solution), ordinary and pressure cooking, germination and fermentation in reducing or removal of antinutritional factors usually present in cowpeas (protease inhibitors, tannins, phytic acid and flatus-producing oligosaccharides (raffinose and stachyose). The results showed that long-time soaking (16 h) in bicarbonate solution caused remarkable reduction in the antinutritional factors. Pressure cooking was more effective than ordinary. Cooking pregerminated cowpeas was most effective. Fermentation completely removed trypsin inhibitor, oligosaccharides and reduced remarkably phytic acid. However, tannins noticeably increased.     

Use of dried pumpkins in wheat bread production

Pumpkins belong to the family of Cucurbitaceae. They are classified to Cucurbita pepo, Cucurbita moschata, Cucurbita maxima and Cucurbita mixta, according to the texture and shape of their stems. The nutritional value of pumpkin fruits is high, varies from one species or cultivar to another. Pumpkins are reach in vitamins C, B₁, B₆, K, and in mineral substances. There are no data found about vacuum microwave dried pumpkin application in wheat bread production. The main purpose of the research was to evaluate quality parameters of microwave vacuum dried pumpkins and to verify its application in wheat bread production. Following quality parameters of pumpkins and bread made with pumpkin additive were evaluated: moisture content (oven – drying method), vitamin C content (iodometric), carotenoid content (spectrophotometric), reducing sugars (LVS 252:2000), colour changes (ColorTec- PCM), total fat content (ISO 6492:1999), degree of bread liking (ISO 4121:2003), bread baking loss and dry off. Quality parameters of non dried pumpkins were: content of reducing sugars − 2.40 g⋅100 g^-1, vitamin C – 0.26 g⋅100 g^-1, carotenoids – 0.50 mg % (in dry matter). The technological parameters for pumpkins drying in vacuum microwave drier were used: pressure (70–50 mmHg), speed of tumbler – 6 rpm, one working cycle and three stages. During the pumpkins drying process a decrease in the following parameters was observed: moisture content – 10.5 times, vitamin C content – 2.0 times; increase of yellowness (b*) value – 1.5 times. The optimal dried pumpkin additive to the wheat dough was 10% of the total flour amount. The wheat bread sample with dried pumpkins additive is richer in carotenoids and reducing sugars comparing to control wheat bread sample. The results of sensory analyses using hedonic rating demonstrated that a higher degree of liking was attributed to the bread sample with dried pumpkins additive (7.3) comparing to control wheat bread sample (6.7).     

Thermal inactivation of Bacillus anthracis Sterne in irradiated ground beef heated in a water bath or cooked on commercial grills

The thermal stability of heat-shocked and non-heat-shocked spores of the virulence-attenuated Sterne strain of Bacillus anthracis was evaluated at select temperatures in irradiated, raw ground beef (25% fat) heated in a water bath or cooked using two different commercial grills. For the former, 3-g portions of inoculated ground beef were packaged in bags that were completely immersed in a temperature-controlled circulating water bath held at 65 °C (149 °F), 70 °C (158 °F), 75°(167 °F), and 80 °C (176 °F) for a predetermined length of time. For the latter, formed ground beef patties (95-g each) were inoculated with spore stock A or B of the Sterne strain and then cooked on a commercial open-flame gas grill or on a commercial clamshell electric grill to achieve target internal temperatures of either 71.1 °C (160 °F), 82.2 °C (180 °F), or 93.3 °C (200 °F). Cooking ground beef patties on commercial grills, resulted in reductions of ca. 0.8 to 3.5 log₁₀ CFU/g for spore stocks A and B of B. anthracis Sterne after heating to 71.1 °C (160 °F), 82.2 °C (180 °F), or 93.3 °C (200 °F) on either the open-flame gas grill which required ca. 9.6 min to reach the target internal temperatures or on the clamshell electric grill which required ca. 4.0 min to reach the target internal temperatures. In comparison, our data using a water bath system and heating at 65° to 80 °C predict nearly 4 log reductions in spore levels for short times, ~½ min, depending possibly on the temperature. Thus, our data suggest that models based on heating ground beef in a water bath is not a good predictor of reductions of levels of spores of B. anthracis Sterne strain that would be obtained when cooking ground beef patties on commercial grills under conditions that may be typically used by consumers and/or retail establishments. Nevertheless, our data validated that cooking ground beef patties on a commercial grill at a temperature considered to be “well-done” and a temperature (71.1 °C;160 °F) recommended by the USDA/FSIS, is effective at killing spores of B. anthracis Sterne.Industrial relevanceHeating ground beef in a water bath or cooking ground beef patties on commercial grills under conditions simulating those that are used by consumers and/or that occur in retail food service establishments is effective at killing spores of B. anthracis Sterne.     

Phytochemical,Toxicological, Biochemical and Haematological Studies on Avocado (Persea americana) in Experimental Animals

The avocado tree belongs to the family lauraceae and is classified as Persea americana. The analysis of the fruits extract revealed the presence of considerable amounts of vitamins A, B₂, C, K, folic acid, lutein, zeaxanthin, coenzyme Q₁₀ and beta-carotene. When administered to wistar rats for acute toxicity studies, the animals did not exhibit any sign of toxicity even when large doses were given. The maximum tolerable dose (MTD) was therefore determined to be ≥ 10 g/kg body weight. The extract was found to significantly decrease (p < 0.05) the activity of liver and heart enzymes in the treated animals when compared with the control. The extract decreased total cholesterol (TC) by 37.97%, triglycerides by 37.87%, very low density lipoproteins(VLDL) by 47,41%, low density lipoproteins(LDL) by 59.57%, and at the same time increased high density lipoprotein (HDL) by 3.64%. The extract also decreased the prothrombin time (PT) and the partial prothrombo plastin time with kaolin (PTTK). These results are discussed with regard to the preventive and possible curative values of this extract as a potential inhibitor of cardiovascular diseases and in the regulation of blood clotting time due to its significant vitamin K content.