Effect of heat processing on phenolic constituents and nutritional quality of sunflower flours

Heat processing of dehulled, defatted sunflower flour resulted in a reduction in phenolic constituents, the destruction of chlorogenic acid (CGA) being more than that of caffeic acid (CA) and quinic acid (QA). Considerable losses in the available lysine rather than total lysine content were observed when sunflower flour was autoclaved at 1 kg/cm² (120 C) for periods varying from 5 to 60 min. The N solubility of sunflower protein in 0.02N NaOH showed a progressive decrease as the duration of heat treatment increased. Moderate heat treatment (15 min at 120 C) of the flour had no significant beneficial effect on in vitro digestibility. Any advantage in decreasing the levels of CGA, CA and QA contents by moderate heat treatment apparently was lost by the decrease in available lysine content, thus lowering the protein efficiency ratio (PER) from 1.97 to 1.71 and Net Protein Utilization (NPU) from 62.7 to 54.8, respectively.     

Cooking procedures for direct consumption of whole soybeans

The purpose of this research was to determine adequate conditions for the preparation of soybeans at home level. In accordance with the results, soaking the soybeans for eight hours in a 0.25% bicarbonate solution, gives the appropriate hydration to the soybeans, which can then be easily cooked. Boiling them at atmospheric pressure during 20 minutes was required to destroy 80% of the soybeans antitrypsin activity, and a high PER was also obtained. Nevertheless, the soybeans texture was not satisfactory; therefore, longer boiling periods were tested so as to establish the most suitable time needed to achieve a softness similar to that of common beans as usually consumed. Softness was measured instrumentally, and the optimal conditions found were: 40 min boiling after 8 hr soaking in a 0.25% bicarbonate solution. Under these conditions, the PER and NPU values increased 18% and 33%, respectively, with respect to those of the casein PER and NPU. It is concluded that with this procedure, large amounts of protein can become available at an equivalent price to US$0.40/kg ($80.00/kg).     

Protein concentrate of the manioc leaf. Extraction, chemical analyses and supplementation with amino acids

The purpose of this work was to prepare a manioc leaf protein concentrate introducing some new procedures on the known methods developed by other authors. Chemical composition and biological quality (PER, Digestibility, NPU and BV) of the protein content were measured for diets prepared with leaf protein concentrate and leaf. Histological studies were carried out in some organs. The protein concentrate and the powdered leaves were supplemented with methionine and lysine, alone and combined. The protein content (N X 6.25) of the concentrate and the leaf was 34% and 25.2%, respectively. Addition of either methionine or lysine alone did not improve the growth of the rats. A better response was obtained when both methionine and lysine supplemented the test materials as indicated by the biological criteria, protein efficiency ratio (PER) true digestibility (TD) and biological value (BV). Histological tests for the organs examined, proved to be normal.     

Use of chickpea (Cicer arietinum L.) in non-dairy formulas. I. Chemical composition and nutritive quality of chickpeas and a comparison with commercial infant formulas

A study was carried out to determine, in rats, the chemical composition and protein quality determinations: PER, NPR and NPU of chick-pea, milk powder and two different commercial infant formulas for babies with lactose intolerance. The formulas studied were "Casec" (calcium caseinate), "Sobee" (soy flour), "Plenilac" (milk powder) and cooked chick-pea flour, alone or supplemented with methionine and/or tryptophan. The protein and fat contents of "Casec" were 88 and 2%, respectively, while chick-pea, "Sobee" and "Plenilac" exhibited 18.9 and 8%, 22 and 18%, 26 and 28%, respectively. The four products were deficient in sulfur amino acids, with "Sobee" exhibiting the lowest chemical score (57), followed by chick-pea (62), "Casec" (68) and "Plenilac" (82). The chick-pea supplemented with methionine was deficient in valine (C.S. 76). The higher values of PER, NPR and NPU were obtained with the chick-pea supplemented with methionine, and with the "Plenilac" samples, while chick-pea without amino acid supplementation, however, had a protein quality similar to "Casec" and to "Sobee". According to these results, therefore, chick-pea alone or supplemented with methionine can be utilized as a milk substitute in malnourished children with lactose intolerance.     

Effect of home-processing in the preparation of pinto beans (Phaseolus vulgaris L.) on the tannin content and nutritive value of proteins

A 3(2) factor design was carried out in order to investigate the different home-cooking treatments applied in the preparation of pinto beans (Phaseolus vulgaris L.) on the nutritive value of their protein. The factors studied were previous soaking, type of cooking and addition of cooking broth. Biological evaluation of the protein was performed, and the protein efficiency ratio (PER) and apparent digestibility of the protein (DAP) values were obtained. The tannin content was measured in hulls, cotyledons and in the cooking broths of each experimental treatment. The most significant effect of the PER value was the type of cooking (P less than 0.0001), followed by the addition of cooking broth (P less than 0.05) as well as a significant interaction between cooking method and addition of broth (P less than 0.025). Soaking did not have significant effects per se or through its interactions in relation to PER. The highest values for PER and DAP were obtained with the boiling treatment without broth. The detrimental effect of the cooking broth can be explained by its tannin content (108.5-272.25 mg Eq. catechin/100g).     

Effect of reheating on iron availability and the protein nutritive value of cooked black bean (Phaseolus vulgaris)]

In Guatemala, at the rural level, beans are prepared for family consumption every two days. Beans are cooked again every 12 hours for 15 minutes prior to their consumption. Due to the adverse effect that the process causes on nutritive value, the present study evaluated the method and preparation practice of beans on protein value; tannin and soluble and ionizable iron content. As to the effect of re-cooking on protein level, findings revealed that there were no significant statistical effects on net protein ratio (NPR) or in protein efficiency ratio (PER) and number of bean cooking. Nevertheless, a constant effect in quality in the first and second cooking procedure was detected. The second cooking gave a similar value as the first. Also, the first and second heating reduced protein digestibility, but the third gave a value similar to the initial one. No changes were observed in the digestibility of dry matter. Relatively high amounts of protein were found in the cooking broth, which was not affected by the number of heating. It was also found that the bean broth contained high levels of tannins in the initial heating, decreasing later significantly. The same was observed in the cooked beans alone and in beans with their broth. With respect to iron, findings showed a relatively high transference of beans to broth, in total iron as well as in soluble, ionizable and insoluble iron. No changes were observed in whole beans without broth caused by number of heatings, on total, soluble or ionizable iron. In beans with their broth, a similar effect was observed, although a slight increase in insoluble iron was detected at the end of heating. A decrease in soluble and insoluble iron was observed in broth with number of heatings. Correlations were calculated among the parameters studied, which suggested an effect of tannins on the bioavailability of iron caused by tannins.     

Evaluation of two methods to determine the polyphenol content in raw and cooked beans and its effect on protein digestibility]

The polyphenolic compounds present in raw and cooked, and dried, with and without the cooking broth of common white, black and red beans (Phaseolus vulgaris) were measured by the Folin-Denis method for total polyphenols, and by the protein precipitation method of Hagerman-Butler, which measures their biological activity. The polyphenol content was measured during 20 consecutive days on the same sample, using three different extracts of volume from each sample. Statistical analysis of the results by the Folin-Denis method indicated that variability among the three aliquots was different for each bean color. A non-parametric analysis, however, indicated that the average in the three levels of concentration for beans of all colors, was the same. A similar analysis of the results by the Hagerman-Butler method demonstrated that variability and average values for the three aliquots were equal for black and red beans but not for white beans. The coefficient of variation was lower for the higher aliquot of the extract. A significant correlation (r = 0.72, P less than 0.05, n = 60) was found between the two methods for all beans using the larger aliquot of the extract. The correlation was highly significant (r = 0.84, P less than 0.05) when white bean values were eliminated. The polyphenolic content varied with seed color and the thermic process reduced their content, as measured by the two methods. The losses in polyphenolics as measured by the Folin-Denis in the cooked beans dried with broth, varied from 31.4 to 36.3%, and from 39.8 to 51.1% for the cooked bean flour dried without broth. The losses by the Hagerman-Butler method were from 25.0 to 93.5% in the cooked bean flours dried with cooking broth, and from 33.3 to 95.7% when dried without the broth. The higher losses were recorded for red beans. In vivo digestibility for cooked bean flours, dried and without broth, were 73.2, 69.6 and 64.5%, and 71.9, 71.9 and 68.8% for white, red and black beans, respectively. A negative correlation (r = -0.39) and significant (p less than 0.05) was found between polyphenolic content in the diet and in vivo protein digestibility.     

Influence of cooking and drying processes at different temperatures on the nutritive value of the protein of mussels (Mytilus edulis)

The effect of steam cooking (96 degrees C for 15 minutes) and drying at two temperatures, 70 degrees C and 110 degrees C, on nutritive value of mussel protein was studied. The measurements were carried out by nitrogen balance techniques in growing rats, and the nutritional parameters studied were: CD, BV and NPU. The crude digestibility (CD) values were: 87 +/- 1 and 82 +/- 1, and the biological values (BV), 80 +/- 1 and 74 +/- 1 for raw mussels, dried at 70 degrees C and at 110 degrees C respectively. This implies a significant decrease in the protein nutritive values of the mussel dried at a higher temperature. Cooking prior to drying significantly improved the digestibility and the biological value of the mussel's protein. In effect, improvement was so great, that the different drying temperatures did not affect the previously cooked product in a different way; therefore, the CD (94 +/- 1 and 94 +/- 1) and the BV (90 +/- 1 and 90 +/- 2) were the same for the mussel's protein, cooked and dried at 70 degrees C or at 110 degrees C.     

Nutritional quality of soybean proteins and casein, thermally damaged, and determined in vivo by an enzymatic method

In this study, the potential of the hepatic activity of the enzyme nucleoside phosphorylase (E. C. 2.4.2.1) as an indicator of dietary protein quality was tested in chickens. For this purpose, a thermal damage of increasing severity was induced on the proteins of casein and soy by heating them in an autoclave (121 degrees C) for 10 to 40 minutes in the presence of glucose. These treatments resulted in variable losses of available lysine, measured chemically, and protein quality, measured by growth assays (PER and NPR) or assays based on nitrogen gained (NPU and nitrogen retained) with chickens. These measurements were then compared with the hepatic activity of the nucleoside phosphorylase measured in the same chicks. The data revealed that the NPU and nitrogen retained procedures were more sensitive than PER or NPR in detecting changes in the protein quality associated with a heat treatment. Moreover, NPU, nitrogen retained and the activity of nucleoside phosphorylase showed that a mild heat treatment of casein, improved the quality of this protein. More prolonged heat treatments, however, caused a reduction in the quality of soy or casein protein as determined by all the methods for measuring protein quality used here, including the enzymatic method. The high correlation coefficients found in this study between the enzymatic method and those based on nitrogen gain or growth, indicate that this method may have a potential as a predictor of the quality of dietary protein.     

Enzymatic hydrolysis of extruded-expelled soy flour and resulting functional properties

Limited hydrolysis (4% degree of hydrolysis) of extruded-expelled soy flour protein (protein dispersibility index=21) that was poor in solubility and other functional properties was evaluated at pilot-plant scale (5 kg of flour) with two endopeptidases and one exopeptidase. Some hydrolysates were merely spray-dried whereas others were jet-cooked at 104°C for 19 s before spray-drying. Solubility, emulsification capacity and stability, foaming capacity and stability, apparent viscosity, and sensory attributes were then characterized. The type of protease used and hydrothermal cooking affected functional and sensory properties. Protein solubility modestly increased with hydrolysis and jet cooking, but emulsification capacity decreased on hydrolysis and was not restored with hydrothermal cooking. Emulsion stability improved in the endopeptidase hydrolysates, but not in the exopeptidase hydrolysates. The foaming capacities of the hydrolysates for both types of enzymes were better than for the unhydrolyzed control. Highly stable foams were obtained after hydrolyzing with exopeptidase and hydrothermal cooking. Ten percent protein hydrolysate dispersions showed large losses in consistency coefficient apparent viscosity, which increased significantly with hydrothermal cooking only for the unhydrolyzed control. Difference-from-control sensory evaluation indicated that both jet-cooked and non-jet-cooked enzyme hydrolysates were different from unhydrolyzed controls.     

Development of an enzymatic fish hydrolysate and its use in instant soup bases

The successful conservation of fish products, at low costs, is a subject of special interest in the developing countries. Conscious of this fact, our group has been studying several fish conservation methods, such as autolysis with high salt concentrations, and has obtained a sauce of high nutritive value and long shelf life. Nevertheless, the reaction process takes from four to six months. In the study herein reported, the hydrolysis was accelerated and controlled by using the following enzymes: papain, HT proteolytic, and Brew (N) zyme. The hydrolysate was then mixed with cereals to prepare instant soups. As results indicated, the best hydrolysate was obtained with Brew (N) zyme at 50 degrees C and 8.30 hours. This hydrolysate contains 93.0 g/100 g crude protein with a protein efficiency ratio (PER) and a net protein utilization (NPU) of 60% that of casein's NPU as well as a content of 0.8% ether extract. The lowest-cost mixtures with the highest nutritive value were: hydrolysate-wheat-soymeal, and hydrolysate-rice-soymeal, with 38.3 and 29.7 protein per 100 g of mixture, respectively, and a NPU of 79.0 and 79.8% in relation to casein, respectively. The soups prepared had a satisfactory acceptance rating. There were no significant differences in flavor and aroma at a confidence level of 95%. The cost per gram of protein is about US$ 0.22 per kg.     

The protein quality of commercial products of texturized soybean protein and meat mixtures

The purpose of the present study was to evaluate the protein quality of eight commercial samples of texturized soybean protein (TSP) collected in the food markets of various Latin American countries. The study also included experiments designed to establish the limiting amino acids in those products, and studies to evaluate the process of texturization by extrusion cooking. Finally, experiments were also carried out to evaluate the effect of replacement of meat by TSP as well as the supplementary value of the latter to tortilla flour. The eight samples were characterized for their functional properties and protein quality. The results obtained indicate that all samples were different in density, water absorption, and nitrogen solubility. Likewise, all samples were different in their lysine, methionine and threonine content, with PER values ranging from 1.75 to 2.31. Protein quality standard value is 2.3. The amino acid supplementation studies showed a positive significant response to methionine addition, particularly in those products exhibiting low PER values. The addition of both lysine and threonine to the methionine-supplemented product, increased PER significantly. The data also demonstrated that replacement of more than 25% of meat protein by TSP protein decreased protein quality of the product, even when a TSP with an accepted protein quality value was used. This product was also found to supplement the quality of tortilla protein. Finally, it was established that the texturization process did not reduce the protein quality of soybean protein. Based on these results, it is concluded that the variability in the protein quality measured in the eight TSP samples was due to the initial quality of the soy flour texturized, which was already damaged before texturization. For this reason, it is recommended that Latin American countries establish TSP quality standards when this product is used as a protein extender for meat, and that appropriate systems be implemented for the quality control of such products.     

Biological value of protein from leaves of Atriplex suberecta]

The study of Atriplex suberecta leaf protein concentrate has been included within our work line entitled "Biological value of the leaf protein of Atriplex" amino acid profile and chemical score. In order to evaluate nitrogen retention, net protein utilization (NPU), true digestibility (TD) and biological value (BV) data were obtained. Weight gain was studied after determining net protein ratio (NPR) and relative net protein ratio (RNPR) with the following results: CS = 96, calculated for sulphur amino acids; NPU = 60 +/- 4.00; TD = 76 +/- 5.20; BV = 87; NPR = 3.34 +/- 2.50 and RNPR = 88%, which enable us to infer that its protein is of good quality. These data, therefore, should indicate that the product studied could be a good complement for cereals, considering its high lysine content (CS superior to 100).     

Germinated soybean protein products: Chemical and nutritional evaluation

Various protein fractions were prepared from non-germinated and germinated soybeans utilizing a combination of calcium chloride and sodium alginate solutions as extractant. Germination tended to improve the nutritional quality of the protein products as measured by protein efficiency ratios (PER of standard rat bioassay). PER values of proteins containing sodium alginate were reduced significantly, which was attributed to inhibition of pepsin proteolysis. Only 30 percent of the trypsin inhibitor activity in raw soybeans was eliminated during germination for three days. Vitamin C content increased from 0 to 25 mg per 100 g (dry basis) during germination.     

Modification of starch–poly(methyl acrylate) graft copolymers by steam jet cooking

Starch-g-poly(methyl acrylate) containing 12.3, 31.9, 51.7, and 58.3% PMA, by weight, were prepared by ceric ammonium nitrate-initiated polymerization of methyl acrylate onto granular cornstarch. The granular structures of these graft copolymers were not disrupted by steam jet cooking at 140°C. At most, only 13% of the polymer was dissolved, and this soluble fraction was comprised largely of starch. The probability of crosslinking within these graft copolymer granules was considered. Physical properties of extruded ribbons depended upon whether or not granular graft copolymers were jet cooked prior to extrusion. Although tensile strengths were not greatly affected by steam jet cooking, cooked samples showed significant increases in both percent elongation and tear resistance. The effects of jet cooking upon the properties of extruded ribbons can be explained by gelatinization of starch within the grafted starch granules. Although jet-cooked granules still remain intact, gelatinization of the starch moiety causes these granules to be less rigid, more deformable, and more easily plasticized by small amounts of water. Loss of starch crystallinity after steam jet cooking was proved by both differential scanning calorimetry and X-ray diffraction. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1021–1029, 1997     

Nixtamalization cooking characteristics of 11 maize varieties

In the present study, 11 maize varieties were analyzed for their nixtamalization cooking quality. The 11 varieties were grown in the same locality and in the same year. The samples were evaluated for their physical characteristics, such as moisture content averaging 13.3%, average 1000 kernel weight (312.5 g), grain hardness through density (1.28 g/ml) and percent floaters (9.5%). These data indicated that all maize varieties had a hard endosperm which is recommended for the nixtamalization cooking process. The 11 varieties were formed on the average by 5.7% seed coat, 11.5% germ and 82.8% endosperm. The low seed coat content suggest a low solids loss during processing. Cooking quality evaluation was done by applying a standard lime cooking procedure to all varieties. An average solid loss of 3.2% was measured, with 0.8% of seed coat still attached to the endosperm. Water absorption at the end of cooking was 40.8% without soaking and 46.9% at the end of soaking. Nixtamal moisture was 47.9% after soaking and only 41.5% at the end of cooking. Cooking time with soaking for 50% moisture in the grain varied from 69 to 122 minutes at 1500 meters over sea level. The cooked grain was dried with hot air and ground however, the particle size obtained was not as that in commercial nixtamalized maize flour. However, the cooking quality parameters to make dough and tortillas were acceptable, with a penetration index of hydrated flour of 178.6 mm, pH 7.97, water absorption index (WAI) of 3.23 g gel/g flour and 4.11% water solubility index (WSI). All flours from the 11 varieties of maize gave acceptable tortillas as evaluated by physical characteristics and sensory quality. However of the 11 varieties 7 including the control were superior for nixtamalization cooking quality.     

Stability of Essential Fatty Acids and Formation of Nutritionally Undesirable Compounds in Baking and Shallow Frying

During cooking oils and fats are exposed to high temperatures that may affect the nutritional quality of foods that are prepared in this way. Concerns have been raised about the degradation of polyunsaturated fatty acids and the formation of potentially harmful compounds during deep frying, but relatively little is known about these changes in other cooking processes. In the present study sponge cakes and fried potatoes were prepared via standardised baking and shallow frying procedures by using different oils and fats (sunflower oil, rapeseed oil, various margarines or butter). The effect of cooking on the retention of two essential fatty acids (linoleic acid and α-linolenic acid) and the formation of trans fatty acids (TFA) and polymerised triacylglycerols (PTG) was evaluated by analyzing fat extracted from the cooked food. It was found that over 95 % of essential fatty acids were retained upon completion of both cooking techniques. The formation of TFA was not significant. Polymerisation was noticeable only in shallow frying, although the final levels of PTG were negligible (<1.3 %). Overall, in contrast to deep frying, oil-based media high in polyunsaturated fatty acids seem to be a good alternative for domestic cooking techniques as they increase the nutritional value of the prepared food.     

Effect of the extrusion process on the functional characteristics and protein quality of quinua (Chenopodium quinoa, Willd)

In order to have available a human food of high nutritive value, and conscious of the protein quality of the quinua, as well as its carbohydrate, vitamin and mineral content, its behavior during the extrusion process was tested in the present study. To eliminate saponins, a simple method was developed which consisted of washing the seeds through an aluminum container, using a wooden stirrer. Seven treatments were studied: washed quinua, washed and cooked quinua, washed and expanded quinua No. 1 and No. 2, and washed and texturized quinua No. 1 and No. 2; casein was used as control. Biological evaluation trials were carried out in Holtzman rats, following the PER method. To detect the possible effects of the processed quinua on the experimental animals, hematological as well as histopathological studies of the vital organs were performed. A maximum PER of 2.43 was obtained for the texturized quinua, 2.16 for the expanded quinua, 2.6 for the cooked quinua, while the casein control yielded a PER of 3.00. The physico-chemical characteristics of the quinua flour were determined, as well as those of the expanded and texturized products. The product obtained was subjected to an organoleptic trial and it can be stated that the results obtained were satisfactory. The product can be consumed directly without major modifications and has an acceptable flavor. The nutritive value of quinua was not impaired; it compared favorably with the best diets recommended for the population, especially of those with a lower income. The results obtained in the present study suggest the possibility of increasing the nutritional value of the product, as well as its acceptability.     

Evaluation of chemical and nutritional characteristics of the seed of the rubber tree (Hevea brasiliensis)

Some chemical and nutritional characteristics of the rubber seed Hevea brasiliensis were studied. The protein content, its amino acid composition as well as the iron, calcium, phosphorus and cyanide (free and bound) concentrations, were determined in the dehulled seed. The effect of soaking, cooking, soaking-cooking and cooking-fat extraction procedure of the seed on the cyanide content and its in vivo protein utilization, was also evaluated. The protein quality was biologically assessed using the protein efficiency ratio (PER). The protein content of the seed was 18%, and the most limiting amino acid was threonine, with a chemical score of 71.6. The iron, calcium and phosphorus contents were 6.2, 109 and 429 mg/100 g, respectively. Its fat content was 48% with a total energy value of 702 kcal/100 g (2,948 Kj/100 g). The total cyanide content in the fresh seed was 130-230 mg/100 g; 6% was in the free form and 94% as bound cyanide. The most effective treatment for reducing the cyanide content was found to be 20 hours of soaking in water, combined with one hour of cooking. The raw seed had a low nutritive value and produced weight loss and death when fed to rats. The protein value, however, improved upon the seed treatment, reaching PER values close to those found in traditional cereals such as corn. It is therefore concluded that the seed of Hevea brasiliensis is a good source of energy, calcium, valine, isoleucine, phenylalanine and tyrosine. In contrast, it is a poor source of threonine, leucine and lysine. Its cyanide content is high, but when removed by treatment, such as soaking in water, cooking or fat extraction, the protein utilization can be improved.     

脱氢二香草醇的合成及LCC的形成机理(Ⅱ)

在合成缩合型木素模型化合物——脱氢二香草醇的基础上,模拟硫酸盐法蒸煮过程,将合成的木素模型物和典型的半纤维素组成部分——木糖进行蒸煮,然后利用酸析沉淀木素、乙酸乙酯抽提等方法将蒸煮后的产物分级,并利用FT-IR、13C-NMR对分级后的各个部分进行分析,探讨传统硫酸盐法制浆过程中木素-碳水化合物复合体(LCC)的形成机理。研究发现,脱氢二香草醇在硫酸盐法蒸煮过程中非常稳定,部分脱氢二香草醇与木糖形成LCC连接,未降解的脱氢二香草醇和新形成的LCC主要存在于乙酸乙酯抽提物中,酸不溶物和酸可溶物内都不存在新形成的LCC结构。