Biological quality of the protein isolated from the leaves of Atriplex numularia

Plant leaf proteins have acquired great relevance during the last two decades because of their well-balanced amino acid composition. A study was therefore undertaken to evaluate the biological quality of the leaf protein of Atriplex numularia. The protein content of the fresh leaves from this plant was found to be 4.70 g/100, with a dry matter content of 18.70 g/100 g. A protein concentrate (PC) from the same material was then obtained by macerating the leaf in a 2% sodium sulfite solution at a pH of 10 and subjecting it to filtration and pressing. The product thus obtained had a dark greenish color and contained 55.42 g/100 g of protein. The amino acid analysis revealed that its protein has a balance similar to that of animal origin proteins, with a lysine and methionine content of 8.5 g/16 g N and 3.0 g/16 g N, respectively. Biological assays were then carried out to evaluate nitrogen utilization, with the following resulting values: net protein utilization (NPU) = 48.3 +/- 2.7; digestibility (D) = 58.0 +/- 1.4, and biological value (BV) = 83. As inferred from the NPU value, nitrogen utilization was low. Therefore, to improve digestibility values, the action of papain on the PC was assayed. The material thus treated was again submitted to biological trials, obtaining, this time a D of 75.4 +/- 1.05, and thus, an improved new NPU value of 54.8 +/- 1.1 (p less than 0.01).     

Chemical composition and nutritive value of the protein of Amaranthus quintensis

An account is given of some considerations concerning the chemical recognition and evaluation by biological methods of the quality of the flour obtained from Amaranthus quitensis seeds, submitted to grinding and sifting. The protein content of the flour (21.70g/100g) can be considered as very important, as well as that of the available lysine (5.20g/16gN). The calcium content was also remarkable (500mg/100g), and the starch ratio reached 45.00g/100g. The amount of nitrates found was 20.00mg/100g, which is an acceptable limit. The research for organic nitro compounds was negative. As for the biologic quality of the protein, the experiments revealed that it has quite an acceptable availability, as demonstrated by the following values: NPU = 42.50 +/- 6.10, D = 68.50 +/- 5.30, VB = 62, NPR = 2.10 +/- 1.80 and RNPR = 42.     

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.     

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.     

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.     

Biologic value of the protein concentrate of Atripex lampa and its value as a complement to wheat flour

The Atriplex lampa, chenopodiáceae, is a very abundant bush in the arid and semiarid regions of our Province. This work was undertaken to characterize from the chemical point of view, both the fresh leaves and the protein concentrate (PC) obtained from them. A second purpose was to determine the biological value of the protein, and to evaluate its capacity as a complement to wheat flour (WF). Through this study, the leaf was shown to have a high content of ashes, sodium, potassium and silica, what accounts for its low palatability. The PC obtained has a protein concentration of 59.37 g/100 g and its biological value is limited by the sulfur amino acids, with a chemical score of 85.70. Since the protein is poorly utilized, this results in a relatively low value of its net protein utilization (NPU), a fact which may be attributed to its low true digestibility. The studies on the complementary effects of PC on WF were made at three levels, i.e., 30, 50 and 60%, respectively. The results revealed that the best complementation, measured by the nitrogen utilization, happened to be when 50% of the protein contribution was provided by the A. lampa protein concentrate.     

Evaluation of the adjusted amino acid score by digestibility for estimating the protein quality and protein available in food and diets

The purpose of the present study was to evaluate the amino acid score adjusted by digestibility to estimate protein quality and utilizable protein in foods and diets, considering net protein utilization (NPU) as a biological reference method. Ten foods of vegetable origin and ten of animal origin, as well as eight mixtures of foods of vegetable and animal origin were studied. When all the foods were considered, a positive (r = 0.83) and highly significant correlation (p less than 0.001) between NPU and the amino acid score adjusted by digestibility was found. When the foods were separated according to their origin, this correlation was positive only for the foods of vegetable origin (r = 0.93) and statistically significant (p less than 0.001). Also, only in those foods were similar values found between NPU and amino acid score adjusted by digestibility, as well as in utilizable protein estimated considering both methods. Caution is required to interpret protein quality and utilizable protein values of foods of animal origin and mixtures of foods of vegetable and animal origin when the amino acid score method adjusted by digestibility, or NPU, are utilized.     

Variations in macronutrients and nutritive value of the protein of canned tuna stored for 3 years after its preparation

The composition in macronutrients and available lysine of canned tuna stored for three years at room temperature, was analyzed. Digestibility (DC), biological value (BV) and net protein utilization (NPU) were determined with Wistar rats tests. The results were then compared to those obtained three years ago, when the canned food was prepared with casein standard protein plus DL-methionine, in order to control any variation that might had occurred in animal behaviour. No variation was found, either in macronutrient composition or in digestibility. However, BV and NPU decreased significantly. Highly significant, and somewhat surprising, was the finding that the amount of available lysine, which had diminished as the can was prepared with respect to the amount found in raw tuna, increased during the storage period.     

Nutritional value of mung bean (Vigna radiata) as effected by cooking and supplementation

The study was conducted to improve the nutritional value of Mung (Vigna radiata) by supplementation with different kinds of meat. Diets were prepared using raw and cooked Mung and then cooked Mung was supplemented with poultry, mutton and beef at 10, 15, and 20 percent levels. Nutritional value of Mung was determined by chemical analysis as well as by rat assay. Mung had 25 percent protein and minor losses were observed during cooking. It had 1.21 percent lysine which was reduced by 43 percent on cooking. Other amino acids also showed losses during cooking. The Protein Efficiency Ratio (PER) of diet containing Mung was significantly reduced on cooking (1.86 vs 1.40). On the contrary cooking resulted in some improvement of Net Protein utilization (NPU) and True Digestibility (TD) of the Mung based diets. Twenty percent level of different meats showed better results in terms of PER, NPU and TD.     

Analysis of the application of methods recommended by FAO/WHO 1973 for determining the protein quality in Chilean food. Effect of the dietary protein concentration

The 1973 FAO/WHO Joint Expert Committee on Energy and Protein Requirements has recommended two methods to adjust the safe level of protein intake according to protein quality: chemical score and net protein utilization (NPU). However, the effect of protein concentration on protein utilization is not considered. The results of the present work, as well as those obtained by other investigators, show that there is an inverse relationship between protein concentration and protein utilization. The net protein utilization (NPU) at 10% of protein-calories or the chemical score adjusted by the nitrogen digestibility can be applied when results are to be projected to national average diets, which have values ranging between 9 and 13%. When it is necessary to evaluate the diet of specific relatively homogeneous population groups, the recommended method should use the NPU determined or calculated in each meal considering the level of protein concentration of the diet as eaten (NPU op). This method takes into account the amino acid complementation in each meal. The data on which these conclusions are based have been presented and discussed.     

Effects of treatment with polyvinylpyrrolidone on nutritional quality of sorghum

The purpose of this paper was to show that a high polyphenolic compound content in the sorghum grain (Sorghum saccharatum, var sugar drip) has an unfavorable influence on the nitrogen absorption. In order to arrive at this conclusion, the tannin content in sorghum flour was reduced by means of a treatment with polyvinylpyrrolidone (PVP) as a complexing agent. Several biological experiments were performed with non-treated flour (S) and with PVP-treated flour (S + PVP). Treatment improved true digestibility (D), having obtained the following values: for S = 31 +/- 2.67, and for S + PVP = 55.8 +/- 3.48 (significance P less than 0.001). The tannin evaluation yielded the following results: S = 1.90 g/100 g, and S + PVP = 0.85 g/100 g reported as tannic acid. The digestibility increase induced a better nitrogenous utilization, the net protein utilization (NPU) values being from 19 +/- 1.58 to 37 +/- 3.36 for S, and S + PVP, respectively.     

Effect of lactose on the evaluation of the nutritive value of casein

The biological evaluation of protein from dairy products such as normal and modified powdered milks where lactose is present, poses difficulties. It is known that when this sugar is contained in high concentrations, and due to its osmotic effect, it causes serious intestinal disorders in rats, thus obstructing the determination of the protein nutritional quality. In the study described herein, efforts were made to determine how lactose affects determination of the nutritional value of casein when this is evaluated by the Net Protein Utilization (NPU) procedure, and by the Relative Net Protein Ratio (RNPR) method. Thirty, and 21-day-old rats were fed with diets containing 10% and 8% of casein respectively, and lactose concentrations varying from 20% to 50%. All experiments lasted 10 days. The results demonstrated that casein's nutritional value did not differ significantly (p greater than 0.05) with lactose concentrations up to 40% in any of both methods, even though intestinal disorders were observed with more frequency and duration as lactose concentration increased.     

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.     

Canning of "humitas" prepared with opaque-2 corn, supplemented with sweet lupine (Lupinus albus var. Multolupa). Nutritional and quality changes

The effects of opaque-2 corn and the complementation with lupin flour on the sensory quality and nutritive value of "humitas" were evaluated. Moreover, the nutritional and quality changes which occur during the retorting of the product canned in two can sizes, were studied. Hybrid and opaque-2 corn were replaced with 6%, 8%, 10% and 12% lupin flour, being 8% the complementation level with the best sensory and nutritional quality. Heat penetration studies of the product canned in N2 and N6 tin cans, were carried out. Total process time at 121 degrees C was 73 min and 147 min, respectively. "Humitas" prepared with hybrid and opaque-2 corn, with and without 8% lupin flour, prior and after sterilization, were subjected to proximate analysis, pH, titratible acidity and available lysine determinations. Biological evaluation of the protein by the net protein ratio (NPR) and digestibility, as well as organoleptic quality and acceptability analyses were also determined. It was concluded that the complementation with 8% lupin flour improves significantly the nutritional value of hybrid corn "humitas", but not that of opaque-2 corn. The canning process affected lysine availability and was directly related to the amino acid concentration, and to the retorting duration. On the other hand, the thermal processing adversely affected the biological quality of protein and some sensory attributes. The 8% lupin complementation was also detrimental for the organoleptic quality of the product.     

Fortification of bread with bean flour (Phaseolus vulgaris). II. Nutritive value of the fortified bread

The protein value of breads containing bean flour (BF) (Phaseolus vulgaris, cv Tórtola) was tested in rats. BF replaced wheat flour by 2, 4, 6, 8 and 10 per cent. Protein content was 9.3 (N x 5.7) per cent and 24.4 (N x 6.25) per cent for wheat flour and bean flour, respectively. The protein content in the control bread was 11.6%, and increased to 12.6% at the 10% level of substitution. Parameters measured were protein efficiency ratio (PER), net protein ratio (NPR), and apparent and true digestibility of the protein. PER, in the control bread, was 1.44; a slight, non-significant increase occurred up to the 10% level of substitution. The control bread showed a NPR value of 2.78, figure which also remained practically unchanged at the higher levels of replacement. Nevertheless, both apparent and true protein digestibility decreased significantly with increasing levels of substitution of WF by BF (p less than 0.05). In conclusion, substitution of WF by BF in bread did not produce the expected increase in protein quality under our experimental conditions.     

Functional and nutritional properties of acylated rapeseed proteins

Rapeseed flour was acylated to various degrees with acetic and succinic anhydrides to produce acetylated rapeseed protein concentrates (SRPC) and succinylated rapeseed protein concentrates (SRPC), respectively. With both acylating agents, approximately 5–82% (ARPC-5 to ARPC-82) and 5–56% (SRPC-5 to SRPC-56) of ε-amino groups of lysine were acylated. Changes in functional properties were monitored; nitrogen solubility, emulsifying properties and specific viscosity were improved by acylation. The effects on functional properties were more pronounced with succinylation than acetylation. The nutritive value of succinylated rapeseed protein concentrates was determined and compared with those of unmodified rapessed protein concentrate and rapessed flour. Succinylation reduced the availability of lysine and decreased (p<0.05) the net protein ratio (NPR) and apparent digestibility coefficient (ADC) of nitrogen in rapessed protein concentrates. Supplementation of SRPC with lysine improved the NPR compared to that of SRPC-56.     

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.     

Characterization of cookies made with deseeded grape pomace

Characterization of cookies made with deseeded grape pomace. The objective of this study was to evaluate deseeded grape pomace as a potential ingredient to elaborate some food products. Cookies were made with flour containing four levels of deseeded grape pomace (0, 5, 7.5 and 10%). Moisture, protein, ashes, fat, tannins and dietary fiber contents were determined in both the deseeded of grape pomace and the cookies. Besides, color, sensorial acceptability and biological evaluations of Net Protein Ratio (NPR), Apparent Digestibility (AD) and True Digestibility (TD) of Protein were determined to the cookies. Substantial amounts of dietary fiber and ashes were found in both the deseeded grape pomace and the cookies. Total dietary fiber increased while adding more deseeded grape pomace. Cookies were well accepted as observed in the sensory evaluation, showing no significative differences among the four levels of deseeded grape pomace addition. The addition of deseeded grape pomace imparted a darker color to the cookies. The dark color was greater in the samples containing more fiber which was indicated by the lower L color value. Regarding nutritional analysis, the higher the deseeded grape pomace addition, the lower the NPR, AD, and TD values. The NPR was affected in greater degree, although these differences were not significant. It is possible to use deseeded grape pomace as an ingredient to make high fiber cookies with acceptable sensorial attributes.     

Biological value of the unicellular protein of Kluyveromyces marxianus var. lactis]

The ever increasing problem of environmental pollution and protein scarcity led us to begin producing protein biomass from cheese whey, having selected for this aim, Kluyveromyces marxianus va. lactis strain, which represents the right relationship between its protein content (53.3% d.w.) and that of the RNA (4.63% d.w.). On the other hand, the distribution of its essential amino acids is balanced, although it shows a deficiency in methionine, its value being 1.5 g/16 gN. The purpose of this work was to assess the biological quality of this protein concentrate, so as to use it in animal feeding. Protein quality was determined by the NPU method (net protein utilization), according to Miller and Bender's technique. Three balanced diets were prepared (10% protein), the test sample with casein, and the rest with protein biomass, one of then supplemented with methionine (0.5 g/100 g food). Based on the results it can be concluded that the biomass analyzed has an adequate biological value (55.37%) for use in animal feeding, especially when methionine as added (60.23%).     

Studies on the development of infant foods from plant protein sources. Part III. Preparation, processing and properties of various products developed

Studies have been carried out on the development of a low-cost, high-quality infant food of low paste viscosity from rice, chickpea (Cicer arietinum) and cow's milk. In order to improve the overall quality of the product, chickpea was processed by different methods prior to its incorporation. A number of formulations was prepared by mixing 52% rice, 30% each, the processed chickpea sample, and 18% whole milk powder. These mixtures were processed by extrusion cooking or drum drying. In the case of the extrusion cooking method, from the nutritional and technological points of view, it was found advantageous to incorporate milk powder after cooking a mixture of rice and chickpea. The values of net protein ratio (NPR) of the products developed, whether processed by extrusion cooking or drum-drying methods, were statistically equal, and not significantly different from those of casein. Supplementing the product with methionine and threonine showed no effect in improving the NPR value, suggesting that these amino acids were not limiting. There were slight differences in the digestibilities of proteins in the products developed and all were lower than that of casein. Depending on the processing method, differences were observed in paste viscosities of the products. After partial hydrolysis of the products with pounds amylase, both the cold and hot paste viscosities were greatly reduced and were comparable with those of whole milk powder. From the results herein reported, it can be concluded that the drum-dried product prepared using rice:chickpea (carbonate presoaked):milk (52:30:18) is the best of all the products developed. Its amino acid composition compares favorably with that of the milk proteins.