Protein digestibility‐corrected amino acid scores,acceptability and storage stability of ready‐to‐eat supplementary foods for pre‐school age children in Tanzania

This study was conducted to evaluate protein quality, acceptability and storage stability of processed cereal–bean–sardine composite foods for pre‐school age children in Tanzania. Four composite products namely corn–bean–sardine meal (CBSM), bean meal (BM), sorghum–bean–sardine meal (SBSM) and rice–bean–sardine meal (RBSM) were formulated to maximize the amino acid score for pre‐school age children and were processed by extrusion, drum‐processing and conventional cooking. The products were evaluated for true protein digestibility (TPD) and protein digestibility‐corrected amino acid score (PDCAAS). The TPD and PDCAAS were highest in the extruded products. The TPD values for the products ranged from 82 to 93%. The PDCAAS values for the composite foods were 64–86% and were greater than the minimum value of 60% recommended by FAO/WHO/UNU. There were no significant (p > 0.05) variations in the amino acid contents for foods processed by extrusion, drum‐processing or conventional cooking. Threonine was most limiting in the CBSM, SBSM and RBSM while methionine + cysteine were most limiting in the BM. Sensory evaluation showed that, relative to the traditional cornmeal—Uji, the extruded CBSM and SBSM had significantly superior (p ≤ 0.05) texture and highly acceptable color and taste. Storage of the products up to 16 weeks at 38 °C resulted in a small but significant increase (p ≤ 0.05) in the malondialdehyde concentrations; nevertheless, the levels remained within the acceptable range found in processed commercial supplements. Total acids, pH and organoleptic attributes did not change significantly (p > 0.05) during storage and the foods were acceptable to the end of the storage period. Copyright © 2005 Society of Chemical Industry     

氨基酸的有效性对于蛋白消化率校正氨基酸评分的影响

蛋白质的传统化学评分是基于相关的氨基酸组成，蛋白消化率校正氨基酸评分综合了蛋白质的传统化学评分和氨基酸有效性的生物学评价。随着蛋白消化率校正氨基酸评分的产生，对于膳食蛋白品质的评价有了一个飞跃。本文重点研究测定蛋白中氨基酸有效性的问题，并讨了采用回肠消化率，粪便消化率，真消化率，实际消化率对于评价蛋白品质的不同影响。     

Effect of soy flour addition and heat-processing method on nutritional quality and consumer acceptability of cassava complementary porridges

BACKGROUND: The nutritional quality of cassava complementary porridge was improved through extrusion cooking and compositing with either defatted or full fat soy flour (65:35 w/w), and product acceptability by mothers with children of the target population was evaluated. RESULTS: The protein digestibility‐corrected amino acid score (PDCAAS) of extrusion‐ and conventionally cooked composite porridges was within the recommendations for complementary foods. The kinetics of starch digestibility showed that all porridges had a rapid rate of starch digestibility, but the rate was lower when defatted soy flour was added and lowest when full fat soy flour was added. The formation of amylase‐lipid complexes as shown by X‐ray diffraction and differential scanning calorimetry can be attributed to the lower digestibility of extrusion‐cooked porridge with full fat soy flour. If fed thrice per day, extrusion‐cooked porridge with defatted or full fat soy flour would meet the energy, protein and available lysine requirements of a child aged 6–8 months receiving low or average nutrients from breast milk. All porridges were well received by Mozambican mothers who use cassava as a staple food. The mean scores for sensory liking of all porridges were 3 and above on a five‐point hedonic scale. CONCLUSION: Extrusion‐cooked cassava/soy flour porridges have good potential for use as high‐energy/high‐protein complementary foods and have acceptable sensory properties. Copyright © 2012 Society of Chemical Industry     

The effect of food dry matter intake on the flow of amino acids at the terminal ileum for rats fed an enzyme‐hydrolysed casein‐based diet

The aim of the study was to determine whether food dry matter intake had an effect on endogenous ileal amino acid flows in the rat when the flows were expressed in units of mg g^?1 dry matter. Eighty 200 g body weight rats were trained for 7 days to consume a casein‐based diet over a daily 3 h feeding period, and then an enzyme‐hydrolysed casein (MW < 5000 Da)‐based diet, with chromic oxide as an indigestible marker, was fed for a further 8 days. The mean ratio of food intake to metabolic body weight over all 80 rats was determined on days 11 and 12. On day 15, food was offered to groups of 10 rats at each of eight intake levels. The intake levels were calculated from the mean food intake value and individual metabolic body weights and scaled in increments of 0.1 by factors ranging from 0.3 to 1.0. Digesta were collected from the terminal ileum 3 h after the start of the meal, and endogenous ileal amino acid flows were determined after amino acid and Cr analyses of the diet and endogenous ileal digesta fractions prepared by centrifugation and ultrafiltration (10 000 Da molecular weight cut‐off). The linear regression relationships between ileal amino acid flows, expressed as mg g^?1 dry matter, and dry matter intakes demonstrated that all slopes were negative but that the slopes for nine of these amino acids were not significantly different from zero (P > 0.05). There were significant slopes (P < 0.05) for the other eight amino acids, although the magnitudes of the effect were small. When the data were re‐examined after removing the lowest feeding level, the slopes for most of these amino acids were no longer statistically significant. The results showed that the measures of amino acid flow (mg g^?1 dry matter), except for isoleucine and cystine, over a wide range of food intakes were not materially affected by food intake. From the perspective of bioassay logistics the results indicate that expressing ileal amino acid flows proportional to dry matter intake is justified over the range of intakes found in practice for determining true ileal amino acid digestibility by the enzyme‐hydrolysed casein method. © 2002 Society of Chemical Industry     

Assessment of Algerian sorghum protein quality [Sorghum bicolor (L.) Moench] using amino acid analysis and in vitro pepsin digestibility

To assess the protein quality and the nutritive value of seven Algerian local sorghum cultivars, the in vitro pepsin digestibility was determined, which ranged from 25.0% to 65.0%, and the amino acid composition of each cultivar was compared with other sorghum cultivars. In addition, the amino acid scores (AAS) and the protein digestibility-corrected amino acid scores (PDCAAS) were calculated. Relative to the WHO protein standard, most of the sorghum cultivars tested, scored very high AAS, with values ranging between 0.9 and 2.6 except for lysine, methionine and cysteine. The PDCAAS were high for Ain Salah cultivars AS1 and AS3, however, all other cultivars showed low values except for leucine. This study confirmed that in terms of both quantity and quality, sorghum proteins could serve as a source of essential amino acids and as a potential source of proteins in the future.     

一种蛋白质游离氨基含量测定方法—三硝基苯磺酸法的探究

三硝基苯磺酸(trinitrobrnzen sulfonic acid,TNBS)法是测定蛋白质中游离氨基含量的方法。该文比较了该方法的2种终止反应条件及分析方法,探究了该方法对不同蛋白质(牛血清蛋白、胰蛋白酶、溶菌酶)的适用性。结果表明,碱性条件下的响应值显著高于酸性(P<0.01);紫外可见分光光度计和酶标仪2种测定方法对蛋白质游离氨基含量的测定结果在一定范围内没有显著差异(P>0.05),紫外可见分光光度计测定结果精确度较高,对浓度变化的响应更灵敏。蛋白质种类不仅影响到该方法的取样浓度,而且蛋白质中的巯基含量会干扰该方法的准确性。     

Determining the contents of protein and amino acids in peanuts using near‐infrared reflectance spectroscopy

BACKGROUND: The protein and amino acid contents of peanuts play a key role in determining their quality and value. Therefore, accurate, nondestructive, quick, and automated measurement of these components would be valuable in a commercial environment. This study explored the feasibility of determining the contents of protein and amino acids in peanuts using near infrared–reflectance spectroscopy (NIRS). RESULTS: 141 peanut samples were collected from 12 provinces in China. The spectra were scanned and obtained with an NIRS system. The determination coefficient and the ratio of the standard deviation in the validation set to the standard error of validation corresponded to 0.99 and 6.53 for protein, 0.88 and 2.52 for Asp, 0.83 and 3.00 for Thr, 0.86 and 2.40 for Ser, 0.87 and 2.57 for Glu, 0.88 and 2.36 for Gly, 0.88 and 3.00 for Leu, 0.89 and 2.88 for Arg, and 0.96 and 7.50 for Cys. CONCLUSIONS: NIRS combined with multivariate calibration has significant potential in determining the protein and amino acid contents of peanuts. This method is suitable for use in an industrial setting owing to its ease of use as well as the relatively low cost of obtaining and running the necessary equipment. Copyright © 2012 Society of Chemical Industry     

Relationships between amino acid composition and nitrogen of foxtail (Italian) millet (Setaria italica) grain of different varieties

The amino acid composition of 13 samples of foxtail millet (Setaria italica L) from six Chinese and one French varieties was determined as a function of their N content (N), which ranged from 1·82 to 3·65 g per 100 g of grain DM. The levels of amino acids in grain DM increased linearly with N with correlation coefficients close to 1 for most of them regardless of foxtail millet genotype or phenotype. Thus simply knowing N enables one to predict the amino acid composition of any foxtail millet grain sample. Amino acids in crude protein of grain (g 16 g^?1N)changed as quadratic functions of N, which decreased for glycine, cysteine, tysine, histidine and arginine, remained nearly constant for valine, threonine, tyrosine, methionine and aspartate plus asparagine, and increased for other amino acids. Foxtail millet appeared as the only cereal in which lysine is the only limiting essential amino acid. However, the lysine score was low and intermediate between that of maize and sorghum, falling from 48 to 31 % when N increased from 1·82 to 3·65 g per WO g DM. The N-to-protein conversion factor strongly increased with N and was the highest of all cereals within the N range studied. The results also showed that the composition of storage proteins accumulated in grains remained constant, with a prolamin to glutelin ratio close to three and independent of grain protein content.     

Effects of AMP-activated protein kinase (AMPK) signaling and essential amino acids on mammalian target of rapamycin (mTOR) signaling and protein synthesis rates in mammary cells

Regulation of mammary protein synthesis potentially changes the relationships between AA supply and milk protein output represented in current nutrient requirement models. Glucose and AA regulate muscle protein synthesis via cellular signaling pathways involving mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK). The objective of this study was to investigate the effects of essential AA (EAA) and acetate or glucose on mTOR and AMPK signaling pathways and milk protein synthesis rates. A bovine mammary epithelial cell line, MAC-T, was subjected to different media containing 0 or 3.5 mmol/L EAA concentrations with 0 or 5 mmol/L acetate or 0 or 17.5 mmol/L glucose in 2 separate 2 × 2 factorial studies. In a separate set of experiments, lactogenic bovine mammary tissue slices were subjected to the same treatments except that the low EAA treatment contained a low level of EAA (0.18 mmol/L). Supplementation of EAA enhanced phosphorylation of mTOR (Ser2448) and eukaryotic initiation factor 4E binding protein 1 (4EBP1, Thr37/46), and reduced phosphorylation of eukaryotic elongation factor 2 (eEF2, Thr56) in MAC-T cells. Concentration of ATP and phosphorylation of AMPK increased and decreased, respectively, in the presence of EAA in MAC-T cells. Acetate, EAA, or glucose numerically reduced AMPK phosphorylation by about 16% in mammary tissue slices. Provision of EAA increased phosphorylation of mTOR and 4EBP1, intracellular total EAA concentration, and casein synthesis rates in mammary tissue slices, irrespective of the presence of acetate or glucose in the medium. Phosphorylation of mTOR had a marginally negative association with AMPK phosphorylation, which was positively related to eEF2 phosphorylation. Casein synthesis rates were positively and more strongly linked to mTOR phosphorylation than the negative link between eEF2 phosphorylation and casein synthesis rates. A 100% increase in mTOR phosphorylation was associated with an increase in the casein synthesis rate of 0.74%·h⁻¹, whereas a 100% increase in eEF2 phosphorylation was related to a decline in the casein synthesis rate of 0.33%·h⁻¹. Although AMPK phosphorylation was responsive to cellular energy status and had a negative effect on mTOR-mediated signals in bovine mammary epithelial cells, its effect on milk protein synthesis rates appeared to be marginal compared with the mTOR-mediated regulation of milk protein synthesis by EAA.     

Changes in saccharide,amino acid and S‐methylmethionine content during malting of barley grown with different nitrogen and sulfur status

BACKGROUND: Changes in saccharide, amino acid and S‐methylmethionine (SMM) concentrations and enzyme activities during the malting of barley grown with different nitrogen (N) and sulfur (S) supplementation were investigated in order to clarify their relationship with N and S fertiliser levels. RESULTS: Concentrations of N and S in barley grain were significantly increased by the addition of N to the culture soil. Application of N decreased the starch concentration in grain. On the other hand, higher N fertilisation increased the β‐glucan concentration in grain and malt, thus decreasing the accessibility of β‐glucanase to its substrates. Proteolytic enzyme activity was significantly higher in the absence (?N treatment) than in the presence (+N treatment) of N fertiliser, making the concentration of the majority of amino acids in malt slightly higher in the ? N treatment. SMM was synthesised in grain after imbibition, and application of N increased the SMM content in malt. CONCLUSION: Although SMM can be controlled to a certain extent during kilning, a balanced supply of N and S during cultivation can also be helpful for the production of malt with lower SMM concentration. Adequate soil management is desirable to maintain the balance between good agronomic performance and high malt quality. Copyright © 2010 Society of Chemical Industry     

Effectiveness of an ultrafiltration device for use with the enzyme‐hydrolysed protein method for determining endogenous ileal nitrogen and amino acid excretion in the pig

The aim of the work was to perform an in vitro study to determine the effectiveness of Centriprep‐10 concentrator devices for use with the enzyme‐hydrolysed protein method for the determination of endogenous ileal nitrogen and amino acid flows. Different amounts of enzyme‐hydrolysed casein (EHC) were added to tubes containing digesta collected from pigs that had received a protein‐free diet for 5–8 days. The samples were centrifuged and then ultrafiltered using Centriprep‐10 concentrators. The precipitate from the centrifugation step was added to the retentate from the ultrafiltration, and this material was analysed for nitrogen and amino acids. The ultrafiltrates were also analysed for nitrogen. The amount of nitrogen that was deemed to have originated from the EHC and remained in the precipitate plus retentate fraction of digesta after processing, expressed as a percentage of the total amount of nitrogen added to the tubes as EHC, ranged from 1.0 to 5.0%. The overall mean amounts of amino acid in the precipitate plus retentate fractions originating from the EHC, expressed as a percentage of the amino acids added to the tubes as EHC, ranged from 2.4 to 5.8%. The results demonstrate that with Centriprep‐10 concentrators there is a less than complete separation of nitrogen and amino acids originating from EHC from endogenous material in digesta, but for most amino acids this is unlikely to be due to binding of the amino acids to digesta. The incomplete separation of EHC from the endogenous fraction of digesta by Centriprep‐10 concentrators may lead to a small overestimation (approximately 2%) of endogenous ileal nitrogen and amino acid flows. © 2001 Society of Chemical Industry     

The use of near‐infrared reflectance spectroscopy (NIRS) to predict the composition of whole maize plants

Near‐infrared reflectance spectroscopy (NIRS) was used to predict the chemical composition of whole maize plants (Zea mays L) in breeding programmes at INIA La Estanzuela, Uruguay. Four hundred samples (n = 400) were scanned from 400 to 2500 nm in an NIRS 6500 monochromator (NIRSystems, Silver Spring, MD, USA). Modified partial least squares (MPLS) regression was applied to scatter‐corrected spectra (SNV and detrend). Calibration models for NIRS measurements gave multivariate correlation coefficients of determination (R²) and standard errors of cross‐validation (SECV) of 0.72 (SECV 9.5), 0.96 (SECV 7.7), 0.98 (SECV 16.5), 0.96 (SECV 34.3), 0.98 (SECV 17.8) and 0.98 (SECV 6.1) for dry matter (DM), crude protein (CP), acid detergent fibre (ADF), neutral detergent fibre (NDF), in vitro organic matter digestibility (IVOMD) and ash in g kg⁻¹ on a dry weight basis respectively. This paper shows the potential of NIRS to predict the chemical composition of whole maize plants as a routine method in breeding programmes and for farmer advice. © 2000 Society of Chemical Industry     

Cooking does not impair the impact of pulsed electric field on the protein digestion of venison (Cervus elaphus) during in vitro gastrointestinal digestion

The present study was conducted to elucidate whether cooking impairs the positive effect of pulsed electric field (PEF) on the digestibility of venison during in vitro gastrointestinal protein digestion. Previous studies have used fresh uncooked meat to demonstrate the effect of PEF on protein digestibility during gastrointestinal digestion neglecting the effect that cooking could induce during meat preparation process. PEF-treated samples (T₁, 10 kV, 90 Hz, 20 µs) were cooked (core temperature of 75 °C) and subjected to in vitro simulated gastrointestinal protein digestion along with non-treated controls. A 3% increase of in vitro protein digestibility was found in cooked PEF-treated venison (P < 0.05). A positive (P < 0.05) impact of PEF processing was observed on overall protein digestion as measured by soluble protein (%) and SDS-PAGE. PEF did not change (P > 0.05) the release of minerals from cooked venison during digestion. Cooking had no negative influence on the mechanism through which PEF operates in improving the protein digestibility of venison.     

Effect of the duration of feeding of a protein‐free diet on endogenous ileal nitrogen and amino acid loss in the growing pig

The aim of the study was to determine whether endogenous nitrogen and amino acid excretions at the terminal ileum change over time in the growing pig fed a protein‐free diet for 8 days. Seven entire male pigs with an overall mean live weight of 81.6 kg (SEM 3.3 kg) and surgically implanted post‐valve T caecum cannulas were fed a semi‐synthetic casein‐based diet for 8 days. Food was withheld from the pigs for 24 h, after which they were fed a protein‐free diet for a further 8 days at a rate of 10% of metabolic body weight per day. Chromic oxide was included in the protein‐free diet as an indigestible marker. Ileal digesta were collected continuously from 13:00 to 18:00 h on each day of the experimental period. Endogenous ileal nitrogen flows were determined for each pig each day the protein‐free diet was given, and endogenous ileal amino acid flows for the first and eighth days. There were no significant (P > 0.05) effects of the duration of feeding of the protein‐free diet on endogenous ileal total nitrogen or amino acid flows, except for the amino acids glycine and cysteine, the flows of which significantly decreased over the 8 day period (P < 0.01 and P < 0.05 for glycine and cysteine respectively), from (mean ± SEM) 1639 ± 217 to 892 ± 212 µg g⁻¹ dry matter intake (DMI) for glycine and from 173 ± 13 to 127 ± 19 µg g⁻¹ DMI for cysteine. The relative contributions (moles of each amino acid as a proportion of total moles of amino acids) of threonine, glycine and cysteine decreased significantly (P < 0.05) and that of proline increased significantly (P < 0.05) during the 8 days that the protein‐free diet was fed to the pigs. © 2000 Society of Chemical Industry     

聚氧化乙烯对大豆分离蛋白静电纺丝影响的研究

初步研究了聚氧化乙烯(PEO)对大豆分离蛋白(SPI)静电纺丝的影响,分析了SPI/PEO共混配比和相应过程参数(电压、溶液流速和接收距离)对共混溶液性质和静电纺丝可纺性的影响,通过扫描电镜对所得纤维形态进行了表征。结果表明,随着溶液中PEO含量的增加,体系的粘度增大,电导率下降,得到的电纺纤维形态均一,直径分布较窄,明显改善了SPI的可纺性;电压、溶液流速和接收距离均对电纺纤维的形成及形貌有一定的影响,三者过高或过低都会导致纤维形貌的变化,形成串珠或颗粒。10wt%SPI/PEO共混溶液的最佳电纺共混比为70/30,电压为15kV,接收距离为10cm,溶液流速为1.5mL/h。      

Physiochemical,textural, sensory properties and probiotic survivability of Chinese Laosuan Nai (protein‐fortified set yoghurt) using polymerised whey protein as a co‐thickening agent

A new Chinese Laosuan Nai (protein‐fortified set yoghurt) was developed using polymerised whey protein (PWP, 0.4%, w/v) as a co‐thickening agent. The prototype was analysed for physiochemical, textural, sensory properties and probiotic survivability and compared with a commercial sample. Experimental yoghurts were significantly higher in pH, protein content, hardness and viscosity (P < 0.01). Microstructure indicated a uniform and denser protein network. Probiotics remained stable for Bifidobacterium during a 10‐week storage period. Results indicated that polymerised whey protein may be a novel protein‐based co‐thickening agent for making Chinese Laosuan Nai.