Effect of preliminary and culinary processing on amino acid content and protein quality in frozen French beans

The aim of the study was to evaluate the content of amino acids and protein quality of French bean pods. The investigated material consisted of the raw vegetable, fresh pods cooked to consumption consistency, and two kinds of frozen products stored for 12 months at ?20 °C and then prepared for consumption: frozen beans obtained using the traditional method (blanching before freezing) and frozen products of the ready‐to‐eat type (cooking before freezing). A comparison of the amino acid content in the product prepared for consumption showed that the lowest quantities were found in French beans obtained using the traditional method; products obtained using the modified technology and beans cooked directly after harvest had similar levels of most amino acids. The content of amino acids in 16 g N was less varied than in 100 g of the product. The protein in all the three products prepared for consumption as well as that in fresh bean pods hardly differs, as confirmed by the values in the essential amino acid index (EAA). The first limiting amino acid was methionine with cystine and the second was lysine.     

Evaluation of the amino acid content and sensory value of flageolet bean seeds (Phaseolus vulgaris L.) as affected by preprocessing methods before freezing

The aim of the work was to evaluate the content of amino acids in flageolet bean seeds, prepared for consumption from frozen products obtained using different methods. One of the frozen products was obtained using the traditional method (blanching–freezing–frozen storage) and then cooked. The other was obtained using the modified technology (cooking–freezing–frozen storage), followed by defrosting and heating in a microwave oven. The culinary and technological processing applied brought about a pronounced decrease in tyrosine content (35–47% in 16 g N). The content of the remaining amino acids decreased or increased in relation to the raw material within the extremes of ?15% to +17%. Sulphur amino acid was the limiting amino acid. Product obtained using traditional method had the higher quality protein (EAA index 144–166) of seeds prepared for consumption. In sensory test products, blanched before freezing were evaluated a bit higher than those cooked before freezing (ready‐to‐eat).     

Discolouration of raw and cooked coloured fleshed potatoes differing in anthocyanins and polyphenols content

Despite variations in the content of polyphenols, the tested potato varieties with red and purple flesh contained similar amounts of anthocyanins. Potatoes of the red-fleshed HBr variety were distinguished by a significant content of pelargonidin-3-feruloylrutinoside-5-glucoside, and those of the purple-fleshed Vitelotte variety were characterised by a significant cyanidin-3-rutinoside content. Immediately after cutting, raw potatoes with red flesh showed a small share of yellow (b* parameter) and double the share of red (a*) as compared to purple-fleshed tubers. A reduction in the share of red dye was observed in purple- and red-fleshed potatoes except Vitelotte and Rosalinde tubers, at both 1 and 4 h after being cut. The flesh colour of cooked potatoes was characterised by low susceptibility to darkening, and purple-fleshed tubers were more saturated by chroma than tubers of red-fleshed varieties.     

Effect of amino acids on Maillard reaction product formation and total antioxidant capacity in white pan bread

Maillard reaction products (MRPs) can be an important dietary antioxidant source. Bread is the most popular bakery product; however, limited information is available on the antioxidant activities of MRPs generated during bread-baking. This paper reports the effect of different amino acids on bread properties, melanoidin formation and antioxidant activities. Totally six amino acids at four different levels were evaluated. Increasing the amount of amino acid led to darker bread crust, higher melanoidin content and stronger antioxidant activity. Among the six amino acids, bread with glycine had the highest melanoidin content and ABTS radical scavenging activity up to 1079.77 ± 8.43 μmol TE mg⁻¹. Bread with lysine had the highest DPPH radical scavenging activity up to 281.97 ± 10.52 μmol TE mg⁻¹. Bread with alanine had the highest crust metal chelating activity compared with others. Adding certain dietary amino acids is a potential approach to enhance the antioxidant capacity of bread products.     

Content of amino acids and the quality of protein in as‐eaten green asparagus (Asparagus officinalis L.) products

The content of amino acids in fresh green spears and in three as‐eaten products was considered, i.e., in fresh asparagus after cooking and in two products obtained from frozen asparagus stored for 12 months at ?20 °C. One of the frozen products was obtained using the traditional method (blanching–freezing–frozen storage) and then cooked. The other was obtained using the modified technology (cooking–freezing–frozen storage); after the storage period the product was defrosted and heated to consumption temperature in a microwave oven. The limiting amino acid of the first order was methionine with cystine, and of the second order leucine. Essential amino acids constituted 40–43% of the total amino acid content. The dominant amino acids were aspartic acid and glutamic acid. The culinary and technological procedures applied brought about a drastic decrease (50–56% in 16 g N) in tyrosine content.     

Effect of technological processing and preservation method on amino acid content and protein quality in kale (Brassica oleracea L. var. acephala) leaves

BACKGROUND: The aim of the investigation was to evaluate the level of amino acids and quality of protein in raw and processed kale leaves. RESULTS: In all samples the dominant amino acids in g kg^?1 raw matter were glutamic acid, aspartic acid and proline. In raw kale leaves the limiting amino acids were lysine, isoleucine and cystine with methionine, and in the remaining products also valine and leucine. Blanched kale leaves contained 88% of the amino acid content in raw leaves, 76% in cooked leaves, and 69–77% and 71–72% of initial levels in frozen and canned products, respectively. In raw, blanched and cooked leaves essential amino acids comprised 44%, 44% and 47%, respectively, of total amino acids; in frozen and canned leaves the proportions were 46% and 44%, respectively. The essential amino acid index was 97 for canned products, 100–109 for frozen leaves, and 117 for raw kale leaves. CONCLUSION: Raw and processed (blanched or cooked) kale leaves are a good source of amino acids. Copyright © 2011 Society of Chemical Industry     

Effect of amino acid,pH and mineral salts on glass transition and flow behaviour of soy protein concentrate

The objective of this study was to assess the effect of proline, mineral salts (NaCl and Na₂SO₄) and pH combined with moisture content on the glass transition temperature (T_g) and flow‐starting temperature (T_f) of soy protein concentrate (SPC). Initial screening of the variables based on fractional factorial design showed insignificant effect of NaCl on T_g and T_f. The design was extended to a face‐centred central composite design (CCD) excluding NaCl and data evaluated by use of response surface methodology. The established model for T_g (R² = 0.824) shows significant negative first‐order effects of moisture, proline and Na₂SO₄, and a positive interaction effect of moisture and Na₂SO₄. The T_f model (R² = 0.937) shows significant negative first‐order effects of moisture and proline, a positive first‐order and negative square effect of pH, and a negative interaction effect of moisture and proline. The main effect on T_g and T_f was 2.2 and 1.3 times higher, respectively, for moisture compared to proline. The study confirms that proline (or other free amino acids) can replace moisture as protein plasticiser in the extrusion process. Minor effects can also be obtained by reduction in pH.     

高效液相色谱法测定熟肉制品中苯甲酸、山梨酸、胭脂红和诱惑红含量

目的建立高效液相色谱法测定熟肉制品中食品防腐剂(苯甲酸和山梨酸)和色素(胭脂红和诱惑红)的分析方法。方法样品经组织捣碎、超声提取、过滤、定容,利用高效液相色谱法检测,甲醇水混合溶液作为流动相,二极管阵列检测器(photo-diode array,PDA)检测,苯甲酸和山梨酸的检测波长为230nm,胭脂红和诱惑红的检测波长为508nm。结果苯甲酸和山梨酸在0.05~0.30mg/mL,胭脂红和诱惑红在2.5~12.5μg/mL范围内,均具有良好的线性关系良好,相关系数r均0.9999。苯甲酸和山梨酸的最低检出限(limit of detection,LOD)范围为1.2~1.8 mg/kg,最低定量限(limit of quantification,LOQ)范围为3.6~5.4mg/kg;胭脂红和诱惑红的LOD范围为0.05~0.1mg/kg,LOQ范围为0.15~0.3 mg/kg。平均加标回收率为94.8%~96.9%,相对标准偏差(relative standard deviation,RSD)为2.4%~4.1%。100份熟肉制品样品中,5份有山梨酸检出,检出率为5.0%,检测结果范围为0.030~0.65g/kg;1份有胭脂红检出,检出率为1.0%,检测结果为0.0023g/kg;3份有诱惑红检出,检出率为3.0%,检测结果范围为0.0036~0.0083g/kg;苯甲酸在所有熟肉制品样品中均未检出。结论该方法灵敏度高,回收率高,检测限低,符合分析要求,适合检测熟肉制品中的苯甲酸、山梨酸、胭脂红和诱惑红。     

氨基酸折算法计算婴幼儿配方粉中乳清蛋白含量方法的评估

目的评价以氨基酸折算法计算婴幼儿配方粉中乳清蛋白含量的方法。方法本实验使用自配的流动相,采用酸水解氨基酸自动分析仪测定婴幼儿配方粉中氨基酸含量,再根据乳清蛋白中天冬氨酸/天冬酰胺、丙氨酸、苯丙氨酸和脯氨酸4种特征氨基酸含量的经验公式折算出婴幼儿配方粉中乳清蛋白占总蛋白的百分比。结果对我国市售多种品牌的婴幼儿配方粉中的水解氨基酸进行了检测,再计算出乳清蛋白含量,发现仅1阶段乳基婴儿配方粉基本符合大于60%的国标规定。结论该氨基酸折算法对婴幼儿配方粉中乳清蛋白含量的定量研究具有参考价值,但对掺有大豆蛋白的产品无法进行准确测定。     

Change in proximate, amino acid and fatty acid contents in muscle tissue of rainbow trout (Oncorhynchus mykiss) after cooking

Changes in proximate, amino acid and fatty acid composition of farmed, commercially important rainbow trout (Oncorhynchus mykiss) after conventional and microwave cooking were analysed. Rainbow trouts cooked in microwave ovens had statistically significant higher total protein, total fat, and ash than electrical oven‐cooked samples. The amounts of essential and nonessential amino acids were not different between cooking methods, but the difference between raw and cooked samples was significant. Lysine, leusine, methionine, threonine, valine, arginine and histidine were found most in microwave‐cooked rainbow trouts whereas isoleucine, tyrosine and phenylalanine were found most in electrical oven‐cooked samples. As total saturated fatty acid and total monounsaturated fatty acids amount were not statistically different between the cooking methods, the difference between raw and cooked fillets was found statistically significant (P < 0.05). There was no statistically significant difference between raw and cooked fillets in total n‐3 and n‐6 contents.     

龙眼干白葡萄酒发酵过程中生物胺和氨基酸含量的变化

本研究利用高效液相色谱技术分析了龙眼干白葡萄酒酒精发酵和苹乳发酵过程中8种生物胺和22种氨基酸含量的变化。结果表明,在酒精发酵过程中8种生物胺含量均很低,而在苹乳发酵过程中迅速增加。发酵结束时干白葡萄酒中亚精胺和乙醇胺含量最高,其次为组胺和羟色胺。这4种生物胺的前体氨基酸在苹乳发酵阶段含量没有明显变化,而其它大部分氨基酸在酒精发酵过程中含量下降,在苹乳发酵过程中含量呈现不同程度升高。因此,我们认为：葡萄酒发酵过程中氨基酸含量变化与其对应生物胺的变化之间没有相关性,葡萄酒中生物胺的组成比例可能主要取决于乳酸菌中氨基酸脱羧酶的种类和活性。     

The effect of moderate pulsed electric fields on autolysis of Saccharomyces cerevisiae and the amino acid content in autolysates

The effect of moderate pulsed electric fields (MPEF) strength on autolysis of Saccharomyces cerevisiae was evaluated in this study. After exposure to MPEF with intensity of 7 kV cm⁻¹ for 4 ms, the integrity of the cell wall was obviously destroyed and the inactivation of S. cerevisiae reached 99.43%. During the subsequent 42-h autolysis process, the release of free α-amino nitrogen of MPEF-treated cells, as well as extracellular protease activity, was significantly (P < 0.05) higher than that of untreated cells. Moreover, exposure to 7 kV cm⁻¹ led to an increase of the total amino acid of 149.36%. In particular, the content of aspartic acid and glutamic acid which are important umami flavour precursors increased by 232.55% and 209.40%, respectively. These results indicate that MPEF will be an effective method to accelerate autolysis of S. cerevisiae for obtaining high-quality yeast extract as flavour enhancers and nutrition supplements.     

Protein quality and amino acid profiles of fish products available in Poland

Chemical analyses were carried out on 18 of the most popular varieties of fish products in the Polish market (canned, smoked, salted and marinated fish of different species), produced by the largest manufacturers and distributors in the country. The contents of the nutritive substances in the fish products (proteins, amino acids, and fats) were determined. To assess the nutritional quality of proteins in these products, the protein digestibility was determined, which ranged from 77.0% to 98.7%, and the amino acid composition of each of these groups of products was compared with that of a standard protein recommended by the World Health Organization (WHO). In addition, protein digestibility-corrected amino acid scores (PDCAAS) were calculated. Relative to the WHO protein standard, most of the fish products tested scored very high, with values ranging between 0.9 and 1.0. This study confirmed that in terms of both quantity and quality, fish products in the Polish market could serve as a significant source of essential amino acids and that the sulphur-containing essential amino acids and lysine present in fish products could supplement the corresponding deficiency in plant proteins. However, it was also indicated that drastic thermal processes, such as sterilisation, could influence the protein digestibility.     

Determination of aromatic amino acid content in cooked meat by derivative spectrophotometry: Implications for nutritional quality of meat

The technique of second derivative spectrophotometry was used to determine the level and the heat stability of the three aromatic amino acids (tryptophan, tyrosine and phenylalanine) in bovine meat (M. Longissimus thoraci). This paper presents a method which measures the second derivative absorbance values at a wavelength specifically assigned to each aromatic amino acid with corrections for the interference from other amino acids at the same wavelength. Three cooking temperatures were tested in this study (60, 100 and 140 °C). Due to important cooking losses, results differ slightly according to the method of calculation (level expressed by gram of wet meat or by gram of proteins). Whatever the calculation method, heating at 60 °C had little effect on aromatic acid levels while higher temperatures had a dramatic effect on aromatic amino acids stability. The stability of the three aromatic amino acids during cooking decreased in the order tryptophan > phenylalanine > tyrosine.     

Dietary fiber,amino acid,fatty acid and tocopherol contents of the edible seaweeds Ulva lactuca and Durvillaea antarctica

The nutritional composition of the edible seaweeds Durvillaea antarctica (frond and stem) and dried Ulva lactuca was determined, including the soluble (SDF), insoluble (IDF) and total (TDF) dietary fiber content, amino acid and fatty acid profiles along with tocopherols and tocotrienols (pro-vitamin E). Results show that U. lactuca contained 60.5 ± 1.5%, and D. antarctica frond and stem 71.4 ± 1.5% and 56.4 ± 0.4% of TDF, respectively. Levels for the different amino acids ranged from 0.7 ± 0.1 to 1508.4 ± 9.5 (mg/100 g protein) in U. lactuca, from 0.2 ± 0.0 to 2019.9 ± 5.2 (mg/100 g protein) in D. antarctica (stem), and from 0.3 ± 0.0 to 1052.6 ± 2.9 (mg/100 g protein) in D. antarctica (leaves). In the three seaweeds, the most abundant fatty acid was C18:1ω9cis which in U. lactuca accounted for 27.42 ± 2.60%; in D. antarctica it was 25.36 ± 3.10% and 25.83 ± 2.52% in leaves and stem, respectively. In D. antarctica, γ-tocotrienol (651.7 ± 5.1 mg/kg), δ-tocopherol (245.9 ± 3.7 mg/kg) and α-tocopherol (179.4 ± 12.1 mg/kg) were determined in fronds, α-tocopherol (258.0 ± 7.2 mg/kg) was determined in stem. U. lactuca, showed a high γ-tocopherol level (963.5 ± 3.8 mg/kg).     

Determination of proximate composition,fatty acid content and amino acid profile of five lesser‐common sea organisms from the Mediterranean Sea

Proximate composition, fatty acid and amino acid analysis of an echinoderm (Paracentrotus lividus), a crustacean (Penaeus kerathurus), a tunicate (Microcosmus sulcatus), and two gastropod molluscs (Littorina littorea and Patella coerulea) were determined. All organisms except M. sulcatus, were found to be good protein sources. P. lividus contained on average 15.1 g/100 g, P. kerathurus 15.6 g/100 g, L. littorea 8.3 g/100 g and P. coerulea 9.2 g/100 g protein. The crustacean contained high percentages of n‐3 fatty acids (28.3 g/100 g fatty acids), the tunicate high percentages of saturated fatty acids (62.2 g/100 g fatty acids) while the gastropod molluscs and the echinoderm had a balanced content of all fatty acid families. The most abundant amino acid in P. kerathurus, M. sulcatus, L. littorea and P. coerulea was glutamic acid (11.13 ± 0.9, 1.05 ± 0.3, 5.39 ± 0.3, 5.55 ± 0.8 g/100 g freeze‐dried sample respectively), while glycine was the most abundant amino acid in P. lividus (10.34 ± 1.0 g/100g freeze‐dried sample).     

冻结方式对凡纳滨对虾贮藏中组织冰晶及品质的影响

新鲜凡纳滨对虾采用液氮、平板及冰柜冻结结合-20 ℃贮藏,研究不同贮藏时间内其组织冰晶形态与品质变化,以评价出最优的冻结方式。结果显示,随着贮藏时间的延长,平板及冰箱冻结的盐溶性蛋白含量、持水性、感官评分显著降低(p<0.05);而液氮冻结形成的冰晶直径比平板速冻小1/3,比冰箱小1/2;冻结后贮藏180 d其挥发性盐基氮(TVB-N值)≤25 mg/100 g,硫代巴比妥酸值(TBA)仅为0.72 mg/100 g,有效抑制了虾肉肌原纤维蛋白变性及脂肪氧化,能较好维持肌肉组织形态和品质,从而使虾肉的货架期延长至180 d以上。     

Addition of amino acids to grape juice of the Merlot variety: Effect on amino acid uptake and aroma generation during alcoholic fermentation

The effects of adding selected amino acids (phenylalanine, alanine, aspartic acid and threonine) to grape juice on the generation of aroma compounds and on amino acid uptake were studied. The fermentation kinetics varied according to the quantities of amino acids added. The fermentations finished more quickly in supplemented juices and their alcoholic content was significantly higher than in the control (p < 0.05). Amino acids were consumed mainly in the first quarter of fermentation. Higher alcohol formation took place at the same time as ethanol formation: with more amino acids present in the medium, more phenyl ethanol (p = 0.01) and benzyl alcohol were formed while isoamyl alcohol production decreased. The contents of isoamyl and phenylethyl acetates, ethyl hexanoate and ethyl octanoate, as well as most fatty acids increased during the fermentation, reaching a maximum for 10% of ethanol; with higher alcoholic contents, their concentrations decreased.     

Fermentation and cooking of sicklepod (Cassia obtusifolia) leaves: changes in chemical and amino acid composition, antinutrients and protein fractions and digestibility

Sicklepod leaves after fermentation and drying are commonly known as Kawal in Sudan. Investigation of the samples showed that the dry matter, oil, fibre and carbohydrates fluctuated during processing. The protein content of Algenina increased to 30.01% while that of Zalngy decreased to 24.32%. Cooking increased the ash content to 19.55% and 20.04% for Algenina and Zalngy samples respectively. For both samples the total energy was decreased to 221.59 and 227.39 kcal per 100 g for the samples respectively. The first limiting amino acid is lysine with a score of 73.9. Although cooking of the sample increased lysine score to 76.00 but still is a limiting amino acid. Sulphur amino acids are the second limiting of Zalngy. The protein fractions fluctuated during processing. Cooking of the samples decreased polyphenols to 890.01 and 620.58 mg per 100 g and phytate to 77.90 and 146.28 mg per 100 g for the samples respectively. However, tannin content increased to 1183.65 and 977.65 mg per 100 g for the samples respectively. For Algenina sample the protein digestibility increased to 50% after cooking but for Zalngy it decreased to 30%.     

Functional,amino acid composition and protein profiling of protein isolates from different pigmented,nonpigmented and improved rice varieties and their effects on starch thermal and dynamic rheological behaviour

The amino acids composition, protein profiling and functional properties of protein isolates from different pigmented rice (PR), nonpigmented rice (NPR) and improved rice (IR) varieties were determined and their effects of incorporation on starch thermal, and dynamic rheological were evaluated to know the possible interactions in food matrix. Protein isolates (PI) from PR and IR showed better foaming capacity and, foam stability than those from NPR. PI from both the PR and IR showed higher proportion of histidine, threonine, valine, methionine, phenylalanine and isoleucine. PI from IR showed higher accumulations of glutelins (31 and 33kDa, 21 and 22 kDa) and prolamins (15kDa, 16kDa, 17 kDa and 20kDa) than those from rice types. Starches from IR showed higher storage modulus (Gʹ) and loss modulus (Gʺ) than that from PR, and NPR, and decreased on addition of PI. PI from PB1121 IR was more suitable for protein enrichment due to more lightness value, and superior functionality (emulsification and foaming properties). Starch-protein interaction affects the functionality, and behaviour of matrix and, developing hypoallergenic infant formulations or other food products.