Cellulose, Hemicellulose and Lignin Content of Raw and Cooked Spanish Vegetables

The content in NDF, ADF, cellulose, hemicellulose, and lignin of 22 raw and 19 cooked vegetables (14 boiled, and 5 fried) widely consumed among the Spanish population was determined according to the method of Van Soest. Cooking generally increases the NDF, ADF and cellulose content on a dry weight basis. Normal size servings of the vegetables were prepared and their NDF, cellulose, hemicellulose and lignin contents calculated. We observed that, with vegetables of common use, a total amount of 15–20 g/day of these fiber components can be obtained; according to current knowledge this implies beneficial physiological effects for a broad human pathology.     

Determination of Neutral Detergent Fiber in Breakfast Cereals: Pentose, Hemicellulose, Cellulose and Lignin Content

Cereals are often promoted as important sources of dietary fiber. Ninety one breakfast cereals available in Canada and four unprocessed wheat brans were therefore analyzed for neutral detergent fiber (NDF) after rapid digestion with α-amylase from porcine pancreas. Many breakfast cereals contained less than 5% NDF. Wheat cereals contained 5–30% NDF, oat cereals contained 5% NDF, and corn and rice contained little NDF. Cereal NDF was predominantly hemicellulose (pentosans); pentose sugars liberated under hydrolysis represented up to 15% of processed bran cereals and 20–25% of unprocessed bran.     

Nonstarch Polysaccharide Fractions of Raw, Processed and Cooked Carrots

The total and soluble nonstarch polysaccharide (NSP) components of raw, processed (canned and frozen) and home-cooked (boiled) Royal Chantenay carrots have been analyzed. NSP fractions were characterized by separation and summation of the monosaccharides resulting from acid hydrolysis of the parent polysaccharides. Total NSP was primarily composed of glucose, ?37%, and uronic acid, ?35%, containing polysaccharides. Soluble NSP was composed of >50% uronic acids. Processing and simulated home-cooking of raw carrots resulted in an increase in the amount of NSP/unit dry weight. Relative to raw carrots, cooking of canned product resulted in the largest (～twofold) increase in total and soluble NSP/unit dry weight. Relative differences in NSP were not as great when compared on a wet weight basis.     

纤维素、半纤维素与木质素间相互作用研究进展

纤维素、半纤维素和木质素是木质纤维生物质细胞壁中的3种主要组分,其通过复杂的相互作用形成超分子网络结构,使木质纤维生物质具有优异的机械性能及抵抗物理、化学和微生物降解的能力,同时也导致生物质预处理和组分分离困难。本文总结了近年来关于纤维素、半纤维素与木质素间相互作用的研究进展,重点介绍了木质素与半纤维素之间的共价键、范德华力和静电作用等,以期在原子-分子水平上充分认识和了解细胞壁结构,为通过基因工程合成易降解的木质纤维原料,或寻找清洁高效的生物质精炼技术提供一定的理论指导。     

木质素与半纤维素对稻草秸秆酶解的影响

分别采用稀酸和酸碱顺序两种方法处理稻草秸秆,20 FPU/g(底物干重)的纤维素酶、底物质量浓度为80 g/L,45℃酶解72 h。结果表明,木质素与半纤维素对纤维素转化为葡萄糖都有较大影响,稀酸处理的秸秆酶解纤维素转化率(43.4%,葡萄糖质量浓度24.1 g/L)是未处理秸秆(16.8%,葡萄糖质量浓度6.2 g/L)的2.6倍,而酸碱顺序处理的秸秆(60.6%,葡萄糖质量浓度47.7 g/L)则是未处理秸秆的3.6倍。采用上述两种方法处理秸秆后,秸秆木质素和半纤维素被移去,秸秆结构发生改变,从而秸秆纤维更易受纤维素酶的攻击,并且秸秆木质素和半纤维素质量分数越低,纤维素的酶解得率就越高。     

High Performance Liquid Chromatographic Determination of Carbohydrates in Raw and Cooked Vegetables

The soluble sugar contents of 17 raw and cooked vegetables were determined by TLC and HPLC. In general, the soluble carbohydrate content of vegetables is low. For raw materials the highest content was found in carrot, red cabbage, egg plant, green bean and leek. Upon cooking the glucose, fructose and total sugar contents decrease and this diminution is more drastic in the case of frying. The amount of sucrose, except in the case of carrot, egg plant and green bean, increases with cooking. The maltose content of the broad bean increases in the culinary process.     

Fiber Contents of Selected Raw and Processed Vegetables, Fruits and Fruit Juices as Served

Pectin and neutral detergent fiber (NDF) contents were investigated for commercially processed foods as served: 10 vegetables, 10 fruits, and 8 fruit juices. Fiber content of fruits ranged from 0.7%?4.5% NDF and 0.28%?0.48% pectin; juices ranged from 0.1%?0.22% NDF and 0.2%?0.39% pectin. Fiber in frozen, canned and cooked vegetables ranged from 1%?4.4% NDF and 0.5%?1% pectin. In general, there is no evidence that any of the food preparation methods was superior. There appears to be no great loss of fiber when food is prepared by typical home methods or commercial processing.     

Selenium Content of Raw and Cooked Marine Species Consumed in Portugal

The present study evaluates the effects of different cooking methods (grilling, frying and boiling) on selenium contents of six marine species commonly consumed in Portugal. Forty-two composite samples of sardine, horse mackerel, gilthead seabream, silver scabbardfish, hake and octopus were digested in a microwave system and analysed by electrothermal atomic absorption spectrometry. The described method is adequate for the analysis of selenium in marine species and meets the requirements of validation and quality control. Mean selenium contents in raw species ranged from 0.35 mg kg⁻¹ to 1.24 mg kg⁻¹. Cooked samples presented mean selenium contents from 0.38 mg kg⁻¹ to 1.85 mg kg⁻¹ in grilled fish, from 1.22 mg kg⁻¹ to 1.28 mg kg⁻¹ in fried fish and from 0.84 mg kg⁻¹ to 0.87 mg kg⁻¹ in boiled fish. No statistically significant differences were determined for selenium levels in raw and cooked samples and in different marine species. Estimated selenium intake agrees well with recommendations and is far below the Upper Tolerable Nutrient Level. This is the first study concerning the evaluation of the effects of cooking methods on selenium contents of marine species consumed in Portugal.     

Composition of Raw and Cooked Potato Peel and Flesh: Amino Acid Content

The nitrogen and total amino acid contents of Katahdin and Pontiac varieties of potatoes are reported for the peel and flesh, before and after cooking. With the exception of glutamic acid and 7-amino-butyric acid, all of the contents were higher in the peel. Losses of nitrogen and amino acids were minor in boiling whole potatoes but greater in oven baking in the peel or in boiling the peeled potato. Microwave cooking losses were less than in oven baking.     

木质素含量对纤维素纳米纤维热稳定性的影响

分别采用热水、绿液及漂白预处理以改变蔗渣和云杉纤维素纳米纤维的木质素含量,探究残余木质素含量对纤维素纳米纤维热稳定性能的影响。结果表明,经过热水预处理制备的蔗渣和云杉纤维素纳米纤维的木质素含量分别比经过绿液预处理制备的蔗渣和云杉纤维素纳米纤维高16.1%和8.9%,比经过漂白预处理制备的蔗渣和云杉纤维素纳米纤维的高22.7%和24.3%,半纤维素含量相对较低。经过热水预处理制备的蔗渣和云杉纤维素纳米纤维的热稳定性分别比经过漂白预处理制备的蔗渣和云杉纤维素纳米纤维的热稳定性提高了约4.3%和5.4%。     

Cholesterol Content of Raw and Cooked Beef Longissimus Muscles with Different Degrees of Marbling

The relationships of marbling level (eight levels from “Moderately Abundant” to “Practically Devoid”) and cooking to cholesterol content of beef longissimus muscle steaks were studied. Only raw steaks with “Practically Devoid” marbling contained significantly less cholesterol (wet basis) than did raw steaks with any of the other seven marbling scores. However, steaks cooked to an internal temperature of 60° or 75°C showed no significant differences in cholesterol content among any of the eight marbling groups. The cholesterol content of cooked steaks was 22–48% higher than that of raw steaks when cooked to 60°C and 38–65% higher when cooked to 75°C; cooking reduced the weight of each steak, thereby increasing the cholesterol content of the steak expressed as a percentage of the cooked weight.     

巨菌草的木素及半纤维素分析

通过碱性硝基苯氧化法测定巨菌草原料中木素结构单元的比例,采用透射电子显微镜(TEM)研究了巨菌草纤维的超微结构和木素分布情况;采用红外光谱研究了巨菌草原料中木素的结构,并与常规的硫酸盐浆和烧碱-蒽醌浆中残余木素结构进行了对比;使用离子色谱法分析了巨菌草原料半纤维素的组成。结果显示,巨菌草原料中愈创木酚基木素结构单元含量较高,达75.63%,对羟苯基木素结构单元和紫丁香基木素结构单元含量较少,分别为10.52%和13.85%。通过TEM观察巨菌草纤维超微切片,巨菌草纤维次生壁外层(S1)较薄;纤维细胞次生壁中层(S2)较厚,占据了细胞壁厚度的大部分,约为S1层的4倍左右,占细胞壁的80%以上;而次生壁内层(S3)最薄。离子色谱分析结果表明,木糖是巨菌草原料半纤维素中最主要的单糖,其含量为56.84%,其次为葡萄糖,其含量为42.48%,阿拉伯糖极少,仅为0.66%;未检测到甘露糖和半乳糖,说明巨菌草原料半纤维素中含痕量或不含甘露糖和半乳糖。     

Variation in the Vitamin and Mineral Content of Raw and Cooked Commercial Phaseolus Vulgaris Classes

Raw and cooked samples of nine different commercial classes of the Phaseolus vulgaris L. species were analyzed for their contents of five water-soluble vitamins and nine minerals. On a 100g dry weight basis, the mean vitamin and mineral values of the raw bean samples amounted to the following: thiamin 0.99 mg, riboflavin 0.20 mg, niacin 1.99 mg, vitamin B₆ 0.49 mg, folic acid 0.30 mg, phosphorus 0.46g, sodium 10.3 mg, potassium 1.54g, calcium 0.15g, magnesium 0.20g, zinc 3.2 mg, manganese 1.4 mg, copper 0.91 mg, and iron 5.84 mg. With a few exceptions variabilities of these nutrients between bean classes exceeded those within classes. Nutrient variabilities in cooked samples, again with a few exceptions, were higher than in the corresponding uncooked material. Retention values of water-soluble vitamins during cooking between bean classes averaged between 70 and 75%. Retention of minerals during cooking ranged from a low of 38.5% for sodium to total retention for calcium, with the majority of the minerals falling into the 80–90% level.     

高木质素麻种原麻处理工艺的探讨

对于低木质素含量麻种的原麻,可以采用传统的脱胶工艺处理;而对于高木质素含量麻种的原麻,则宜采用无酸预处理重二煮工艺处理,可获得良好的效果。     

Moisture, Fat and Cholesterol Content of Some Raw; Barbecued and Cooked Organ Meats of Beef and Mutton

The effect of barbecueing and conventional cooking methods on moisture, fat and cholesterol content in brain, heart, kidney, liver, and tongue of local Iraqi; beef and mutton were studied. Moisture, fat and cholesterol content differed significantly (P ≤ 0.05) between raw and barbecued samples and between raw and cooked samples of both beef and mutton organ meats, except for those mentioned. The lower moisture in barbecued and cooked samples probably caused a relative increase in fat and cholesterol content. Minor differences were observed in raw, barbecued and cooked organ meats between beef and mutton in terms of moisture, fat and cholesterol content at similar animal ages.     

Hindrance of Hemicellulose and Cellulose Hydrolysis by Pectic Substances

Treating the tissue of the grapefruit segment membrane with pectinase and cellulase decreased the content of xylose and glucose significantly more than the sum of the separate effects. The synergistic effect obtained by the combination of pectinase and cellulase showed that the pectic substance sterically masked the hemicellulose and cellulose. Breaking down the barrier of the pectic substance with pectinase allowed a significant increase in the hydrolysis of the hemicellulose and cellulose. Preparation of alchol-insoluble solids from fresh tissue modified the structure of the pectin in the cell wall and prevented its steric hindrance to breakdown of hemicellulose and cellulase. Extraction of pectic substances from the tissue by NaOH greatly increased cellulose hydrolysis by cellulase.     

Nitrate and Nitrite Methods of Analysis and Levels in Raw Carrots, Processed Carrots and in Selected Vegetables and Grain Products

Methods for quantitative estimation of nitrate and nitrite were compared. Levels of these ions were measured in vegetables and grain products and effects of processing on nitrate and nitrite levels in carrots were measured. These data allow more accurate estimation of ingestion levels and suggest means to reduce exposure to these ions. High performance liquid chromatography (HPLC) had better precision and recoveries than either a classical Cd-Griess method nitrate or a Griess method for nitrite. Nitrate concentration by HPLC varied greatly within and between vegetables, ranging from 1 μmol/100g in mushrooms to 5000 μmol/100g in celery and averaging 9.7 ± 4.4 μmol/100g in grains. Nitrate levels in vegetables sold as “organic” were not different (p<0.05) from conventional vegetables. No nitrite was detected in either vegetables or grains. Nitrate was unevenly distributed in carrots with the core having the most. Storage of carrots at -18°C for 10 wk did not alter nitrate levels and no nitrite developed. Fifty-seven percent of nitrate was leached into cooking liquid when frozen carrots were boiled. Thirty-two percent of nitrate was lost during canning and 47% of the remainder was in the liquid. No nitrite developed during 10 wk of canned storage.     

山核桃加工、贮藏前后总多酚含量及其抗氧化活性的变化

采用Folin-Ciocalteu法测定未加工、加工和贮藏的山核桃仁中总多酚的含量,同时研究山核桃仁总多酚的总抗氧化能力、还原力和对羟自由基的清除率。结果表明：未加工、加工和贮藏的山核桃仁提取液中总多酚质量浓度分别为1065.4、319.78mg/L 和204.4mg/L。以2140mg/L 的VE作为标准对照,总抗氧化能力和还原力：未加工山核桃＞VE＞加工山核桃＞贮藏山核桃;羟自由基清除率：VE＞未加工山核桃＞加工山核桃＞贮藏山核桃。总抗氧化能力、还原力和羟自由基的清除率与总多酚含量密切相关,总多酚是山核桃仁中重要的抗氧化物质。     

Nutrient Contents of Raw and Cooked Cowpea Leaves

SEEDS OF COWPEA (Vigna unguicullata) cultivar MM₄ obtained from Kenya were grown for their leaves as a vegetable. The mean crude protein contents of the leaves from the 1981 and 1982 seasons were 32.8 and 34.3% of total solids, respectively, and leaves were a particularly good source of minerals, including iron, calcium, phosphorus and zinc. Levels of vitamin C, total carotene, and free and total folacin were 410 mg, 57 mg, 334 meg and 2012 meg, respectively, per 100g of solids. Freshly harvested leaves cooked by a traditional Kenyan technique retained 88% of their crude protein and substantial quantities of minerals. Losses in vitamin C and free and total folacin were 87%, 49% and 66% while their recoveries in the cooking water were 5.6%, 20% and 12%, respectively. Carotene in the cooked leaf solids increased slightly. Comparisons with other leafy vegetables indicate good potential for processing.