"Degree of Elasticity" Determination in Solid Foods

Specimens of a variety of foods (banana, cheese, frankfurter, jelly candy, marshmallow, and potato) were subjected to four compression-decompression cycles at two prefailure deformation levels (12.5–15 and 20–25%). Total and percent recoverable work in each cycle were determined using a universal testing machine interfaced with a computer. The magnitude of recoverable work, its strain dependency and response to successive cycles were characteristic of each material. Percent recoverable work was unrelated, however, to strength (stress at failure), deformability, and stiffness. The general level of recoverable work was about 60–80% of total work in the materials commonly considered “elastic” and 20–50% in those known as “plastic.”     

Extrusion and characterization of thermoplastic starch sheets from "macho" banana

Starch isolated from macho banana was oxidized by using 2.5% and 3.5% (w/w) of sodium hypochlorite. Native and oxidized starches with glycerol were processed using a conical twin screw extruder to obtain thermoplastic laminates or sheets, which were partially characterized. Oxidized banana starches presented higher moisture and total starch but lower ash, protein, lipids, and apparent amylose content than the native starch. Micrographs of sheets from oxidized starches showed wrinkles and cavities presumably caused by the plasticizer, but with less free glycerol and unplasticized starch granules than those from native starch. Sheets from oxidized starch showed a notorious increase in all thermal parameters (To, Tp, and ΔH), mechanical properties (tensile strength, elongation at break, and elasticity), and solubility. Banana starch X-ray diffraction patterns corresponded to a mixture of the A- and B-type polymorphs, with apparently slightly higher crystallinity in oxidized specimens than in native starch. A similar trend was observed in the corresponding sheets. PRACTICAL APPLICATION: Due to the pollution problem caused by the conventional plastics, there has been a renewed interest in biodegradable sheets, because they may have the potential to replace conventional packaging materials. Banana starch might be an interesting raw material to be used as edible sheet, coating or in food packaging, and preservation, because it is biodegradable, cheap, innocuous, and abundant.     

军人人体尺寸数据库抽测样本量的确定

计算建立中国军人服装用人体尺寸数据库所需抽测的样本量，并根据实际建库男，女军人样本量，计算了百分位数的估计量所能达到的绝对精度。     

Identification and characterization of potential autochthonous starter cultures from a Croatian "brand" product "Slavonski kulen"

The microbial population of a traditional Croatian fermented sausage "Slavonski kulen" was isolated, identified and subjected to technological and functional characterization in order to select potential autochthonous functional starter cultures. Dominant microflora were lactic acid bacteria (LAB), followed by staphylococci. Identification of isolated lactobacilli showed domination of Leuconostoc mesenteroides and Lactobacillus acidophilus while Staphylococcus xylosus and Staphylococcus warneri outnumbered the staphylococcal microbiota. Most of the isolated LAB and Staphylococcus species displayed good growth in the presence of 5% of NaCl and at 12, 18 and 22°C. All LAB and most of the staphylococci possess proteolytic activity and only Staphylococcus xylosus had lipolytic activity. All lactobacilli and staphylococci isolates produced significant concentrations of lactic acid (as determined by HPLC) and showed antimicrobial activity against pathogenic test microorganisms. Dominant LAB and Staphylococcus species displayed growth in the presence of 1% bile. Most of the staphylococci and all of lactobacilli showed sensitivity to all antibiotics tested.     

微探针法测定"北京烤鸭" 皮下导热系数的研究

采用非稳态微探针法测定"北京烤鸭"皮下导热系数.结果显示,鸭坯皮下含水率为6.55%～14.2%时,导热系数值在0.1178～0.1973W/(m·K)之间变化,且呈线性相关趋势.     

微探针法测定“北京烤鸭”皮下导热系数的研究

采用非稳态微探针法测定“北京烤鸭”皮下导热系数。结果显示,鸭坯皮下含水率为6.55%～14.2时,导热系数值在0.1178W/(m·K)～0.1973W/(m·K)之间变化,且呈线性相关趋势。     

食品添加剂部分氢化木松香季戊四醇酯的测定与表征

建立了食品添加剂部分氢化木松香季戊四醇酯定性表征和定量分析方法。采用红外光谱法、环球法对部分氢化木松香季戊四醇酯进行定性分析,采用化学滴定法对其酸值进行定量分析,结果表明食品添加剂部分氢化木松香季戊四醇酯红外光谱与FCC标准谱图一致,软化点及酸值也符合FCC要求。     

SPME/GC-MS分析荔枝汁中的挥发性化合物

运用顶空固相微萃取和气相色谱一质谱联用法对荔枝汁(妃子笑)中的主要挥发性成分进行定性和定量分析,并对其分析条件进行优化.结果表明,分析的最优条件为:萃取样品温度50℃,时间40min,250℃下脱附5min;该方法相对标准偏差(RSD)在4.27%～9.33%之间,精密度和重现性较好;利用该方法在荔枝(妃子笑)中共检测出41种挥发性成分,主要为醇类、烯类、醛类、酯类和脂肪酸类化合物.     

"杂项"光度法测定无水硝中硫酸根含量

为便于无水硝的生产控制及产品质量分析，参照国家标准方法，寻找一种决速、简便的硫酸根(SO4^2-)含量测定方法-以氯化钡为沉淀剂，以阿拉伯胶做保护剂的分光光度法。     

液液萃取和顶空固相微萃取结合气相色谱-质谱联用技术分析牛栏山二锅头酒中的挥发性物质

采用浸入式固相微萃取(DI-SPEM)、液液萃取(liquid-liquid extraction,LLE)结合气相色谱-质谱联用(GC-MS)技术对牛栏山二锅头的风味物质进行了定性研究,并采用保留指数法对定性结果进行了验证.共获得了101种香味化合物的确切定性结果,其中包括35种酯类、13种酸类、15种醇类、5种醛类、1种酮类、15种芳香族及酚类、5种呋喃类、2种吡嗪类、3种缩醛类、1种硫化物、6种其他类化合物.此次实验为进一步深入研究牛栏山二锅头风味物质奠定了基础,也拓展了SPME技术在白酒风味分析中的应用.     

Determination of the mercury complexation characteristics of dissolved organic matter in natural waters with "reducible Hg" titrations

A new method for the determination of the concentration and conditional stability constant of dissolved organic matter that binds mercury (Hg) has been developed using an in vitro assay of reducible Hg. The technique is a wet chemical analogue to electrochemical approaches now in use for ligand studies of many other trace transition metals in natural waters. Ligand characteristics are obtained from additions of ionic Hg to buffered lake, river water, and seawater and determination of the wet chemically reducible fraction following equilibration of the spike. This approach is robust, as demonstrated by (i) analysis using three reducing agents of varying strengths, (ii) replicate analyses, (iii) comparison to well-characterized complexing species (chloride and EDTA) using a competitive ion-exchange resin, and (iv) kinetic studies. Results indicate that Hg-complexing equivalents are present in the dissolved phase (<0.2 microm) ranging from <1 to >60 nN concentrations and with log conditional stability constants (log K') in the range of 21-24. Only one ligand class was found in the natural waters analyzed. There was indirect evidence for a class of organic ligands that formed reducible complexes with Hg in freshwater. Such ligand characteristics indicate that the vast majority of ionic inorganic Hg dissolved in freshwater and coastal saltwaters is associated with organic complexes. Concentrations, affinities, and kinetics implicate multidentate chelation sites as the principal complexing moieties for Hg and discourage the use of humic carboxylic acids as a proxy for the ligands/functional groups.     

Single-particle characterization of four "Asian Dust" samples collected in Korea, using low-Z particle electron probe X-ray microanalysis

A single-particle analytical technique, named low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA), employing an ultrathin window X-ray detector and enabling the quantitative determination of even low-Z elements such as C, N, and O, is applied to characterize "Asian Dust" samples, collected in ChunCheon, Korea, during four Asian Dust storm events on March 7, 2000, April 7, 2000, March 22, 2001, and May 17, 2001. In this study, it is demonstrated that single-particle analysis using the low-Z particle EPMA provides detailed information on various types of chemical species in the samples. The most abundantly encountered particles, both in coarse and fine fractions, are aluminosilicates. The relative abundances of those particles on the basis of their size are different between the four Asian Dust samples. The sample collected on March 7, 2000 did not experience any chemical modification during its transport because the sample does not contain particles of chemical species that result from atmospheric reactions. The sample collected on April 7, 2000 contains both genuine and reacted sea-salt particles. The genuine sea-salts are in the form of a mixture of NaCl and MgCl2 entrained during their passage over the Yellow Sea. The reacted sea-salts particles are encountered very much in fine fraction. The sample collected on March 22, 2001 shows somewhat significant chemical modification both for CaCO3 and sea-salts particles. For this sample, a significant number of reacted CaCO3 and sea-salt particles, such as those containing nitrate and/or sulfate, are encountered, implying that CaCO3 and sea-salts particles have reacted with sulfur or nitrogen oxide species during their long-range transport. The sample collected on May 17, 2001 experienced the most extensive chemical modification during its transport. In addition to the observation of the extensively reacted CaCO3 and sea-salt particles, reacted K2CO3 particles are also extensively encountered in this sample, which implies that K2CO3 species should be regarded as an additional important chemical species in the study of the chemical modification of Asian Dust particles during long-range transport.     

Determination and evaluation of the parameters affecting the choice of veal meat of the "Ternera de Aliste" quality appellation

The aim of the present work was to determine and assess the parameters affecting the choice of veal under the "Ternera de Aliste" quality appellation. The parameters affecting the choice proved to be colour, taste, odour, hardness and juiciness. Using these parameters, sensory evaluation, both analytical (with trained judges, QDA) and affective (with consumers, the home-use test) was carried out on four veal types, and the relative preferences for the samples assessed. Colour, hardness and losses due to cooking were also analysed instrumentally. The results revealed that the methodology is important for discriminating small differences between samples. The same trend was observed for the results of the panel of judges, consumers, and instrumental analyses regarding both hardness and juiciness. Regarding the determinant parameters in the choice of veal, in raw meat consumers prefer light colours but when expressing their general relative preferences for samples, juiciness, taste and hardness of the cooked meat had the greatest weight.     

Determination and risk characterization of polycyclic aromatic hydrocarbons of tea by using the Margin of Exposure (MOE) approach

Food Science and Biotechnology - Tea is one of the most frequently consumed drinks due to its favourite taste and the health benefit. Tea is produced by several processes and drying is very...