甲苯胺兰——过氧化氢体系催化光度法测定痕量铜（Ⅱ）

基于铜（Ⅱ）在稀硫酸介质中强烈催化过氧化氢氧化甲苯胺兰褪色反应及其动力学条件，建立了测定痕量铜（Ⅱ）的新方法。方法的线性范围为０～０．５μｇ／２５ｍｌ，检出限为１．８×１０－９ｇ／ｍｌ，可用于花生、黄豆和茶叶中铜（Ⅱ）的测定     

催化光度法测定皮革中的痕量甲醛

研究了催化光度法测定痕量甲醛的方法—罗丹明B法。在磷酸溶液中,痕量甲醛对溴酸钾氧化罗丹明B的退色反应有催化作用,研究了其反应条件,选择最佳试验条件,并进行干扰分析,考察了该法的精密度和准确度,建立测定痕量甲醛的催化光度分析新方法,方法的线性范围为0·15~6·00mg·L-1,检出限为9·7×10-4mg·L-1。方法简便、快速,选择性好。     

新试剂BTHQSA光度法测定食品中微量铅

新试剂（７－苯并噻唑－２－偶氮）－８－羟基喹啉－５－磺酸在弱酸性ＨＡＣ－ＮａＡＣ介质中与铅显色较灵敏，在入ｍａｘ６００ｎｍ测定，表观摩尔吸光系数为７．８×１０＾４Ｌ·ｍｏｌ＾－１·ｃｍ＾－１，利用该试剂测定食品样中的微量铅，结果可靠。     

高灵敏分光光度法测定食品中痕量钴——采用5-Br-PADAP-OP体系

研究了在非离子表面活性剂ＯＰ存在下，用５－Ｂｒ－ＰＡＤＡＰ作显色剂，吸光光度法测定微量钴的分析方法及最佳条件。该法对钴在０～２０μｇ／２５ｍｌ范围内符合比耳定律，表观摩尔吸光系数为１．０３×１０５Ｌ／ｍｏｌ·ｃｍ。方法操作简便、快速，灵敏度高，选择性好，应用于食品中痕量钴的测定，结果满意。     

葡萄糖的化学发光检测法及对发酵过程糖耗曲线的测定

本文首次将葡萄糖和Ｃｕ~（２＋）的氧化反应与Ｃｕ~（２＋）催化下鲁米诺和Ｈ_２Ｏ_２的化学发光反应偶联，建立了葡萄糖的化学发光（ＣｈｅｍｉｌｕｍｉｎｅｓｃｅｎｃｅＣＬ）检测法，并成功地测定了酒精酵母发酵过程中的糖耗曲线。该方法操作简便，线性范围宽（１０~（－６）～１０~（－３）ｍｏｌ／Ｌ）。Ｆ－检验结果表明，ＣＬ法的测量精度明显高于传统的２，５－二硝基水扬酸比色法（ＤＮＳ法）。ＣＬ法的变异系数和最低检测限分别为２．６％和２．３×１０~（－６）ｍｏｌ／１（０．２ｍｌ，８３ｎｇ），均大大小于ＤＮＳ法的变异系数（５．０％）和最低检测限（１．１１×１０~（－５）ｍｏｌ／Ｌ，３ｍｌ，６μｇ）。     

催化分光光度法测定酒中痕量铅的研究

基于α，α’—联吡啶作活化剂，在硫酸介质中，铅（Ⅱ）催化过氧化氢氧化酸性铬兰Ｋ裉色的指示反应，建立了一种灵敏度较高的测定痕量铅（Ⅱ）的新方法，其灵敏度为１．８３×１０￣（－１１）ｇ／ｍｌ，线性范围为０～０．２５μｇ／２５ｍｌ。用于白酒中痕量铅的测定，结果满意。     

阻抑动力学分光光度法测定食品中痕量碘

研究了在稀H2SO4介质中,痕量碘离子对NO2-催化溴酸钾氧化甲基橙的阻抑作用,建立了测定痕量碘离子的阻抑动力学光度分析的新方法。测定碘离子的线性范围为0~0·6μg/mL,检出限为7·8×10-9g/mL。     

催化分光光度法测定痕量钴的研究

研究了在碱性介质中，钴（Ⅱ）催化过氧化氢氧化间硝基苯基荧光酮的褪色反应及动力学条件，建立了催化动力学光度法测定痕量钴（Ⅱ）的新方法．检测限为６．５４×１０－１２ｇ／ｍｌ，线性范围为０～３．５ｎｇ／１０ｍｌ，变异系数为２．６７％．用于测定医用维生素Ｂ１２针剂中的痕量钴．     

转谷氨酰胺和酪蛋白钠重构小牛肉的研究

不同肉重百分比的转谷谷氨酰胺酶（０，０．１％，０．０５％，０．１０％）和酪蛋白钠（０．５％，１．０％，１．５％，２．０％）联合分组添加于切割（２ｃｍ×２ｃｍ×２ｃｍ）的小牛肉块间，在５℃下反应不同时间（１ｈｒ，２ｈｒｓ，５ｈｒｓ）；对重构的样品分别测定其结合力，以判断转谷氨酰胺酶在蛋白质分子间形成共价交联的能力。结果表明：０．０５％转谷氨酰胺酶与１．０％酪蛋白钠联合反应时间１ｈｒ，获得了较理想的重     

《中国乳品工业》第29卷(2001)总目次

●专题报道《中国乳品工业》杂志编委会会议纪要…………………………（１·４）回顾与展望……………………………………………………（１·５）乳品工业应积极面对WTO……………………………………（１·３０）２０００年强化奶粉产品质量抽查情况…………………………（１·３３）夯实基础练好内功…………………………………………（２·４）●研究报告乳蛋白水解物中的苦肽研究…………………………………（１·８）芦荟酸奶的研制…………………………………………………（１·１２）一种新型复合微生态制剂的研制………………………     

Genetic and environmental variability in starch,fatty acids and mineral nutrients composition in cowpea (Vigna unguiculata (L) Walp)

Fifteen cowpea cultivars grown in three locations (Kano (12°00′N 8°31′E), Mokwa (9°17′N 5°04′E) and Ago-Iwoye (6°58′N 4°00′)) between 1993 and 1994 were analysed for genotype, environmental and genotype×environment variability for starch (g kg⁻¹), fatty acids (% of total oil) and mineral nutrients (g kg⁻¹) composition. There were significant environmental as well as genetic effects on these nutritional qualities. The environmental effect accounted largely for the variability observed in starch (60%), palmitic acid (80%), arachidic acid (100%), potassium (100%), phosphorus (81%) and manganese (86%), while the genotypic effect accounted largely for the variability observed in linoleic acid (50%), linolenic acid (50%) and copper (68%) contents. Correlation coefficient (pooled data) from the three locations indicated that starch was positively correlated to palmitic acid (r = 0·21, 0·01< P < 0·05), potassium (r = 0·80, P < 0·001) and phosphorus (r = 0·65, P < 0·001), but negatively correlated to oleic (r = −0·23, 0·01< P < 0·05), linoleic (r = −0·67, P < 0·001) and linolenic acid (r = −0·74, P < 0·001) contents. Starch showed a strong positive correlation with magnesium content (r = 0·75) and a strong negative correlation with copper (r = −0·73) and iron (r = −0·62) at the genetic level. This research established the degree of variability for these characters in cowpea. © 1998 Society of Chemical Industry.     

RAPID ANALYSIS OF WHOLE MALT USING NEAR INFRARED REFLECTANCE SPECTROSCOPY

Near infrared (NIR) reflectance spectroscopy has been evaluated for the analysis of whole malt. Good agreement has been obtained between NIR and reference methods for moisture and total nitrogen. A correlation coefficient (r) of 0·974 and a standard error of prediction (SEP) of 0·13% was obtained for the moisture measurement. Similarly the correlation between methods for total nitrogen analysis was 0·964 with a SEP of 0·049%. In addition, NIR spectroscopy can be used to predict wort composition from scans on whole malt, without the need for mashing. Hot Water Extract (r 0·951, SEP 2·1 1°/kg), total carbohydrates (r 0·946, SEP 0·07%), fermentable sugars (r 0·903, SEP 0·11%), total soluble nitrogen (r 0·900, SEP 0·027%), free amino nitrogen (r 0·857, SEP 1·0 mg/100 ml) and fermentability (r 0·884, SEP 0·90%) can be measured using this technique. Since no sample preparation is required, NIR spectroscopy provides a rapid method for simultaneous measurement of all these parameters in under two minutes.     

Simultaneous multi-channel hydride generation atomic fluorescence spectrometry determination of arsenic,bismuth, tellurium and selenium in tea leaves

A novel, rapid and sensitive method for the simultaneous multi-channel hydride generation atomic fluorescence spectrometry (HG-AFS) determination of total arsenic (As), total bismuth (Bi), total tellurium (Te) and total selenium (Se) in tea leaves was proposed. The operating parameters of self-made multi-channel HG-AFS were optimised, including negative high voltage of photo multiplier tube (PMT), the flow rates of carrier and shield gas, observation height and lamp currents. The conditions of hydride generation for As, Bi, Te and Se were studied in details. Under optimal conditions, the method detection limits (MDL) for As, Bi, Te and Se in tea leaves were 0.0152 μg g⁻¹, 0.0080 μg g⁻¹, 0.0022 μg g⁻¹ and 0.0068 μg g⁻¹, respectively. The proposed method was successfully applied to the simultaneous determination of As, Bi, Te and Se in various tea leaves and the spike recoveries were in the range of 90–103%. The accuracy of method was validated by analysing a tea certified reference material. The obtained values were consistent with the certified ones.     

Cell-Constituents,Tannin Levels by Chemical and Biological Assays and Nutritional Value of Some Legume Foliage and Straws

Twenty six straw and 15 foliage samples of Lathyrus sativus , Vicia narbonensis , V sativa and V ervilia were analysed for ash, crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), extractable phenols (Pe), extractable tannins (Te), extractable condensed tannins (CTe), protein precipitation capacity (PPC) and in vitro characteristics predicted from Hohenheim gas test. The content of crude protein in the foliage was significantly higher than that of the straws (152·6 vs 64·5 g kg⁻¹), while ash (82·8 vs 116·8 g kg⁻¹), NDF (332·7 vs 523·5 g kg⁻¹) and ADF (205·2 vs 369·9 g kg⁻¹) were significantly lower. For straws of L sativus , V narbonensis and V sativa , there was no significant difference in the protein and ADF contents, whereas ash and NDF contents were significantly lower and higher respectively in L sativus as compared to V narbonensis or V sativa . Predicted from gas volumes, the organic matter digestibility (OMD: 70 vs 56%) and metabolisable energy (ME: 9·7 vs 7·3 MJ kg⁻¹) were significantly higher for the foliage compared to straws. The OMD of L sativus straws was significantly lower compared to the straws of V narbonensis and V sativa . The OMD and ME of the straws of second year was significantly lower than those of the first year. The CP, OMD and ME of V sativa foliage were higher than that of V narbonensis . There was no difference in the cell constituents, OMD and ME of foliage samples of V sativa harvested in May 1992 and June 1992. The contents of Pe, Te and CTe of straws were 1·08%, 0·43% and 0·33%, respectively, and those of foliage were 2·27%, 1·30% and 1·63%, respectively. PPC was not detected for any of the foliage and straw samples. The results suggested that the tannin levels of legume straws investigated are negligible and those of the legume foliage are very low. This does not appear to adversely affect their nutritive value since the maximum decrease in OMD by the tannins was about 3% units.     

Activity of trisodium phosphate compared with sodium hydroxide wash solutions against Listeria monocytogenes attached to chicken skin during refrigerated storage

The potential of using trisodium phosphate (TSP) and sodium hydroxide (NaOH) to reduce Listeria monocytogenes populations in chicken skin was studied. Raw chicken legs inoculated with L. monocytogenes were dipped in water (control), in 8% (pH=12·59), 10% (pH=12·68) and 12% (pH=12·75) (w/v) TSP solutions, or in NaOH solutions of equal pH values to those of TSP: 0·175%, 0·200% and 0·220% (w/v). Surface pH values and L. monocytogenes counts of chicken skin were determined immediately after treatment (day 0) and after 1, 3 and 5 days of storage at 2°C. Compared with water dipping, TSP and NaOH treatments significantly (P<0·05) reduce Listeria populations at days 0, 1, 3 and 5 of refrigerated storage. Bacterial reductions varied between 1·12 and 3·34 log₁₀ cycles for TSP-treated samples and between 1·80 and 3·28 log₁₀ cycles for NaOH treated samples. The observed reductions in all treated samples were significantly (P<0·05) greater following storage. The concentration of the TSP solution was a significant factor in reducing the populations of L. monocytogenes. However, bacterial reductions were similar in samples treated with different concentrations of NaOH. The TSP or NaOH treatments resulted in relatively high residual surface pH values (8–9) initially and throughout storage. The pH values were significantly higher in the samples treated with TSP than in those treated with NaOH.     

Chemical evaluation of the effect of roasting on the nutritive value of maize (Zea mays, Linn.)

This study reports on the effects of roasting on the chemical composition of maize (Zea mays). Proximate analysis showed no significant difference (p > 0·05) between raw and roasted maize in ether extract, crude protein, crude fibre, ash and carbohydrate content; except moisture content (p < 0·05), which showed a 42·3% decrease. Elemental composition analysis showed decreases of potassium (13·8%) and calcium (41·1%). Significant differences (p < 0·05) were observed for vitamins B₁, B₂ and C contents with 26·8%, 32·4% and 35·1% destruction, respectively. Amino acid analysis showed losses for lysine (26·7%), iso-leucine (20·8%) and leucine (23·4%).There was significant (p < 0·05) variation in phytic acid, oxalic acid, tannin and hydrocyanic acid with reductions of 15·4%, 6·02%, 51·3% and 34·6% respectively.The effect of these changes on the nutritive value of roasted maize is discussed.     

Could the Dumas Method Replace the Kjeldahl Digestion for Nitrogen and Crude Protein Determinations in Foods?

Increased demand for determinations of nitrogen (N), and hence crude protein (CP), has led to wider use of the Dumas method in place of the traditional Kjeldahl methods. Although Kjeldahl N (KN) and Dumas N (DN) represent different N fractions, published studies on infant formula, animal feed and meat products have indicated that DN could replace KN with little practical impact on the reliability of the N values obtained. This study was conducted to establish whether DN determination could replace that of KN in a broader range of foods for CP calculation. Statistical analysis was performed on in-house assayed KN and DN values together with published KN and DN values for selected food products. In the range 0·05–6·8% N, KN may be estimated from DN with the equation: KN=1·00^(P<0·01)×DN-0·09^(P=0·50) (n=101, R²=0·98, P-regression<0·01). Because N levels in individual groups of food did not span the entire range of N contents, KN: DN ratios were calculated for each food group. KN: DN ratios differed significantly (R²=0·25, P<0·01) from group to group. Ratios of 1·01 for dairy, 1·00 for oilseeds, 0·99 for feed, 0·98 for infant formulas, 0·95 for cereals, 0·94 for meats, 0·89 for vegetables, 0·80 for fish and 0·73 for fruits were valid for the estimation of KN and CP using DN data. CP was independently calculated as CP1=H×KN or CP2=H×KN: DN×DN, where H is the nitrogen to protein conversion factor for the food group. Mean differences between CP1 and CP2 values were 0% for dairy, oilseeds, feed, infant formulas and baby foods, cereals, meat and meat products, vegetables and vegetable products and fruit, and 1% for fish. These results suggest that DN may replace KN for the determination of N and CP in selected food groups when appropriate coefficients are used. © 1997 SCI.     

Proximate analysis of the flesh and anatomical weight composition of skipjack tuna (Katsuwonus pelamis)

Skipjack tuna (K. pelamis) was assessed for its proximate and anatomical compositions with a view to establishing its nutritive and technological usefulness. Analysis of the muscle revealed that it contained between 69·0% and 72·6% moisture, 1·59% and 2·57% lipid, 22·4% and 25·5% protein, 1·53% and 2·42% ash and 0·87% and 3·21% salt.The mean percentage yields of trunk, head and viscera were 69·7%, 23·0% and 7·03%, respectively. On average, a total waste yield (head plus viscera) of about 30% was obtained. The technological implications of this analysis on the development of tuna fisheries in Nigeria are discussed.     

The choline content of feed ingredients and mixed feeds determined by an enzymatic assay

A recently developed procedure for the determination of choline in ingredients and feeds was utilised to establish the levels and the variability of choline in a series of ingredients and to compare the analysed and calculated choline values of mixed feeds. The concentrations of choline in samples of maize (7), canola meal (3), wheat middlings (1) and dehydrated bakery product (1) were, respectively, 1·55±0·18, 7·59±0·08, 2·35 and 2·39 g kg⁻¹, all higher than ingredient composition table values. Choline contents lower than table values were found in samples of poultry by-products (7) and meat and bone meal (6): 2·18±0·87 and 1·08±0·29 g kg⁻¹, respectively. The average choline concentration found in samples of dehulled soybean meal (7) was 2·73±0·18 g kg⁻¹, similar to table values. The choline in samples of poultry fat (2) averaged 0·48±0·02 g kg⁻¹. Significant correlations between the concentrations of choline and of some components of the proximate analysis were found. The analysed choline concentrations in mixed feeds were only 1·4% lower than the calculated levels based on the ingredient analyses. The procedure was adequate for choline determination in ingredients or mixed feeds. The high variability in the choline content of some ingredients may require analysis for proper feed formulation. © 1998 Society of Chemical Industry.     

Compositional analysis and viscosity measurements of commercial oat brans

Chemical analysis of commercial oat brans (n=10) collected from five different countries showed wide variations in the contents of starch (40–61%), crude protein (9·6–21%), crude fat (8·2–12%), ash (2·0–4·1%), dietary fibre (10·7–19·4%) and mixed-linkage β-glucan (4·7–8·3%). A significant correlation (r=0·83; P<0·005) between the contents of total and extractable mixed-linkage β-glucan was found. Reproducible increases in viscosity were noted for all samples when the finely ground samples were dispersed in phosphate buffer and viscosity development was followed for 100 min. Addition of mixed-linkage β-glucanase greatly reduced the viscosity. Addition of amyloglucosidase, with no detectable mixed-linkage β-glucanase activity, increased viscosity, which could be related to an increased solubilisation of mixed-linkage β-glucan. Highly significant correlations (r>0·90) were found between the contents of both total and extractable mixed-linkage β-glucan and viscosity after dispersion. © 1998 SCI.