TITRIMETRIC DETERMINATION OF TOTAL ALDEHYDES IN CINNAMON BARK AND LEAF OILS USING CHLORAMINE-T REAGENT

A titrimetric method for determining cinnamaldehyde has been developed; it is based on the quantitative reaction of the aldehyde with semicarbazide hydrochloride to form the semicarbazone. The semicarbazone is removed and the excess unreacted semicarbazide determined iodometrically using chloramine-T reagent. Two moles of chloramine-T are required per mole of the semicarbazide. The method has been used in the routine quality evaluation of cinnamon oils and the samples required are about 0.02 g for bark oils and 0.05 g for leaf oils.     

ULTRAVIOLET SPECTROPHOTOMETRIC DETERMINATION OF PROTEIN IN SOME FOOD PRODUCTS

SUMMARY— The spectrophotometric method of estimating the protein content of whole milk at wavelength 280 nm (Nakai and Le, 1970) was modifed for corned beef, flour, bean and egg yolk. A clear solution was obtained by adding 50% sulfuric acid or 2N sodium hydroxide with and without 7–8M urea depending on solubility of the food products. The protein content was calculated from the absorbance at 280, 243 or 215 nm on o spectrophotometer. The correlation coefficient between the absorbance and the protein by Kjeldahl method was 0.99, 0.99, 0.99 and 0.99 with the coefficient of variability of Kjeldahl protein for absorbance of 1.8, 4.1, 3.8 and 4.1% for bean, corned beef, egg yolk and flour, respectively.     

DETERMINATION OF BENZOIC AND SORBIC ACID IN TURKISH FOOD USING HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

Benzoic and sorbic acid levels in different brands of jam, candied chestnut, carbonated drink, pickle, black table olive, green table olive, wholemeal/brown bread and white bread, which are available on the Turkish market, were determined by high-performance liquid chromatography with diode array detector (235–254 nm). Chromatographic separation was achieved with a C18 column and acetate buffer (pH 4.74)–methanol mixture (70:30) as a mobile phase. The levels of benzoic and sorbic acid in the analyzed samples were in the range of not detected to 662 mg/kg or L, and not detected to 432 mg/kg or L, respectively. Only one sample (jam) presented a preservative although not permitted by the legislation enforced in Turkey. The levels of preservative in the other samples were determined in legal limitations. According to the results, the utilization of benzoic and sorbic acid is lower than the certain legal limitations permitted by legislation to be used.

PRACTICAL APPLICATIONS

The amount of the sorbic and benzoic acid used as preservatives during food processing is important for consumer health. Determination of the amounts of the preservatives mentioned above will be possible in a short period of time (11 min) with the methods used in this study (high-performance liquid chromatography). According to the results obtained from study and data about food consumption, daily intake amount of these preservatives (benzoic and sorbic acid) will be able to be defined in Turkey, separately.     

抗冻蛋白及其在食品中的应用

阐述了抗冻蛋白的发现、分子结构、分类及其功能特性和抗冻机制，并讨论了抗冻蛋白在食品技术中的应用。     

DETERMINATION OF CARBOXYMETHYLCELLULOSE IN FOOD PRODUCTS

SUMMARY –A method was developed to determine sodium carboxymethylcellulose (CMC) in food products containing three or more hydrocolloids after prior removal of interfering substances. Papain was used to digest the proteins; calcium chloride was added to precipitate algin and pectic acid and sulfated hydrocolloids were then precipitated by cetylpyridinium chloride (CPC) in the presence of 0.5M NaCl. Celite 535 or Hyflo Super Cel was added, the mixture filtered over Reeve angel No. 202 paper and the residue washed with 0.01% CPC-0.01M NaCl. The filtrate and washings were collected and diluted with distilled water to attain a final concentration of 0.2M NaCl at which concentration the CMC was precipitated selectively by CPC. The mixture was filtered over a Celite 535 or Hyflo Super Cel column and the residue washed with 0.5M Na₂SO₄ and then with 0.01% CPC-0.01M NaCl until the washings were negative to the phenol-H₂SO₄ reagent. Finally, the residue on the column was washed with hot 30% H₂SO₄ and the hydrolyzed CMC in the eluate determined by the 2,7-naphthalenediol test. Based on the amount added to mixtures, recoveries of 75–86% were obtained from milk and other highly complex and proteinaceous products, with a standard deviation of ± 0.58 mg, when 10 mg of CMC were added. The determination is critically dependent upon the degree of substitution (DS) of the CMC. As a consequence, the method cannot be applied with absolute certainty to unknown samples.     

改性植物蛋白的研究及应用

简要介绍了植物蛋白的功能性质及改性方法,重点综述改性植物蛋白在食品加工中的应用,并展望改性植物蛋白在食品加工中的应用前景.     

CHANGES IN THE FRYING MEDIUM DURING DEEP-FRYING OF FOOD RICH IN PROTEINS AND CARBOHYDRATES

Changes in the frying medium (rapeseed oil) during controlled deep-frying of sliced potatoes and cod fillets and oil heated without them were compared. Fifteen frying cycles were conducted each day for five days. Results showed that oil after frying of cod fillets contained 10% less triacylglycerol (TAG) polymers and 40% less TAG dimers than other oils. Other parameters (iodine and anisidine values and absorption value at 233nm) showed that less thermooxidative products formed during frying of food rich in proteins. Oil after frying of cod fillets was darker and its acid value was significantly higher than that for other oils. Content of TAG polymers and dimers for oil after frying of sliced potatoes and oil heated without food was equal. The relative loss of C18:2 acid and decrease in iodine value showed that oil after heating without food underwent more intensive thermooxidative transformation than other oils.     

食品中金属元素的检测方法

针对食品中危害人体健康的主要有害金属元素，总结了包括物理法、化学法、生物法在内的一系列实用、方便、可行的检测方法，探讨了每一种具体检测方法的原理及其优缺点，指出不同检测方法的使用范围、检测底限以及其在使用过程中存在的问题。     

微波消解ICP-AES法测定食品中重金属的研究

用硝酸-过氧化氢作消解液,用微波消解法处理样品,采用ICP-AES法测定食品中锌、铁、锰、铜、镉、铬、砷等7种重金属元素的含量.测定结果的相对标准偏差RSD<6%,加标回收率在92.6%～106%之间,检出限在0.764 μg/L～1.537 μg/L之间.该方法快速、稳定、准确,测定结果令人满意,适合食品中重金属元素的测定.     

APPLICATION OF MULTIVARIATE STATISTICAL METHODS TO THE ANALYSIS OF THE COST, NUTRITIONAL AND SENSORIAL QUALITY FOR SOME PROTEINS USED IN FOOD FORMULATIONS

Incomplete proteins, of lower nutritional value, are usually more available and less expensive than complete high quality proteins. In the development or reformulation offood products, sensory,“nutritional‐quantitative” and economic aspects may be superimposed on the “nutritional‐qualitative” aspects, to the detriment of consumers. In the present study, three protein ingredients were mixed at different proportions and their nutritional and sensory properties were evaluated by a multivariate approach, using principal component analysis (PCA) in order to identify the type of association between these properties and cost. A strong positive correlation was observed between nutritional quality and cost of the mixtures, with a correlation coefficient of the order of 0.82, while the vector concerning the sensory quality was practically orthogonal to the nutritional vector, suggesting a low correlation between these two features. Thus, we recommend that the protein quality be evaluated, classified and, if possible, expressed on the label especially in foods destined to institutional programs of children's foods, hospital diets and foods used as meal substitutes.     

食品中单增李斯特菌的存在现状及检测方法研究进展

单核细胞增生性李斯特菌（简称单增李斯特菌）是常见的食源性致病菌,该菌可广泛存在于多种食品中,如肉制品、奶制品、水产品、蔬菜等,该菌在欧美国家曾导致多次的食物中毒的爆发,因此对食品中单增李斯特菌的快速检测非常必要,就单增李斯特菌在食品中的污染情况和检测方法作一综述。     

DETERMINATION OF STABLE ISOTOPE RATIOS IN FOOD ANALYSIS

Within the last few years, stable isotope analysis has gained increasing importance in authenticity control of food and food ingredients. The development of the methodology from its start in the geological sciences is reviewed, the requirements and the specific features of the technique in the area of food quality assessment are outlined, and the progress in instrumentation during the last few decades is described. Scope and limits of the analysis of stable isotope ratios to assess the quality and to determine the origin are demonstrated for foods, such as fruit juice, wine, spirits, or beer. The classical approaches investigating hydrogen, carbon and oxygen isotopes as well as strategies including elements, such as nitrogen and sulfur, are reviewed. The present state of the art and future possibilities of the methodology are discussed.