2种方法检测食品模拟物中矿物油含量的比较研究

目的 考察离线固相萃取-气相色谱-氢火焰离子化检测器法(off-line solid phase extraction-gas chromatography-flame ionization detector,off-line SPE-GC-FID)与高效液相色谱-气相色谱-氢火焰离子化检测器在线联用法(on-line...     

超高效液相色谱法测定传统发酵酸粥的游离氨基酸含量

为了准确测定传统发酵食品酸粥中的氨基酸含量,采用6-氨基喹啉基-N-羟基琥珀酰亚胺基甲酸酯衍化氨基酸,衍生物使用超高效液相色谱进行定量分析.超高效液相色谱的分析参数为:使用Waters BEH C18柱,甲酸铵和乙腈为流动相,采用梯度洗脱的方法,使用二极管阵列(PDA)检测器,在260 nm条件下,9 min之内可检测...     

棒状薄层色谱/氢火焰离子化检测器(TLC/FID)在脂质分析中的应用

介绍了棒状薄层色谱/氢火焰离子化检测器(TLC/FID)技术的发展和工作原理,并对它的应用作了介绍.TLC/FID作为一种定性定量分析手段可以有效地应用于对脂肪酸、脂肪酸聚合物、油脂酯交换产物和甘三酯等简单脂质的分离分析,还可以应用于油脂中氧化、聚合甘三酯含量的分析,磷脂的组分组成等复杂脂质的研究中.TLC/FID在石油化工、有机高分子等其他领域中也有广泛的应用.这些应用表明TLC/FID作为一种分离分析方法具有分离效果好、分析精度高、操作简便、采用微量试样进行分析、省时、对试样处理简单等优点.     

RP-HPLC-PAD法测定迷迭香中乌索酸和齐墩果酸的含量(英文)

采用反相高效液相色谱二极管阵列检测器法分离、测定迷迭香中乌索酸和齐墩果酸的含量。色谱条件:Kromasil C18色谱柱(4.6mm×250mm,45μm),检测波长210nm、流动相为甲醇:水:磷酸(88:12:0.1)、流速0.8mL/min、柱温30℃条件下实验。乌索酸进样量在0.10～4.00μg范围内,平均回收率为100.6%,乌索酸峰面积的相对标准偏差为1.6%。齐果酸进样量在0.05～2.00μg范围内,平均回收率为98.7%,相对标准偏差为1.2%。该法灵敏度高、重现性好、准确。可用于测定迷迭香中这两种三萜类酸的含量。     

高效液相-蒸发光散射检测器(HPLC-ELSD)测定食品中三氯蔗糖的方法研究

建立用高效液相-蒸发光散射检测器（HPLC—ELSD）快速准确测定酱油、配制酒等食品中三氯蔗糖的方法。样品经前处理后,用HPLC—ELSD进行检测。仪器条件为流动相乙腈／水为20／80,流速为1．0mL／min,雾化气流量为2．9L／min,漂移管温度为106℃。结果表明,该方法在0-100wedmL范围内曲线方程的相关系数R2为0．9996,方法检出限为0．5mg／kg,样品回收率大于90％,RSD小于5％。该方法操作简便、稳定可靠,适用于配制酒等食品中三氯蔗糖的检测。     

不同方法制备的扇贝水解液风味物质及氨基酸含量的比较研究

为得到营养丰富,海鲜味浓郁的扇贝水解液,采用顶空固相微萃取(HS-SPME)与气相色谱-质谱联用(GC-MS)技术分析两种水解液的风味物质,采用高效液相色谱(HPLC)法测定两种水解液游离氨基酸含量,结果表明:方法1(利用风味蛋白酶水解碎贝柱)的水解液风味物质有51种,醇、醛、酮、酯、烃类和其他物质含量分别为29.985%、24.819%、2.509%、1.861%、26.300%和13.975%,数量分别为8、17、3、5、9和9种;游离氨基酸总量(TAA)为53.408mg/g,必需氨基酸含量(ETAA)为22.304mg/g。方法2(利用枯草杆菌中性蛋白酶和风味蛋白酶分段水解碎贝柱)的水解液风味物质有34种,醇、醛、酮、酯、烃类和其他物质含量分别为15.303%、54.647%、0.802%、3.340%、8.559%和17.417%,数量分别为3、11、1、4、4和11种;TAA46.401mg/g,ETAA19.596mg/g。     

油茶籽油中苯并(a)芘的快速检测方法研究

目的:建立一种反相高效液相色谱法快速测定油茶籽油中苯并（a）芘含量的新方法。方法:样品经溶剂提取后直接进行检测,采用岛津InertsilODS-SPC18色谱柱,以90%乙腈-10%水为流动相,流速为1.0mL/min,荧光检测器。结果:苯并（a）芘的浓度在0.5～50μg/mL范围内时,峰面积与含量具有良好的线性关系（r=0.9994）;方法的精密度良好,平均相对标准偏差为1.01%,平均加标回收率为93.8%。结论:前处理简单、结果准确可靠、方法易于推广。      

油茶籽油中苯并(a)芘的快速检测方法研究

目的:建立一种反相高效液相色谱法快速测定油茶籽油中苯并(a)芘含量的新方法。方法:样品经溶剂提取后直接进行检测,采用岛津InertsilODS-SPC18色谱柱,以90%乙腈-10%水为流动相,流速为1.0mL/min,荧光检测器。结果:苯并(a)芘的浓度在0.5～50μg/mL范围内时,峰面积与含量具有良好的线性关系(r=0.9994);方法的精密度良好,平均相对标准偏差为1.01%,平均加标回收率为93.8%。结论:前处理简单、结果准确可靠、方法易于推广。     

The effects of probiotic cultures on the organic acid content,texture profile and sensory attributes of Tulum cheese

The aim of this study was to evaluate the effects of Lactobacillus acidophilus and Bifidobacterium animalis subsp. lactis on the organic acid, texture profile and sensory attributes of Tulum cheese. The acidity of sample increased throughout the storage. Storage time influenced the organic acid content of samples (P < 0.0001). Lightness decreased while redness increased (P < 0.05). Cohesiveness decreased during storage, whereas the values of all other Texture Profile Analyses (TPA) parameters increased. The samples produced with L. acidophilus had the highest texture and acceptability ratings, whereas samples produced with B. animalis subsp. lactis had the highest flavour score.     

Compositional,biochemical and textural changes during ripening of Tulum cheese made with different coagulants

In the present study, biochemical, chemical and texture changes in Tulum cheeses made using calf rennet and microbial rennets (Aspergillus niger protease and Rhizomucor miehei protease) were compared during ripening for up to 90 days. A total of 15 free fatty acids (FFAs) were detected in the cheese samples. The peroxide values (PV) of the cheeses increased significantly (P < 0.05) during ripening and the cheese made with calf rennet had the highest PV. Proteolysis in the cheeses increased as the ripening time increased. α_s1‐casein and β‐casein degradation was higher in cheeses manufactured with R. miehei protease. Cheeses made with calf rennet were significantly (P < 0.05) harder, more adhesive, more cohesive and more resilient than those made with microbial rennet.     

Influence of selected lab cultures on the evolution of free amino acids, free fatty acids and Fiore Sardo cheese microflora during the ripening

Fiore Sardo Protected Denomination of Origin is a traditional Sardinian (Italy) hard cheese produced exclusively from whole raw ovine milk and coagulated with lamb rennet paste. Currently, Fiore Sardo is still produced by shepherds at the farmhouse level without the addition of any starter culture and the cheese-making process is characterized by significant waste. The first objective of the present work was to investigate the autochthonous microflora present in milk and Fiore Sardo cheese in order to select lactic acid bacterial (LAB) cultures with suitable cheese-making attributes and, possibly reduce the production waste. Secondly, the ability of selected cultures to guarantee cheese healthiness and quality was tested in experimental cheese-making trials. In this study, we show that the typical lactic microflora of raw ewe's milk and Fiore Sardo cheese is mostly composed of mesophilic LAB such as Lactococcus lactis subsp. lactis, Lactobacillus plantarum and Lactobacillus casei subsp. casei. Moreover, strains belonging to the species were selected for cheese-making attributes and used in experimental cheese-making trials carried out in different farms producing Fiore Sardo. The evolution of the cheese microflora, free amino acids and free fatty acids during the ripening showed that the experimental cheeses were characterized by a balanced ratio of the chemical constituents, by a reduced number of spoilage microorganisms and, remarkably, by the absence of production waste that were significant for the control cheeses.     

Prediction of processed cheese instrumental texture and meltability by mid-infrared spectroscopy coupled with chemometric tools

The objective of this study was to determine the potential of mid-infrared spectroscopy coupled with multidimensional statistical analysis for the prediction of processed cheese instrumental texture and meltability attributes. Processed cheeses (n = 32) of varying composition were manufactured in a pilot plant. Following two and four weeks storage at 4 °C samples were analysed using texture profile analysis, two meltability tests (computer vision, Olson and Price) and mid-infrared spectroscopy (4000–640 cm⁻¹). Partial least squares regression was used to develop predictive models for all measured attributes. Five attributes were successfully modelled with varying degrees of accuracy. The computer vision meltability model allowed for discrimination between high and low melt values (R² = 0.64). The hardness and springiness models gave approximate quantitative results (R² = 0.77) and the cohesiveness (R² = 0.81) and Olson and Price meltability (R² = 0.88) models gave good prediction results.     

Effects of plant-based content,flavor and texture information on consumer satisfaction with non-fried ramen

The purpose of this study was to screen flavor information for positioning of non-fried ramen products and to examine the applicability of plant-based ingredient content in flavor communication. Effects of information related to savoriness, spiciness, menu name, plant-based ingredient content (%), and texture of samples on informed satisfaction were examined using home–use tests and online surveys. In order to form a regression model that explained variations in the informed satisfaction of non-fried ramen samples, we created indices that integrated the importance of information and the congruence of information with flavor perception. We have confirmed that effects of congruence on increasing satisfaction were higher than those of importance of information. When congruence/importance was used as an independent variable, a quadratic regression equation has explained the variations on satisfaction levels with an R² value of 72.7% (p = 0.006). Considering the positive congruence effect that plant-based ingredient percentages and perceived flavors had on informed satisfaction levels, communication schemes are needed to promote foods that have high percentages of plant-based ingredients.     

Taste and flavor of artisan and industrial Manchego cheese as influenced by the water-soluble extract compounds

The correlation between chemical and sensory analysis of the water-soluble extract compounds with molecular weight less than 1,000 Da (WSE < 1,000 Da) from Manchego cheese at different stages of ripening, as well as the influence of the pasteurization processes, has been studied. Free amino acids, peptides and volatile compounds were more abundant in raw milk cheeses WSE < 1,000 Da. Further fractionation of the WSE < 1,000 Da was carried on by gel permeation chromatography and amino acids, peptides, ions and volatiles were determined in the fractions. The same fractions were also subjected to organoleptic evaluation. Volatile compounds were related to the aroma and small peptides and amino acids to the taste. Volatile compounds were mainly alcohols and ketones. Fresh and floral notes were detected in the 4-month-old cheeses, which evolved into more intense and complex flavors in the 8-month-old cheeses. Peptides detected in the fractions were mainly hydrophilic. Umami taste was predominant in most of the fractions and it could be related to the presence of glutamic and aspartic acids in these fractions. Salty taste was perceived with high intensity in the fractions with a high content of salts. Bitter taste was mainly detected in the last eluting fractions and it was attributed to the Tyr, Phe and Trp residues found in these fractions. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Production and characterization of a tributyrin esterase from Lactobacillus plantarum suitable for cheese lipolysis

Lactobacillus plantarum is a lactic acid bacterium that can be found during cheese ripening. Lipolysis of milk triacylglycerols to free fatty acids during cheese ripening has fundamental consequences on cheese flavor. In the present study, the gene lp_1760, encoding a putative esterase or lipase, was cloned and expressed in Escherichia coli BL21 (DE3) and the overproduced Lp_1760 protein was biochemically characterized. Lp_1760 hydrolyzed p-nitrophenyl esters of fatty acids from C2 to C16, with a preference for p-nitrophenyl butyrate. On triglycerides, Lp_1760 showed higher activity on tributyrin than on triacetin. Although optimal conditions for activity were 45°C and pH 7, Lp_1760 retains activity under conditions commonly found during cheese making and ripening. The Lp_1760 showed more than 50% activity at 5°C and exhibited thermal stability at high temperatures. Enzymatic activity was strongly inhibited by sodium dodecyl sulfate and phenylmethylsulfonyl fluoride. The Lp_1760 tributyrin esterase showed high activity in the presence of NaCl, lactic acid, and calcium chloride. The results suggest that Lp_1760 might be a useful tributyrin esterase to be used in cheese manufacturing.     

Rapid simultaneous determination of organic acids,free amino acids,and lactose in cheese by capillary electrophoresis

A capillary electrophoresis (CE) method for the simultaneous separation of 11 metabolically important organic acids (oxalic, formic, citric, succinic, orotic, uric, acetic, pyruvic, propionic, lactic, and butyric), 10 amino acids (Asp, Glu, Tyr, Gly, Ala, Ser, Leu, Phe, Lys, and Trp), and lactose has been optimized, validated, and tested in dairy products. Repeatability and linearity were calculated for each compound, with detection limit values as low as 0.2 x 10(-2) mM for citric acid and Gly. The method was applied to analyze yogurt and different varieties of commercial cheeses. This method yielded specific CE patterns for different varieties of cheese. Also, it has been shown to be sensitive enough to measure small changes in composition of some of those compounds in fresh cheese stored under accelerated ripening conditions for 2 d at 32 degrees C (e.g., from 1728.3 +/- 45.0 to 1166.7 +/- 4.5 mg/100 g of DM in the case of lactose, or from 23.5 +/- 0.6 to 76.8 +/- 16.7 mg/100 g of DM in the case of acetic acid).     

Identification of free fatty acids and some other volatile flavour compounds from Swiss cheese using on-line supercritical fluid extraction-gas chromatography

On-line supercritical CO₂ extraction - gas chromatography was applied to the isolation and identification of free fatty acids and other volatile compounds of young and ripe Swiss cheese (Emmental) produced in Finland. Extractions were carried out using a micro-cartridge at 40 °C temperature and 10 MPa pressure and the volatile fractions were analysed by DB-WAX column (polyethylene glycol phase) with flame ionization detection and mass spectrometry. The total time of analysis was less than 2.5 h. Acetic acid and propionic acid predominated over the C12–C18 acids, the longer chain fatty acids increasing in concentration during the ripening of the cheese. Due to the high proportions of fatty acids, further fractionation is required for analysis of the less abundant aroma compounds such as alcohols, carbonyls and lactones.     

Lipolysis,proteolysis and sensory properties of ewe’s raw milk cheese (Idiazabal) made with lipase addition

In this paper, we describe the effect of the addition of pregastric lipase on the composition and sensory properties of Idiazabal cheese. Free fatty acids (FFA), partial glycerides, free amino acids (FAA), gross composition and sensory characteristics were determined at different ripening times in cheeses manufactured with three different amounts of commercial animal lipase or with lipase-containing artisanal lamb rennet paste. The addition of lipase increased the content of total FFA, particularly of short-chain FFA, and that of total partial glycerides in cheeses. Unexpectedly, lipase utilization significantly affected total FAA concentration, which decreased in cheeses elaborated with high lipase amount. In general, Val, Glu and Leu were the major FAA, and their concentrations depended, mainly, on ripening time. Lipase addition had significant influence on the sensory characteristics of the cheeses, increasing scores for most of the flavour and odour attributes of the cheese. Principal component analysis (PCA) was done including dry matter, FFA, FAA, partial glycerides and odour and flavour attributes of the cheeses. It indicated that aroma and flavour parameters of Idiazabal cheese and the content of short-chain FFA and diglycerides were highly correlated to first principal component (PC1), while texture parameters, compositional variables and FAA were correlated to the second principal component (PC2).