Sorption of Flavor Compounds by Low Density Polyethylene Film

The interactions of aldehydes, methyl ketones, methyl esters, sulfur compounds and alkylpyrazines with low density polyethylene (LDPE) were investigated. LDPE film, suspended on a stainless steel support, was immersed in simulated milk ultrafiltrate containing a flavor compound. After shaking the glass bottles containing the solutions and film samples for 24 hr at room temperature (24 ± 2°C), the flavor compound was extracted from both the LDPE samples and the SMUF, and quantitated using gas chromatography. The sorption was: aldehydes (C₇-C₁₀) 11% to 63%, methyl ketones (C₇-C₁₀) 1.5% to 43.0%, methyl esters (C₇-C₉) 6.0% to 42.0%, and sulfur compounds 8.5% to 21%. Insignificant levels of alkylpyrazines were sorbed. For all flavor compound classes, as carbon chain length increased, the quantity of sorbed flavor compounds increased.     

Oxygen Permeability of Low Density Polyethylene as a Function of Limonene Absorption: An Approach to Modeling Flavor "Scalping"

A procedure was developed to measure adsorption (scalping) of limonene by low density polyethylene. The polymer was mounted on an oxygen electrode. Limonene absorption produced an increase in oxygen permeability which appeared proportional to limonene concentration. Diffusion coefficients calculated from permeation curves were similar to diffusion coefficients calculated on a weight change basis.     

Oxidation of d-Limonene in Presence of Low Density Polyethylene

Headspace oxygen contents of sodium citrate-water buffers containing d-limonene with and without low density polyethylene (LDPE) were measured on a weekly basis for 10 wk. d-Limonene was readily sorbed into LDPE. Results indicated first order kinetics for limonene oxidation. GC/MS analyses determined production of limonene oxidation end-products, including d-carvone, carveol, limonene oxide, perrilaldehyde and linalool, as well as α-terpineol, a hydrolysis product. Headspace oxygen contents of the d-limonene/buffer (control) samples were lower thau that of the d-limonene/buffer/LDPE samples, suggesting a higher oxidation rate in the control than in LDPE. Oxidation rate constants and half-lives were 5.9 × 10^-3 log(%O₂) wk^-1, t_1/2= 116 wk for control and 1.2 × 10^-3 log(%O₂) wk^-1, t_1/2= 580 wk for LDPE samples, respectively.     

柑橘乳化香精的稳定性研究

选用柠檬油为原料,纯胶为乳化剂,以乳化香精的吸光度变化率为评价指标,借助单因素试验和正交试验,优化制备稳定乳化香精的工艺条件.对于纯胶的乳化来说,影响最大的是乳化剂浓度,其次是均质转速,然后是增稠剂浓度,影响最小的是均质时间.纯胶乳化稳定性最佳的务件是:6%的纯胶作乳化剂,0.5%的卡拉胶作增稠剂,在数显高速分散均质机的转速为4500r/min下均质25min,乳化香精的吸光度变化率为10.13%,变化率最小,乳化效果最好.     

新型反应型鸡肉香精的制备及其挥发物的分析

以鸡肉酶解物和HVP液为主要原料,在pH5.0下,125℃反应40min制得了鸡肉味较强、总体香气较好的鸡肉味香精,该香精的挥发物经分离、浓缩和GC/MS分析后,鉴定出的40种化合物中有8种是在煮鸡肉中鉴定出的关键香味化合物。     

Analysis of Volatiles Related to Warmed over Flavor of Cooked Chevon

The development of warmed over flavor (WOF) in cooked chevon was monitored from its Tenax trapped volatiles by direct gas chromatography (GC). WOF markers, pentanal, hexanal, heptanal, 2,-3-octanedione and nonanal were identified from volatile profiles obtained with packed poly MPE coated Tenax-GC column. These volatile markers as well as the total volatiles increased over 6 days storage of cooked chevon at 4°C. Increase in hexanal was more rapid than the other WOF markers. Results suggest WOF development in cooked chevon is more rapid than reported rates for other cooked meats.     

Evaluation of the Contribution of Flavor Volatiles to the Aroma of Beef by Surface Response Methodology

The contribution to beef aroma of some compounds previously identified in the flavor volatiles from cooked beef was estimated by surface response methodology. In general, heterocyclic compounds containing oxygen, nitrogen and/or sulfur and unsaturated alcohols gave higher predicted scores and had lower optimum concentrations than ketones, aldehydes, alkanes or saturated alcohols. It was further demonstrated that hydrophilic compounds are more likely to contribute to meat aroma than hydrophobic compounds, thus, verifying a more important role for water-soluble compounds in contributing to meat flavor. On testing mixtures of compounds, the optimum concentrations were generally lower, but there was a greater range in maximum scores. Special significance is given to the fact that highest scoring two-component mixture (2-acetyl-3-methylpyrazine and H₂S) resulted from combining the two single compounds that scored highest alone. Furthermore, the reaction mixture of H₂S with 4-hydroxy-5-methyl-3(2H)-furanone gave the highest predicted score in the entire study. Thus, results indicate that the surface response method offers promise for unraveling the complexity of the meat flavor system.     

石墨炉原子吸收法测定烟用香精中的镉

建立了硝酸-过氧化氢微波消解、纵向塞曼自动背景校正、石墨炉原子吸收法测定烟用香精中镉(Cd)含量的方法,并采用该方法测定了30个烟用香精样品中的Cd含量。结果表明:①Cd含量测定的适宜条件为:硝酸钯作为基体改进剂,灰化温度600℃,原子化温度1300℃;②镉的检出限0.029μg/L,回收率96.5%～102.0%,RSD≤2.9%;③5个香精样品中未检出Cd,11个样品的Cd含量为0.08～0.18mg/kg,10个样品的Cd含量为0.21～0.38mg/kg,4个样品的Cd含量为0.41～0.53mg/kg。     

Orange Flavor Absorption Into Various Polymeric Packaging Materials

Citrus oil components (from cold-pressed and terpeneless oils), which contribute substantially to flavor of orange juice, were shown to be absorbed into various polymeric materials [low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP), and surlyn (S)] used in aseptic packaging. Equilibration of absorption took place within 4 days, while extraction of the oil constituents occurred in 24 hr when higher temperatures were used. Substantial absorption of oil constituents by LDPE and S occurred while highly crystalline polymers (PP and HDPE) did not absorb much. The degree of absorption also depended on the nature of the oil constituents. Absorption was higher for terpene constituents followed by sesquiterpenes and aldehydes. Swelling factors showed that highly crystalline polymers (HDPE and PP) swelled less than crystalline polymeric materials. Citrus oil affected the crystallinity of the polymers by lowering their melting point and percent crystallinity.     

Interactions of Citrus Flavor Compounds with Polypropylene Films of Varying Crystallinities

Equilibrium sorption levels at 23°C were determined individually for two citrus flavor components (d-limonene and 1-carvone) into ground and unground polypropylene films of different crystallinities. Sorption levels at equilibrium were also determined for a mixture of the two flavor compounds. Aqueous solutions of the flavor compounds (200 ppm carvone and 1000 ppm limonene) were employed. Concentrations of flavors remaining in solution before and after exposure were measured by high performance liquid chromatography (HPLC). Results indicated flavor compound polarity, polymer crystallinity and the presence of other flavor compounds in a mixture influenced sorption behavior.     

热反应对鸡肉味香味料挥发性成分影响初探

用同时蒸馏提取技术对由半胱氨酸、硫胺素、味精、葡萄糖、I +C、甘氨酸、丙氨酸组成的经热反应产生的鸡肉味香味料的挥发性成分进行了分离和浓缩 ,所得到的浓缩物用GC MS技术定量分析 ,共鉴定出 40余种化合物 ,并计算出它们的含量。其中 ,重要的肉味化合物如 2 甲基 3 呋喃硫醇、二 (2 甲基 3 呋喃基 )二硫、(2 甲基 3 呋喃基 ) (2 甲基 4,5 二氢 3 呋喃基 )二硫、二 (2 甲基 4,5 二氢 3 呋喃基 )二硫、呋喃、噻吩等被鉴定出来 ,并对其感觉特性及形成途径进行了简略说明     

Reduction of Warmed-Over Flavor Volatiles from Freeze-Dried Lean by Supercritical CO2 Extraction

Supercritical carbon dioxide (SC-CO₂) was used to extract warmed-over flavor (WOF) volatiles from cooked, freeze-dried beef at 40°C and pressures of 10.3 MPa or 30 MPa after 2 days storage. WOF markers, hexanal, heptanal, octanal, nonanal, and 2,3-octanedione, were identified in the volatiles profile of precooked beef by dynamic headspace extraction and gas chromatography-mass spectrometry before and after CO₂ extraction. TBARS and levels of WOF markers increased over 2 days storage. There was a reduction in WOF markers at both extraction pressures. The higher pressure led to greater reduction of WOF markers (e.g., hexanal: 73.5%) than the lower pressure (e.g., hexanal: 60.3%), notably for heptanal and nonanal. SC-CO₂ may be applicable for reducing WOF volatiles from precooked meats.     

Volatiles in Skin of Low Dose Irradiated Fresh Chicken

Fresh chickens were irradiated with up to 1200 krad at 0–5°C. Volatile compounds from the skin and subcutaneous fat of these chickens, and from unirradiated controls, were analyzed by gas chromatography. Acceptability of the odor of the chickens was also evaluated. Other samples (0 and 300 krad) were evaluated by chemical and sensory analysis after storage at 4°C. Analysis of volatiles indicated that levels of octane, l-octene, hexanal, and nonane increased regularly with radiation dose. Amount of total volatiles was greater in unstored irradiated samples than in controls, but this was reversed after storage. After 14 days, the irradiated sample still had acceptable odor, while the control ahd severely deteriorated.     

Polyethylene Film Packaging of Citrus Fruit: Containment of Decaying Fruit

Decaying grapefruit (Citrus paradisi Macf.) stored under nonventilated conditions caused a substantial reduction in the oxygen and an increase in the carbon dioxide concentrations in the atmosphere. A comparable increase in the internal carbon dioxide concentration of sound fruit in the same container was also observed. Low oxygen caused an increase in the ethanol concentration in the juice of the sound fruit and the development of an undesirable stale flavor. Containment of the decaying fruit in polyethylene film limited the oxygen depletion. Thus, flavor quality of sound fruit from the containers with PE film-sealed decaying fruit was comparable to that of sound fruit stored in the absence of decaying fruit.     

Interaction Between Polyethylene Laminated Cartons and Aseptically Packed Citrus Juices

The quality of citrus juices aseptically packed into laminated cartons and glass jars was evaluated at three temperatures. Model solutions were used to elucidate effect of contact surface on components in the product. The extent of browning and loss of ascorbic acid was found to be greater in cartons than in glass. The d-limonene content of the juices in cartons was reduced by about 25% within 14 days of storage due to absorption by the polyethylene. Sensory evaluation showed a significant difference after 10 – 12 wk between juices packed in glass and cartons stored at ambient temperatures.     

食用香精相对密度不确定度评估的研究

通过建立采用香料相对密度的测定GB/T 11540-2008中的检验方法测定的不确定度评定的模型,对检测过程中可能引入的不确定度来源进行了分类和量化,较为全面的评定了各个不确定度分量,并提出了应用该方法检测的不确定度评定结果。分析了香料相对密度的不确定度的分量及其来源,并通过计算各分量的不确定度得出检测结果的合成标准不确定度。香精的相对密度为1.043 6,扩展不确定度U=0.003 6,置信水平P=95%,k=2。不确定度的主要来源为仪器本身偏差的影响、比重瓶的示值误差、重复性测量的影响、方法复现性的影响,保证检测过程其它干扰因素,保证检测过程中的准确性。     

Lipase Mediated Synthesis of Low Molecular Weight Flavor Esters

Screening 27 commercial lipases showed that enzymes from Candida cylindracea, Pseudomonas fluorescens and Mucor miehei (immobilized) promoted synthesis of selected low molecular weight esters in nonaqueous systems. Maximum production after 24 hr incubation was obtained with substrate concentrations of 0.05 mol/L for isopentyl acetate, 0.2 mol/L for ethyl butyrate and 0.3 mol/L for isopentyl butyrate. Yield of butyl butryate was almost 100% at acid substrate greater than 0.2 mol/L. Substrate inhibition was observed with P. fluorescens lipase but not with C. cylindracea or M. miehei lipases, up to 1 mol/L. Hexane, octane and decane could be used as reaction media except for ethyl butyrate synthesis where hexane was the medium of choice. Poor synthesis was achieved when methylene chloride was used.     

椪柑果醋液态发酵工艺及香气成分的GC-MS分析

以椪柑为原料,通过正交试验设计研究酒精发酵和醋酸发酵的最优工艺。采用固相微萃取-气相色谱-质谱联用技术鉴定椪柑果醋中的挥发性风味物质,结果表明:椪柑果醋液态发酵最佳条件是:酿酒酵母添加量0.10%,发酵温度28℃,表观糖度18°Brix,醋酸接种量8%,发酵温度30℃,通气程度1/5。经GC-MS分析鉴定,液态发酵的椪柑果醋共含66种挥发性物质,其中乙酸是椪柑果醋中含量最高的挥发性成分,占风味总量的40.80%;酯类化合物是最主要的风味物质,占25.92%;柠烯是重要的特征香味组分,占2.74%。