Inverse gas chromatographic method for measurement of interactions between soy protein isolate and selected flavor compounds under controlled relative humidity

An inverse gas chromatographic (IGC) method was developed to study the binding interactions between selected volatile flavor compounds and soy protein isolate (SPI) under controlled relative humidity (RH). Three volatile probes (hexane, 1-hexanol, and hexanal) at very low levels were used to evaluate and validate system performance. On the basis of the thermodynamic data and the isotherms measured at 0% RH, 1-hexanol and hexanal had higher binding affinities than hexane, which could be attributed to hydrogen-bonding interactions with SPI. At 30% RH, 1-hexanol and hexanal were retained less than at 0% RH, indicating possible competition for binding sites on the SPI surface between water and volatile probe molecules. Results showed that the thermodynamic data determined were comparable to the available literature values. Use of IGC allowed for the rapid and precise generation of sorption isotherms. Repeatability between replicate injections and reproducibility across columns were very good. IGC is a potentially high-throughput method for the sensitive, precise, and accurate measurement of flavor-ingredient interactions in low-moisture food systems.     

Inverse gas chromatographic evaluation of the influence of soy protein on the binding of selected butter flavor compounds in a wheat soda cracker system

Binding of selected volatile butter flavor compounds to wheat vs soy-containing crackers was studied by inverse gas chromatography (IGC), sensory evaluation, and equilibrium sorption measurements. IGC data showed greater binding of gamma-butyrolactone and butyric acid to both types of crackers than either diacetyl or hexanal, possibly due to the involvement of stronger binding forces such as hydrogen bonding and even ionic forces in the case of butyric acid. The presence of soy proteins did not affect binding of diacetyl and hexanal but increased binding of strongly interacting compounds gamma-butyrolactone and especially butyric acid, probably through enhanced matrix polarity. In agreement with the IGC data, sensory evaluation results showed that the headspace aroma intensities were similar between the two diacetyl-flavored crackers, while they significantly differed between the butyric acid-flavored crackers. In addition, equilibrium sorption measurement data showed that binding of butyric acid was higher in the soy-containing cracker, but sorption of diacetyl to the two crackers did not significantly differ.     

Sorption of volatile flavor compounds by microcellular cereal starch

Wheat starch based microcellular foam (MCF) forms of (dry) starch possess a significant percentage of micropores in the range of 5-14 A. The present study confirmed earlier preliminary studies that MCF starch (in a 0.25-1.0 mm diameter bead form) is effective in sorbing and lowering the headspace partial pressure of many volatile compounds in a manner similar (although less efficient) to that exhibited by other microcavity sorbants such as charcoal. It was found that the proportion of polar compounds sorbed was much greater than the proportion of nonpolar compounds. A major portion of the sorbed volatile compound was readily displaced from the MCF microcellular starch by the addition of water. These properties make this form of edible starch a potential useful carrier of flavor compounds for dried foods.     

Transcriptome profiling of heat-resistant strain Bacillus licheniformis CGMCC3962 producing Maotai flavor

Although Maotai flavor liquor is exclusive due to its soy sauce flavor, knowledge of its key compound and production mechanism is still scarce until now. To gain insight into the production mechanism of soy sauce flavor, a soy sauce flavor producing strain with high efficiency and heat-resistant capability was obtained, and the metabolic mechanism of the strain was investigated with the technique of microarray profiling. Because high temperature was a key factor for soy sauce flavor production, the global gene expression of this heat-resistant strain fermented at 55 °C was analyzed. Except for the responsive increase of heat shock proteins, which maintained cell survival during heat stress, biosynthesis of cysteine was also up-regulated. In addition, some metabolites were significantly increased when cysteine was added to the fermentation medium, such as 2,3-butanediol, 3-hydroxy-2-butanone, and tetramethylpyrazine, which were important flavor compounds in soy sauce flavor liquor and might be related with soy sauce flavor. The results indicated that cysteine might play an important role in the formation of soy sauce flavor compound, and it might act as an indirect precursor or stimulator of soy sauce flavor formation. This was the first use of the microarray profiling tool to investigate the fermentative strains for Chinese traditional liquor, which would allow a deeper insight into the mechanism of the formation of soy sauce flavor compound.     

Effect of beta-cyclodextrin on aroma release and flavor perception

Binding and release of volatile compounds to and from beta-cyclodextrin were measured in model aqueous systems using static equilibrium headspace and dynamic headspace dilution. Beta-cyclodextrin decreased the static equilibrium headspace for some volatiles (e.g., ethyl octanoate and decanone) due to binding, but dilution studies demonstrated that binding was readily reversible. Dynamic release of hydrophobic volatile compounds was similar to that observed from emulsions. When beta-cyclodextrin was added to fat free yogurt, the release of a commercial lemon flavoring was modified and was similar to release from a regular fat yogurt. Sensory difference testing confirmed the release results. The data demonstrate that beta-cyclodextrin can be used to modify flavor delivery in both model and real systems; the effects in the latter are sensorially significant.     

Water solubility of flavor compounds influences formation of flavor inclusion complexes from dispersed high-amylose maize starch

High-amylose maize starch, with and without native lipid, was used to make inclusion complexes with flavor compounds to investigate the effect of water solubility of flavor compounds on inclusion complex formation. Two pairs of terpenes, having high and low water solubility, were used. Aqueous starches were dispersed by heat before adding the flavor compound. The amounts of starch, native lipid, and flavor compound in precipitates were determined, and inferences about the physical state were made using data from X-ray diffraction and differential scanning calorimetry. The water solubility of the flavor compound was related to the extent of inclusion complexation. For the higher water solubility flavor compounds, starch yield and flavor entrapment were higher, producing precipitates with the V 7 pattern. Complex formation with the low-solubility flavor compounds was most effective in the presence of native lipid, producing precipitates with the V 6 pattern. The lipid in native high-amylose maize starch may enhance complexation with low-solubility compounds by forming ternary coinclusion complexes of starch-lipid-flavor.     

Real-time monitoring of thermal flavor generation in skim milk powder using atmospheric pressure chemical ionization mass spectrometry

The feasibility of monitoring volatile flavor compounds formed by thermal treatment of skimmed milk powder in real time by atmospheric pressure chemical ionization mass spectrometry (APCIMS) was established. Skim milk powder samples were heated isothermally (70 to 120 degrees C) at different moisture contents (2.2 and 12.7 g water/100 g dry solids). Headspace was sampled and analyzed continuously in full scan mode (30-180 amu) by APCIMS. The identity of the volatile compounds monitored by APCIMS was confirmed by coupled GC-EI-APCIMS. The concentration measured by the APCIMS was the net effect of three processes, namely formation of the compound, partition from the skim milk powder into the gas phase, and dilution due to the headspace sampling method used. Preliminary experiments established that the technique could follow the effects of heating temperature and moisture content on the formation of selected compounds from skim milk powder.     

Current knowledge of soft cheeses flavor and related compounds

Cheese aroma is the result of the perception of a large number of molecules belonging to different chemical classes. The volatile compounds involved in the soft cheese flavor have received a great deal of attention. However, there has been less work concerning the volatile compounds in the soft smear-ripened cheeses than in the mold-ripened cheeses. This paper reviews the components that contribute to the characteristic flavor in the soft cheeses such as surface-ripened, Camembert-type, and Blue cheeses. The sensory properties and quantities of the molecules in the different cheeses are discussed.     

Effect of sucrose on the perceived flavor intensity of chewing gum.

The release of sucrose and menthone from chewing gum was measured in-mouth and in-nose, respectively, during eating. Swabs of saliva were taken from the tongue and analyzed using a rapid, direct liquid-mass spectrometry procedure. Menthone concentration in-nose was monitored on a breath-by-breath basis using direct gas phase atmospheric pressure chemical ionization-mass spectrometry. Simultaneously with the volatile release, trained panelists followed the change in mint flavor by time-intensity (TI) analysis. Two types of commercial chewing gum were analyzed. Both showed that the panelists perception of mint flavor followed sucrose release rather than menthone release. The temporal analysis of the chemical stimuli, with simultaneous TI analysis, provided unequivocal evidence of the perceptual interaction between nonvolatile and volatile flavor compounds from chewing gum.     

钾肥对甘薯块根营养成分的影响及其与烘烤风味的关系

  【目的】  探讨不同施钾量条件下食用型甘薯块根烘烤后风味品质的变化，及其与生块根中关键营养成分和烘烤后特征挥发性物质的关系。  【方法】  选用烟薯25和北京553两个鲜食型甘薯品种，在山东农业大学农学实验站进行田间小区试验。设置4个钾肥 (K₂O) 用量，分别为0、12、24、36 g/m2。在甘薯收获期，测定了块根中主要营养成分含量以及烘烤后挥发性物质含量，同时对块根烘烤后的风味进行评价。  【结果】  施用钾肥不同程度地提高了甘薯块根中可溶性糖、淀粉、可溶性蛋白、维生素C、β-胡萝卜素和纤维素含量，提高了烘烤后甘薯中挥发物质二丙酮醇、苯乙醛、壬酸、4-乙烯基愈创木酚、丁酸丁酯、未知物-1、十五烷酸、植物醇和香叶基香叶醇的浓度，提高了风味评分。4个钾肥处理中，各成分含量以施钾量24 g/m2处理达到或者接近最高。通过逐步回归和通径分析发现，施用钾肥改善块根烘烤后风味品质的关键营养成分是果糖、葡萄糖、氨基酸、可溶性蛋白质、支链淀粉和蔗果三糖，施用钾肥改善块根烘烤后风味的主要特征挥发性物质是丁酸丁酯、苯乙醛和未知物-1。  【结论】  施用钾肥主要通过提高甘薯收获期块根中营养物质含量和块根烘烤后有益挥发性物质（如苯乙醛、丁酸丁酯等）的浓度，改善块根的烘烤风味。在本试验条件下，K₂O用量为240 kg/hm2为最适用量。     

Modeling dynamic flavor release from water

A mathematical model derived from the convective mass transfer theory was developed to predict dynamic flavor release from water. A specific mass transfer correlation including a new term for volatile permeability was applied. The model was entirely based on physicochemical constants of flavor compounds and on some parameters of an apparatus used for validation. The model predicted a linear pattern of release kinetics during the first 30 s and large differences of absolute release for individual compounds. Both calculated and experimentally determined release profiles of a test mixture of flavors showed good agreement.     

Infusion of volatile flavor compounds into low-density polyethylene

Supercritical fluids can extract components from some matrixes (e.g., fat and flavors from food) as well as infusing additives into synthetic polymer matrixes. To study the feasibility of infusing flavors into matrixes as a potential flavoring mechanism, a wide range of volatile flavor compounds was infused into a well-defined synthetic polymer (low-density polyethylene) using supercritical carbon dioxide. The polymer was then extracted, and the amount of infused compound was determined. The effects of time, temperature, pressure, rate of depressurization, volatile concentration, and volatile properties on the degree of infusion were studied. Infusion with supercritical carbon dioxide achieved much higher loadings of the polymer (0.01 to 6.87 mg/g LDPE, depending on the volatile molecule being infused) compared to those achieved by static diffusion. Forty-five volatiles were infused, from which a model was developed to predict infusion as a function of certain physicochemical properties.     

Behavior of flavor compounds in model food systems: a thermodynamic study

Physicochemical parameters, such as hydrophobicity, water solubility, and volatility, of four flavor compounds (ethyl acetate, ethyl butyrate, ethyl hexanoate, and 2-pentanone) were determined. The amount of flavor compounds released from different model matrices (mineral water, purified triolein, an oil-in-water emulsion, a carbohydrate matrix, and a complex matrix containing lipids and carbohydrates) into the gaseous phase was determined at thermodynamic equilibrium, at 37 degrees C, by static headspace gas chromatography. The degree of interaction between the flavor compounds and the matrix components was shown by measuring the percentage retention using the water matrix as the reference. The partition of flavor compounds was principally dependent on their hydrophobicity. Physicochemical interactions that occurred in the different media led to different degrees of flavor retention. An impact of fat on flavor retention was demonstrated when a water matrix and an oil-in-water matrix or carbohydrate and complex matrices were compared. A carbohydrate impact on flavor compound retention was also detected, which was evident even in the presence of lipids.     

Effect of xanthan on flavor release from thickened viscous food model systems

The influence of xanthan concentration (0, 0.02, 0.1, 0.4, and 0.8% w/w) and bulk viscosity on the release of 20 aroma compounds of different chemical classes (5 aldehydes, 4 esters, 5 ketones, 3 alcohols, and 3 terpenes) was evaluated in xanthan-thickened food model systems having different viscosities. Interactions between flavor compounds and xanthan were assessed by measuring air-liquid partition coefficients, K, of aroma compounds in pure water and in the xanthan solutions by static headspace gas chromatography. Mass transfer of aroma compounds was estimated by dynamic headspace gas chromatography. Notably, limonene and some of the esters and aldehydes exhibited decreased K values in the presence of xanthan, indicating that the release of these volatile aroma compounds was reduced due to interaction with the xanthan matrix. The degree of interaction depended on the physicochemical characteristics of the aroma compounds. A similar tendency was observed at nonequilibrium with the decreases in release rates being most pronounced for limonene, followed by the esters and aldehydes, with no effect for ketones and an apparent "salting out" effect for alcohols. The reduction in flavor release by xanthan was thus dependent on the physicochemical properties of the aroma compounds and was apparently a result of the aroma-xanthan interactions and not influenced by the viscosity of the system itself.     

Evaluation of aroma compounds contributing to muskmelon flavor in Porapak Q extracts by aroma extract dilution analysis

The flavor of the Miyabi variety of Japanese muskmelon was extracted according to the Porapak Q column method (PQM) and evaluated by using aroma extract dilution analysis (AEDA) method. The overall odor of the PQM extracts was perceived as having a natural muskmelon-like odor, suggesting that the PQM was able to extract volatile compounds in muskmelon fruit without degradation of original flavor. Forty-six odorant compounds [Kovats index (KI), 961 < or = KI < or = 2605] were found by GC-sniffing in PQM extracts, confirming the effectiveness of PQM in trapping a wide range of volatile compounds in muskmelon flavor. The 46 odorants could be divided into three groups on the basis of their odor attributes: fruity note (KI < 1300); green, grassy, or cucumber-like note (1300 < KI < 2020); and sweet note (KI > 2020). When the original extracts were diluted in AEDA analysis, seven odorants could still be detected by GC-sniffing at a flavor diluation (FD) factor of 128 or above: one had a fruity note (compound 3); four had a cucumber-like, green, or grassy note (compounds 12, 17, 21, and 23); and two had a sweet note (caramel-like or yakitori-like) (compounds 32 and 34).     

Binding of flavor compounds and whey protein isolate as affected by heat and high pressure treatments

The interactions of whey protein isolate (WPI) and flavor compounds (2-nonanone, 1-nonanal, and trans-2-nonenal) were investigated, and the influence of flavor compound structure and heat and high pressure denaturation on the interactions were determined by using headspace solid-phase microextraction (SPME) and gas chromatography (GC). The binding of WPI and the flavor compounds decreased in the order trans-2-nonenal > 1-nonanal > 2-nonanone. The differences in binding can be explained with hydrophobic interactions only in the case of 2-nonanone, whereas the aldehydes, in particular trans-2-nonenal, can also react covalently. Heat and high pressure treatment affected protein-flavor interactions depending on the structure of the flavor compound. Upon both heat and high pressure denaturation, the binding of 2-nonanone to WPI decreased, while the binding of 1-nonanal remained unchanged, and the affinity for trans-2-nonenal increased rapidly. The results suggest that hydrophobic interactions are weakened upon heat or high pressure denaturation, whereas covalent interactions are enhanced.     

Application of the porapak q column extraction method for tomato flavor volatile analysis

The Porapak Q column method (PQM) was compared to the method of simultaneous distillation extraction (SDE) under reduced pressure for extraction of the volatile compounds produced by tomato cv. Momotaro. The PQM was found to be effective at trapping and isolating many low and high boiling point volatile compounds and at producing the very desirable natural ripe tomato flavor of extracts. The SDE method was less effective in isolating the higher boiling point volatile compounds and caused deterioration of volatile compounds due to the heating process that takes place during extraction, resulting in an unpleasant boiled green tomato flavor of extracts. The advantages of using the PQM are its simplicity and its high efficiency in isolating many volatile compounds from nonvolatile materials at room temperature. A total of 367 volatile compounds were isolated by the PQM. Of these, hexanal, (Z)-3-hexenal, (E)-2-hexenal, 2- and 3-methylbutanol, and 2-phenylethanol were relatively more abundant than other compounds and (Z)-3-hexenal showed the highest relative amount.     

Precursors of chicken flavor. II. Identification of key flavor precursors using sensory methods

Sensory evaluation was used to identify flavor precursors that are critical for flavor development in cooked chicken. Among the potential flavor precursors studied (thiamin, inosine 5'-monophosphate, ribose, ribose-5-phosphate, glucose, and glucose-6-phosphate), ribose appears most important for chicken aroma. An elevated concentration (added or natural) of only 2-4-fold the natural concentration gives an increase in the selected aroma and flavor attributes of cooked chicken meat. Assessment of the volatile odor compounds by gas chromatography-odor assessment and gas chromatography-mass spectrometry showed that ribose increased odors described as "roasted" and "chicken" and that the changes in odor due to additional ribose are probably caused by elevated concentrations of compounds such as 2-furanmethanethiol, 2-methyl-3-furanthiol, and 3-methylthiopropanal.     

Binding of 2-nonanone and milk proteins in aqueous model systems

Interactions of the model flavor compound 2-nonanone with individual milk proteins, whey protein isolate (WPI), and sodium caseinate in aqueous solutions were investigated. A method to quantify the free 2-nonanone was developed using headspace solid-phase microextraction followed by gas chromatography with flame ionization detection. Binding constants (K) and numbers of binding sites (n) for 2-nonanone on the individual proteins were calculated. The 2-nonanone binding capacities decreased in the order bovine serum albumin > beta-lactoglobulin > alpha-lactalbumin > alpha s1-casein > beta-casein, and the binding to WPI was stronger than the binding to sodium caseinate. All proteins appeared to have one binding site for 2-nonanone per molecule of protein at the flavor concentrations investigated, except for bovine serum albumin, which possessed two classes of binding sites. The binding mechanism is believed to involve predominantly hydrophobic interactions.     

基于判别分析法的金华火腿挥发性风味物质的形成过程分析

为了弄清金华火腿风味物质的形成过程,以60只杂交猪后腿为原料,按照传统工艺加工金华火腿,用气质联用仪(GC-MS)分析了6个工艺点的肌肉中挥发性风味物质的出峰面积,并用判别分析法分别研究了用挥发性风味物质的出峰面积和出峰面积占总出峰面积的百分率建立的判别函数判断金华火腿加工程度的可能性.研究结果表明,用金华火腿挥发性风味化合物的峰面积进行逐步判别分析,有20种挥发性化合物进入判别函数,而用峰面积占总出峰面积的百分率进行逐步判别分析,有17种挥发性化合物进入判别函数,建立的两套判别函数都能准确判别火腿的加工程度.结果提示:金华火腿风味化合物是在加工过程中逐步形成的,在不同加工阶段,火腿特征风味化合物的含量及其比例各具特征,可以用以辨别火腿的加工时间.