Effect of processing on flavor precursor amino acids and volatiles of sesame paste (tehina)

The content of flavor precursor free amino acids in dehulled sesame seeds, subjected to roasting (R), steaming (S), roasting plus steaming (RS) and microwaving (M), was determined and compared with those of the raw (RW) seeds. R, RS, and S had major effects in reducing the content of free amino acids from 2360 μg/g to 582, 795 and 884 μg/g, respectively; M had no effect on the content of free amino acids. Meanwhile, flavor volatiles of the raw and processed seeds were compared by means of a dynamic headspace analyzer/gas chromatograph-mass spectrometer. Volatiles of RW seeds contained 85 compounds, whereas under the analytical conditions employed, seeds subjected to R, RS, S, and M had 117, 97, 93 and 87 compounds, respectively. Among volatiles identified in the RW seeds were 36 hydrocarbons, 8 aldehydes, 4 ketones, 8 alcohols, 2 acids, 2 esters, and 1 pyrazine. The only pyrazine identified in the RW seeds was 2,5-dimethylpyrazine. Pyrazines, generally recognized as contributors to the roasted aroma of foods, were more numerous (10 in R, 6 in RS, 2 in S, and 2 in M) and prevalent (8.71% in R, 2.97% in RS, 2.04% in S, 0.53% in M, and 0.25% in RW) in the volatiles of processed sesame seeds. The chemical nature of pyrazines also depended on the process employed. Multivariant analysis indicated a highly negative correlation between the loss of free amino acids and production of volatile flavor compounds in the R and RS samples, while the M sample remained unchanged. Furthermore, both R and RS seeds contained dimethyl sulfide and dimethyl disulfide, whereas no sulfur-containing compounds were present in other samples. Of the processed seeds, the flavors of R and RS samples were considered as acceptable, and the flavor intensity of the former was deemed stronger than that of the latter by the experimenters.     

Formation of Benzo(a)pyrene in Sesame Seeds During the Roasting Process for Production of Sesame Seed Oil

The main aim of this research was to enhance the understanding of the formation mechanisms of benzo(a)pyrene (BaP) during roasting of sesame seeds (SS). BaP levels in hot‐ and cold‐pressed sesame seed oil (SSO) were evaluated to correlate oil technology and BaP formation. Extracted principal components from SS were roasted either singly or in mixtures at 230 °C for 30 min. BaP was measured by HPLC with fluorescence detection. The results showed that BaP levels in hot‐pressed SSO were significantly higher than those in cold‐pressed SSO (p < 0.05), BaP formation mostly occurred during SS roasting and increased with roasting temperature (between 80 and 280 °C) and time (from 10 to 50 min). Furthermore, the BaP level in the roasted hulled SS (3.64 μg/kg) was higher than it was in roasted whole SS (1.63 μg/kg). The maximum BaP level observed (5.03 μg/kg) was detected in a roasted mixture of SS protein and SSO. The addition of sesame protein to protein‐free SSO promoted the formation of BaP, which suggests that the pyrolysis products of protein and triacylglycerols are probably important precursors in BaP formation.     

Flavor components of olive oil—A review

The unique and delicate flavor of olive oil is attributed to a number of volatile components. Aldehydes, alcohols, esters, hydrocarbons, ketones, furans, and other compounds have been quantitated and identified by gas chromatography-mass spectrometry in good-quality olive oil. The presence of flavor compounds in olive oil is closely related to its sensory quality. Hexanal, trans-2-hexenal, 1-hexanol, and 3-methylbutan-1-ol are the major volatile compounds of olive oil. Volatile flavor compounds are formed in the olive fruit through an enzymatic process. Olive cultivar, origin, maturity stage of fruit, storage conditions of fruit, and olive fruit processing influence the flavor components of olive oil and therefore its taste and aroma. The components octanal, nonala, and 2-hexenal, as well as the volatile alcohols propanol, amyl alcohols, 2-hexenol, 2-hexanol, and heptanol, characterize the olive cultivar. There are some slight changes in the flavor components in olive oil obtained from the same oil cultivar grown in different areas. The highest concentration of volatile components appears at the optimal maturity stage of fruit. During storage of olive fruit, volatile flavor components, such as aldehydes and esters, decrease. Phenolic compounds also have a significant effect on olive oil flavor. There is a good correlation between aroma and flavor of olive oil and its polyphenol content. Hydroxytyrosol, tyrosol, caffeic acid, coumaric acid, and p-hydroxybenzoic acid influence mostly the sensory characteristics of olive oil. Hydroxytyrosol is present in good-quality olive oil, while tyrosol and some phenolic acids are found in olive oil of poor quality. Various off-flavor compounds are formed by oxidation, which may be initiated in the olive fruit. Pentanal, hexanal, octanal, and nonanal are the major compounds formed in oxidized olive oil, but 2-pentenal and 2-heptenal are mainly responsible for the off-flavor.     

Examination of the Modified Villavecchia Test for Detecting Sesame Oil

The official methods of the American Oil Chemists’ Society recommend the modified Villavecchia test Cb 2-40 for detecting sesame oil in animal and vegetable fats and oils. The test is based on the reactivity of sesamol and sesamolin to furfural under acidic conditions. Although the contribution of sesamol and sesamolin to the reaction has been reported, little information is available on how the test performed with oils prepared from different sesame varieties or for effects of roasting conditions of seeds. The objective of this study was to clarify the contribution of various lignans to the Villavecchia test results. Chromogenic products of the Villavecchia test with sesame oil prepared from different varieties of sesame seeds gave different absorbance intensities at 520 nm, and the absorbance intensities were positively correlated with the content of sesamolin in sesame oil. Roasting conditions affected the content and concentration of lignans in sesame oil, and consequently the corresponding chromogenicity of the Villavecchia test. Roasting seeds at 230 °C for 5 min caused a significant loss of sesamolin in oil, the level of sesamol increased, and the absorbance intensity at 520 nm of the corresponding Villavecchia testing product also increased. Roasting seeds at 280 °C for 5 min caused loss of sesamin and the disappearance of sesamolin from the resultant oil, whereas the level of sesamol increased. These results provide guidance for determining the utility of the Villavecchia test for detecting sesame oil in mixtures of other foods.     

Quantitation of flavor volatiles in oxidized soybean oil by dynamic headspace analysis

A dynamic headspace procedure was developed for isolating the volatiles from oxidized soybean oil and trapping them on an adsorbent under conditions that gave minimal decomposition of hydroperoxides (50°C for 30 min at a helium flow of 75 mL/min). The volatiles were desorbed from the adsorbent and separated by gas chromatography (GC) on a methyl silicone capillary column. Equations were derived from theoretical considerations that allowed the actual concentration of each flavor component in the oxidized oil to be calculated from the area of the GC peaks. The reliability of the method and calculations was demonstrated by recovery experiments. The concentration of 2-heptanone in a mineral oil emulsion, equivalent in flavor intensity to each component, was calculated and summed to estimate the overall flavor intensity of the samples. The overall estimations were compared with the concentrations of 2-heptanone observed to be equivalent in flavor intensity to the oxidized oil samples when these were tasted in emulsion. The concentrations of individual components calculated from the headspace volatiles data were all present at concentrations below their flavor thresholds, and the simple sum of the intensities of their flavors generally accounted for less than half of the flavor intensities of the oil samples. The differences in the headspace and sensory analyses might be attributed to the flavor of the unoxidized oil, synergistic interactions, and/or the presence of unmeasured flavors components.     

Influence of roasting conditions on fatty acids and oxidative changes of Robusta coffee oil

The aim of this study was to determine the influence of roasting conditions, including elevated humidity of air used in the process, on the properties of coffee oil. Beans of Robusta coffee were roasted in a laboratory convective roaster with a possibility of changing the temperature, humidity, and velocity of roasting air. Roasting temperatures from 190 to 216°C, air humidity from 0.07 to 1%, and air velocity of 0.5 and 1 m/s were used. Parameters analyzed in roasted beans were: oil content, fatty acids composition, including trans fatty acids using the GC/FID method and indicators of oxidation level, namely peroxide value and content of conjugated dienes and trienes. Also a thermal profile of oil with the use of the DSC method and finally the bean aroma were evaluated. For maintaining the maximal amount of PUFA, the most favorable roasting conditions were, either, roasting at relatively high temperature and short time, or roasting at low temperatures. Using moderately high temperature resulted in the highest oxidative changes, but on the other hand, the aroma of received beans presented the best sensory properties. For the best nutritional properties, the best roasting conditions were: temperature 210°C and 1% humidity content in roasting air at 1 m/s flow velocity. In such conditions roasted beans obtained a very high quality aroma, and the roasting time was relatively short. Practical applications: This research concerns the quality of oil obtained from roasted coffee beans. The composition of coffee oil changes slightly during roasting, but nevertheless it might be a source of peroxides and trans fatty acids in human diet. In industrial processing coffee oil is extracted from the remains left over from instant coffee production, and it is a popular agent for aromatizing food products. Thus, in this kind of processing, roasting conditions that limit the unfavorable changes of coffee oil should be used.     

Oilseed volatile analysis by supercritical fluid and thermal desorption methods

A knowledge of the volatile components present in an oil sample can provide important information relative to supercritical fluid extraction (SFE) process design, the current oxidative state of the oil, as well as the concentration and presence of important flavor volatiles in the oil. Volatile compounds from supercritical fluid-extracted oils were analyzed by headspace gas chromatography (GC) methods to determine if there were differences in the volatile profiles when two different methods of desorption were used. Canola, corn, soybean and sunflower seeds were extracted with supercritical carbon dioxide at 8000 psi and 50°C. Tenax porous polymer traps, attached at the exhaust port of the SFE apparatus, were utilized to collect the volatile components during the extractions. The volatile compounds on the Tenax trap were desorbed onto a GC column by both thermal and supercritical fluid techniques. Desorption temperature for the thermal method was 150°C, while conditions for the SFE technique were 50°C and 2000 psi. The lower-boiling volatiles from each oilseed were greater when desorbed by thermal means from the Tenax than by SFE; however, SFE desorbed the highermolecular weight compounds that were not removed by the thermal desorption method. Hexanal tended to be desorbed in comparable amounts by both methods. The SFE-based desorption technique provides a unique analysis method for the determination of both volatile and semivolatile compounds, as well as executing desorption under nonoxidative, low-temperature conditions that do not contribute to the degradation of lipid components.     

Virgin rapeseed oils obtained from different rape varieties by cold pressed method – their characteristics,properties, and differences

The aim of the present study was to compare different rape varieties. For this purpose oil from six different varieties of rapeseeds was cold pressed under laboratory conditions. In the obtained rapeseed oils the fatty acids composition and minor components, characteristic values (acid value; AV and TOTOX), oxidative stability (DSC test), and volatiles were determined and a sensory evaluation was carried out. The highest oxidative stability was found for oil from sample 5 (IP = 158 min), which also has the lowest amount of C18:3 (7.8%), chlorophylls (0.083 mg/kg), and metals (Cu²⁺ 0.02 mg/kg and Fe²⁺ 0.08 mg/kg). This oil has also the lowest AV (0.17 mg KOH/g), which may be related to the lowest moisture content of the seeds prior to extraction. It was characterized by the highest rapeseed flavor intensity. The lowest induction period was observed for samples 3 and 6 (100 min). Although sample 3 had the same low level of metals as sample 5 and the highest concentration of tocopherols (635 mg/kg), PUFA (33.9%), and AV (1.37 mg KOH/g) it also had the lowest intensity of rapeseed flavor among the analyzed oils. Sample 6, despite its low percentage of PUFA (24.7%), conjugated diens and triens, and the lowest content of total volatiles (0.4Vs), had the highest concentration of metals (Cu²⁺ 0.04 mg/kg and Fe²⁺ 0.34 mg/kg).     

Aqueous Enzymatic Extraction of Oil and Protein Hydrolysates from Roasted Peanut Seeds

To evaluate the effects of the roasting process on the extraction yield and oil quality, peanut seeds were roasted at different temperatures (130–220 °C) for 20 min prior to the aqueous extraction of both oil and protein hydrolysates with Alcalase 2.4 L. Roasting temperatures did not significantly affect the yields of free oil, whereas the temperature of 220 °C led to a reduced recovery of protein hydrolysates. The color and acid values of peanut oils did not change significantly with roasting temperatures. The enzyme-extracted oil with roasting at 190 °C had a relatively low peroxide value, a strong oxidative stability, and the best flavor score. Using the same seed-roasting temperature (190 °C), quality attributes such as color, acid and peroxide values, phosphorus content and oxidative stability of the enzyme-extracted oil were better than those of the oil obtained by an expeller. After the peanut seeds were roasted at 190 °C for 20 min, with a seeds-to-water ratio of 1:5, an enzyme concentration of 2%, and an incubation time of 3 h, the yields of free oil and protein hydrolysates were 78.6 and 80.1%, respectively. After demulsification of the residual emulsion by a freezing and thawing method, the total free oil yield increased to 86–90%.     

Volatile compounds produced during deodorization of soybean oil and their flavor significance

Freshly deodorized soybean oil has a characteristic nutty flavor but often yields no detectable headspace volatiles. The cause of this flavor was investigated by deodorizing soybean oil in an apparatus with a double cold trap that allowed the volatile compounds formed from the initial decomposition of hydroperoxides to be collected separately from those produced during the normal deodorization process. The chief volatile components from the normal deodorization process were hydrocarbons, which contributed little to no odor to the oil. The compounds with the greatest odor were carbonyls, especially heptanal and cis-4-heptenal. Although these components should accumulate at some steady-state concentration in an oil during its deodorization, none seemed to account for the flavor of the deodorized oil. By using a particle detector, it was shown that small particles could be generated in the human mouth that could provide a mechanism to bring oil with nonvolatile flavor components into contact with the olfactory organ. Attempts to separate possible nonvolatile flavors in deodorized oil from triacylglycerides by chromatography on alumina or reaction with 2,4-dinitrophenylhydrazine were unsuccessful. Possibly, the flavor is caused by the glycerol esters themselves.     

Babassu Oil (Orbynia phalerata), an Artisanal Product: Process Optimization of Seed Roasting on Yield,Phenolic Compounds,and Antioxidant Capacity

Babassu oil has high concentrations of phenolic compounds. When seeds are preheated, these compounds tend to migrate to the oil depending on the degree of roasting applied. This study aims to optimize the roasting conditions of babassu seeds using response surface methodology (RSM) and the desirability functions. A central composite rotational design (CCRD) is employed to investigate the effects of two independent variables, temperature (X₁) and roasting time (X₂) which significantly affected response variables, namely yield (%), total phenolics content (TPC), number of phenolic compounds, oxygen radical absorbance capacity, acid value and peroxide value. The quadratic model is adjusted for most responses. The roasting temperature of 222 °C and the roasting time of 43 min are standardized as ideal conditions. Thus, the oil produced at the optimized conditions shows a yield of 54.47% and TPC of 91.53 mg GAE/100 g. In the control oil sample, the presence of phenolic compounds analyzed by HPLC-DAD is not observed while under optimized conditions, seven phenolic compounds are observed. The model of optimized conditions shows a good correlation between the predicted and experimental values. In general, these results demonstrate the effectiveness of optimum roasting conditions in improving the quality of bioactive compounds in babassu oil. Practical Applications : This work aims to optimize the babassu seeds roasting process to obtain oil with a greater number of phenolic compounds and better antioxidant capacity. As the first study on babassu seeds roasting, it contributes to the generation of important data in relation to the identification and quantification of phenolic compounds in the oil. Finally, the optimum roasting conditions established in this work can be explored commercially in babassu oil extraction.     

Volatile compounds produced during deodorization of soybean oil and their flavor significance

Freshly deodorized soybean oil has a characteristic nutty flavor but often yields no detectable headspace volatiles. The cause of this flavor was investigated by deodorizing soybean oil in an apparatus with a double cold trap that allowed the volatile compounds formed from the initial decomposition of hydroperoxides to be collected separately from those produced during the normal deodorization process. The chief volatile components from the normal deodorization process were hydrocarbons, which contributed little to no odor to the oil. The compounds with the greatest odor were carbonyls, especially heptanal and cis-4-heptenal. Although these comonpents should accumulate at some steady-state concentration in an oil during its deodorization, none seemed to account for the flavor of the deodorized oil. By using a particle detector, it was shown that small particles could be generated in the human mouth that could provide a mechanism to bring oil with nonvolatile flavor components into contact with the olfactory organ. Attempts to separate possible nonvolatile flavors in deodorized oil from triacylglycerides by chromatography on alumina or reaction with 2,4-dinitrophenylhydrazine were unsuccessful. Possibly, the flavor is caused by the glycerol esters themselves.     

Various interactions in chocolate flavor

More than 300 volatile compounds have been identified in roasted cocoa beans and its products, making chocolate one of the most complicated natural flavors. Most beans, after harvesting, are subjected to a fermentation that is an important step in the formation of flavor precursors. Roasting is essential to the development of chocolate flavor both with respect to the loss of undesirable volatiles and the generating of key aroma compounds. Flavor is modified to meet demand using blends of beans and through variation in roasting conditions and the mechanical treatments employed to process beans into chocolate liquor and coating. The effect of fermentation and roasting on certain chemical properties related to flavor in chocolate is reviewed. Particular attention is given to monocarbonyls, headspace volatiles, pyrrole aldehydes and alkylpyrazines. One of 13 papers presented in the symposium “Flavor Research in Fats and Fat Bearing Foods,” AOCS Meeting, Atlantic City, October 1971. Presented in part in the symposium “Thermally Produced Flavor Components,” American Chemical Society Meeting, Washington, D.C., September 1971. Paper No. 4135 in the Journal Series of the Pennsylvania Agricultural Experiment Station.     

分子蒸馏处理香料烟浸膏制备烟用香料

为了更好地精制富集烟草特征香味成分,采用分子蒸馏技术对溶剂法制备的香料烟浸膏进行分离,并对馏分进行GC/MS分析。GC/MS结果显示,在不同温度段,香料烟浸膏致香成分得到富集,特别是40～60℃馏分中香料烟重要香味成分茄酮达到了17%。评吸结果显示：原香料烟提取物能增香及提高香气质,但残留明显。经分子蒸馏处理后,40℃以下馏分香气质较好,香气量不足,余味舒适;40～60℃馏分香气质好,丰富烟香,口腔舒适,改善烟气状态;60～80℃馏分增加香气量,舌面口腔有残留;蒸余物则对烟气增香无明显影响。     

Detection of adulteration of sesame and peanut oils via volatiles by GC × GC–TOF/MS coupled with principal components analysis and cluster analysis

The method of headspace coupled with comprehensive two‐dimensional GC–time‐of‐flight MS (HS‐GC × GC–TOF/MS) was applied to differentiate the volatile flavor compounds of three types of pure vegetable oils (sesame oils, peanut oils, and soybean oils) and two types of adulterated oils (sesame oils and peanut oils adulterated with soybean oils). Thirty common volatiles, 14 particular flavors and two particular flavors were identified from the three types of pure oils, from the sesame oils, and from the soybean oils, respectively. Thirty‐one potential markers (variables), which are crucial to the forming of different vegetable oil flavors, were selected from volatiles in different pure and adulterated oils, and they were analyzed using the principal component analysis (PCA) and cluster analysis (CA) approaches. The samples of three types of pure vegetable oil were completely classified using the PCA and CA. In addition, minimum adulteration levels of 5 and 10% can be differentiated in the adulteration of peanut oils and sesame oils with soybean oils, respectively. Practical applications: The objective was to develop one kind of potential differentiated method to distinguish high cost vegetable oils from lower grade and cheaper oils of poorer quality such as soybean oils. The test result in this article is satisfactory in discriminating adulterated oils from pure vegetable oils, and the test method is proved to be effective in analyzing different compounds. Furthermore, the method can also be used to detect other adulterants such as hazelnut oil and rapeseed oil. The method is an important technical support for public health against profit‐driven illegal activities.     

Endogenous antioxidants and stability of sesame oil as affected by processing and storage

The effect of processing of coated and dehulled sesame seeds on the content of endogenous antioxidants, namely sesamin, sesamolin, and γ-tocopherol in hexane-extracted oils, was studied over 35 d of storage under Schaal oven test conditions at 65°C. Seeds examined were Egyptian coated (EC) and dehulled (ED) and Sudanese coated (SC) varieties. Processing conditions of raw (RW) seeds included roasting at 200°C for 20 min (R), steaming at 100°C for 20 min (S), roasting at 200°C for 15 min plus steaming for 7 min (RS) and microwaving at 2450 MHz for 15 min (M). The sesamin content in fresh oils from EC, ED, and SC raw seeds was 649, 610, and 580 mg/100 g oil, respectively. Corresponding values for the content of sesamolin in oils tested were 183, 168 and 349 mg/100 g oil, respectively. Meanwhile, the content of γ-tocopherol, the only tocopherol present in the oils, ranged from 330 to 387 mg/kg sample. The effect of processing on changes in the sesamin content in oils from coated seeds was low and generally did not exceed 20% of the original values. On the other hand, oils from dehulled seeds underwent a more pronounced decrease in their sesamin content than the oil from coated seeds after 35 d of storage at 65°C. The corresponding changes in sesamolin and γ-tocopherol contents were more drastic. The RS treatment, which would be the optimal to prepare sesame oil with better quality, was found to retain 86, 80 and 60% of the sesamin, sesamolin and γ-tocopherol, respectively, originally present in the seeds after the storage period. The loss in the content of endogenous antioxidants present in the oils paralleled an increase in their hexanal content.     

芦柑香精的调配

采用GC/MS联用方法对冷榨芦柑油进行分析,得到57种芦柑油香气成分。对芦柑香韵进行分类,并阐述了芦柑香韵的诸个香原料的香气、运用及调香技巧。通过多次试验得到芦柑香精的6种香韵及其百分含量：果皮香韵0.1%～2%,果髓香韵0.02%～1%,果汁香韵20%～90%,水果香韵0.1%～1%,青香韵0.01%～0.2%,花甜香韵0.1%～1%。由以上6种香韵组成的芦柑香精其香气轻快,果香新鲜清甜,又有成熟的芦柑果皮的香气。     

分子蒸馏技术在烟用香料提取分离中的应用

采用分子蒸馏技术富集烟叶碎片萃取物中的致香物质。通过正交试验优化得到最佳分离条件：压力0.1Pa、温度60℃、转子转速250r·min-1、进料流速70mL·h-1。卷烟加香试验表明：该馏出物能够增补卷烟香气中的清甜香韵,增加香气的透发飘逸感,是一种适宜卷烟加香的理想香精制品。     

磷酸活化焙烧-酸浸法富集低品位还原钛渣

以钒钛磁铁矿经煤基直接还原-电炉熔分工艺生产的钛渣为原料,采用磷酸活化焙烧-稀硫酸浸出方法去除杂质提高钛渣品位. 钛渣的物相包括黑钛石、辉石(玻璃相)、塔基洛夫石、镁铝尖晶石等. 考察了磷酸焙烧活化过程中各因素对钛渣晶型转化的影响及稀硫酸浸出过程中各因素对主要杂质(Ca, Mg, Al, Si)浸出的影响,得到优化的工艺条件为：焙烧温度1273 K,焙烧时间100 min,磷酸加入比例7.1%(w),酸浸温度110℃,硫酸浓度5%(w),液固质量比10:1,浸出时间120 min,在该条件下钛渣中TiO2含量由52.54%提高至68.31%.     

HS-SPME-GC-MS／O分析品牌香皂的特征呈香成分

应用固相微萃取法（SPME）富集结合GC-MS分离检测技术,研究了品牌香皂中的挥发性成分,并采用气相色谱一嗅觉检测（GC一（））技术对品牌香皂中的呈香化合物进行了筛选和鉴定。分析结果表明,HS-SPME-GC-MS与GC-O芳香萃取物稀释分析（AEDA）方法相结合不仅能分析被试样品的组成,还可用来鉴别香皂中呈香化合物的类别、香气强度及各自对总体香气的贡献。