Comparison of Tomatillo and Tomato Volatile Compounds in the Headspace by Selected Ion Flow Tube Mass Spectrometry (SIFT-MS)

ABSTRACT: The concentration of 31 volatiles were measured in the headspace of tomatillos using selected ion flow tube-mass spectrometry (SIFT-MS), and were compared with those in vine-ripened tomato, roma tomato, cherry tomato, and grape tomato. None of the volatiles were higher in the headspace of tomatillos than of tomatoes. Compounds (E)-2-octenal, (E)-2-pentenal, 2-isobutylthiazole, 6-methyl-5-hepten-2-one, and phenylacetaldehyde were significantly lower in tomatillo than in the tomato varieties in the headspace. After blending, volatiles in the headspace increased, and then decreased after reaching a maximum concentration, due to further degradation or depletion. Compounds (E)-2-pentenal and 1-penten-3-one reached a maximum concentration later than (E)-2-hexenal, (Z)-3-hexenal, and hexanal for tomatillo and tomatoes. The slope of the ratio of (E)-2-hexenal and (Z)-3-hexenal was not significantly different for any of the samples, implying that the activity of cis/trans isomerase was not different between tomatillos and tomatoes.     

Analysis of Selected Volatile Organic Compounds in Split and Nonsplit Swiss Cheese Samples Using Selected‐Ion Flow Tube Mass Spectrometry (SIFT‐MS)

Splits/cracks are recurring product defects that negatively affect the Swiss cheese industry. Investigations to understand the biophysicochemical aspects of these defects, and thus determine preventive measures against their occurrence, are underway. In this study, selected‐ion, flow tube mass spectrometry was employed to determine the volatile organic compound (VOC) profiles present in the headspace of split compared with nonsplit cheeses. Two sampling methodologies were employed: split compared with nonsplit cheese vat pair blocks; and comparison of blind, eye, and split segments within cheese blocks. The variability in VOC profiles was examined to evaluate the potential biochemical pathway chemistry differences within and between cheese samples. VOC profile inhomogeneity was most evident in cheeses between factories. Evaluation of biochemical pathways leading to the formation of key VOCs differentiating the split from the blind and eye segments within factories indicated release of additional carbon dioxide by‐product. These results suggest a factory‐dependent cause of split formation that could develop from varied fermentation pathways in the blind, eye, and split areas within a cheese block. The variability of VOC profiles within and between factories exhibit varied biochemical fermentation pathways that could conceivably be traced back in the making process to identify parameters responsible for split defect.     

Alkylpyrazines and Other Volatiles in Cocoa Liquors at pH 5 to 8, by Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS)

ABSTRACT:  Cocoa beans were alkalized before or after roasting and made into cocoa liquor before analyzing by SIFT-MS. In both alkalized-before-roasting and alkalized-after-roasting samples, there were significantly higher concentrations of alkylpyrazines for the samples with pH above 7 than pH below 7. At pH 8, the concentrations of 2,3-, 2,5-, and 2,6-dimethylpyrazine (DMP), 2,3,5-trimethylpyrazine (TrMP), 2,3,5,6-tetramethylpyrazine (TMP), and 2,3-diethyl-5-methylpyrazine (EMP) in the samples alkalized-before-roasting were higher than those in the samples alkalized-after-roasting. Volatiles increased under conditions that promoted the Maillard reaction. The partition coefficient was not significantly affected by pH from 5.2 to 8. The ratios of TrMP/DMP and DMP/TMP increased while the ratio of TMP/TrMP decreased as the pH increased. The concentrations of Strecker aldehydes and other volatiles followed a similar pattern as that of the alkylpyrazines. High pH favors the production of alkylpyrazines and Strecker aldehydes.
Practical Applications: Cocoa beans alkalized-before-roasting had higher levels of many important chocolate aroma volatiles than those alkalized-after-roasting. Thus, alkalizing before roasting should produce a stronger cocoa aroma. The higher the pH, the higher the concentrations of these important volatiles. There was little change in volatile concentration at acid pH. Above pH 7, volatile levels increased rapidly with increasing pH. To maintain the recommended ratio of tetramethylpyrazine to trimethylpyrazine, a longer roasting time or higher temperature is needed for cocoa liquor with a pH below 6.5, while a shorter roasting time or lower temperature is needed for cocoa liquor with a pH above 7.     

Application of Selected Ion Flow Tube Mass Spectrometry Coupled with Chemometrics to Study the Effect of Location and Botanical Origin on Volatile Profile of Unifloral American Honeys

Abstract: Ten Ohio and Indiana honey samples from star thistle (Centaurea Americana), blueberry (Vaccinium spp.), clover (Trifolium spp.), cranberry (Vaccinium spp.), wildflower, and an unknown source were collected. The headspace of these honeys was analyzed by selected ion flow tube mass spectrometry and soft independent modeling of class analogy (SIMCA). SIMCA was utilized to statistically differentiate between honeys based on their composition. Ohio honeys from star thistle, blueberry, and clover were similar to each other in volatile composition, while Ohio wildflower honey was different. Indiana honeys from star thistle, blueberry, and wildflower were different from each other in volatile composition, while clover and cranberry honeys were similar. Honeys from Ohio and Indiana with the same floral origins were different in volatile composition. Furfural, 1‐octen‐3‐ol, butanoic, and pentanoic acids were the volatiles with the highest discriminating power between types of floral honey. Methanol and ethanol followed by acetic acid were at the highest levels in most honeys, though furfural was at the highest concentration in Indiana blueberry honey, while 1‐octen‐3‐ol was at the highest concentration in Indiana wildflower honey. The highest concentration of volatile compounds was in Indiana wildflower honey followed by Ohio wildflower honey, while the lowest concentration of volatile compounds was observed in Ohio clover honey followed by Indiana clover honey. Practical Application: Using chemometrics, concentrations of volatile compounds in different honeys can be used to determine the influence of botanical and geographical origins on aroma, which is important for the quality of honey. Characterization of volatile compounds can also be a useful tool for assessing honey quality.     

Discrimination of Swiss Cheese from 5 Different Factories by High Impact Volatile Organic Compound Profiles Determined by Odor Activity Value Using Selected Ion Flow Tube Mass Spectrometry and Odor Threshold

Swiss cheese contains more than 200 volatile organic compounds (VOCs). Gas chromatography‐mass spectrometry has been utilized for the analysis of volatile compounds in food products; however, it is not sensitive enough to measure VOCs directly in the headspace of a food at low concentrations. Selected ion flow tube mass spectrometry (SIFT‐MS) provides a basis for determining the concentrations of VOCs in the head space of the sample in real time at low concentration levels of parts per billion/trillion by volume. Of the Swiss cheese VOCs, relatively few have a major impact on flavor quality. VOCs with odor activity values (OAVs) (concentration/odor threshold) greater than one are considered high‐impact flavor compounds. The objective of this study was to utilize SIFT‐MS concentrations in conjunction with odor threshold values to determine OAVs thereby identifying high‐impact VOCs to use for differentiating Swiss cheese from five factories and identify the factory variability. Seventeen high‐impact VOCs were identified for Swiss cheese based on an OAV greater than one in at least 1 of the 5 Swiss cheese factories. Of these, 2,3‐butanedione was the only compound with significantly different OAVs in all factories; however, cheese from any pair of factories had multiple statistically different compounds based on OAV. Principal component analysis using soft independent modeling of class analogy statistical differentiation plots, with all of the OAVs, showed differentiation between the 5 factories. Overall, Swiss cheese from different factories was determined to have different OAV profiles utilizing SIFT‐MS to determine OAVs of high impact compounds.     

Changes in flavour release from rehydrated: Diced bell peppers (Capsicum annuum) by artificial saliva components in three mouth model systems

The effect of artificial saliva components on flavour release from dehydrated diced red bell peppers (Capsicum annuum) was studied in a mouth model system. This measured the dynamic headspace under oral conditions, such as temperature, volume of the mouth, salivation, and mastication (DHM). The results were compared with a dynamic headspace (DH) and a purge-and-trap (PT) model system. Volatile compounds were analysed by gas chromatography, using flame ionisation detection (FID), mass spectrometry (MS), and sniffing port detection (SPD). SPD revealed that only 12 of the 47 compounds identified by MS and FID possessed odour activity. For all saliva compositions FID peak areas of volatile compounds were largest in the PT system, followed by DHM and DH, respectively. In the PT system the less volatile compounds were relatively better released than other volatile compounds in comparison with the DHM and DH system, for all salivas. The saliva components mucin and α-amylase caused a relative decrease in release of the less volatile compounds in all model systems. An overall decrease in FID peak areas of volatile compounds by the latter components was observed in model system DH only.     

Determination of Volatile and Semivolatile Contaminants in Meat by Supercritical Fluid Extraction/Gas Chromatography/Mass Spectrometry

Meat products that were exposed to a warehouse fire were collected and examined to identify contaminants present in the samples. An extraction method using supercritical carbon dioxide at 100 atm and 60°C was developed to analyse and characterise volatile and semi-volatile compounds from the samples. The major volatile compounds were lipid oxidation products, such as hexanal and nonanal. Volatiles concentrations from fire-exposed meat products were compared to control samples to determine compositional differences. Aromatic and polycyclic aromatic hydrocarbons were identified, and naphthalene was measured in suspected fire-damaged meat products. Direct supercritical extraction from the meat samples proved to be a rapid and reproducible method to assess contamination in commercial meat products.     

Important odorants of sweet bell pepper powder (Capsicum annuum cv. annuum): differences between samples of Hungarian and Morrocan origin

 By application of gas chromatography–olfactometry on aroma extracts prepared from Hungarian sweet bell pepper powder (HBP) and Moroccan sweet bell pepper powder (MBP), 35 and 42 odour-active compounds were detected in the HBP and the MBP, respectively. The identification experiments, in combination with the flavour dilution (FD) factors obtained by application of aroma extract dilution analysis, revealed that β-ionone (violet-like), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (furaneol; caramel-like), 3-hydroxy-4,5-dimethyl-2(5H)-furanone (Sotolon; seasoning-like) and 2- and 3-methylbutanoic acids had the highest odour activities (FD factors of 8192 to 32768) among the 33 odorants that could be identified in the HBP. All odorants identified in the HBP were also characterized as odour-active volatiles in the MBP. The overall different aroma of the Moroccan sample could, however, be attributed to the lower FD factors of the five key odorants mentioned above and, in addition, to the higher FD factors of 10 odorants not present among the aroma compounds of the HBP, e.g. (Z)-1,5-octadien-3-one. In total, 20 odour-active volatiles are reported here for the first time as volatile bell pepper constituents. Received: 30 July 1999 / Revised version: 11 October 1999     

Effects of previous frozen storage on chemical, microbiological and sensory changes during chilled storage of Mediterranean hake (Merluccius merluccius) after thawing

The present work aimed to investigate the influence of freezing (−20 °C for 6 months) on the susceptibility of hake to chemical, microbiological and sensory spoilage once thawed and stored in ice. Thus, volatile and biogenic amines, counts of psychrotrophic and mesophilic bacteria, enterobacteria, pseudomonads and Shewanella together with sensory evaluation (of raw and cooked samples) were monitored during 14 days of iced storage in both fresh and frozen-thawed hake (Merluccius merluccius). At the beginning of ice storage, freshness parameters were equivalent in both batches (fresh and frozen-thawed hake), but different behaviour was observed during the iced storage. Overall, levels of volatile and biogenic amines increased much later and then decreased to lower values in frozen-thawed hake in accordance with the delay of microbial development in comparison with fresh hake. On the contrary, sensory spoilage occurred earlier in frozen-thawed hake. Therefore, the usual accepted or regulated limits of acceptability of chemical and microbiological parameters would not be suitable for freshness assessment of frozen-thawed hake.     

Evaluation of lipid oxidation and oxidative products as affected by pork meat cut, packaging method, and storage time during frozen storage (-10 degrees C)

ABSTRACT:  Lipid oxidation and oxidative volatiles as affected by pork meat cut and packaging method during frozen storage at –10 °C were evaluated. Pork belly cut had higher thiobarbituric acid reactive substance (TBARS) and pH values than did the loin, whereas the loin had higher free fatty acid (FFA) values than that of the belly cut. Peroxide values increased with increased storage time, but were not affected by pork meat cut and packaging method. Volatiles with carbon numbers less than 10 in the belly cut were higher than those in the loin cut, whereas those with carbon numbers greater than 10 in the loin cut were higher than those in belly cut. Most volatiles were decreased with increased storage time, except for propane. Both 4-pentenal and 4-methyl-2-hexanone in the belly cut showed a positive correlation with FFA, whereas 2,4-dimethyl-1-heptene and 9-octadecenal in the loin cut were positively correlated with TBARS and FFA, respectively, even though the values were not high enough to predict the degree of lipid oxidation.     

不同解冻方式对智利竹筴鱼船上冻品贮藏品质的影响

以挥发性盐基氮（TVB-N）、三甲胺氮（TMA-N）、组胺以及硫代巴比妥酸（TBA）含量为指标,研究了不同解冻方式对智利竹筴鱼在-18℃下冻藏6个月品质的变化。结果表明,流水解冻相对于室温解冻和4℃解冻,在TBA和组胺含量上有显著性差异（p<0.05）,而室温解冻和4℃解冻在TVB-N,TMA-N,TBA和组胺上组间差异不显著（p>0.05）。结果表明,4℃解冻对于鱼体品质变化的控制较为理想。      

干辣椒及辣椒粉中罗丹明B含量的调查与分析

目的了解我国市售干辣椒及辣椒粉中罗丹明B的含量状况,分析违法添加罗丹明B的可能性和含量,为提出罗丹明B经济获利水平下添加行为的评判提供数据支持。方法使用随机抽样原则,在餐饮店、食品商店超市和农贸市场,随机采集干辣椒及辣椒粉,采用液相色谱-串联质谱法检测。结果在2 107份样品中,检出罗丹明B72份(干辣椒21份,辣椒粉51份),检测值在0.2×10-3~11.9 mg/kg之间,干辣椒检测值均0.1 mg/kg;辣椒粉中,23份样品检测值0.1 mg/kg,12份样品检测值在0.1~0.5 mg/kg之间,13份样品检测值在0.5~5.0 mg/kg之间,仅3份样品检测值5.0 mg/kg,且农贸市场和散装样品罗丹明B的检出率高。结论市售干辣椒及辣椒粉中存在违法添加罗丹明B的情况,辣椒粉问题为更严重。     

GC-MS结合电子鼻分析1-MCP处理对线椒低温贮藏期挥发性物质的影响

采用顶空固相微萃取-气相色谱-质谱（head space solid-phase microextraction and gas chromatographymass spectrometry,HS-SPME-GC-MS）联用并结合电子鼻技术检测线椒的挥发性成分,研究1-甲基环丙烯（1-methylcyclopropene,1-MCP）处理对线椒在10 ℃贮藏过程中挥发性成分变化的影响。结果表明,HS-SPMEGC-MS方法共检测出52 种挥发性成分,主要为醛类、醇类和酯类物质,1-MCP处理减缓了线椒醛类、酯类、酸类物质相对含量的降低,同时抑制了醇类、烃类以及其他类挥发性物质相对含量的增加,1-MCP处理可以保持线椒良好的挥发性物质成分变化,延缓其风味的改变;用电子鼻对线椒在10 ℃贮藏期间挥发性物质进行主成分分析、负荷加载分析及线性判别分析,结果均表明,1-MCP处理对线椒挥发性物质的影响主要在贮藏期第15～35天,10 ℃贮藏线椒在第15天的挥发性成分相对含量变化较大,是其新鲜度变化的拐点。     

Quality change in Bombay duck (Harpadon nehereus) surimi during frozen storage using different freezing methods

To inhibit the quality deterioration caused by the frozen storage of surimi products, this work investigated the effect of freezing methods, including raw-freezing-setting-heating, raw-setting-freezing-heating, and raw-setting-heating-freezing, on quality changes in surimi gel. The moisture loss, physical–chemical properties, and protein structure conformation of surimi gel derived from Bombay duck (BD) were assessed following frozen storage periods of 20, 40, and 60 days. The findings suggest that the raw-setting-heating-freezing method yielded optimal surimi gel properties with extended frozen storage time. Employing this approach led to a reduction in thawing loss, while cooking loss remained constant. After 60 days of frozen storage, the hardness exhibited an initial increase followed by a subsequent decrease, and water-holding capacity increased to 68.2%. Notably, the impact on surimi gel during the late stage of frozen storage was more pronounced throughout the formation of ice crystals, resulting in decreased disulfide bond content. Scanning hematoxylin–eosin (HE) staining slices of samples following thawing and heating demonstrated that the raw-setting-heating-freezing method could better resist the effect of ice crystals in frozen storage period on surimi tissue, while the gel on setting process could delay the erosion imposed on by ice crystals during frozen storage. This study provides a scientific foundation for the industrialization on frozen BD surimi products.     

Quality changes during the frozen storage of sea bass (Dicentrarchus labrax) muscle after pressure shift freezing and pressure assisted thawing

Quality of frozen sea bass muscle stored (1, 3 and 5 months) at two levels of temperature (−15 and −25 °C) after a pressure shift freezing process (200 MPa) — PSF — and/or a pressure assisted thawing process (200 MPa) — PAT — was evaluated in comparison with samples frozen and thawed using conventional methods (air-blast AF and AT, respectively). Frozen storage of high-pressure treated samples did not significantly affect initial quality of frozen muscle. Thus, parameters related to protein denaturation and extractability, water holding capacity and color presented similar values than those obtained for not stored samples. In addition, the improvement of the microstructure achieved by PSF application remains unchanged during frozen storage. On the other hand, conventional treated samples experienced significant changes during frozen storage, such as protein denaturation, and water holding capacity and color modifications. Storage temperatures did not have influence in the quality of PSF and PAT samples, but it showed some effects in AF muscle.Industrial relevance: This work demonstrates the potential application and benefits of high pressure (HP) in the freezing and thawing of fish meat in comparison to conventional methods, due to an improvement on the cellular integrity of the tissue. Although some negative effects are produced during processing with HP, no additional modifications occur during the frozen storage. The studied methodologies seemed to be very suitable for fish freezing and thawing, especially for products which will be frozen stored and/or cooked.     

Analysis of factors affecting volatile compound formation in roasted pumpkin seeds with selected ion flow tube-mass spectrometry (SIFT-MS) and sensory analysis

Pumpkin (Cucurbita pepo and maxima) seeds are uniquely flavored and commonly consumed as a healthy roasted snack. The objective was to determine dominant volatiles in raw and roasted pumpkin seeds, and the effect of seed coat, moisture content, fatty acid ratio, total lipids, reducing sugars, and harvest year on volatile formation. Sensory was conducted to evaluate overall liking of seed variety and texture. Seed processing included extraction from the fruit, dehydration, and roasting (150 °C). Oil extraction was done using soxhlet, fatty acid profile using Gas Chromatography Flame Ionization Detector, and reducing sugars using 3,5-dinitrosalicylic acid and UV-spectroscopy. Headspace analysis of seeds was performed by selected ion flow tube-mass spectrometry (SIFT-MS). Volatiles dominating in raw pumpkin seeds were lipid aldehydes, ethyl acetate, 2,3-butandione, and dimethylsulfide. Compounds contributing to roasted aroma include alkylpyrazines and Strecker and lipid aldehydes. Overall, hull-less seeds had higher volatile lipid aldehydes and Strecker aldehydes. Seeds dehydrated to a moisture content of 6.5% before roasting had higher initial and final volatile concentrations than seeds starting at 50% moisture. Higher oil content resulted in higher lipid aldehyde formation during roasting with a moderate correlation between free fatty acid ratio and corresponding lipid aldehyde. Harvest year (2009 compared with 2010) had a significant impact on volatile formation in hull-less seeds, but not as much as variety differences. No significant correlation was found between reducing sugars and volatile formation. Sensory showed that hull-less seeds were liked significantly more than hulled seeds. PRACTICAL APPLICATION: Elucidation of aromatic flavor development during roasting with SIFT-MS provides information on flavor release and offers better control during processing. Knowledge of volatiles in raw and roasted pumpkin seeds and effects of seed coat, moisture content, seed composition, and harvest date will allow for better control over the production/storage/transportation process and a more educated decision during selection of a variety for production of pumpkin seeds in the snack food industry.     

鳙鱼鱼糜在冻藏过程中理化性质变化的研究

研究了不同温度冻藏条件下鳙鱼(Aristichthysnobilis)鱼糜的品质变化。鳙鱼鱼糜分别冻藏于-10℃、-20℃和-30℃条件下,冻藏过程中肌原纤维蛋白质Ca2 -ATPase活性和总-SH含量不断下降,冻藏20周后分别下降至新鲜样品的16.9%、64.1%、77.4%和53.1%、60.2%、66.1%,凝胶强度也呈现下降趋势,同Ca2 -ATPase活性和总-SH含量变化相一致。鱼糜微结构表明,不同温度冻藏条件下,鱼肉蛋白质中冰结晶大小有很大差异,冰晶的影响是导致蛋白质变性的主要原因。