焙炒时间对芝麻油风味及芝麻氨基酸含量的影响

本文主要研究焙炒时间对芝麻油挥发性风味成分及芝麻中氨基酸含量(以芝麻脱脂粕中氨基酸含量为依据)的影响。经过不同时间焙炒的芝麻,用水代法提油,然后采用顶空固相微萃取(HS-SPME)结合GC/MS技术,检测芝麻油中的挥发性风味成分。随着焙炒时间的延长,吡嗪类、吡咯类、吡啶和嘧啶类、含硫类、呋喃类、酚类物质的相对含量逐渐增多,醛类、醇类、烃类和环氧烃类等物质的含量逐渐减少。对芝麻脱脂粕中18种氨基酸含量的检测数据显示,随着焙炒程度加深,氨基酸含量呈总体下降趋势,其中精氨酸、丝氨酸、赖氨酸和胱氨酸的含量减少明显,这4种氨基酸对芝麻油香味的形成可能起到了重要的作用。     

Effects of roasting conditions of sesame seeds on the oxidative stability of pressed oil during thermal oxidation

Oxidative stability of sesame oil (SO) prepared from sesame seeds roasted at 213, 230, and 247 °C for each 14, 21, or 28 min was determined at 180 °C heating condition by 2,2-diphenyl-1-picrylhydrazyl (DPPH), conjugated dienoic acid (CDA) value, headspace oxygen analysis, and profile changes of sesamol and sesamolin. As sesame seeds were roasted with longer time and higher temperature, more sesamol was found in SO. SO from sesame seeds roasted at 247 °C for 28 min had the highest oxidative stability based on the results of CDA and headspace oxygen. Absorbance of DPPH from SO roasted at 230 and 247 °C showed different patterns compared to those from SO at 213 °C during thermal oxidation. Sesamol was continuously generated with the decrease of sesamolin in SO from 230 to 247 °C while sesamol in SO from 213 °C did not increase during 180 °C heating. Higher oxidative stability of SO may be related with the continuous generation of sesamol from the degradation of sesamolin during thermal oxidation rather than the initial antioxidant content.     

The potential of different techniques for volatile compounds analysis coupled with PCA for the detection of the adulteration of olive oil with hazelnut oil

This paper investigates the effectiveness of three rapid methods of volatile compounds analysis with subsequent principal component analysis (PCA) treatment of data for differentiation between virgin olive oil samples adulterated with hazelnut oil. Tested methods included comparison of chromatograms of volatiles obtained using SPME-fast GC-FID, volatiles analysis by electronic nose based on MOS sensors (HS-Enose), and by direct coupling of SPME to MS (SPME-MS). Volatile compounds were analyzed also by SPME-GC/MS technique. Data obtained as a result of SPME-GC/MS was subjected to PCA. SPME-GC–MS analysis with subsequent PCA yielded good results, however being time consuming. The three methods of analysis of volatiles, with subsequent PCA treatment of data, allowed detection of olive oil adulteration with different contents of hazelnut oil ranging from 5 to 50% (v/v).     

Volatile compounds of black cumin seeds (Nigella sativa L.) from microwave-heating and conventional roasting

The volatile compounds in raw, conventionally roasted and microwave roasted black cumin (Nigella sativa L.) seeds at 0.45 kW for 2, 4, and 8 min, were analyzed by headspace-SPME gas chromatography-mass spectrometry. Among the 38 volatile compounds identified, the major compounds were thymoquinone and p-cymene in all samples. The levels of these compounds decreased with roasting. However, concentrations of pyrazines and furans increased significantly as a result of roasting and these compounds may affect the flavor of roasted black cumin seeds. Methyl pyrazine and 2,5-dimethylpyrazine were major pyrazines, formed at high concentration in seeds roasted for 8 min and in conventional roasting.     

Effects of Roasting Conditions on the Changes of Stable Carbon Isotope Ratios (δ13C) in Sesame Oil and Usefulness of δ13C to Differentiate Blended Sesame Oil from Corn Oil

Abstract: Differentiating blended sesame oils from authentic sesame oil (SO) is a critical step in protecting consumer rights. Stable carbon isotope ratios (δ¹³C), color, fluorescence intensity, and fatty acid profiles were analyzed in SO prepared from sesame seeds with different roasting conditions and in corn oil blended with SO. Sesame seeds were roasted at 175, 200, 225, or 250 °C for 15 or 30 min at each temperature. SO was mixed with corn oil at varying ratios. Roasting conditions ranging from175 to 250 °C at the 30 min time point did not result in significant changes in δ¹³C (P > 0.05). Values of δ¹³C in corn oil and SO from sesame seeds roasted at 250 °C for 15 min were −17.55 and −32.13 ‰, respectively. Fatty acid ratios, including (O + L)/(P × Ln) and (L × L)/O, where O, L, P, and Ln were oleic, linoleic, palmitic, and linolenic acids, respectively, showed good discriminating abilities among the SO blended with corn oil. Therefore, using different combinations of stable carbon isotope ratios and some fatty acid ratios can allow successful differentiation of authentic SO from SO blended with corn oil. Practical Application: Adulteration of sesame oil with less expensive oils such as corn oil or soybean oil to reduce cost is a common unethical practice in Korea. Due to the unique and strong flavor of sesame oils that may mask other weaker flavors, however, differentiating authentic sesame oils from blended oils is difficult. This study showed that the roasting process did not significantly affect the ratios of the stable carbon isotope (δ¹³C) in sesame oils. δ¹³C was confirmed to be a reliable parameter. Moreover, some fatty acid ratios were designed to discriminate between blended sesame oil with corn oil and authentic sesame oil.     

辣椒籽油的制备及其挥发性香味物质的研究

利用亚临界低温萃取技术对经过炒制前处理的辣椒籽进行萃取制备得到辣椒籽油,并采用同时蒸馏结合GC-MS法,分析了不同的炒制温度(120~200℃)和炒制时间(5~25 min)对辣椒籽油中的挥发性成分和脂肪酸成分的影响。在炒制时间为5 min,炒制温度低于140℃时,芳樟醇、月桂烯、双戊烯是辣椒籽油的主要香气物质,当温度高于140℃时,吡嗪类化合物和2-戊基呋喃是辣椒籽油的主要香气物质。在炒制温度为140℃,炒制时间为5 min时,辣椒籽油中的芳樟醇、月桂烯、双戊烯的含量分别达到最大值,随着炒制时间的增加,辣椒籽油中的2,3,5,6-甲基四吡嗪和2-戊基呋喃的含量在20 min时达到了最大值。辣椒籽油中主要的脂肪酸成分是棕榈酸(11.57%)、油酸(76.16%)和亚油酸(7.14%)。     

Effects of roasting conditions on the physicochemical properties and volatile distribution in perilla oils (Perilla frutescens var. japonica)

Abstract: Perilla seeds have more than 60% of α‐linolenic acid, one of omega‐3 essential fatty acids. Headspace volatiles and physicochemical properties including color, fluorescence intensity, and the oxidation products in perilla oil (PO) from perilla seeds roasted at different conditions were analyzed. Roasting temperature was 150, 170, 190, and 210 °C, and roasting time was 15 and 30 min at each roasting temperature. PO from higher roasting temperature and longer roasting time had lower L* values, higher a*, b*, and chroma values, more brown pigments and fluorescence intensity, and more conjugated dienoic acids. Pyrazines were major volatiles in PO, and furans, sulfur‐containing compounds, and hydrocarbons were also detected by a solid phase microextraction gas chromatography/mass spectrometry. In PO, 2,5‐Dimethylpyrazine and 2‐furancarboxaldehyde were 2 major volatiles. The principal component analysis of volatiles showed the 1st principal component (PC1) and the 2nd principal component (PC2) express 56.64% and 22.72% of the volatile variability in PO, respectively, which can differentiate PO prepared from roasting conditions clearly. Some physicochemical properties especially brown pigment and volatiles were positively correlated with each other in PO. Practical Application: Perilla oil (PO) from perilla seeds possesses more than 60% of α‐linolenic acid, one of omega‐3 fatty acids. Roasting process has been used to extract oil from perilla seeds. Understanding physicochemical properties of PO from diverse roasting conditions are important steps to produce PO in food industry. Roasting process induces darkening of color, increase of fluorescence intensity, and brown pigments in PO. Pyrazines and furans are major headspace volatiles in PO roasted above 170 °C. The results of this study can help to produce PO in industrial scales with desired headspace volatiles, colors, and oxidative state.     

Volatile distribution in garlic (Allium sativum L.) by solid phase microextraction (SPME) with different processing conditions

Treatments of autoclaving, high temperature aging (aged-black garlic), crushing, and roasting at 100, 150, and 200°C were applied to alter the volatile profiles of garlic (Allium sativum L.). Headspace volatiles in samples were analyzed by a solid phase microextraction (SPME)-GC/MS. Total peak areas of crushed-raw garlic were the highest and those of aged-black garlic clove were the lowest. Crushing effects were clearly observed in raw garlic, aged-black garlic, and roasted garlic at 200°C for 60 min. Sulfur-containing volatiles including diallyl disulfide and diallyl trisulfide were major volatiles. Generally, peak areas of diallyl disulfide decreased when garlic received autoclaving and roasting treatment while diallyl trisulfide and allyl methyl trisulfide increased during heat treatment compared to raw garlic. Roasting at 200°C for 60 min caused the formation of pyrazines greatly in garlic. Principal component analysis (PCA) for the volatile profiles by SPME-GC/MS could discriminate types of processed garlic successfully.     

Changes in volatile compounds of peanut oil during the roasting process for production of aromatic roasted peanut oil

The changes in volatile compounds composition of peanut oil during the roasting process of aromatic roasted peanut oil (ARPO) production were investigated. The analyses were performed by gas chromatography-mass spectrometry combined with headspace solid phase microextraction (HS-SPME/GC-MS). Among the volatiles identified in ARPO, the N-heterocyclic chemical class possessed the highest relative percentage area (RPA) 61.68%, followed by O-heterocyclic group with an RPA of 24.57%. Twenty pyrazines were considered to be the key contributors to the intense nutty/roasty flavor typical of ARPO. Compounds that increased significantly in concentration during the roasting process were mainly Maillard reaction products, as well as compounds derived from Strecker degradation and lipid peroxidation. The results clearly showed that the roasting process was necessary to obtain the typical nutty/roasty aroma of ARPO. PRACTICAL APPLICATION: ARPO is the traditional edible oil in China that possesses a characteristic strong nutty and roasty flavor that distinguishes it from other edible vegetable oils. During the production, the roasting process is the crucial factor for the formation of the typical roasted peanut aroma that plays an important role in sensory quality of peanut oil. In our investigation, not only the volatile changes of peanut oil pressed from relevant peanut seeds roasted at different roasting time were determined, but also the contributions of identified volatiles on the typical nutty/roasty flavor of ARPO were discussed. Our work clearly demonstrated the significant effect of roasting process on the typical flavor formation of ARPO. The results are valuable as scientific guidance for the roasting process that better satisfy demands of the peanut oil industries for better flavor.     

不同热加工方式芝麻酱风味物质的差异

利用电子鼻(E-nose)和顶空固相微萃取结合气-质联用(SPME-GC-MS)分别对炒制、烤制、微波三种热加工方式下的芝麻酱挥发性风味物质测定分析,以筛选最适宜的芝麻酱热加工工艺。结果表明,电子鼻能够较好的区分出三种加工方式制成的芝麻酱,SPME-GC-MS分析得出,芝麻酱的风味物质主要为吡嗪类、醛类、呋喃类、醇类物质,其中吡嗪类物质在微波方式下含量最高达31.09%,炒制和烤制含量分别为:14.97%和24.36%;醛类则在炒制芝麻酱中含量最高达17.17%;此外醇类物质在三种加工方式下含量都较高,均大于30%。研究表明,运用E-nose和SPME-GC-MS能够较好的分析不同热加工方式下芝麻酱挥发性风味物质的变化,微波加热制成的芝麻酱主要挥发性香味物质种类和含量更高。     

Determining degree of roasting in cocoa beans by artificial neural network (ANN)‐based electronic nose system and gas chromatography/mass spectrometry (GC/MS)

BACKGROUND

Roasting is a critical step in chocolate processing, where moisture content is decreased and unique flavors and texture are developed. The determination of the degree of roasting in cocoa beans is important to ensure the quality of chocolate. Determining the degree of roasting relies on human specialists or sophisticated chemical analyses that are inaccessible to small manufacturers and farmers. In this study, an electronic nose system was constructed consisting of an array of gas sensors and used to detect volatiles emanating from cocoa beans roasted for 0, 20, 30 and 40 min. The several signals were used to train a three‐layer artificial neural network (ANN). Headspace samples were also analyzed by gas chromatography/mass spectrometry (GC/MS), with 23 select volatiles used to train a separate ANN.

RESULTS

Both ANNs were used to predict the degree of roasting of cocoa beans. The electronic nose had a prediction accuracy of 94.4% using signals from sensors TGS 813, 826, 822, 830, 830, 2620, 2602 and 2610. In comparison, the GC/MS predicted the degree of roasting with an accuracy of 95.8%.

CONCLUSION

The electronic nose system is able to predict the extent of roasting, as well as a more sophisticated approach using GC/MS. © 2018 Society of Chemical Industry     

Effect of Infrared Heating on the Formation of Sesamol and Quality of Defatted Flours from Sesamum indicum L.

ABSTRACT:  Infrared (IR) heating offers several advantages over conventional heating in terms of heat transfer efficiency, compactness of equipment, and quality of the products. Roasting of sesame seeds degrades the lignan sesamolin to sesamol, which increases the oxidative stability of sesame oil synergistically with tocopherols. IR (near infrared, 1.1 to 1.3 μm, 6 kW power) roasting conditions were optimized for the conversion of sesamolin to sesamol. The resultant oil was evaluated for sesamol and tocopherol content as well as oxidative stability. The defatted flours were evaluated for their nutritional content and functionality. IR roasting of sesame seeds at 200 °C for 30 min increased the efficiency of conversion of sesamolin to sesamol (51% to 82%) compared to conventional heating. The γ-tocopherol content decreased by 17% and 25% in oils treated at 200 and 220 °C for 30 min, respectively. There were no significant differences in the tocopherol content and oxidative stability of the oil. Methionine and cysteine content of the flours remained unchanged due to roasting. The functional properties of defatted flours obtained from either IR roasted or conventionally roasted sesame seeds remained the same.
Practical Applications: Sesame oil is stable to oxidation compared to other vegetable oils. This stability can be attributed to the presence of tocopherols and the formation of sesamol, the thermal degradation product of sesamolin—a lignan present in sesame. Roasting of sesame seeds before oil extraction increases sesamol content which is a more potent antioxidant than the parent molecule. The conversion efficiency of sesamolin to sesamol is increased by 31% by infrared roasting of seeds compared to electric drum roasting. This can be used industrially to obtain roasted oil with greater oxidative stability.     

微波预处理对芝麻油风味、营养和安全品质的影响

本实验系统研究微波预处理对芝麻油风味、感官、营养和安全品质的影响,旨在为微波产香技术在芝麻油中的应用提供理论参考。芝麻籽经不同功率（0、180、360、540、720 W和900 W）微波预处理6 min,再经液压压榨制得芝麻油。利用溶剂辅助风味蒸发、顶空固相微萃取结合气相色谱-质谱-嗅闻技术在芝麻油中鉴定出91 种香气活性物质。芝麻油的杂环类气味物质（吡嗪、吡咯、吡啶、噻唑、噻吩和呋喃）总含量与微波功率呈正相关,羰基类气味物质（醛、酮和酯类）总含量随着微波功率的增大先升高后降低。随着微波功率的增大,芝麻油的烤芝麻味、坚果味、焦糊味、烟熏味和苦味感官强度逐渐增强,土腥味、木质味和生青味强度持续减弱。微波预处理芝麻籽的出油率（30.02%～31.93%）与功率呈正相关,显著高于生芝麻籽（24.89%）。微波预处理提高了芝麻粕的氮溶解指数（nitrogen solubility index,NSI）（由11.7%升至18.07%）和芝麻油中生育酚含量（由392.18 mg/kg增至462.92 mg/kg）,且最高NSI和生育酚含量分别出现在540 W和700 W微波预处理后。芝麻油中芝麻酚（13.01～15.78 mg/100 g）、杂环胺（33.19～143.88 ng/g）和多环芳烃（0.40～9.03 ng/g）的含量与微波功率呈正相关,其中多环芳烃和杂环胺的含量均未超过国家标准限量。综上所述,适度的微波预处理可以赋予芝麻油浓郁的香气,提高芝麻油的营养成分含量和氧化稳定性,同时提高芝麻粕蛋白的利用价值。因此,微波作为一种新型产香技术在芝麻油加工和芝麻粕蛋白的高值化利用中具有明显的优势和良好的应用前景。     

Effect of roasting conditions on color and volatile profile including HMF level in sweet almonds (Prunus dulcis)

Microwave, oven, and oil roasting of almonds were used to promote almond flavor and color formation. Raw pasteurized almonds were roasted in a microwave for 1 to 3 min, in an oven at 177 °C for 5, 10, 15, and 20 min; and at 135 and 163 °C for 20 min, and in oil at 135, 163, and 177 °C for 5 min and 177 °C for 10 min. Volatile compounds were quantified in the headspace of ground almonds, both raw and roasted, by selected ion flow tube mass spectrometry. Strong correlations were found between L value, chroma, and 5-(hydroxy methyl)-2- furfural; and were independent of roasting method. Raw almonds had lower concentrations of most volatiles than roasted almonds. Conditions that produced color equivalent to commercial samples were 2 min in the microwave, 5 min at 177 °C in the oven, and 5 min at 135 °C in oil. Microwave heating produced higher levels of most volatiles than oven and oil roasting at commercial color. Sensory evaluation indicated that microwave-roasted almonds had the strongest aroma and were the most preferred. Oil-roasted almonds showed significantly lower levels of volatiles than other methods, likely due to loss of these volatiles into the oil. Alcohols such as benzyl alcohols and strecker aldehydes including benzaldehyde and methional were at higher concentrations than other volatiles in roasted almonds. The oxidation of lipids to form alkanals such as nonanal and degradation of sugars to form furan type compounds was also observed. The Maillard reaction contributed to the formation of more of the total volatiles in almonds than the lipid oxidation reaction. PRACTICAL APPLICATION: The level of 5-(hydroxy methyl)-2- furfural (HMF), color, volatile profile, and sensory perception can be used to develop the best roasting method, time, and temperature for almonds. The rate of color development and the production of volatiles differ under different roasting conditions. Based on the color, volatile, and sensory assessments of the 3 almonds, the use of microwave technology as a process for roasting almonds reduces processing time and leads to an almond product with better flavor than oven or oil roasting.     

Effect of roasting on colour and volatile composition of pistachios (Pistacia vera L.)

Pistachios have been roasted following the Iranian traditional method (soaking in salty water, drying and roasting at 135 °C). Three Iranian pistachio cultivars (Ahmad Aghaei, Akbari and Kaleghouchi) were compared for their volatile compositions, colour and odour intensity. Lightness decreased in the course of roasting, which resulted from Maillard reaction. Raw pistachios had lower concentrations of most volatiles than roasted. A total of twenty‐six compounds were detected in roasted pistachios; these included aldehydes, terpenes, alcohols and only two pyrazines and one furan. These mixtures of volatiles implied that the Iranian roasting system is very soft, and samples retained most of the vegetable notes from fresh pistachios and some roasted notes were generated as well (from 2‐ethyl‐5‐methylpyrazine and 2,6‐dimethyl‐3‐ethylpyrazine). Sample from cultivar Akbari presented higher odour intensity than those by the other two cultivars, due mainly to higher concentrations of pyrazines developed during the roasting step.     

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.     

Effect of roasting method and oil reduction on volatiles of roasted Pistacia terebinthus using direct thermal desorption-GCxGC-TOF/MS

Pistacia terebinthus fruit was roasted by either the traditional pan-roasting method or by coupled convection-microwave oven roasting (at two different settings). Cold pressing to reduce the oil content was carried out on samples either before or after the various roasting processes. Oil content of all samples was reduced to approximately 21.8 g/100 g by cold pressing. This allowed the grinding of the roasted fruit into powder form. The volatile compounds of these samples were investigated using direct thermal desorption coupled with gas chromatography. The main compounds found in all samples were acetic acid, limonene, α-pinene, β-pinene, 2-carene and δ-muurolene. Removal of oil was seen to decrease the number of volatile compounds found in roasted fruit (irrespective of roasting method) when compared with previous studies. Compounds specifically relating to coffee aroma (pyrazines, furans and furanones) were seen to be increased when cold pressing was carried out before the roasting process rather than afterwards.     

Characterization of Turkish-Style Boiled Coffee Aroma by Gas Chromatography and Mass Spectrometry and Descriptive Analysis Techniques

The characteristic volatiles of light, medium, and dark roasted Turkish-style boiled coffee brews were studied by headspace solid-phase micro extraction/gas chromatography-mass spectrometry and sensory flavor profile analysis. Sixty-five volatile compounds, including furans, pyrazines, pyrroles, phenols, pyridines, ketones, oximes, alcohols, aldehydes, thiophenes, benzenes, and terpenes, were isolated from Turkish-style boiled coffee samples. The flavor profile analysis showed Turkish coffee brews as roasted/burnt, spicy, bitter, acidic, sweet, salty, astringent (dry), woody, fermented, earthy, and tobacco-like flavor characteristics. It was concluded that Turkish coffee was rich in furans, pyrazines, pyrroles, and phenols giving its roasted/burnt, spicy, woody, and fermented flavor characteristics.     

Monitoring of cocoa volatiles produced during roasting by selected ion flow tube-mass spectrometry (SIFT-MS)

Selected ion flow tube-mass spectrometry (SIFT-MS) was used to measure the real-time concentrations of cocoa volatiles in the headspace during roasting. Alkalized and unalkalized Don Homero and Arriba cocoa beans were roasted at 120, 150, and 170 °C in a rotary roaster. The concentrations of total alcohols, acids, aldehydes, esters, ketones, and alkylpyrazines increased, peaked, and decreased within the timeframe used for typical roasting. The concentrations of alkylpyrazines and Strecker aldehydes increased as the roasting temperature increased from 120 to 170 °C. For most of the volatile compounds, there was no significant difference between Arriba and Don Homero beans, but Arriba beans showed higher concentrations of 2-heptanone, acetone, ethyl acetate, methylbutanal, phenylacetaldehyde, and trimethylpyrazine. For unalkalized Don Homero beans (pH 5.7), the time to peak concentration decreased from 13.5 to 7.4 min for pyrazines, and from 12.7 to 7.4 min for aldehydes as the roasting temperature increased from 120 to 170 °C. Also, at 150 °C roasting, the time to peak concentration was shortened from 9 to 5.1 min for pyrazines, and from 9.1 to 5 min for aldehydes as the pH increased from 5.7 to 8.7. PRACTICAL APPLICATION: SIFT-MS allows for real-time monitoring of the key volatile compounds contributing to chocolate flavor, with minimal sample preparation, thus can be used to facilitate adjusting the roasting conditions, such as temperature and time, to optimize chocolate flavor during roasting. Real-time monitoring during roasting can also be used to evaluate the flavor quality of different types of beans by comparing the concentrations of key flavor compounds.     

Contribution of coffee proteins to roasted coffee volatiles in a model system

A simple roasting model using a mineral oil bath was set up to study the effects of coffee proteins on the formation of coffee volatiles during roasting. Green coffee powder was separated into four fractions, and the highest concentration of volatile compounds was observed in the roasted sample of the water extract fraction. Sugar degradation products were the dominant compounds. The addition of coffee proteins into the nonprotein water extract fraction catalysed sugar degradation and enhanced the production of selected volatiles. Higher amounts of coffee protein correlated with the concentration of pyrazines. Coffee protein also increased sucrose degradation in the roasting of sucrose with coffee protein. However, the results from colour measurements indicated that a greater amount of protein produced a lighter colour. These results demonstrated the important contribution of coffee proteins in the formation of coffee volatiles and colour.