| Sesame paste is a fragrant and nutritious condiment that is often used in cold dishes and hot pots in China and is a favorite among consumers.At present,research on the flavor and quality of sesame paste mainly focuses on the volatile compounds and physical properties;there is little research on aroma compounds,sensory qualities,nutritional component and safety qualities.This study is dedicated to establishing a sensory lexicon of sesame paste,obtaining key aroma compounds of sesame paste,exploring the influence of different hot processing methods on aroma compounds and comprehensive quality of sesame paste,and analyzing the relationship between aroma compounds and sensory attributes.The main research contents and conclusions are as follows:(1)In this study,sensory lexicon for sesame paste were generated based on GB/T 16861-1997 <Identification and Selection of Descriptors for Establishing Sensory Profiles through Multivariate Analysis>,and 233 sensory descriptors for sesame paste were reduced to 85 to form a sensory wheel for sesame paste.Geometric means,correlation analysis,and principal component analysis combined with comments from sensory evaluation panel were used to reduce the number of descriptors to 20.These 20 key sesame paste attributes were defined,reference samples were sought,and intensity values were assigned to establish a glossary of key sensory attributes.By quantitative descriptive analysis of sesame paste with key sensory attributes,the difference in sensory characteristics of sesame paste was obtained at different roasting temperatures and different origins,and the effectiveness of the sensory lexicon of sesame paste was verified.(2)The sesame paste was prepared by roasting the sesame seeds in an electric frying pan under light(150°C),medium(170°C)and deep(190°C)heating conditions for 40 minutes.The aroma compounds of the roasted sesame paste and the raw sesame paste were extracted by simultaneous distillation extraction(SDE),and the extract was analyzed by gas chromatography-olfactometry-mass spectrometry(GC-O-MS)to determine the key aroma compounds of the sesame paste after dilution analysis(AEDA).A total of 50 aroma compounds were identified in sesame paste,and 16 key aroma compounds were found to have an outstanding contribution to the overall flavor of sesame paste.There are six key aroma compounds in raw sesame paste,among which methional(caramel,roasted)and 5-ethyl-2-methyloctane(green)had the greatest effect on the flavor of raw sesame paste.7 key aroma compounds were identified in sesame paste prepared from light-roasted seeds,with methional(caramel,roasted)having the greatest influence on the flavor of sesame paste prepared from light-roasting seeds.8 key aroma compounds were identified in sesame paste prepared from medium-roasting seeds,with benzeneacetaldehyde(floral,green)had the greatest effect on the flavor of sesame paste prepared from medium-roasting seeds.11 key aroma compounds were identified in sesame paste prepared from seeds of deep roasting,among which 3-methylbutanal(bitter coffee)and 2,3-dimethylpyrazine(steamed rice,roasted)had the greatest effect on the flavor of sesame paste prepared from seeds of deep roasting.For the first time,butyl propyl oxalate(yogurt)was identified as a key aroma compound in the preparation of sesame paste at different roasting levels.(3)Sesame paste was prepared by heating sesame seeds at different hot air temperatures(150°C,170°C and 190°C)for 40 min.Solvent-assisted flavor evaporation(SAFE)and headspace solid phase microextraction(HS-SPME)were used to extract the volatile compounds of sesame paste,the aroma compounds of sesame paste were analyzed using GCO-MS,and the effects of hot air heating on the nutritional qualities of crude protein,total sugars,tocopherols and free amino acids,functional components such as sesame lignans and polyphenols,and sensory quality were explored.A total of 27 aroma compounds were identified in sesame paste.Among them,aldehydes and heterocyclic compounds account for the largest proportion.With an increase in temperature,the total concentration of aldehydes aroma compounds showed an increasing trend,giving a grassy and medicinal note to the sesame paste.The heterocyclic aroma compounds were mainly pyrazines,which mainly gave roasted,caramel and steamed rice note of the sesame paste,and their concentrations increased significantly with increasing temperature(p<0.05),which had an important contribution to the overall flavor of the sesame paste.The sensory evaluation results are consistent with the aroma compound analysis results.A total of 15 free amino acids were detected in sesame paste,including 6 essential amino acids.With increasing hot air temperature,the content of free amino acids,total sugars and crude protein decreased,sesamine in sesame lignans was converted to sesamol,the concentration of polyphenolic compounds increased significantly(p<0.05),and the functional quality of sesame paste was improved.(4)Sesame paste was prepared by microwave high-power(720 W)and low-power(360W)heating of sesame seeds for different times(270 s,390 s,510 s).The aroma compounds of sesame paste were extracted by SAFE and analyzed by GC-O-MS,and the relationship between the aroma components and sensory properties of sesame paste was explored by combining the sensory evaluation results,and the effects of microwave heating on the nutritional quality of sesame paste,such as crude protein,total sugar and free amino acids,the safety quality such as heterocyclic amines and polycyclic aromatic hydrocarbons,and functional components such as tocopherols and sesame lignans were explored.The results showed that 36 aroma compounds were identified in sesame paste prepared by microwave heating,including 15 newly identified aroma compounds.The concentration of heterocyclic aroma compounds increased with increasing microwave time,and its concentration and quantity were relatively high.The heterocyclic aroma compounds observed include pyrazines,furans,thiophenes and thiazoles,which mainly gave roasted note to sesame paste.The concentration of ester and alkane compounds first increased and then decreased.The aldehydes mainly presented the flavor of bitter coffee,scallion oil and floral.The sensory evaluation results showed that the over-roasted,burnt bitterness and the burnt aroma of the sesame paste gradually increased with increasing power and time,while the sweet,raw melon seed and green note gradually decreased,which was consistent with the aroma compound analysis results.Total sugar and crude protein content gradually decreases with increasing microwave power and time.17 free amino acids were detected in the preparation of sesame paste by microwave heating,of which 7 were essential amino acids,and their content decreased significantly with increasing microwave time and power(p<0.05).The fatty acid composition did not change significantly.With increasing microwave power and time,sesamolin was transformed into sesamol with stronger antioxidant,and the concentration of γ-tocopherol reached its maximum under appropriate microwave conditions.Benzo [a] pyrene was not detected in all the sesame pastes,and PAH4(benzo [a] anthracene,chrysene and benzo[b] fluoranthene and benzo [a] pyrene combined)were dictated in concentration well below the maximum limit of European Union standard which is set at 10 ng/g.In summary,this study established a sensory lexicon of sesame paste,identified key aroma compounds of sesame paste,and analyzed the effects of hot air heating and microwave heating on the aroma compounds and comprehensive quality of sesame paste,providing a basis for the study of sesame paste sensory lexicon,aroma compounds and comprehensive quality. |
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