Shiqing Song

Rapid measuring and modelling flavour quality changes of oxidised chicken fat by electronic nose profiles through the partial least squares regression analysis.

The objective of this study was to investigate whether an electronic nose, comprising 18 metal oxide semiconductor gas sensors, could be used for measuring and modelling flavour quality changes of refined chicken fat during controlled oxidation. Partial least squares regression (PLSR) was applied to determine the predictive relationships between the chemical parameters, GC-MS data, free fatty acid profiles and electronic nose responses for controlled oxidation of refined chicken fat. The results showed that peroxide value (PV) and acid value (AV) were significantly well predicted by the electronic nose responses, whereas p-anisidine value (p-AV) was found to be fairly well predicted especially for deeply oxidised chicken fat. Thus, this study gave evidence of the electronic nose system to be a promising device for future at- or on-line implementation in oxidation control of chicken fat for producing meat flavourings.

Effect of enzymatic hydrolysis with subsequent mild thermal oxidation of tallow on precursor formation and sensory profiles of beef flavours assessed by partial least squares regression.

Effects of different pretreatments of tallow on flavour precursor development and flavour profiles of beef flavours (BFs) were evaluated. Analysis of free fatty acids and volatiles of tallow by GC and GC-MS indicated that the enzymatic hydrolyzed-thermally oxidized tallow formed the most characteristic flavour precursors compared with others. The results of descriptive sensory analysis confirmed that beef flavour 4 from enzymatic hydrolyzed-thermally oxidized tallow had the strongest beefy, meaty and odour characteristics, followed by beef flavour 2 from oxidized tallow. Electronic nose data confirmed the accuracy of the sensory analysis results. The correlation analysis of 51 volatile compounds in tallow and sensory attributes of BFs showed that some compounds, especially aldehydes, made a significant contribution to sensory attributes. Correlation analysis of free fatty acids and sensory attributes through partial least squares regression (PLSR) confirmed that the moderate enzymatic hydrolysis-thermal oxidation pretreatment of tallow was necessary to achieve the characteristic beef flavour.

A novel method for beef bone protein extraction by lipase-pretreatment and its application in the Maillard reaction

Five beef bone hydrolysates were obtained by different enzyme treatment schemes, including papain (M), combination of porcine pancreatic lipase and papain (Z+M, combination of lipase and papain (Y+M), Protamex (F), combination of porcine pancreatic lipase and Protamex (Z+F). The degree of hydrolysis (DH), free amino acids and molecular weight distribution of these hydrolysates were evaluated. To further explore the differences between these five hydrolysates, Maillard reaction products (MRPs) were prepared using a xylose/cysteine/hydrolysate model. It was found that the DH, content of low molecular weight peptides and amino acids of hydrolysates increased significantly after lipase pre-treatment. GC-MS showed that the total content of furans, pyrroles and thioethers in MRPs Y+M increased by 78.0% compared with MRPs M, while in MRPs Z+F, pyrazines increased by 44.1% compared with MRPs F. Examining the sensory characteristics of the MRPs, the MRP from the hydrolysate of Y+M had the best mouthful, umami and meaty characteristics. The correlation analysis further confirmed that an appropriate lipase pre-treatment could improve the flavour of MRPs.

Development of a solid phase microextraction protocol for the GC-MS determination of volatile off-flavour compounds from citral degradation in oil-in-water emulsions.

The conditions for headspace solid phase microextraction (HS-SPME) analysis of volatile off-flavour compounds in citral emulsion were determined. Type of SPME phase (65 μm PDMS/DVB, 100 μm PDMS and 75μm CAR/PDMS), adsorption temperature and salt concentration were significant factors affecting total peak area in the gas chromatogram and optimised in one factor experiments. Then, adsorption temperature (30-50°C), adsorption time (20-40 min), and salt concentration (0-6M) were studied to develop HS-SPME condition for obtaining the highest extraction efficiency. PDMS/DVB in 65 μm was the optimum fiber because of high adsorption efficiency and good reproducibility. The optimal condition was adsorption at 50°C for 40 min and 6M salt added to sample. Good Linearity, high recovery, good reproducibility and low limit of detection (LOD) for all off-odour compounds according to the optimised SPME conditions indicated that the SPME procedure was applicable for the analysis of the degraded citral products in headspace volatile of emulsion.

Tobacco alkaloids reduction by casings added/enzymatic hydrolysis treatments assessed through PLSR analysis

Based on encouraged development of potential reduced-exposure products (PREPs) by the US Institute of Medicine, casings (glucose and peptides) added treatments (CAT) and enzymatic (protease and xylanase) hydrolysis treatments (EHT) were developed to study their effect on alkaloids reduction in tobacco and cigarette mainstream smoke (MS) and further investigate the correlation between sensory attributes and alkaloids. Results showed that the developed treatments reduced nicotine by 14.5% and 24.4% in tobacco and cigarette MS, respectively, indicating that both CAT and EHT are potentially effective for developing lower-risk cigarettes. Sensory and electronic nose analysis confirmed the significant influence of treatments on sensory and cigarette MS components. PLSR analysis demonstrated that tobacco alkaloids were positively correlated to the off-taste, irritation and impact attributes, and negatively correlated to the aroma and softness attributes. Additionally, nicotine and anabasine from tobacco leaves positively contributed to the impact attribute, while they negatively contributed to the aroma attribute (P<0.05). Meanwhile, most alkaloids in cigarette MS positively contributed to the impact and irritation attributes (P<0.05). Hence, this study paved a way to better understand the correlation between tobacco alkaloids and sensory attributes.

Comparison of Intensities and Binary Interactions of Four Basic Tastes between an Electronic Tongue and a Human Tongue

For detection of single taste intensities and binary interactions using an electronic tongue (E-tongue) and the human tongue (H-tongue), the 4 basic flavor substances of sucrose, caffeine, citric acid, and sodium chloride were used. A linear fit was performed using response values of the E-tongue and concentrations of the basic tastes. The taste intensity of the E-tongue was positively correlated with sour and salty substances, but negatively correlated with sweet and bitter substances. All taste intensities were positively correlated with the 4 flavor substances using the H-tongue. A mathematical model of the 4 taste substances on both the E-tongue and H-tongue exhibited a semi-logarithmic form. There were synergistic, dampening, or offset effects on the taste intensity of each flavor substance in binary systems. H-tongue and E-tongue results were consistent for sweet/bitter and salt/sour interactions. H-tongue and E-tongue results were contradictory for salt/sweet and sweet/sour interactions.

Identification of aroma types and their characteristic volatile compounds of Chinese faint-scent cigarettes based on descriptive sensory analysis and GC–MS and partial least squares regression

Abstract To characterize the aroma types of Chinese faint-scent cigarettes, eight different Chinese cigarette brands were characterized by quantitative descriptive sensory analysis and gas chromatography–mass spectrometry (GC–MS). The results showed that the aromatic faint-scent type was related to freshness, flowery and acidic notes. One hundred and fourteen volatile compounds were detected in the mainstream smoke by GC–MS, and 67 of them were selected as specific compounds correlated to aroma types of faint-scent by partial least squares regression. The correlation results indicated that freshness note was significantly positive correlated to 2,3-dimethyl-2-cyclopenten-1-one (B) and megastigmatrienone (B), while methyl hexadecanoate, palmitic acid ethyl ester, megastigmatrienone (A, C), 4-tert-butyl-2,6-dimethylacetophenone, furfuryl alcohol and oleic acid showed significantly negative correlation to it; acidic note showed significantly negative correlation to furfuryl formate, 3-methyl-2-cyclopenten-1-one, furfuryl alcohol, oleic acid and 5-methyl furfural; flowery note was significantly positively correlated with crotonic acid, while it was negatively correlated to palmitic acid ethyl ester and megastigmatrienone (A).

Multi-analysis of Odorous Compounds in Finger Citron (Citrus medica L. var. sarcodactylis Swingle) and Certification of Key Compounds

Abstract Up to date, researches on finger citron (Citrus medica L. var. sarcodactylis Swingle) odorous compounds were mostly based on its essential oil. However odor is subject to be influenced at the process of extracting, which indicates that odorous analysis on fresh finger citron is necessary. Odorous compounds in pulp and skin of finger citron were respectively analyzed by headspace solid-phase micro-extraction (HS-SPME) and purge and trap (P&T) with Tenax TA absorbent. There were 44 and 45 odorous compounds detected from flesh (A) and peel (B) of Jinghua finger citron (JFC) by gas chromatography-mass spectrometry (GC-MS) respectively. The results showed that P&T method and HS-SPME could be used complementarily in identification of odorous compounds in finger citron. Otherwise, there were 43 and 40 odorous compounds with high similarity extracted by HS-SPME detected from A and B by comprehensive two-dimensional gas chromatography combined with quadrupole-mass spectrometry (GC×GC-qMS) respectively. Additionally, there are 23 odorous compounds with odor activity value (OAV) > 1. And major contributors to JFC aroma were identified as limonene, α-pinene, β-pinene, myrcene, γ-terpinene, β-phellandrene, terpinolene, ethyl octanoate, linalool, geraniol, citral, leaf alcohol, citronellol etc. by partial least squares regression (PLSR).