Sensor-array-based evaluation and grading of beef taste quality

N,N'-Diphenylthiourea electrochemical sensor for the detection of l-glutamate and Aspartate in beef

This study was conducted to design an electrochemical sensor for detection of l-glutamate (L-Glu) and Aspartate (Asp), which contribute largely to the umami taste of beef. Using N, N'-diphenylthiourea (DPTU), polypyrrole (PPy), and polyvinyl chloride (PVC), a composite electrode (DPTU/PVC/PPy/Pt) was prepared for rapidly electrochemical detection of l-Glu and Asp. The surface morphology of the synthesized functionalized electrode was characterized by Field Emission Scanning Electron Microscopy (FESEM). Potentials of umami amino acids accounted for 97.8%, while six interferential amino acids existed. The linear correlation between the content of l-Glu and Asp in beef broth was studied under different treatment conditions. The sensor compared with an amino acid analyzer well detected the contents of l-Glu and Asp in beef broths, with a coefficient of 0.991 in Pearson correlation analysis and an accuracy of 88.9%. The proposed electrochemical sensor showed good concurrence with previously reported methods and was effectively employed for the quantification of l- Glu and Asp in beef. PRACTICAL APPLICATION: The sensor exhibits the good performance with high stability and high accuracy. And it is a potential sensing platform with good reproducibility, making the proposed method suitable and reliable for routine analysis of L-Glu and Asp in beef. This method was proved promising for quantitative detecting amino acids in beef.

A modified nanocomposite biosensor for quantitative l-glutamate detection in beef

A new biosensor for detecting l-glutamate (l-Glu) in beef was developed. Firstly, a bare Au electrode was surface-modified by gold nanoparticles (Au NPs), graphene oxide (GO), and chitosan (CS) as immobilized materials, and then its surface was connected with l-glutamate oxidase (GluOx). The modified Au NPs/GO/CS electrode was characterized by scanning electron microscopy, and the formation mechanism was elaborated. The response current of the l-Glu biosensor maximized to 0.08 mA at pH 7.5 and 0.09 mA at 30 °C, with a detection range of 0.2-1.4 mM and a detection limit of 0.023 mM. The l-Glu biosensor had high accuracy, and its results linearly fitted with those of the amino acid analyzer with a coefficient of 0.996. The l-Glu biosensor had high selectivity, repeatability, and stability and detected higher l-Glu content in the cooked beef than in the raw beef.

Optimization of beef broth processing technology and isolation and identification of flavor peptides by consecutive chromatography and LC-QTOF-MS/MS

To investigate the flavor peptides of beef broth obtained under optimized stewing conditions, separation procedures such as ultrafiltration, Sephadex G-15 column chromatography, and reversed-phase high-performance liquid chromatography were employed to isolate the umami taste peptides. Sensory evaluation was combined with liquid chromatography-mass spectrometry to detect the flavor peptides. The optimization of the stewing process conditions was studied using the orthogonal method, which indicated that time had the most significant effect on the taste efficiency of sensory evaluation, followed by the mixed spices, sucrose, and salt. The optimized cooking conditions included 3.5 hr of cooking time, 1.800 g of sucrose, 2.125 g of salt, and 1.500 g of mixed spices. The results showed that six peptides, including SDEEVEH, AEVPEVH, GVDNPGHP, GSDGSVGPVGP, SDGSVGPVGP, and DEAGPSIVH, were detected in sample X1M1; and seven peptides, including VAPEEHPT, VVSNPVDIL, VGGNVDYK, PFGNTHN, EAGPSIVHR, VDFDDIQK, and DEAGPSIVH, were detected in sample X2M2. This study compared the flavor peptides in stewed beef before and after the optimization, and thus provided a basis for the improvement of beef processing technology.

Flavor Components Comparison between the Neck Meat of Donkey, Swine, Bovine, and Sheep

Donkey in China is well known for its draft purpose and transportation; however, donkey meat has attracted more and more consumers in recent years, yet it lacks sufficient information on its flavor components compared to other main meats. Therefore, in this study, volatile flavor compounds in neck meat of donkey, swine, bovine, and sheep were classified by electronic nose, then confirmed and quantified by gas chromatography-mass spectrometry. High-performance liquid chromatography (HPLC) and gas chromatography were used to quantify free fatty acid, amino acid, and flavor nucleotide. A total of 73 volatile compounds were identified, and aldehydes were identified as the characteristic flavor compounds in neck meat of donkey, bovine, swine and sheep in proportion of 76.39%, 46.62%, 31.64%, and 35.83%, respectively. Particularly, hexanal was the most abundant volatile flavor. Compared with other neck meat, much higher unsaturated free fatty acids were present in donkeys. Furthermore, neck meat of donkeys showed essential amino acid with highest content. Thus, special flavor and nutrition in donkey neck meat make it probably a candidate for consumers in other regions besides Asia.

Effects of three types of bone marrow extracts treated with different treatment methods on the taste of chicken soup

Bone marrow extracts (BME) are good flavor enhancing substance. Three types of BME (from porcine, chicken and bovine) were treated by enzymatic hydrolysis or Maillard reaction. To explore their effects on soup taste, they were added into chicken and non-chicken soups. The contents of free amino acids, nucleotides, peptides and soluble solids in the soup were measured and the taste activity value and equivalent umami concentration value were calculated, in addition to sensory evaluation. These parameters were weighted according to a certain ratio. Most taste-active substances increased upon enzymatic hydrolysis, while reached their maximum values after Maillard reaction. In addition, the presence of chicken alleviated bitter and fatty tastes in soups added with bone extracts, thus causing the soup to be more flavorful. Sensory evaluation results revealed that umami and kokumi tastes of soups supplemented with Maillard reaction-treated bone marrow extracts were more intense.

A predictive model for the evaluation of flavor attributes of raw and cooked beef based on sensor array analyses

There are currently no standardized objective measures to evaluate beef flavor attributes, especially the comparison between raw beef and cooked beef. Beef flavor attribute is one of the most significant parameters for consumers. This study described a predictive model using a 12-ion-sensor array and sensory properties to evaluate beef flavor attributes based on potential. Then the number of sensors was reduced to six via variance of analysis, and these six sensors were reserved with the saturated calomel reference electrode to constitute a new sensor array. Sensitive flavors of each sensor were selected through multiple comparative analysis. Results showed that the accuracy rate of classifying five basic flavors (acidity, sweetness, bitterness, saltiness, freshness) using the new sensor array was 100%. The processing methods used were based on multivariate statistical methods done with the cluster analysis (CA). Results were compared to sensory evaluation using genetic algorithm (GA). From GA, the accuracy rates of raw and cooked beef were 85.0% and 90.0%, which was consistent with the sensory analysis results. Moreover, reducing the number of sensors could decrease the data dimensionality and detection time. Also raw beef instead of cooked beef could be used in flavor attributes evaluation. This model could become an important method for evaluating beef flavor attributes repeatedly and objectively.

Isolation and identification of the umami peptides from shiitake mushroom by consecutive chromatography and LC-Q-TOF-MS

Umami is critical to the taste of shiitake mushroom. To isolate and identify umami peptides, fractions from hydrolyzed dried shiitake mushroom were separated by ultrafiltration, gel filtration chromatography (GFC), and reversed-phase high-performance liquid chromatography (RP-HPLC). Separations were combined with sensory evaluations (grading and taste dilution analysis) and analysis of electronic tongue, which were used to identify the most umami component in shiitake mushroom. Low-molecular-weight fractions (MW < 3 kDa) have the strongest flavor in the shiitake mushroom hydrolysate. In the 3 subfractions separated from low-molecular-weight fractions (MW < 3 kDa) by GFC, the second subfraction (F2) was selected for RP-HPLC analysis. The first peak (G1) in RP-HPLC was identified by LC-Q-TOF-MS, and 2 tripeptides and 3 dipeptides were identified. The amino acid sequence of these peptides were Gly-Cys-Gly, Glu-Pro-Glu, Cys-Met, Val-Phe, and Gly-Glu.

A PVC/polypyrrole sensor designed for beef taste detection using electrochemical methods and sensory evaluation

An electrochemical sensor for detection of beef taste was designed in this study. This sensor was based on the structure of polyvinyl chloride/polypyrrole (PVC/PPy), which was polymerized onto the surface of a platinum (Pt) electrode to form a Pt-PPy-PVC film. Detecting by electrochemical methods, the sensor was well characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The sensor was applied to detect 10 rib-eye beef samples and the accuracy of the new sensor was validated by sensory evaluation and ion sensor detection. Several cluster analysis methods were used in the study to distinguish the beef samples. According to the obtained results, the designed sensor showed a high degree of association of electrochemical detection and sensory evaluation, which proved a fast and precise sensor for beef taste detection.

Comparison of non-volatile umami components in chicken soup and chicken enzymatic hydrolysate

Umami taste is an important part to the taste of chicken. To isolate and identify non-volatile umami compounds, fractions from chicken soup and hydrolysate were prepared and analyzed. Amino acids were analyzed by amino acid analyzer. Organic acids and nucleotides were determined by ultra-performance liquid chromatography. Separation procedures utilizing ultrafiltration, Sephadex G-15 and reversed-phase high-performance liquid chromatography were used to isolate umami taste peptides. Combined with sensory evaluation and LC-Q-TOF-MS, the amino acid sequences of 12 oligopeptides were determined. The amount of taste compounds was higher in chicken enzymatic hydrolysate than that of chicken soup. Eight oligopeptides from chicken enzymatic hydrolysate were identified, including Ala-Asp, Ala-Met, His-Ser, Val-Glu, Ala-Glu, Asp-Ala-Gly, Glu-Asp and Ala-Glu-Ala. Four oligopeptides from chicken soup were identified, including Val-Thr, Ala-His, Ala-Phe and Thr-Glu.