Abstract:Pummelo (Citrus maxima) is one of the major native species of citrus, of which the skin peel contains a rich amount of essential oil (EO) in its flavedo part. EO could be extracted by using cold pressing, water distillation, simultaneously distillation and extraction (SDE), solvent-assisted fluid extraction (SAFE), and super critical fluid extraction of carbon dioxide (SFE-CO₂). Among these extraction methods, EO, prepared by the cold pressing, possesses the best aroma close to the natural pummelo aroma. Sensory evaluation, gas chromatograph (GC), GC-mass spectrometer (MS), GC-olfactory (O), and electronic nose have been used to analyze the pummelo EO. Albeit high resolution mass spectrometer and time of flight mass spectrometry have not been applied yet. Pummelo EO is mainly composed of terpenes and terpenoids, plus a small amount of aldehydes, alcohols, and esters. Particularly, the beta-myrcene content in the pummelo EO is higher than that in other citrus EOs. In addition, EO from different pummelo species has different aromatic profiles. The aroma profile of GuanXi pummelo EO is dominated by green, lemon,and fruit notes while LiangPing pummelo EO has a strong aroma of citrus and sweet note. Meanwhile, Shatian pummelo EO has a strong minty note. It is known that environmental factors, including sunlight, storage temperature, and oxygen have significant effects on the composition of EO and remarkable impact on its aroma profile. In particular, UV-irradiation is the major factor causing the irreversible deterioration to the pummelo quality. Pummelo EO has shown many valuable applications in pharmaceutical, food, and cosmetics industries. Thus, pummelo EO is worthy to be studied in more depth.

Abstract:Zanthoxylum bungeanum, belonging to Rutaceae family and Zanthoxylum L. genus, is one of the traditional “eight major condiments” in China, which is an important ingredient in many kinds of traditional Chinese medicines due to the functional activites of cold-dispelling, dehumidification, anaesthesia, and acesodyne. China has the highest planting area and yield of Zanthoxylum bungeanum. As the economic tree plants, Zanthoxylum bungeanum has the ecological, social, and economical benefites. Recently, the planting area of Zanthoxylum bungeanum has been increasing at the speed of 20%~30%. It has been widely accepted that Zanthoxylum bungeanum has diversely medical functions, such as antioxidant activities, insecticidal activities, anaesthesia, anti-inflammatory and analgesic, hypolipidemic, removing wrinkles, anticancer, and so on. As the special functional ingredients, alkylamide compounds (or hemp flavor substance) possess many biological properties. However, the mechanism of these biological properties were not fully understood. Therefore, Zanthoxylum bungeanum has not been fully applied in medicines and daily chemical products. This review summarizes updated researches on the main species of alkylamide compounds in Zanthoxylum bungeanum and their respective physiological functions in order to provide necessary reference for the further systematic study.

Abstract:Capsaicinoids, main capsaicin and dihydrocapsaicin, are a group of chemicals naturally occurring in chilli peppers with bioactive properties, such as analgesic, anti-cancer, weight loss, and lowering blood glucose and lipid. The metabolic disorder of body glucose and lipid is one of the main factors that lead to obesity, hyperlipidemia, and diabetes. Capsaicinoids have better effects on glucose control, lipid-lowering, and weight loss in animal and human experiments and the mechanisms have been widely noted. This paper reviewed effects of capsaicinoids on regulating glucose and lipids metabolism, and the possible mechanisms of capsaicinoids acted on capsaicin receptor TRPV1 channel, dietary carbohydrate and lipids digestion and absorption, the gut microbiota and the relation gene in liver, pancreas, adipose tissue, and nervous system. This review could provide a reference for the utilization of capsaicinoids.

Abstract:The extracellular polysaccharide (EPS) from Lactobacillus plantarum plays important roles in the special texture and flavor of fermented dairy products. These EPSs possess biological activities such as immunomodulation, antitumor and regulating the balance of intestinal flora and so on, which can be used in food and medicine fields. However, the yield of Lactobacillus plantarum EPS is relatively low, factors affecting the EPS production are strain specific, and the influence of Lactobacillus plantarum EPS on the stability of the products is still rarely studied. The optimal fermentation conditions obtained by single factor experiments and response surface analysis were as follows:peptone 10g/L, yeast extract powder 5g/L, glucose 20g/L, potassium hydrogen phosphate 2.0g/L, anhydrous sodium acetate 5.0g/L, sodium citrate 5.0g/L, magnesium sulfate 0.2g/L, manganese sulfate 0.05g/L, twain 80 1.0mL/L, fermentation temperature 30℃, fermentation time 24h, and initial pH of culture medium of 6.5. The maximal production of EPS was 250.21mg/L under the above conditions. The results of rheological characteristics studies indicated that the EPS aqueous solution exhibited the increased viscosity as the concentration of the EPS and the share rate increased, and shear thickening properties. The scanning electron microscopy verified the cuboid microstructure of the EPS molecules, facilitating stabilization of the texture and water retention in solution. Application of this EPS for preparation of acid milk beverage showed that the use of the EPS could improve stability of the beverage, indicating that the EPS from Lactobacillus plantarum K25 can be potentially used as a novel food stabilizer.

Abstract:The key flavor compounds of fermented milk produced by six strains of S. thermophiles isolated from different regions were analyzed by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) technology, combined with aroma threshold and relative odor activity value (ROAV). The results showed that the total of 63 volatile compounds were finally detected in these fermented milk, including aldehydes, ketones, acids, esters, alcohols, aromatics, and hydrocarbon compounds. Among them, 12 kinds of volatile compounds, such as diacetyl, acetoin, acetaldehyde, and 2-nonanone had higher ROAV (ROAV≥1), which contributed greatly to the overall flavor of fermented milk. Principal component analysis and comparative analysis of similarity demonstrated that there was a high similarity among the flavor compounds of S. thermophilus fermented milk from the same area while that from different regions was lower. The results indicated that the pressure of growth environment can exert an influence on the aroma-producing characteristics of the fermented milk of the strain.

Abstract:This study assessed the proliferation factors and culture conditions for the growth of a Saccharomyces cerevisiae TR2 isolated from Xinjiang traditional fermented camel milk and established its kinetic model, which could reflect the high density fermentation and the application of Saccharomyces cerevisiae in milk beer production. The carbon source, nitrogen source, inorganic salts, species and concentrations of the growth factors in culture medium were screened by the single factor test. Meanwhile, the compositions of culture medium and fermentation conditions of Saccharomyces cerevisiae were optimized by response surface and orthogonal methods. Moreover, the strain growth and the kinetic model of glucose consumption were fitted nonlinearity by Matlab software. The results showed that the optimal medium was glucose 53.4g/L, peptone 21.5g/L, yeast extract 10g/L, and KH₂PO₄ 2.98g/L. Under the fermentation conditions of initial pH 5, shaking speed at 150r/min, inoculum concentration 5%, liquid volume 60mL, incubation time 16h and incubation temperature 28℃, the cell number reached to 6.64×10⁸CFU/mL. The predictive value of the kinetic model for the fermentation process was well fitted to the experimental value, and the fitting degrees were 0.9973 and 0.9784. It concluded that the model could reflect the fermentation process of the strain in batches.

Abstract:In order to screen Lactobacillus to ferment yak milk rapidly with characteristic flavor, the growth of 8 strains of wild Lactobacillus and acid production were studied. The volatile flavor composition of single-strain fermented skim milk was analyzed by gas chromatography-mass spectrometry (GC-MS). The 4 wild Lactobacillus strains could not only ferment skim milk rapidly but also provide characteristic volatile flavor to fermented yak milk, combined with the sensory analysis to evaluate the volatile flavor characteristics of the yak yogurt. The results showed that yak yogurt with high flavor preference contained higher esters and aldehydes, with esters content of 9.82μg/kg and aldehydes content of 174.64μg/kg. Acids, sulfur compounds and alcohols were lower in these samples than the others, and the contents of acids were between 366.51 and 495.84μg/kg. Meanwhile, the content of sulfur compounds was below 5.05μg/kg and the contents of alcohols were less than 1.42μg/kg. The gelation of whole yak milk took a long time in the fermentation process and the hydrolysis by lipase generated the off-flavor components, most of which are short-chain fatty acids and some ketones, etc. The strains which can result in higher levels of fruity substances such as esters, aldehydes will help to improve the quality of yak yogurt and have potential application for the development of yak dairy products.

Abstract:In this study, the optimum preparation conditions of Lentinula edodes soup were evaluated by the single factor experiment and orthogonal experiment and then the flavor characterization and contents of non-volatile compounds in Lentinula edodes and Lentinula edodes soup were comparatively analyzed by high performance liquid chromatography. Results indicated that the sensory evaluation and dissolution ratio of Lentinula edodes soup was better when the cooking temperature, cooking time and quality concentration of Lentinula edodes were 120℃, 45min, and 0.050g/mL, respectively. During the boiling, non-volatile compounds in Lentinula edodes were transferred to the Lentinula edodes soup which resulted in the contents of organic acids, soluble sugars (polyols) and 5'-nucleotides were significantly higher than in Lentinula edodes after boiling (p<0.05). In addition, the contents of characteristic flavor amino acids in Lentinula edodes soup also were markedly higher than in Lentinula edodes after boiling (p<0.05). However, the contents of most non-volatile compounds in boiled Lentinula edodes and Lentinula edodes soup were lower than in raw Lentinula edodes.

Abstract:Four fungi, strain 231#, 320#, 322#, and 333# were isolated from infected jujube, sweet cherry, apricot, and blueberry fruit. All the fungal pathogens were identified as Alternaria Nees by morphological characterization. Analysis of rDNA ITS sequence showed that strain 320# and 322# were both closely related to A. alternata (AY625056.1). In contrast, strain 231# and 333# showed close phylogenetic relationship with A. tenuissima (KP324980.1). The biolog microbial identification system with FF MicroPlate was applied in the 95 carbon and nitrogen sources utilization tests, and the carbon metabolic fingerprinting showed that four strains have 86 carbon sources in common, including 78 optimal carbon sources and 8 unavailable carbon sources.Moreover, strain 231# was closely related to A. alternata (Fr.) Keissl. There were some difference between rDNA ITS sequence and carbon metabolic profiling of four strains.

Abstract:In order to study the changes of nutritional compositions of black water chestnuts during fermentation process, the contents of protein, fat, pH values, reducing sugar, flavonoids, polyphenol, and melanoidin were determined at the key control points of the process. Results showed that the pH value decreased and other nutrients significantly increased. The black water chestnuts had higher nutritional contents after a specific fermentation process, which had some health functions.

Abstract:Total volatile basic nitrogen (TVB-N) content is an important indicator for pork freshness detection. In order to detect the concentration of hydrogen sulfide gas during the deterioration of pork, tunable diode laser absorption spectroscopy (TDLAS) was designed. Meanwhile, the content of TVB-N in the same environment was measured using the GB method. And the relationship between the concentrations of TVB-N and H₂S in the corruption process of fresh pork at 25℃ and 70% relative humidity (RH) was explored. The results showed the contents of TVB-N and H₂S in the fresh pork gradually increased, and the H₂S concentration was positively correlated with the TVB-N content at different time points (p<0.02). Therefore, it is possible to measure the TVB-N content indirectly by TDLAS detection in the process of pork degeneration. The TVB-N content can be obtained quickly with high accuracy and the efficiency of meat detection is improved.

Abstract:The study established a simple and rapid method for the determination of Bacillus cereus. According to the 16S RNA gene sequences of Bacillus cereus available in Genbank, specific primers and exo probe were designed for establishing real-time recombinase polymerase amplification(real-time RPA).The RPA reaction was performed successfully at 39℃ and the results were obtained within 20min. This method could specifically detect Bacillus cereus, but could not detect other bacteria. The study showed that the detection limit of real-time RPA was 1.0×10-3ng/μL with genomic DNA of Bacillus cereus, which was the same as the real-time PCR method. Bacillus cereus in artificially contaminated rice samples with a bacterial concentration of 1.5×10⁴CFU/g could be detected after 6-13min by real-time RPA; when the bacterial concentration was 1.5×10⁵CFU/g, the Bacillus cereus could be detected at least 30 min by real-time PCR (the Ct value was between 20 and 31).