Changes in the volatiles,chemical components,and antioxidant activities of Chinese jasmine tea during the scenting processes

Chinese jasmine tea, a type of flower-scented tea, is produced by repeatedly mixing the base tea with the aromatic flowers of Jasminum sambac. The aim of this study was to analyze the changes in the volatiles, chemical components, and antioxidant activities of Chinese jasmine tea during six rounds of the scenting processes. The results indicated that benzyl alcohol, linalool, benzyl acetate, (Z)-3-hexenyl benzoate, methyl anthranilate, indole, and α-farnesene were seven major volatile compounds of jasmine tea. Moreover, the total amount of the volatile compounds increased gradually with increasing scenting rounds. The absorption of linalool became saturated quickly, while those of the other six major volatile compounds exhibited nearly linear increases throughout all six repeated scenting rounds. Importantly, the value of the jasmine tea flavor index, an evaluating indicator of the aroma quality, gradually increased with the progression of the repeated scenting rounds. The change of each detected taste component was less than 15% during six rounds of the scenting process. The antioxidant activities of the tea samples decreased in the first two rounds and later increased in the succeeding four rounds of the scenting process. However, the antioxidant activity of the finished tea was lower than that of the base tea, being significantly correlated with the change of catechin concentration. The findings provided insight into the changes in the volatiles, chemical components, and antioxidant activity of Chinese jasmine green tea during the repetitious scenting process, which could provide beneficial insight on improving the quality grade of the tea.     

细菌纤维素的生物合成及在食品工业的应用

细菌纤维素是经微生物发酵形成的新型生物合成材料,具有机械强度高、吸水性能好、纯度高、结晶度高等优良特性,广泛应用于食品工业等领域。已报道的产细菌纤维素的细菌有醋酸菌属(Acetobacter)、根瘤菌属(Rhizobium)、八叠球菌属(Sarcina)、土壤杆菌属(Agrobaeterium)、假单胞菌属(Preudomonas)、无色杆菌属(Achromobacter)、固氮菌属(Azotobacter)、气杆菌属(Aerobacter)和产碱菌属(Alcaligenes)这9个属中的某些种,真正能够应用于工业化生产细菌纤维素的只有醋酸菌中的几个种,他们是木醋杆菌(Acetobacter xylinum)、醋化醋杆菌(Acetobacteraceti)、产醋醋杆菌(Acetobacteracotigenum)和巴氏醋杆菌(Acetobacter pastcurianum)。本文通过分析近期国内外与细菌纤维素相关文献,对其高产菌种选育、培养基优化和发酵模式等方面的研究进行综述,并展望其在食品工业中的应用前景,为进一步深入研究细菌纤维素提供理论基础和科学依据。     

凝固型黑豆酸豆奶生产工艺的研究

目的 确定以带皮黑豆为主要原料的凝固型乳酸菌发酵黑豆酸豆奶的生产工艺.方法 将带皮黑豆制备成培养液,通过对发酵产物进行感官评价,从干酪乳杆菌FJAT-7928、嗜热链球菌FJAT-7927和植物乳杆菌FJAT-7926的不同组合中筛选出最佳组合作为发酵剂,通过单因素和正交试验确定培养液中乳糖、番茄汁、奶粉和白砂糖的最佳...     

Phenolic compounds and the biological effects of Pu-erh teas with long-term storage

Pu-erh tea has gained more and more popularity and attracted much attention for its various biological effects. The objective of this study was to determine the active phenolic compounds and the biological effects of 15 differently aged Pu-erh teas. The results showed that 43 active phenolics, containing 7 flavan-3-ols, 11 organic acids, and esters, 3 proanthocyanidin dimers, 2 benzotropolones, and 20 flavonoid glycosides were identified based on high-performance liquid chromatography coupled to electrospray ionisation and quadrupole time-of-flight tandem mass spectrometry (HPLC-ESI-QTOF-MS/MS). In particular, 2’-O-galloylhyperin and quercetin-3-O-p-coumaroyl-rhamnosyl-arabinosyl-hexoside were identified from constituents of tea for the first time. The 15 Pu-erh teas exhibited strong DPPH and ABTS scavenging activity in a concentration-dependent manner with IC₅₀ 0.99–2.12 and 0.97–2.67 mmol Trolox equivalent antioxidant capacity/g, respectively. All of the Pu-erh teas tested significantly inhibited the proliferation of SMMC-7721 cells, in a dosage-dependent manner. Of the 15 Pu-erh teas examined, the cake tea P6 had the strongest effect on SMMC-7721 cells with IC₅₀ = 65.88 ± 3.53 µg/mL. The others Pu-erh teas had an IC₅₀ = 96 – 509 µg/mL. Our results also indicated that not all the older Pu-erh teas display stronger anti-activities and anti-cancer than the younger ones and the youngest Pu-erh tea did not possess the highest level of active components. This study provides useful information for consumers to deeply understand the chemical constituents and bioactivity of Pu-erh tea preserved for a long time.     

Preparation and characterization of flax biocomposites made of seed mucilage reinforced by fibers

Natural biocomposites were prepared from flax fibers and mucilage polysaccharides extracted from flax seeds, as a matrix, in two steps: impregnation and compression molding. The ribbons were preimpregnated with water plasticized mucilage. Solid mucilage (30%, w/w) was added to the ribbon impregnated with 20% mucilage, and the composite was compression molded. The solidified mucilage was homogeneous and rigid (2 GPa) with an elastic deformation of approximately 1%. The mechanical properties of the composites were in the ranges of 7–10 GPa, 300–400 MPa and 4–5% for the modulus, maximal strength and strain, respectively. The two latter parameters were larger than the ones for the fiber. The experimental values of the modulus and strength were in accordance with the values computed using the rule of mixture, which indicated a good interface between the fibers and the matrix. This was confirmed visually with scanning electron microscopy. The water sorption behavior of the composites was intermediate between the mucilage and the fiber alone.     

不同乳酸菌荔枝汁发酵特性及其贮藏稳定性的研究

目的为荔枝乳酸菌发酵饮料的研发筛选优良菌株。方法比较9种乳酸菌在荔枝汁中发酵48 h的活菌数、 pH值和酸度,并观察发酵液在4℃储存条件下这些指标的变化。结果植物乳杆菌FJAT-13737(LactobacillusplantarumFJAT-13737)和德氏乳杆菌FJAT-43773(Lactobacillusdelbrueckii FJAT-43773)发酵荔枝汁48 h的活菌数最高,达109 CFU·mL~(-1),但在0～7 d储存期内降至108 CFU·mL~(-1)。嗜热链球菌FJAT-43774 (Streptococcus thermophilus FJAT-43774)、嗜酸乳杆菌FJAT-13772(Lactobacillus acidophilus FJAT-13772)和发酵乳杆菌FJAT-13771(LactobacillusfermentumFJAT-13771)发酵液中的活菌数较低,至储存28 d时,活菌数在107 CFU·mL-1,显著低于其他乳酸菌活菌数(P0.05)。不同菌株荔枝汁发酵液在储存期的最终pH值在3.74～3.93之间,差异不显著(P0.05)。短乳杆菌FJAT-43776(Lactobacillus brevis FJAT-43776)的荔枝汁发酵液的酸度最高,为140.9°T。在储存期内,不同菌株发酵的荔枝汁的酸度均呈上升趋势,最终酸度在245.8～165.4°T之间。结论为新型荔枝乳酸菌发酵饮料的研发奠定实践基础。     

荔枝汁-大豆蛋白培养基鼠李糖乳杆菌发酵过程脂肪酸组的变化动态

目的解析荔枝汁-大豆蛋白培养基鼠李糖乳杆菌发酵过程脂肪酸组的变化动态。方法利用气相色谱-质谱(gas chromatography-mass spectrometry,GC-MS)脂肪酸自动测定仪,分析植物原料荔枝汁、大豆蛋白(豆浆)、荔枝汁+大豆蛋白(体积比为1:1)培养基的脂肪酸组成,以及鼠李糖乳杆菌FJAT-13807(Lactobacillus rhamnosus FJAT-13807)发酵前后和发酵过程脂肪酸组的变化。结果荔枝汁-大豆蛋白复合培养基经过鼠李糖乳杆菌FJAT-13807发酵脂肪酸组成发生显著变化(P0.05),发酵前脂肪酸标记30条,发酵后上升到53条,增加了76.77%,脂肪酸总量增加115.01%;脂肪酸标记可分为高含量(2条)、中含量(10条)和低含量(41条)3组,其中高含量组的脂肪酸标记C16:0和C18:1ω9c,含量占比超过45%,具有乳杆菌种属特征;鼠李糖乳杆菌FJAT-13807发酵过程中,脂肪酸组和活菌数变化趋势相近;发酵1h,活菌数达8.7×10~7 CFU/mL,此时,脂肪酸总量达1426116(响应值);发酵1-6 h,活菌数略有下降,为6.20×10~7 CFU/mL,脂肪酸总量相应下降为1106592(响应值);发酵6～12 h,活菌数含量急速上升到高峰56.00×10~7 CFU/mL,相应的脂肪酸总量也急速上升到2349101(响应值)。结论乳杆菌发酵能显著增加脂肪酸组的种类和含量,C16:0和C18:1ω9c为乳杆菌种属特征脂肪酸标记,可通过检测脂肪酸总量的变化,可以监测乳杆菌数量变化动态。     

黄粉虫内生菌的分离鉴定及其对淀粉、纤维素和木质素的降解活性的测定

目的 分离培养黄粉虫体内细菌, 并测定这些菌对淀粉、纤维素及木质素的降解活性。方法 对黄粉虫表面消毒, 以LB和高氏一号培养基分离虫体内部细菌并进行16S rRNA基因序列分析。变色圈法测定降解活性。结果 共分离到8株细菌, 16S rRNA基因序列分析表明, 1株属于肠球菌属, 3株属于乳酸球菌属, 2株属于芽胞杆菌属, 另2株属肠杆菌属。水解酶测定结果表明, 菌株FJAT-18107具有淀粉和木质素水解作用, 其16S rRNA基因序列与解淀粉芽胞杆菌Bacillus amyloliquefaciens (NR_075005)最相似。结论 本研究为了解昆虫内生菌功能提供了参考。     

博落回生物碱提取工艺优化

目的探讨优化博落回叶片中生物碱的提取方法。方法采用甲醇提取法、超声-甲醇提取法、超声-甲醇补足提取法、超声-乙醇提取法和乙醇提取法5种方法提取博落回叶片中的生物碱,采用高效液相色谱法(high performance liquid chromatography,HPLC)测定其中原阿片碱(protopine,PRO)、别隐品碱(allocryptopine,ALL)、血根碱(sanguinarine,SAN)和白屈菜红碱(chelerythrine,CHE)4种生物碱的含量。结果超声-甲醇补足提取法提取光泽县野生博落回叶中的总生物碱含量最高,为(104.939±0.449) mg/g。三明明溪、南平光泽2地博落回叶片均有4种生物碱,所有提取方法提取的生物碱含量都满足ALL PRO SAN≈CHE。超声与回流相比提取率更高,乙醇为提取溶剂时,超声辅助的影响较小。结论超声-甲醇补足提取法为博落回生物碱的最优提取方法,此方法适用于博落回中总生物碱的提取。