环丙沙星在溶液中固液表面能的测定

采用激光法测定了环丙沙星在纯水和水－乙醇溶液（水体积分数23％）中的溶解度，介稳区和不同条件下的诱导期。根据经典成核理论和诱导期理论，推导了固液表面能与诱导期的理论关系，应用该理论关系计算了环丙沙星在溶液中的固液表面能，为环丙沙星初级成核与晶体生长研究提供了重要的参数。     

Thermodynamic properties of metamizol monohydrate in pure and binary solvents at temperatures from (283.15 to 313.15)K

The thermodynamic properties of metamizol monohydrate in pure solvents (methanol,ethanol,n-propanol and isopropanol) and two binary mixed solvent systems including (methanol + ethanol) and (methanol +isopropanol) were measured from 283.15 K to 313.15 K by gravimetric method under atmospheric pressure thought as 0.1 MPa.The modified Apelblat equation,the CNIBS/R-K equation,the Hybrid model and the NRTL model were used to correlate the solubility of metamizol monohydrate,respectively.The results show that the solubility of metamizol monohydrate in all the tested solvents increases with the rising temperature which means that it has temperature dependence.What's more,the effects of solvent components of the binary solvent mixtures on solubility were discussed,it illustrates that the increasing of the molar fraction of methanol gives the system a greater dissolving power.Furthermore,according to the NRTL model,the enthalpy,the Gibbs energy and the entropy of the mixing process were also obtained and discussed.     

Dietary creatine monohydrate has no effect on pork quality of Danish crossbred pigs

Creatine content in the muscle may delay postmortem lactate formation and postpone the pH decline, hence potentially improving the water-holding capacity (WHC) as shown in a previous study including purebred Duroc pigs, although the same study did not find any effect on meat from purebred Landrace pigs. In the present study Danish D(LY) crossbreeds were supplemented with 0 or 50g creatine monohydrate (CMH)/d for five days prior to the slaughter. CMH supplementation had no effect on meat quality indicators (pH and temperature), meat quality attributes (WHC and colour) or eating quality (juiciness and tenderness) of meat from the D(LY) crossbred pigs. As a consequence the D(LY) crossbreed was classified as a non-responder to CMH supplementation.     

高效液相色谱法测定肌酸粉中一水肌酸、肌酸酐和双氰胺含量

目的 建立一种同时检测肌酸粉中一水肌酸,肌酸酐和双氰胺含量的检测方法。方法 样品用水溶解稀释至一定溶度,过滤膜即得样品供试液。采用高效液相色谱法测定,10 mmol/L磷酸二氢钠溶液(氨水调PH至10.5)作为流动相,检测波长为220nm,流速0.8ml/min,外标法定量。结果 本方法在10 min内完成3种目标化合物的分离分析。试样中一水肌酸浓度在0.204~1.02 mg/mL的范围内与峰面积的线性关系良好, 相关系数r＞0.999。在3水平不同浓度一水肌酸标准品添加下,一水肌酸的回收率为97.9%。试样中肌酸酐浓度在0.530~6.36μg/mL的范围内与峰面积的线性关系良好, 相关系数r＞0.999。在3水平不同浓度肌酸酐标准品添加下,肌酸酐的回收率为99.0%。试样中双氰胺浓度在0.0531~0.637μg/mL的范围内与峰面积的线性关系良好, 相关系数r＞0.999。在3水平不同浓度双氰胺标准品添加下, 双氰胺的回收率为106.1%。结论 该方法快速、准确、灵敏, 适合同时测定肌酸粉中一水肌酸,肌酸酐和双氰胺含量。     

Influence of food matrix on absorption of flavour compounds by linear low‐density polyethylene: proteins and carbohydrates

The effects of differences in food matrices on the absorption of four flavour compounds (limonene, decanal, linalool and ethyl 2‐methyl butyrate) into linear low‐density polyethylene (LLDPE) were studied using a large volume injection GC ‘in vial’ extraction method. Food components investigated included β‐lactoglobulin (β‐lg), casein, pectin, carboxymethylcellulose (CMC), lactose and saccharose. β‐lg interacted irreversibly with decanal (P < 0.01) and suppressed absorption of the latter by LLDPE by more than 50% after 14 days of exposure. Casein was capable of binding limonene and decanal (p < 0.05) by hydrophobic and covalent interactions, resulting in decreased absorption of 40% and 90%, respectively. The absorption rates of limonene, and to a leaser extent decanal, were decreased in presence of pectin and CMC. Increasing viscosity slowed down diffusion of flavour compounds from the matrix to LLDPE. An increase of absorption (p < 0.01) was observed for linalool and ethyl 2‐methyl butyrate, due to a ‘salting out’ effect caused by lactose and saccharose. The absorption of decanal was decreased (p < 0.01) after 14 days of exposure in the presence of lactose, saccharose and CMC. There might be an interactive effect between a sugar (residue) and decanal. Knowledge of the composition of a food matrix and packaging material is necessary to estimate the amount of flavour absorption. © 2000 Society of Chemical Industry     

Isomerization of lactose over natural sepiolite

Sepiolite (a hydrated magnesium silicate) was investigated as a catalyst for the isomerization of lactose. Factors such as temperature, concentration and time were studied. The main reaction product was lactulose; small amounts of epilactose, galactose, tagatose and 3-deoxypentulose were also formed. Product distribution indicated that the reaction routes were isomerization of the disaccharide followed by degradation of lactulose.     

Influence of calcium and phosphorus, lactose, and salt-to-moisture ratio on Cheddar cheese quality: changes in residual sugars and water-soluble organic acids during ripening

Cheddar cheese ripening involves the conversion of lactose to glucose and galactose or galactose-6-phosphate by starter and nonstarter lactic acid bacteria. Under ideal conditions (i.e., where bacteria grow under no stress of pH, water activity, and salt), these sugars are mainly converted to lactic acid. However, during ripening of cheese, survival and growth of bacteria occurs under the stressed condition of low pH, low water activity, and high salt content. This forces bacteria to use alternate biochemical pathways resulting in production of other organic acids. The objective of this study was to determine if the level and type of organic acids produced during ripening was influenced by calcium (Ca) and phosphorus (P), residual lactose, and salt-to-moisture ratio (S/M) of cheese. Eight cheeses with 2 levels of Ca and P (0.67 and 0.47% vs. 0.53 and 0.39%, respectively), lactose at pressing (2.4 vs. 0.78%), and S/M (6.4 vs. 4.8%) were manufactured. The cheeses were analyzed for organic acids (citric, orotic, pyruvic, lactic, formic, uric, acetic, propanoic, and butyric acids) and residual sugars (lactose, galactose) during 48 wk of ripening using an HPLC-based method. Different factors influenced changes in concentration of residual sugars and organic acids during ripening and are discussed in detail. Our results indicated that the largest decrease in lactose and the largest increase in lactic acid occurred between salting and d 1 of ripening. It was interesting to observe that although the lactose content in cheese was influenced by several factors (Ca and P, residual lactose, and S/M), the concentration of lactic acid was influenced only by S/M. More lactic acid was produced in low S/M treatments compared with high S/M treatments. Although surprising for Cheddar cheese, a substantial amount (0.2 to 0.4%) of galactose was observed throughout ripening in all treatments. Minor changes in the levels of citric, uric, butyric, and propanoic acids were observed during early ripening, whereas during later ripening, a substantial increase was observed. A gradual decrease in orotic acid and a gradual increase in pyruvic acid content of the cheeses were observed during 12 mo of ripening. In contrast, acetic acid did not show a particular trend, indicating its role as an intermediate in a biochemical pathway, rather than a final product.     

Influence of dietary creatine monohydrate and carcass cooling rate on colour characteristics of pork loin from different pure breeds

Increased creatine content in the muscle may delay postmortem (pm) lactate formation and postpone pH decline, hence potentially affect the colour of pork. The influence of dietary supplementation with 0 or 50 g creatine monohydrate (CMH)/d for 5 days prior to slaughter and two cooling rates of pig carcasses on the colour characteristics of pork loin from purebred Duroc and Landrace pigs was investigated. CMH increased the content of creatine phosphate in pork loin measured immediately following bleeding, delayed early pm pH decline and gave rise to less red and yellow colour, probably due to induction of a more pronounced oxidative muscle metabolism. A faster cooling rate pm induced darker and less yellow colour in loins from Duroc and Landrace pigs, while only loins from Landrace became less red. Loins from Duroc pigs were darker, less red and less yellow than loins from Landrace pigs, due to slower pH decline and a higher ultimate pH in these loins. Colour stability of pork loin during chill storage, measured as oxidation to metmyoglobin, was not affected by dietary CMH, cooling rate or pig breed. Consequently, the registered differences in colour between treatments during storage were merely due to the degree of initial blooming, and more attention to factors of importance for the degree of blooming should be in focus in future studies of factors of importance for meat colour.     

Plasma concentrations of glucagon-like peptide 1 and 2 in calves fed calf starters containing lactose

The objective of this study was to evaluate the effects of lactose inclusion in calf starters on plasma glucagon-like peptide (GLP)-1 and GLP-2 concentrations and gastrointestinal tract development in calves. Holstein bull calves (n = 45) were raised on an intensified nursing program using milk replacer containing 28.0% CP and 15.0% fat, and were fed a texturized calf starter containing 0 (control), 5.0 (LAC5), or 10.0% (LAC10; n = 15 for each treatment) lactose on a DM basis. Lactose was included in the starter by partially replacing dry ground corn in pelleted portion of the starter. All calf starters were formulated with 23.1% CP. The ethanol-soluble carbohydrate concentrations of the control, LAC5, and LAC10 starters were 7.3, 12.3, and 16.8% on a DM basis, respectively. Starch concentrations of the control, LAC5, and LAC10 starters were 29.7, 27.0, and 21.4% on a DM basis, respectively. All calves were fed treatment calf starters ad libitum. Blood samples were obtained weekly from 1 to 11 wk of age, and used to measure plasma GLP-1, GLP-2, and insulin concentrations, serum β-hydroxybutyrate (BHB) concentration, and blood glucose concentration. At 80 d of age, calves were euthanized, and weights of the reticulorumen, omasum, abomasum, small intestine, and large intestine tissue were measured. Serum BHB concentration was higher for calves fed the LAC10 (171 μmol/L) starter than for those fed the control (151 μmol/L) and LAC5 (145 μmol/L) starters. Plasma GLP-1 and GLP-2 concentrations did not differ between treatments. However, relative to the baseline (1 wk of age), the plasma GLP-1 concentration was higher for the LAC10 (125.9%) than for the LAC5 (68.2%) and control (36.8%), and for the LAC5 than for the control (36.8%). Moreover, similar differences between treatments were observed for GLP-2 concentration relative to the baseline (88.2, 76.9, and 74.9% for LAC10, LAC5, and control treatments, respectively). The serum BHB concentration was positively correlated with the plasma GLP-1 concentration (r = 0.428). Furthermore, the plasma GLP-1 concentration was positively correlated with the insulin concentration (r = 0.793). The weights of the reticulorumen, omasum, abomasum, small intestine, and large intestine were not affected by the treatments. In conclusion, inclusion of lactose in calf starters resulted in higher plasma GLP-1 and GLP-2 concentrations, and BHB might be associated with higher plasma GLP-1 concentration.     

Prior lactose glycation of caseinate via the Maillard reaction affects in vitro activities of the pepsin-trypsin digest toward intestinal epithelial cells

The well-known Maillard reaction in milk occurs between lactose and milk proteins during thermal treatment, and its effects on milk nutrition and safety have been well studied. A lactose-glycated caseinate was prepared via this reaction and digested using 2 digestive proteases, pepsin and trypsin. The glycated caseinate digest was assessed for its in vitro activities on rat intestinal epithelial cells in terms of growth proliferation, anti-apoptotic effect, and differentiation induction using caseinate digest as reference, to verify potential effects of the Maillard reaction on these activities of caseinate digest to the cells. Two digests had proliferative and anti-apoptotic effects, and reached the highest effects at 0.02 g/L of digest concentration with treatment time of 24 h. In comparison with caseinate digest, glycated caseinate digest always showed weaker proliferative (5.3–14.2%) and anti-apoptotic (5.9–39.0%) effects, and was more toxic to the cells at 0.5 g/L of digest concentration with treatment time of 48 h. However, glycated caseinate digest at 2 incubation times of 4 to 7 d showed differentiation induction higher than caseinate digest, as it could confer the cells with increased activities in lactase (16.3–26.6%), sucrase (22.4–31.2%), and alkaline phosphatase (17.4–24.8%). Transmission electron microscopy observation results also confirmed higher differentiation induction of glycated caseinate digest. Amino acid loss and lactose glycation partially contributed to these decreased and enhanced activities of glycated caseinate digest, respectively. The Maillard reaction of caseinate and lactose is thus shown in this study to have effects on the activities of caseinate digest to intestinal epithelial cells.