Procyanidin Content of Grape Seed and Pomace, and Total Anthocyanin Content of Grape Pomace as Affected by Extrusion Processing

ABSTRACT: Grape juice processing by‐products, grape seed and pomace are a rich source of procyanidins, compounds that may afford protection against chronic disease. This study was undertaken to identify optimal extrusion conditions to enhance the contents of monomers and dimers at the expense of large molecular weight procyanidin oligomers and polymers in grape seed and pomace. Extrusion variables, temperature (160, 170, and 180 °C in grape seed, and 160, 170, 180, and 190 °C in pomace) and screw speed (100, 150, and 200 rpm in both) were tested using mixtures of grape seed as well as pomace with decorticated white sorghum flour at a ratio of 30 : 70 and moisture content of 45%. Samples of grape seed and pomace were analyzed for procyanidin composition before and after extrusion, and total anthocyanins were determined in pomace. Additionally, chromatograms from diol and normal phase high‐performance liquid chromatography were compared for the separation of procyanidins. Extrusion of both grape by‐products increased the biologically important monomer and dimers considerably across all temperature and screw speeds. Highest monomer content resulted when extruded at a temperature of 170 °C and screw speed of 200 rpm, which were 120% and 80% higher than the unextruded grape seed and pomace, respectively. Increases in monomer and dimer contents were apparently the result of reduced polymer contents, which declined by 27% to 54%, or enhanced extraction facilitated by disruption of the food matrix during extrusion. Extrusion processing reduced total anthocyanins in pomace by 18% to 53%. Practical Applications: Extrusion processing can be used to increase procyanidin monomer and dimer contents in grape seed and pomace. Procyanidins in grape by‐products have many health benefits, but most are present as large molecular weight compounds, which are poorly absorbed. Extrusion processing appears to be a promising technology to increase levels of the bioactive low molecular weight procyanidins.     

LC-MS method development to evaluate major triterpenes in skins and cuticular waxes of grape berries

Predominant triterpenes (free oleanolic acid, β-sitosterol and β-sitosterol-3-O-β- d -glucoside) in skin and cuticular wax of grape berries have been analysed by liquid chromatography–mass spectrometry (LC-APCI-MS). The validity of the developed method was established by determining linearity, recovery, precision, accuracy, limit of detection and quantification. Detection limits were in the range of 0.12–0.25 mg L⁻¹, and linearity values ranged up to 105 mg L⁻¹. The repeatability of the method was good. High variability was found among the measured grape varieties based on triterpene content, quantitites of oleanolic acid of cuticular wax ranged from 31.53 mg kg⁻¹ to 162.01 mg kg⁻¹ of the twelve analysed samples. The highest sitosterol content was measured in the sample 'Othello' (73.12 mg kg⁻¹), while maximum sitosterol glucoside content was also found in 'Othello' variety (13.68 mg kg⁻¹). The results showed that the study on triterpenes could be an informative tool to characterise grape varieties.     

Natural compounds to preserve fresh fish burgers

Natural antimicrobial compounds to control the quality decay of a fresh fish burger were studied. In particular, thymol, lemon extract and grape fruit seed extract (GFSE), at 20, 40 and 80 ppm, have been tested against the main spoilage microorganisms inoculated in fish burgers stored at 5 °C. The evolution of mesophilic and psychrotrophic bacteria was also monitored. The sensorial quality decay was determined by means of a panel test, which assessed odour, colour, texture, drip loss and general appearance during the storage period. Results show that all the active substances efficiently slowed down the growth of the spoilage microorganisms. In particular, GFSE was the most efficient against Photobacterium phosphoreum , Shewanella putrefaciens and mesophilic bacteria, whereas thymol was the most efficient against both psychrotrophic bacteria and Pseudomonas fluorescens . Microbial growth was the factor limiting fresh fish burger acceptability.     

Grape,apple and pineapple juice characterisation and detection of mixtures

Several multivariate statistical methods (principal component, cluster, stepwise discriminant and multiple linear regression analysis) were applied to analytical data obtained by conventional methods and to analytical data for free amino acids, in an attempt to distinguish between grape, apple and pineapple juice. Analysis for methionine, proline, asparagine, arginine and glutamic acid made it possible to differentiate among the 34 samples of grape, apple and pineapple juices studied. Multiple linear regression analysis of computer-simulated mixtures of grape and apple juices made it possible to detect the proportion of each fruit within the blend.     

葡萄啤酒的工艺研究

将葡萄汁或葡萄原酒与啤酒生产工艺相结合,生产出既具有玖瑰葡萄香味又不失啤酒风味的葡萄啤酒新产品,其基本工艺是将葡萄汁或葡萄原酒以原料方式加入到啤酒生产中,啤酒花采用煮沸法制出酒花汁也加入到啤酒生产中,从而制做出清爽型啤酒的新产品.     

正交设计优化酿酒葡萄皮渣色素提取及其抗氧化性测定

以酿酒葡萄皮渣为原料,在单因素实验基础上,利用正交设计优化了超声波辅助提取色素工艺,并研究了该色素的抗氧化性能。结果表明,超声波辅助提取葡萄皮色素的最佳工艺为浸提液pH3,固液比为1：20,提取温度为60℃,浸提时间为50min;该色素具有较强的抗氧化能力。     

"赛美蓉"与"长相思"葡萄汁挥发性风味物质的分析

通过顶空固相微萃取结合气相色谱-质谱联用技术分析赛美蓉和长相思澄清葡萄汁挥发性风味物质组成,初步定性77种挥发性风味物质,二者共有组分46种。其中醇类物质的种类最多,所占比例最高,分别达到了72.76%和77.69%;酯类物质的种类数量居第二,但所占比例较低,分别为3.67%和2.12%;醛类物质虽然只有8种,但其比例却分别达21.99%和18.82%。主要挥发性组分感官特征分析显示:表现为果香的物质种类最多,表现为清香的物质总离子流量和比例最高。     

液态法生产葡萄果醋工艺条件的研究

实验以酿酒葡萄为原料,采用液态发酵法生产葡萄果醋。试验研究了其生产工艺,分析了温度、醋酸添加量、酒度对醋酸发酵的影响。结果表明:在酒精发酵阶段,糖度与酒度的变化呈负相关;在醋酸发酵阶段,酒度与酸度的变化呈负相关,其发酵的最佳组合为温度为31℃、醋酸添加量为10%、酒度为10%。     

Modelling of heat and moisture transport during drying black grapes

In this work, heat and moisture transport occurred during drying of black grapes in a laboratory dryer were investigated. In the experiments, the air was passed through the chamber at a variety of flow rates (0.5, 0.75, 1.0 and 1.25 m s^?1) and temperatures (40, 50, 60 and 70 °C). Thermal and moisture diffusivities were determined. The possibility of expressing the moisture removal from the grapes was searched with the fourteen one‐layer drying models selected from the literature. Among all the models, the Page model was found the best for explaining the experimental results. The effects of the drying temperature and air velocity on the constants and coefficients of Page model and diffusivities were also investigated by multiple combinations of the different equations as the linear, power, logarithmic, exponential, polynomial, inverse polynomial and Arrhenius type by non‐ linear regression analyses. Models obtained were also analysed statistically using t‐test, RMSE, MBE and χ².