Physical Properties of Gelidium corneum–Gelatin Blend Films Containing Grapefruit Seed Extract or Green Tea Extract and Its Application in the Packaging of Pork Loins

ABSTRACT:  Edible Gelidium corneum –gelatin (GCG) blend films containing grapefruit seed extract (GFSE) or green tea extract (GTE) were manufactured, and the quality of pork loins packed with the film during storage was determined. Tensile strength (TS) and water vapor permeability (WVP) of the films containing GFSE or GTE were better than those of the control. The film's antimicrobial activity against Escherichia coli O157:H7 and Listeria monocytogenes increased with increasing antimicrobial concentration, resulting in a decrease in the populations of bacteria by 0.77 to 2.08 and 0.91 to 3.30 log CFU/g, respectively. Pork loin samples were inoculated with E. coli O157:H7 and L. monocytogenes . The samples packed with the GCG film containing GFSE (0.08%) or GTE (2.80%) had a decrease in the populations of E. coli O157:H7 and L. monocytogenes of 0.69 to 1.11 and 1.05 to 1.14 log CFU/g, respectively, compared to the control after 4 d of storage. The results showed that the quality of pork loins during storage could be improved by packaging them with the GCG film containing GFSE or GTE.     

石花菜多糖的提取工艺及其抗氧化活性研究

利用水提醇沉法提取石花菜多糖（GAP）,通过单因素和正交实验考察了温度、时间、料液比和提取次数等因素对GAP提取率的影响。结果表明,GAP的最适宜提取工艺条件是：料液比为1g∶30mL,温度75℃,时间2h,提取3次。GAP对羟基自由基、超氧阴离子自由基的清除实验表明,GAP具有良好的抗氧化活性,而且对2种自由基的清除能力强弱顺序是.OH〉O2-.。     

Original article: Use of nano‐clay (Cloisite Na+) improves tensile strength and vapour permeability in agar rich red algae (Gelidium corneum)–gelatin composite films

In this study, we aimed to improve the physical properties of Gelidium corneum–gelatin (GCG) film by including nano‐clay in the film‐forming solution and tested the antimicrobial properties of the thymol‐containing composite film as a packaging material for chicken breast. Addition of nano‐clay improved the physical properties of GCG film. The tensile strength of the GCG film containing 1% Cloisite Na⁺ was 38.13 MPa, compared to the 26.65 MPa for the GCG film. The water vapour permeability of the GCG film was 3.56 ng m m^?2sPa, while that of the GCG film with 1% Cloisite Na⁺ was 3.24 ng m m^?2sPa. Incorporation of thymol into the film had its antimicrobial activities against Escherichia coli O157:H7 and Listeria monocytogenes. When used to pack chicken breast, the GCG/nano‐clay film containing thymol inhibited microbial growth during storage.     

细毛石花菜多糖自由基清除能力和理化性质的研究

该文通过研究细毛石花菜(Gelidium crinale)多糖提取物对自由基的清除能力及理化性质,为细毛石花菜的高值化加工利用提供实验依据.以细毛石花菜为原料,用0.1 mol/L的HCl提取制备细毛石花菜多糖,并对其理化性质和抗氧化活性进行研究.结果显示,细毛石花菜多糖中总糖占比为70.51％,还原糖占比为8.42％...     

石花菜醇提物抑菌活性和抗氧化活性研究

本实验研究了石花菜醇提物的抑菌活性和抗氧化活性。采用生长速率法测定各相提取物的抑菌活性,结果表明石花菜含有丰富的抗病原真菌资源;采用水杨酸法和邻苯三酚法分别测定各相提取物对羟基自由基和超氧阴离子自由基的清除能力,结果表明石花菜有较强的抗氧化能力。同时对各相提取物进行了系统的化学成分定性检测,结果表明石花菜的生物活性可能与其中含有的海藻多糖、黄酮、甾体皂甙、内酯及香豆素等活性成分有关。     

响应面法优化石花菜酸奶发酵工艺研究

采用响应面法优化石花菜酸奶发酵工艺。采用中心组合试验设计,考察不同双歧杆菌接种量、石花菜添加量、蔗糖添加量、发酵时间对感官评价（R1）、活菌数（R2）两个指标的影响。结果表明,石花菜琼胶寡糖能增加酸奶的持水力,改变酸奶的组织状态。石花菜酸奶发酵的最佳工艺条件为蔗糖添加量11%、石花菜添加量20%,双歧杆菌接种量1.5%,发酵时间为6 h,感官评分为80分,活菌数为2.65×109 CFU/mL。     

Mechanical properties of a Gelidium corneum edible film containing catechin and its application in sausages

ABSTRACT:  We prepared an edible Gelidium corneum (GC) film containing catechin and examined the microbial growth and quality change during storage of sausages packaged with the film. Incorporation of catechin in the film improved film tensile strength and water vapor permeability. The film's antimicrobial activity against Eschericha coli O157:H7 increased with increasing catechin concentrations and resulted in a decrease in the populations of the bacteria by 1.93 log CFU/g at 150 mg of catechin. For the sausage samples inoculated with E. coli O157:H7 and Listeria monocytogenes, the samples packed with the GC film showed a decrease in populations of E. coli O157:H7 and L. monocytogenes by 1.81 and 1.44 log CFU/g, respectively, compared to the control after 5 d of storage. In addition, the sausage samples packed with the GC film had lower degrees of lipid oxidation. The results suggest that sausages can be packed with GC film to extend shelf life.     

低场核磁共振技术测定石花菜对酸奶水分迁移及超微结构的影响

利用低场核磁共振及其成像技术对比了石花菜酸奶和酸奶水分迁移特性;并采用环境扫描电镜对石花菜酸奶超微形貌特征进行观察分析。结果表明,石花菜酸奶在发酵及储藏过程中的水分含量变化幅度小于不添加石花菜的酸奶,持水性增强;确定了前期发酵最优时间为6 h,冷藏后熟最优时间为24 h;通过环境扫描电镜观察发现石花菜酸奶中酪蛋白胶束与石花菜琼胶分子间相互缠结,蛋白链球颗粒粘结在致密的琼胶网络结构之中。     

IMPROVING ENERGY EFFICIENCY IN COMBINED MICROWAVE-CONVECITVE DRYING

ABSTRACT

Convective-microwave drying has been recognized as a convenient option for drying of valuable materials. However, the advantages of the method must be carefully evaluated in order to establish the limits for full scale operating conditions because, as demonstrated in this work, the reduction in the absolute drying time as a function of the applied microwave power is devalued by an increase in the unabsorbed microwave energy, decreasing the overall energy efficiency of the drying process.

Experimental study of the energy efficiency of combined microwave-convective drying of agar gel and Gelidium seaweeds was carried out in a laboratory scale microwave-convective dryer by continuously following the absorption of microwave energy by the sample as well as the change of the sample mass during the drying process, under different operating conditions. Several drying strategies based on the on-off application of the microwave power were proposed and evaluated from the point of view of both drying kinetics and energy efficiency in order to program and rationalize the use of microwave energy in the combined microwave-convective drying process.     

Preparation and mechanical properties of edible rapeseed protein films

Edible films were manufactured from rapeseed oil extraction residues. To prepare rapeseed protein (RP) films, various concentrations of plasticizers and emulsifiers were incorporated into the preparation of a film-forming solution. The optimal conditions for the preparation of the RP film were 2% sorbitol/0.5% sucrose as plasticizer and 1.5% polysorbate 20 as an emulsifier. In addition, RP blend films were prepared. Gelidium corneum or gelatin was added to improve the physical properties of the RP film, and the highest tensile strength value of the films was 53.45 MPa for the 3% RP/4% gelatin film. Our results suggest that the RP-gelatin blend film is suitable for applications in food packaging. PRACTICAL APPLICATION: Edible RP films prepared in the present investigation can be applied in food packaging.