جستجوی مقالات مرتبط با کلیدواژه "enzymatic treatment" در نشریات گروه "کشاورزی"

The current investigation was conducted to study the effect of Persian gum (PG) and microbial transglutaminase (MTGase) on textural characteristics of ultrafiltrated semi-fat white cheese during 60 days of cold storage. In order to produce semi-fat cheeses, PG was used at three levels of 0, 0.25, and 0.5% and MTGase enzyme at three levels of 0, 0.5 and 1 unit (U) per gram of protein. Cheese samples without any treatment were considered as control samples. The findings of this study revealed that addition of PG, opposite to MTGase, caused a significant reduction of the cheese pH values ​​(p < 0.05). During the storage period, the pH values ​​of all cheese samples decreased, but statistically there was a significant difference only between the first and 30th days of storage. During the storage period, the addition of PG led to a decrease in the amount of hydration of the samples until the 30th day of storage, but then the amount of hydration of the samples increased until the end of the 60th day. The results obtained from the analysis of the texture characteristics revealed that MTGase treatment up to 0.5 U decreased the firmness, gumminess, springiness and chewability and increased the adhesiveness of the cheese samples, but using a higher amount of the enzyme (1 U) caused a significant contrary change in the mentioned trend (p>0.001). Also, the addition of PG decreased the firmness, cohesiveness, gumminess, springiness and chewability and increased the adhesiveness of the cheese samples (p < 0.001). In general, with the passage of time during the cold storage, all the textural parameters, except adhesiveness, decreased significantly. The results of this research showed that it is possible to produce cheese with good quality by using the levels of 0.25 to 0.5% PG and 0.5 units of MTGase.

Paper made of recycled fibers has less strength compared to virgin fibers due to the multiplicity of recycling. Several solutions have been proposed to solve this problem consist of specialized enzymes application. While the applications of enzymes in the pulp and paper industry is still in the research and development stage, but some of them have pioneered the technology to operate. There are various methods to increase recycled fiber bonding and improves the paper strength. Oxidant enzymes such as cellulase and laccase are one of the methods that could accelerate delignification. Laccase-mediator system has the greatest effect on increasing of paper strength according to previous studies. Common Low molecular weight of mediator such as ABTS or HBT are the best non-phenolic lignin oxidizing that have been used yet. In order to increase the strength of recycled paper the effect of laccase treatment on old corrugated container (OCC) pulp was investigated in this study. OCC pulp was obtained from headbox of recycled paper factory in the north of Iran (Afrang Noor), and then was fractionated by Bauer-McNett classifier. HBT mediator was selected to treatment of OCC pulp by laccase. The pulp was treated by the enzyme in the adjusted conditions including consistency: 2%, pH: 5, reaction time: 2 hours, and reaction temperature: 60 °C in dosing levels of 0.005%, 0.01% , and 0.015 % based on oven-dried weight of pulp. Handsheet making and characteristic measurement carried out by TAPPI test methods and also statistical analysis was conducted using completely randomized design. Fiber classification result showed that fines constitute about 31% of weight of the pulp. There are significant differences at 1% level among the pulp strength properties of OCC which treated with laccase enzyme. Tensile and burst indices significantly were increased compared to the control using 0.005% of laccase. Multiple Duncan test showed that the average of these two indices by using 0.005% and 0.015% laccase (based on O.D. weight of pulp) had no significant difference and placed in the same statistical group. The variation trend of tear index unlike the other indices was observed and concora medium test (CMT) decreased at all levels of the treatments. OCC pulp treated with 0.005% laccase-HBT (based on O.D. weight of pulp) is recommended according to the important role of tensile and burst strength in test liner for packaging industry. Due to decreasing of Concora medium test (CMT) by the enzyme, laccase application is not suitable for making corrugated paper.

In this study, effect of enzymatic deinking on mechanical properties of deinked pulp old coated magazine was investigated. The protocol for the enzymatic treatment of old coated magazine on a laboratory scale using cellulase and combination of callulase: lipase was developed as an effective method for paper recycling. The old coated magazine was prepared and pulped with pulp consistency for 4% and the pulping time for 2,5 min, temperature 20 and 50 C, at neutral PH. Then the pulps were deinked by Denver flotation cell at the laboratory of Azad University, science and research branch of Tehran. The study focused on analyzing the effects of enzyme treatment on mechanical strength of old magazine deinked pulp.The results showed that enzymatic treatment increased the mechanical strengths of the treated pulp compared to the control pulp except tear strength. The results of freeness showed that enzymatic treatment decreased the freeness of treated pulps. However, increasing the temperature of pulp decreased the freeness more.