5758

5373

كارشناسي ارشد

علوم و صنايع غذايي

اصفهان:دانشگاه صنعتي اصفهان، دانشكده كشاورزي

1389

هفده،152ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

جواد كرامت، محمد حسين عزيزي

مهدي كديور، زهره اميري

28/1/90

علي نصيرپور، احمد ارزاني

مهندسي كشاورزي

ID5373

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

35 The Effects of Storage Freezing and Baking Conditions of Pre Baked Bread on the Staling of Full Baked Breads Leila Kaviani L kaviani@ag iut ac ir Date of Submission 2011 3 1 Department of Food Science and Technology Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi M0hham hosein Azizi mh azizi tm@yahoo com Supervisors Javad Keramat keramat@cc iut irAbstractConsidering the population growth and the high consumption of bread in the country it is not possibleto produce high quality bread with common traditional methods It seems that the industrialproduction of bread is the only way forward to meet this need Bakery products have a short shelf lifeafter production and they become quickly stale This includes a series of physicochemical changesthat cause the loss of freshness and reduces the quality of bread By applying various additives andenzymes bakeries and scientist have put lots of efforts to delay this process One of the methods usedto increase the shelf life of bread is adding a freeze stage to the production process that can beconducted in two forms A freezing the dough before baking due to physical damages to thestructure of protein networks and also the damages brought about to the yeast during storage atfreezing temperatures the final bread size in this method is reduced B freezing bread after the partialbaking this method has different advantages such as selling fresh bread at any time of day no need tothe skilled labor no need to special facilities for the preparation of bread and also increasing the lifecycle of the bread and reducing the wastes In the present paper to study effects coddling and freezingstorage on the level of staling in the final product different samples of bread were pre baked at 7 14and 21 minutes and were consequently stored one three and five weeks at the temperature of 18 C After the freezing periods all samples were de iced and the baking process were completed After thisstage to evaluate the level of staling each sample was kept in the refrigerator temperature in a periodof 1 to 5 days To control the level of staling different variables such as the amount of retrogradationof starch firmness and color of bread crust were measured by DSC Instron and Hunter Lab machinesand sensory evaluation of samples was also conducted by 7 trained assessors Test results showed thatincreasing the pre baking time with reducing the amount of moisture of pre baked bread prior tofreezing has an important role in improving the texture of the final bread Because the damagescaused by the growth of ice crystals during the freezing time and destruction of granules of starch andthe gluten network results in the hardening of bread tissue and increases the retrogradation of starch On the other hand staling in samples with time shorter pre baking in similar circumstances occursmore quickly The results showed that by increasing the storage time in 4 C retrogradation ofstarch in all samples would be increased Sensory evaluation also confirms the testing results andassessors judging the quality of the bread confirmed that the sample with 7 minutes of time pre bakedhad an undesirable texture quality Keywords pre baked bread freezing stailing Instron Hunter lab DSC

جواد كرامت، محمد حسين عزيزي

مهدي كديور، زهره اميري

علي نصيرپور، احمد ارزاني