Abstract

To investigate the causes of food waste in Zanjan city, 30 bakery stores were selected randomly and by going directly to them, the components of the formulation that make up the bread was collected containing samples of flour , yeast , yeast bread consumption production. In this study the qualitative properties of yeast, the amount of bread waste, bread bakery shelf-life and moisture preservation were determined. Microbiological analysis were done on five types of flour, 6 types  of  yeast  and  24  types  of  sourdough  used  in  baking.  Furthermore,  consumption  of  soda  was determined (in  breads  with  a  pH  greater  than  6.2)  or its  use  in  the  production  of  bread  as  a  yeast alternative. The qualitative features of yeast showed that the half of the yeast samples had not ability to produce enough gas which was an effective technological problem at Zanjan bakeries (6.9%). Microbiological tests showed that the used yeast infected by E. coli but in the bread flour samples, the results  comply  with  the  standard.  Microbial  populations  in  different  sourdough  samples  were  very versatile and varied quantitatively with each other. Studies showed that about 5 percent of bakeries have used of soda as an alternative to yeast. Amount of the bread wastes reached to 27/17 % which the 0.5 % owned soda consumption, 6.9% belonged to low quality yeast and 5.17 % was due to non-compliance with fermentation time. The shelf life of bread and moisture preservation in pita bread with  a low pH level of 6.2 significantly were higher than breads with a pH greater than 2/6 respectively. So, due to the lower performance of yeast and lack  of  the  needed  time  for  properly  fermentation,  also  the  poor  quality  of  processed  breads  with baking  soda,  it  is  recommended  to use the healthy bakery yeast and sourdough with uniformity of microbial characteristics.