Low-bacterial Production Of Wheat Flour And Its Effects On Flour Quality

Fresh noodle products are popular because of their freshness,unique flavor and taste,while the short shelf life limits their development.The high bacterial content of wheat flour is the main reason for the high initial bacterial content and the short shelf life of fresh noodles.High bacterial content will make flour mildew easily,and even produce mycotoxins;meanwhile,when wheat flour is processed into fresh noodles,microorganisms will grow and multiply rapidly,resulting in acidification and mildew,and shortening the shelf life of noodles.In order to decrease the number of microorganisms in wheat flour and improve the safety quality of wheat flour and flour-based products,this paper was focused on the low-bacterial processing of wheat flour,as well as its impacts on the quality of wheat flour.Firstly,the microbial changes in wheat cleaning stage were studied.The results showed that the microbes in wheat grains were decreased significantly with the cleaning process going on(p<0.05),but increased dramatically as the tempering time going on.After wheat wiping,the total plate count,the yeast and mould count,and the mesophilic aerobic spores in wheat were decreased by 1.29,1.13,and 0.25 lgCFU/g,respectively.After tempering,the total plate count,the yeast and mould count,and the mesophilic aerobic spores in wheat were decreased by 1.61,1.54,and 0.49 lgCFU/g,respectively.Secondly,Results showed that tempering with water under high cleanliness,slightly acidic electrolyzed water(SAEW)and steam could reduce the number of microbes in wteat grains significantly(p<0.05).Compared to tempering with deionized water,the total plate count,along with the yeast and mould count in wheat was decreased by 0.65 and 0.49 lgCFU/g when tempering with 70 mg/L SAEW,while the total plate count,and the yeast and mould count in straight flour were decreased by 0.72 and 0.62 lgCFU/g,respectively,but the mesophilic aerobic spores showed little difference.After tempering with SAEW,there was no significant difference on the quality parameters of straight flour.However,the protein was aggregated and the dough structure of clear flour was enhanced.At the same time,the starch viscosity was decreased significantly(p<0.05),and the activities of PPO and LA in clear flour and bran were inhibited.When the steam treatment time was 320 s,the total plate count,the yeast and mould count,and the mesophilic aerobic spores in wheat were decreased by 2.10,2.34,and 0.87 lgCFU/g,respectively.While the total plate count,the yeast and mould count,and the mesophilic aerobic spores in wheat flour were decreased by 1.74,1.99,and 1.01 lgCFU/g,respectively.Nuclear magnetic resonance results showed that wheat tempering with steam(WTS)accelerated the water migration in wheat grains,which shortened the tempering time from 24 h to 7.5 h.Meanwhile,after WTS,the dough development time along with stability time was increased,which represented that the gluten network structure was enhanced.The gelatinization degree was increased while the gelatinization temperature was decreased,and the starch viscosity was increased first and then decreased.In addition,the activities of PPO,LA and LOX were significantly inhibited.Thirdly,results showed that after treating wheat with ozone(TWO)or pre-debranning treatment(PDT),the number of microbes in wheat flour was reduced significantly(p<0.05)while the ash content and particle size of wheat flour were both increased with the content of damaged starch decreased.When the treatment time was 60 min,the total plate count,the yeast and mould count,and mesophilic aerobic spores in wheat flour were decreased by 1.33,1.16 and 0.63 lgCFU/g,respectively.At the same time,after TWO,the dough development time and the stability time of wheat flour were increased with the protein SDS solubility decreased,which represented that the gluten network structure was enhanced.Moreover,the starch viscosity was increased.When the debranning rate was 4.46%,the total plate count,the yeast and mould count,and the mesophilic aerobic spores in wheat were decreased by 1.29,1.14 and 0.61 lgCFU/g,respectively.The total plate count,the yeast and mould count,and the mesophilic aerobic spores in wheat flour were decreased by 1.06,1.15 and 0.65 lgCFU/g,respectively.Finally,the microbial content in different flour streams and the effects of comprehensively antibacterial measures on the number of microbes in straight flour were also studied.The results showed that the microbial content of the front reduction flour was the lowest,and the microbial content of the bran was the highest.Generally speaking,the clean flour had lower microbial content,while the clear flour had higher microbial content.The number of microorganisms in each flour stream was decreased after different antimicrobial treatment,and the treatment method showed better antimicrobial effect when close to the wheat cortex.After comprehensive treatment,the total plate count,the yeast and mould count,and the mesophilic aerobic spores of straight flour were 3.09,2.27 and 1.87lgCFU/g,respectively.