| Fire-roasted chilli sauce is a traditional Bai fermented food unique to Yunnan,made from a selection of fresh millet chillies from the mountainous areas of the Yunnan-Guizhou plateau,which are then fermented in an earthen jar at a high temperature using a characteristic heritage process.It is widely consumed by the local people of Yunnan and is popular with tourists because of its unique flavour and long shelf life.The traditional production of fire-roasted chilli sauce is mostly home made,with long fermentation cycles and natural fermentation susceptible to seasonal and environmental uncertainties,resulting in unstable product quality,high acidity,poor taste and possibly even many safety hazards.In this thesis,we used the Yunnan Bai hot chilli sauce as the research object,selected suitable and excellent lactic acid bacteria to ferment it,and made a food ferment with excellent performance,and optimised the processing process of fermenting hot chilli sauce.Finally,the physicochemical indexes and microorganisms of the fermentation process of fire-roasted chilli sauce inoculated with fermenting starter were analysed to provide a scientific and theoretical basis for effectively shortening the fermentation time of traditional fire-roasted chilli sauce,ensuring the quality and safety of fire-roasted chilli sauce,and providing a certain scientific and theoretical basis for further industrial development of related industries.The main conclusions are as follows:(1)Screening of excellent lactic acid bacteria fermentation strains.Sixteen strains of lactic acid bacteria were selected for the screening of good lactic acid bacteria for fermentation.The acid production capacity,salt tolerance and growth curve of lactic acid bacteria were used as indicators for the initial screening,and the nitrite degradation capacity was used as an indicator for the re-screening.After screening,three strains of Lactobacillus acidipiscis,Lactobacillus pentosaceus,and Lactobacillus farciminis,numbered M15,M12 and N5 were obtained as fermentor candidates.Three strains of Lactobacillus were found to have high growth capacity,with M15 having the highest acid production capacity and the lowest p H value of 3.5;N5 being more salt tolerant;and M12 being the fastest growing strain with the highest absorbance at 22 h of fermentation.The antagonism test showed that there was no antagonism between the three strains of lactic acid bacteria,and M15,N5 and M12 with 99.57%,98.74% and 98.55% of nitrite degradation respectively were finally selected as the dominant lactic acid bacteria strains for the subsequent fermentation of Fire-roasted chilli sauce.(2)Study on the fermentation performance of the dominant lactic acid bacteria.M15,M12 and N5 were used as fermenting strains for the fermentation of Yunnan Bai Fire-roasted chilli sauce.The p H value,total acid,nitrite residue and sensory evaluation of the fermented Fire-roasted chilli sauce were compared with those of the natural fermented Fire-roasted chilli sauce without inoculated bacteria to explore its potential as a fermenting starter for Fire-roasted chilli sauce.The best strain ratio of M15:M12:N5= 1:2:2 was obtained from the mixed bacteria test,and the fermentation performance of this compound formula was good,with p H 3.76,total acid content 1.36%,nitrite content 0.21 mg/kg and Sensory score 81,which was significantly higher than that of the single strain fermented and naturally fermented The Sensory score was 81,which was significantly higher than that of the single strain fermented and naturally fermented Fire-roasted chilli sauce.(3)Development of fermenting starters for Fire-roasted chilli sauce.M15,M12 and N5 were made into lactic acid bacteria slurry in the optimal ratio of 1:2:2,and then vacuum freeze-dried with different protectants to investigate the effect of different protectants on the survival rate of lyophilised strains.The results showed that the protective starter formulation 2,with 12% skim milk,1% alginate,1% monosodium glutamate and 3%glycerol,had the best freeze-drying protection effect,and the survival rate of the strain after freeze-drying was 90.82%.(4)Optimisation of fermentation process conditions for Fire-roasted chilli sauce.The developed fermenting starter was inoculated into the Fire-roasted chilli sauce at 3%inoculum,and through single-factor experiments and response surface optimization,the best process for Fire-roasted chilli sauce was determined to be 5.11% fermenting starter addition,5 days fermentation time,6.45% sugar addition,3.49% salt addition and 35℃fermentation temperature.The fermented Fire-roasted chilli sauce produced under these conditions had a homogeneous colour,a distinctive sour and spicy aroma,a good taste and a harmonious structure.(5)Effect of fermentation with fermenting starters on the quality of fire-roasted chilli sauce.On the basis of the optimum process conditions,a comparative analysis of the changes in the physicochemical indexes of the fermented Fire-roasted chilli sauce in the test group inoculated with fermenting starter and the control group in the natural fermentation process was conducted,The total acid content(1.35%)and sensory score(85points)of the product were much higher than those of the control group(0.54%,64 points),indicating that the direct-injection fermentative starter has excellent fermentation performance and can significantly improve the quality and safety and sensory quality of the Fire-roasted chilli sauce,and has certain potential for application.(6)Analysis of volatile flavour substances in fire-roasted chilli sauce by GC-IMS technique.A total of 55 volatile flavour substances were detected in Fire-roasted chilli sauce samples,mainly esters(14),alcohols(12)and ketones(11);the differences between Fire-roasted chilli sauce made by two different fermentation methods were analysed by two-dimensional difference spectroscopy,fingerprinting and PCA analysis.good,with a substantial increase in volatiles such as esters and alcohols and a relative decrease in volatiles such as aldehydes and ketones.There were differences in the characteristic flavours of the two Fire-roasted chilli sauce,with significant changes in the aroma composition of the fermented Fire-roasted chilli sauce. |
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