Preparation of lactic acid bacteria compound starter cultures based on pasting properties and its improvement of glutinous rice flour and dough

The effects of 5 lactic acid bacteria(LAB)fermentation on the pasting properties of glutinous rice flour were compared,and suitable fermentation strains were selected based on the changes of viscosity,setback value,and breakdown value to prepare LAB compound starter cultures.The results revealed that Latilactobacillus sakei HSD004 and Lacticaseibacillus rhamnosus HSD005 had apparent advantages in increasing the viscosity and reducing the setback and breakdown values of glutinous rice flour.In particular,the compound starter created using the two abovementioned LAB in the ratio of 3:1 had better performance than that using a single LAB in improving the pasting properties and increasing the water and oil absorption capacity of glutinous rice flour.Moreover,the gelatinization enthalpy of the fermented samples increased significantly.For frozen glutinous rice dough stored for 28 days,the viscoelasticity of frozen dough prepared by compound starter was better than that of control dough,and the freezable water content was lower than that of control dough.These results indicate that compound LAB fermentation is a promising technology in the glutinous rice-based food processing industry,which has significance for its application.

Effect of a compound starter cultures inoculation on bacterial profile and biogenic amine accumulation in Chinese Sichuan sausages

Effects of a starter culture composed of Lactobacillus sakei,Pediococcus pentosaceus,Staphylococcus xylosus and S.carnosus at the ratios(m/m)of 1:1:1:1 on bacterial profile and biogenic amine accumulation in Chinese Sichuan sausages were demonstrated.In starter culture-inoculated sausages,Lactobacillus spp.,Pediococcus spp.and Staphylococcus spp.were predominant bacterial genus and their relative abundances ranged from 70.14%to 25.98%,57.66%to 14.08%,and 15.71%to 13.40%during fermentation,respectively.Accordingly,Lactobacillus spp.and Weissella spp.were predominant bacterial genus and their relative abundances ranged from 63.14%to 24.70%and 49.40%to 11.96%during spontaneous fermentation,respectively.Furthermore,the abundances of undesirable microorganisms such as Yersinia spp.,Enterobacter spp.,Acietobacter spp.and Psychrobacter spp.were lower than that of the control.The levels of histamine,putrescine,tyramine and cadaverine in Chinese Sichuan sausages with starter cultures inoculation were significantly lower(P<0.05)than that of the control,and were decreased by 83.09%,69.38%,51.87%and 57.20%,respectively,at the end of the ripening.These results revealed that the starter cultures inoculation was a better alternative for microbial quality improvement and biogenic amine reduction of Chinese Sichuan sausages with good sensory attributes.

Contribution of mixed commercial starter cultures to the quality improvement of fish-chili paste,a Chinese traditional fermented condiment

This study evaluated the effects of commercial starter cultures on the microbial counts,protein degradation,biogenic amines and volatile compounds in fermented fish-chili paste.Four inoculated groups with different starter cultures and one group without inoculation were investigated.The results revealed that the application of mixed starter cultures promoted the growth of lactic acid bacteria and yeast,while effectively inhibited the Enterbacteriaceae counts compared with the spontaneously fermented group.The inoculation with mixed starter cultures resulted in higher levels of umami-tasting free amino acids(FAAs)in all inoculated groups.Highest content of sweet-tasting FAAs was found in group HS(Pichia anomala+Staphylococcus xylosus+Staphylococcus carnosus+Pediococcus pentosaceus+Pediococcus acidilactici),and much lower bitter-tasting components were presented in group HW(Pichia anomala+Staphylococcus xylosus+Staphylococcus carnosus),HS and HV(Pichia anomala+Lactobacillus plantarum).In addition,total levels of biogenic amines detected in all inoculated samples were significantly lower compared with control,especially the content of tyramine(P<0.05).For the volatile compounds,more esters as well as less undesirable odor substances such as aldehydes,were exhibited in four inoculated groups.

Development of Starter Culture for the Production of African Condiments and Seasoning Agents

As a process, food fermentation dates back at least 6000 years and is likely to be derived from microbial interactions of an appropriate nature. Fermentation has allowed our ancestors to survive the winter season in temperate and cooler regions and those in the tropics to survive the periods of drought by improving food shelf-life and safety. Traditional fermentation process is still used as a replacement where there is no refrigeration or other means available for food storage. In general, fermented foods can be defined as foods produced through controlled microbial growth and the conversion of food components through enzymatic actions. They are generally appreciated for characteristics such as pleasant taste, aroma, texture and improved cooking and processing properties. Microorganisms contribute to the development of characteristic properties such as taste, smell, visual appearance, texture, shelf-life and protection by virtue of their metabolic activities. Enzymes indigenous to the raw materials may play a role in enhancing these characteristics. The use of starter cultures is a hallmark of industrial food fermentation and their introduction has been followed by a continuous search to improve them. Examples of desired properties in starter cultures include robustness during manufacturing, fast growth, high biomass yield and product yield and specific organoleptic properties. Quality, safety and acceptability of traditional fermented foods may be significantly improved through the use of starter cultures selected on the basis of multifunctional considerations, also taking into account the probiotic concept and possibilities offered for improved health benefits. Focused studies toward the introduction of starter cultures for small-scale fermentations seem more than justified, and in fact, deserve the highest priority.

3D printed lactic acid bacteria hydrogel:cell release kinetics and stability

In this study,a new type of 3 D printed living biological hydrogel was developed by integrating lactic acid bacteria(LAB)into biocompatible and non-toxic polymer materials.Interestingly,the living materials loaded with LAB can be freeze-dried and reused for more than 100 times.The bio-hydrogel can be used to co-culture different LAB and keep its fermentation performance stable in long-term use.The release kinetics model and response surface method were used to simulate and optimize the bacteria release mode in the bio-hydrogel.The results show that the release of bacteria from hydrogel is regulated by the coupling of Fickian diffusion and polymer swelling.The stability of LAB hydrogel was evaluated by reuse experiments.The images of confocal microscopy and scanning electron microscope showed that the bacteria with high cell viability were distributed in the hydrogel and intact structure of the living hydrogel was maintained after 100 times of reuse as yoghurt starter.In conclusion,the 3 D printed LAB bio-hydrogel developed in this study has the advantage of reuse and sustainability,which is expected to open up a new way for the preparation of food culture starter.

Influence of the starter culture on the volatile profile of processed cocoa beans by gas chromatography–mass spectrometry in high resolution mode

Cocoa is the main component of chocolate.It is widely accepted that cocoa quality largely depends on the processing,especially the fermentation step.Traditionally,fermentation takes place spontaneously by the endogenous microbiota;however,the process can lead to poor quality and heterogeneity of the final product.In this study,we evaluated the influence of the starter culture on the profile of volatiles during fermentation of commercial volumes of Mexican cocoa.Volatiles were also analyzed in post-fermented cocoa samples obtained after drying,roasting,and conching.Our results revealed a most desirable volatile profile in cocoa fermented with starter culture,mainly due to the higher relative content of alcohols(40%)and aldehydes(3.5%),but also due to a lower acidity(<1%)as compared to endogenous fermentation(acids,65%;alcohols,2%;and aldehydes<0.5%).Additionally,it is remarkable,the higher content of pyrazines in the inoculated samples after processing.

Perspective on the use of synthetic biology in rudimentary food fermentations

Rudimentary food fermentation can be defined as a spontaneous process of conversion of food components through enzy-matic action.A great variety of fermented foods are produced using spontaneous approaches;however,cocoa and coffee represent the most important agricultural commodities on international markets.As a manner to increase the efficiency of these processes,starter cultures have been developed and applied under field conditions.The selection process begins with the recovery of microbial strains from spontaneous fermentation through phenotypic and metabolic traits.Next,mutation-based breeding is used to develop and improve well-adapted starter cultures.With advances in synthetic biology,especially in the last decade,the development of robust cellular fabrications with high fermentative capacity has become easier-largely due to the development of genomic approaches,such as next-generation sequencing techniques,CRISPR-Cas system and bioinformatics tools.This review brings prospects on the use of synthetic biology to design new robust strains for use in cocoa and coffee fermentations,but which can be extended to other rudimentary foods.In addition,metabolic traits and target genes(e.g.,UvrA,RecA,GPD1,and GPP2)are proposed as a starting point for the improvement of cocoa and coffee starters.Finally,the regulatory and safety requirements for these food crops are addressed.This review aims to stimulate research on the process of fermentation and the associated synthetic biology tools to produce fermented food efficiently and sustainably.

Recent developments of lactic acid bacteria and their metabolites on foodborne pathogens and spoilage bacteria:Facts and gaps

Lactic acid bacteria(LAB)are common microorganisms found in various ecosystems including in plants,fermented foods,and the human body.Exploring the biodiversity of lactic acid microflora and characterization of LAB is a new approach to form a variety of starter communities to create innovative nutritional food matrices.There has been growing interest in LAB isolated from non-dairy environments as these bacteria exhibit significant metabolic diversity and have unique taste-forming activities.Disease may be prevented,or treated by LAB but the treatment of disease conditions with LAB is highly dependent on the host's microbiome and diet and varies in both effectiveness and side effects from individual to individual.Future perspectives on the study of LAB may be related to the expansion of our knowledge in the fields of genetics and genetic engineering.The application of genetic science may help to improve existing strains and develop new strains with characteristics designed for specific purposes.Therefore,the preservative effects of LAB and their metabolites,as well as their interaction on the growth of food borne pathogens and food spoilage microorganisms were elucidated.In addition,the competitive models for microbial growth between LAB and other microorganisms as well as the role of LAB in the elimination of toxic compounds in food products were discussed.Moreover,the review provided an overview of the risks and benefits of using LAB in the food industry.