Microcystis aeruginosa/Pseudomonas pseudoalcaligenes interaction effects on off-flavors in algae/bacteria co-culture system under different temperatures

We conducted an experiment to study the interaction effects of Microcystis aeruginosa and Pseudomonas pseudoalcaligenes on off-flavors in an algae/bacteria co-culture system at three temperatures（24, 28 and 32℃）. Gas chromatography-mass spectrometry was applied to measure off-flavor compounds dimethyl sulfide（DMS）, dimethyl trisulfide（DMTS）,2-methylisoborneol, geosmin（GEO） and β-cyclocitral. During the lag phase of co-cultured M. aeruginosa（first 15 days）, P. pseudoalcaligenes significantly increased the production of DMS, DMTS and β-cyclocitral at all three temperatures. In the exponential phase of co-cultured M. aeruginosa（after 15 days）, M. aeruginosa became the main factor on off-flavors in the co-culture system, and β-cyclocitral turned to the highest off-flavor compound. These results also indicated that DMS, DMTS and β-cyclocitral were the main off-flavor compounds in our M. aeruginosa/P. pseudoalcaligenes co-culture system. Univariate analysis was applied to investigate the effects of M. aeruginosa and P. pseudoalcaligenes on the production of off-flavors. The results demonstrated that both M. aeruginosa and P. pseudoalcaligenes could increase the production of DMS and DMTS, while β-cyclocitral was mainly determined by M. aeruginosa. Our results also provide some insights into understanding the relationship between cyanobacteria and heterotrophic bacteria.

Sensory-directed flavor analysis of key odorants compounds development of French fries and oils in the break-in,optimum and degrading frying stage

The flavor is a decisive sensory characteristic that determines the popularity of French fries(FFs).During high-oleic rapeseed oil(RO)frying,the flavor development of FFs showed three noticeable stages including break-in(3.5%-7.5%of total polar compounds(TPC)),optimum(7.5%-22.18%of TPC),and degrading stages(above 22.18%of TPC).Further,in order to distinguish the key aroma compounds in each stage,the FFs prepared in RO at TPC of 3.5%(FF4),14.5%(FF15),and 26.96%(FF27)and their relevant oils(RO4,RO15,RO27)were selected for sensory-directed analysis.The results revealed that the FF4 had low contents of(E,E)-2,4-decadienal(deep-fried odor)which also caused lower sensory score in FF4 sample.The higher contents of(E,E)-2,4-decadienal in FF15 induced its higher deep-fried odor.The FF27 had higher hexanoic acid(sweaty odor),heptanoic acid,nonanoic acid,benzene acetaldehyde(stale odor),and trans-4,5-epoxy-(E)-2-decenal(metallic odor)compared with FF4 and FF15,thus leading to the undesirable flavor of FF27.Moreover,the decrease of 2,5-dimethylpyrazine and 2-ethyl-6-methyl-pyrazine in FF27 induced the lower roasty flavor,which may also lead to the decline of the sensory score.Similarly,the higher contents of(E)-2-undecenal,hexanoic acid,heptanoic acid,and nonanoic acid in RO27 lead to increase its rancid score and thus lower the sensory score.

Trace analysis of off-flavor/odor compounds in water using liquid-liquid microextraction coupled with gas chromatography--positive chemical ionization-tandem mass spectrometry

A rapid, inexpensive and laboratory friendly method was developed for analysis of off-flavor/odor compounds in fresh and salt water using gas chromatography with chemical ionization-tandem mass spectrometry. Off-flavor/odor compounds, included geosmin, 2- methylisobomeol （MIB）, 2-isobutyl-3-methyoxypyrazine （IBMP）, and 2-isopropyl-3-methoxypyrazine （IPMP）. Using this method, a single sample can be extracted within minutes using only 1 mL of organic solvent. The ion transitions for IPMP, IBMP, MIB, and geosmin were 153 〉 121, 167 〉 125, 152 〉 95, and 165 〉 109, respectively. The linearity of this method for analyzing MIB ranged from 4 to 200ng·L^-1, and from 0.8 to 200ng·L^-1 for the other analytes. Method recoveries ranged from 97% to 111% and percent relative standard deviations ranged from 3% to 9%, indicating that the method is accurate, precise, and reliable.

Overview on pulse proteins for future foods:ingredient development and novel applications

We are facing the challenge of climate change and food insecurity for a growing population.The current mode of animal protein production via animal agriculture is resource-intensive and unsustainable.Therefore,there is a need to find alternative sources of food protein that are environmentally sustainable.Plant-based proteins,specifically pulse-based proteins,provide a promising solution to the problem.This review aims to provide an overview and perspective on extraction,functionality,digestibility,sensory,and new food applications of pulse proteins.Two main methods,namely wet fractionation and dry fractionation are used to extract pulse-based proteins.As compared to dry fractionation,wet fractionation yields high purity protein,but the process alters the structure and function of the proteins.Various biochemical and physical techniques can be used to assist wet extraction process to increase protein yield and/or reduce extraction time.The main techno-functional properties of plant-based proteins determining their practical applicability are solubility,water/oil holding capacity(WHC/OHC),gelation,emulsification,foaming,and rheological properties.Nutritionally,pulse proteins are deficient in one or more essential amino acids.Strategies to overcome the deficiency are discussed.Volatile and non-volatile compounds inherent to pulses or developed during processing are mostly responsible for the off flavors in the extracted protein.Approaches to improve the pulse protein flavor and remove or modify off-flavors are discussed.Pulse-based protein ingredients have applications in bakery products,pasta,meat analogues,dairy alternatives,and beverages.Beyond these applications,there is a need to explore novel applications of pulse proteins in infant and children’s formula,beverages,breakfast cereals,flavor development,and extruded snack products,develop new applications such as personalized and precision nutrition and bioactive peptides,and employ innovative technologies such as 3D printing,extrusion,and artificial intelligence for pulse protein research.This review presents the current status,limitations,and future perspectives for developing pulse protein ingredients as future foods.This review aims to foster thinking and generate novel ideas for future research.