Salting-out Assisted Liquid-Liquid Extraction for Analysis of Caffeine and Nicotinic Acid in Coffee by HPLC-UV/Vis Detector

A salting-out assisted liquid-liquid extraction method followed by high performance liquid chromatography with ultravio-let-visible detector(SALLE-HPLC-UV/Vis)has been proposed for determination of caffeine and nicotinic acid in raw and roasted coffee samples.Various parameters affecting chromatographic separations including mobile phase composition,injec-tion volume,flow rate and column temperature were studied.Experimental parameters affecting the extraction efficiency of SALLE method such as type and volume of the organic solvent,type and amount of salt,pH of the sample,and concentration of the ion-pairing reagent were also studied and thereby optimum conditions were established.The calibration curves which were constructed at five different concentration levels using the optimum conditions exhibited good linearity,with the coef-ficient of determination(R2)0.999 and 0.995 for caffeine and nicotinic acid,respectively.The limits of detection(LOD)and quantification(LOQ)which were determined at 3 and 10 times signal-to-noise ratio were 0.05 and 0.13 mg/L for nicotinic acid and 0.20 and 0.63 mg/L for caffeine,respectively.Intra-and inter-day precision studies were demonstrated satisfactory precision with RSD values below 10.Relative recoveries were also studied,and their results were ranging from 82-122%for both raw and roasted coffee samples.The findings demonstrated that the proposed method could be used as an effective and best alternative for the determination of caffeine and nicotinic acid in raw and roasted coffee samples.

Antimicrobial potential of aqueous coffee extracts against pathogens and Lactobacillus species:A food matrix application

Coffee is recognized by its bioactive potential,mainly antioxidant and antimicrobial activity.The aim of this study was to evaluate the antimicrobioal potential of aqueous extracts of Coffea arabica(AR)(roasted)and Coffea canephora[roasted(CR)and green(CG)]against patogens Salmonella Typhimurium and Escherichia coli,and probiotics Lactobacillus plantarum and Lactobacillus rhamnosus.Firstly,the strain's sensitivity were tested by disk diffusion method,followed by the evaluation of growth kinetics(lag phase duration,maximum specific growth rate and logarithmic increase in the population)in culture media and in a food matrix(milk)by the adjustment of Gompertz predictive model.In the step of strain sensivity tests,S.Typhimurium and E.coli were sensitive against all coffee extracts from 0.5%to 5.0%,while the Lactobacilli growth were not affected.In the growth kinetic tests in culture media,roasted coffees extracts reduced logarithmic increase in the population and maximum specific growth rate and improved lag phase for S.Typhimurium;for E.coli the growth was completely inhibited with 2.5%CR and 5.0%AR.The correlations between growth parameters with coffee bioactive contents suggested that melanoidins had the main antimicrobial effect.In the step of food matrix application(growth kinetics in milk),the addition of 5.0%CR reduced S.Typhimurium and E.coli multiplication,while the probiotics L.plantarum and L.rhamnosus where not inhibetd,suggesting a selective effect of coffee extracts as an antimicrobial agent,which may be of great interest for the food industry,especially for probiotic foods application.