Simultaneous analysis of carbohydrates and organic acids by HPLC-DAD-RI for monitoring goat's milk yogurts fermentation

Abstract

During yogurt manufacture, the lactose fermentation and organic acid production can be used to monitor the fermentation process by starter cultures and probiotic bacteria. In the present work, a simple, sensitive and reproducible high-performance liquid chromatography with dual detectors, diode array detector and refractive index was validated by simultaneous analysis of carbohydrates and organic acids in goat milk yogurts. In addition, pH and bacterial analysis were performed. Separation of all the compounds was performed on an Aminex HPX-87H column (300×7.8 mm, 9 µm) utilizing a 3 mmol L(-1) sulfuric acid aqueous mobile phase under isocratic conditions. Lactose, glucose, galactose, citric, lactic and formic acids were used to evaluate the following performance parameters: selectivity, linearity, precision, limit of detection (LOD), limit of quantification (LOQ), decision limits (CCα), detection capabilities (CCβ), recovery and robustness. For the method application a six goat milk yogurts were elaborated: natural, probiotic, prebiotic, symbiotic, cupuassu fruit pulp, and probiotic with cupuassu fruit pulp. The validated method presented an excellent selectivity with no significant matrix effect, and a broad linear study range with coefficients of determination higher than 0.995. The relative standard deviation was lower than 10% under repeatability and within-laboratory reproducibility conditions for the studied analytes. The LOD of the method was defined from 0.001 to 0.003 µg g(-1), and the LOQ from 0.003 to 0.013 µg g(-1). The CCα was ranged from 0.032 to 0.943 µg g(-1), and the CCβ from 0.053 to 1.604 µg g(-1). The obtained recovery values were from 78% to 119%. In addition, the method exhibited an appropriate robustness for all parameter evaluated. Base in our data, it was concluded that the performance parameters demonstrated total method adequacy for the detection and quantification of carbohydrates and organic acids in goat milk yogurts. The application of the method was successfully applied to monitoring different goat milk yogurts during fermentation.

Different Ultrasound Exposure Times Influence the Physicochemical and Microbial Quality Properties in Probiotic Goat Milk Yogurt

“…The pH values of yogurt samples during storage ( Figure 2 ) coincided with those reported in the literature (4.1–4.6) for goat’s yogurt samples during cold storage [ 4 , 53 ]. During yogurt processing, the fermentation of lactose into organic acids by LAB lowers the pH value [ 49 ]; therefore, the most critical factor related to pH change during the dairy fermentation process is the LAB activity [ 38 ].…”

“…Lactose and lactic acid are the major disaccharide and organic acid, respectively, in fermented dairy products [ 52 , 53 ], as observed herein ( Table 2 ). However, the lactose values (40.16 to 44.99 mg g −1 ) reported for goat’s fermented milk [ 53 ] were slightly lower than those found by us (48 to 50 mg g 1 ) in goat’s milk yogurts ( Table 2 ). It can be justified by possible differences between both studies regarding the lactose content in the unfermented milk used to elaborate fermented dairy products.…”

Milk from different species on physicochemical and microstructural yoghurt properties

“…Carbohydrates (lactose, galactose, and glucose) and organic acids (lactic, citric, and formic acids) were determined by high-performance liquid chromatography (HPLC). Extraction of these molecules was carried out as described by González de Llano et al (1996) with slight modifications (COSTA et al, 2016b). Briefly, 5 mL of H 2 SO 4 (45 mmol/L) was added to 1 g of yoghurt samples and homogenized for 1 min in the vortex.…”

Lactose Hydrolysis and Organic Acids Production in Yogurt Prepared With Different Onset Temperatures of Enzymatic Action and Fermentation

“…Although a lower level of lactose results in a higher level of glucose and galactose, as it is seen in traditional yogurts (20) , the addition of the enzyme showed a significantly lower lactose content, however, galactose and glucose values were not very high. The lactose hydrolysis by enzymatic via is one of the most evaluated strategies to achieve yogurt with low lactose content (14) .…”