A comprehensive review on yogurt syneresis: effect of processing conditions and added additives.

Yogurt, produced by the lactic fermentation of milk base, is an important dairy product worldwide. One of the essential sensory properties of yogurt is the texture, and some textural defects such as weak gel firmness and syneresis likely occur in various types of yogurts, affecting consumer acceptance. In this regard, various strategies such as enrichment of milk-based with different additives and ingredients such as protein-based components (skimmed milk powder (SMP), whey protein-based powders (WP), casein-based powders (CP), and suitable stabilizers, as well as modification of processing conditions (homogenization, fermentation, and cooling), can be applied in order to reduce syneresis. The most effective proteins and stabilizers in syneresis reduction are CP and gelatin, respectively. Furthermore, yogurt's water holding capacity and syneresis can be affected by the type of starter cultures, the protolithic activity, production of extracellular polysaccharides, and inoculation rate. Moreover, optimizing the heat treatment process (85 °C/30 min and 95 °C/5 min), homogenization (single or dual-stage), incubation temperature (around 40 °C), and two-step cooling process can decrease yogurt syneresis. This review is aimed to investigate the effect of fortification of the milk base with various additives and optimization of process conditions on improving texture and preventing syneresis in yogurt.

Rapid determination of ampyra in urine samples using dispersive liquid-liquid microextraction coupled with ion mobility spectrometry.

Ampyra (AMP, 4-Aminopyridine) is a potassium channel blocker that attracts growing research interest due to its adverse effects at high doses. The fast analysis of AMP is challenging because it typically requires complex analytical techniques. In this research, we developed and validated a novel method to assess the fast and quantitative analysis of AMP from real samples. This method combines the strength of ion mobility spectrometry (IMS) for rapid detection and the dispersive liquid-liquid microextraction as a fast and effective preconcentration method for the preconcentration/extraction of AMP. In this method, Ag nanoparticles were used as modifier agents. Moreover, the proposed mechanism for interaction of AMP with AgNPs was investigated based on the quantum theory of atoms in molecules (QTAIM) analysis. Also, the sensitivity of the proposed method was improved through the application of a delay on the carrier gas flow after sample injection. Under the optimum conditions, the developed method detected AMP in the linear range of 0.4-16 µmol L-1 with a detection limit of 0.12 µmol L-1. Finally, the developed method was successfully employed to quantify AMP in urine samples. Method validation was performed by comparing our results with those obtained by HPLC-UV/Vis, confirming the applicability of the proposed method for the AMP analysis in real samples. The proposed method will open up a new door toward developing simple, fast, and effective analytical methods.

Polycyclic aromatic hydrocarbons (PAHs) content of edible vegetable oils in Iran: A risk assessment study.

Totally forty samples (23 brands) of different types of edible oils including frying oil (n = 14), blended oil (n = 13), sunflower oil (n = 6), corn oil (n = 5) and canola oil (n = 2) from Iran's market were analyzed for PAHs content by a High-performance liquid chromatography coupled with fluorescence detector. Also, the Health risk assessment in the adults and children consumers were estimated by the calculating margin of exposure (MOE) and the incremental lifetime cancer risk (ILCR) in the Monte Carlo Simulation (MCS) method. Approximately all of the samples contained different amounts of PAHs, while concentrations of BaP, PAH 4, PAH 8 and PAH 13 were reported as 0.90-11.33, 3.51-84.03, 7.41-117.12 and 129.28-19.54 µg/kg, respectively. Light polycyclic aromatic hydrocarbons corresponded to 65% of total PAHs while the remaining 35% belonged to heavy polycyclic aromatic hydrocarbons. Based on BaP content, 12 samples were above the standard limits (2 µg/kg) which set by the Standard Organization of Iran and the European Union, whereas 15 samples exceeded maximum limit 10 µg/kg set for PAH 4 established by EU. Percentile 95% of MOE in the adults due to ingestion of sunflower, corn, frying and blended oils were determined as 4.10E+5; 4.05E+5; , 2.17E+5, 2.33E+5, respectively and in the children due to ingestion of sunflower oil, corn oil, frying oil and blended oil were calculated as 5.38E+4, 4.49E+4, 2.86E+4, 3.37E+4. Regarding the percentile of 95% ILCR in the adults due to ingestion of sunflower oil, corn oil, frying oil and blended oil were reported as 4.5E-6, 4.17E-6l, 5.20E-6, 4.93E-6 and also this value in the children in the same rank order of products can be summarized as 3.43E-5, 3.94 E-5, 3.17E-5, 3.76E-5. The rank order of edible oils investigated based on MOE was sunflower oil > corn oil > blended oil > frying oil; and based on ILCR, frying oil > blended oil > sunflower oil > corn oil. The health risk assessment according to MCS method indicated that adults and children are not at considerable health risk; MOE ≥ 1E+4 and ILCR < 1E-4).

Extraction of caffeine and catechins using microwave-assisted and ultrasonic extraction from green tea leaves: an optimization study by the IV-optimal design.

In this research, optimal conditions for extraction of caffeine and polyphenols were established from Iranian green tea leaves. In the first step, caffeine was extracted with efficacy about 86% versed to 4.5% of EGC + EGCG. The EGCG + EGC was extracted from partially decaffeinated green tea leaves through microwave-assisted extraction (MAE) and ultrasound-assisted extraction (USE) with efficiency levels of 95 and 85%, respectively. The best results for the MAE process were obtained with 7.8 min and three number of extraction cycles and for the USE process were as followed: time 57 min, temperature 65 °C, and the number of extraction cycles 3. The total phenol content values at the best conditions of MAE and the USE processes were 125 ± 5 and 96 ± 6 mg gallic acid/g DW. The 50% inhibition (IC50) on 1,1-diphenyl-2-picrylhydrazyl (DPPH) were 56 and 66 mg/g of phenol for the MAE and USE processes.

Furanic compounds and furfural in different coffee products by headspace liquid-phase micro-extraction followed by gas chromatography-mass spectrometry: survey and effect of brewing procedures.

In this study, the levels of furan, 2-methylfuran, 2,5-dimethylfuran, vinyl furan, 2-methoxymethyl-furan and furfural in different coffee products were evaluated. Simultaneous determination of these six furanic compounds was performed by a head space liquid-phase micro-extraction (HS-LPME) method. A total of 67 coffee powder samples were analysed. The effects of boiling and espresso-making procedures on the levels of furanic compounds were investigated. The results showed that different types of coffee samples contained different concentrations of furanic compounds, due to the various processing conditions such as temperature, degree of roasting and fineness of grind. Among the different coffee samples, the highest level of furan (6320 µg kg⁻¹) was detected in ground coffee, while coffee-mix samples showed the lowest furan concentration (10 µg kg⁻¹). Levels in brewed coffees indicated that, except for furfural, brewing by an espresso machine caused significant loss of furanic compounds.

Determination of polycyclic aromatic hydrocarbons in smoked fish samples by a new microextraction technique and method optimisation using response surface methodology.

Microwave-assisted extraction coupled with dispersive liquid-liquid microextraction as a recently introduced method was applied to determine polycyclic aromatic hydrocarbons in Iranian smoked fish. The results showed that the interaction of hydrolysing solution volume with ethanol ratio, volumes of extracting and disperser solvent is significant in the obtained model. Optimized conditions were: a hydrolysing solution volume 10 ml with 50% ethanol, a pH of 5, and extracting and disperser solvent volumes of 150 and 500 µl respectively. The level of 16 polycyclic aromatic hydrocarbons (PAHs) was determined in 80 smoked fish consisting of four species. The contamination of benzo[a]pyrene in all samples except three was below the European Commission's maximum level of 2 µg kg(-1) for smoked fish, while the ∑4 PAHs (benzo[a]pyrene, chrysene, benzo[a]anthracene and benzo[b]fluoranthene) were between 3 and 12 µg kg(-1) wet weight in all samples. Of the species examined, Hypophthalmichthys molitrix had the highest PAHs (∑16).

Microwave-assisted extraction and dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry for isolation and determination of polycyclic aromatic hydrocarbons in smoked fish.

A simple and efficient method was developed using microwave-assisted extraction (MAE) and dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry (GC-MS) for the extraction and quantification of 16 polycyclic aromatic hydrocarbons (PAHs) in smoked fish. Benzo[a]pyrene, chrysene and pyrene were employed as model compounds and spiked to smoked fish to assess the extraction procedure. Several parameters, including the nature and volume of hydrolysis, extracting and disperser solvents, microwave time and pH, were optimized. In the optimum condition for MAE, 1g of fish sample was extracted in 12 mL KOH (2M) and ethanol with a 50:50 ratio in a closed-vessel system. For DLLME, 500 µL of acetone (disperser solvent) containing 100 µL of ethylene tetrachloride (extraction solvent) was rapidly injected by syringe into 12 mL of the sample extract solution (previously adjusted to pH 6.5), thereby forming a cloudy solution. Phase separation was performed by centrifugation and a volume of 1.5 µL of the sedimented phase was analyzed by GC-MS in select ion monitoring (SIM) mode. Satisfactory results were achieved when this method was applied to analyze the PAHs in smoked fish samples. The MAE-DLLME method coupled with GC-MS provided excellent enrichment factors (in the range of 244-373 for 16 PAHs) and good repeatability (with a relative standard deviation between 2.8 and 9%) for spiked smoked fish. The calibration graphs were linear in the range of 1-200 ng g(-1), with the square of the correlation coefficient (R(2))>0.981 and detection limits between 0.11 and 0.43 ng g(-1). The recoveries of those compounds in smoked fish were from 82.1% to 105.5%. A comparison of this method with previous methods demonstrated that the proposed method is an accurate, rapid and reliable sample-pretreatment method that gives very good enrichment factors and detection limits for extracting and determining PAHs from smoked fish.