Publications by authors named "Niloufar Rafiee Tari"

2 Publications

  • Page 1 of 1

Emulsion acid colloidal stability and droplet crystallinity modulate postprandial gastric emptying and short-term satiety: a randomized, double-blinded, crossover, controlled trial in healthy adult males.

Am J Clin Nutr 2021 May 8. Epub 2021 May 8.

Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada.

Background: Emulsion droplet triacylglycerol (TAG) crystallinity and colloidal stability can alter the postprandial metabolism, although evidence of their interactive effects is limited.

Objectives: This acute meal crossover study investigated the influences of droplet TAG crystallinity at 37°C and colloidal gastric stability on gastric emptying (GE), acute lipemia, and satiety.

Methods: We gave 15 healthy adult males (mean ± SD age, 24.9 y ± 4.5 y; BMI, 26.0 kg/m2 ± 2.0 kg/m2; fasting TAG, 0.9 mmol/L  ± 0.3 mmol/L) 250 mL of four 20% palm stearin or palm olein emulsions with similar particle size distributions and containing partially crystalline droplets that remained stable (SS) or destabilized (SU) or containing liquid droplets that remained stable (LS) or destabilized (LU) when exposed to simulated gastric conditions. Baseline and 6-h postprandial ultrasound gastric antrum measurements, satiety visual analogue scales (VAS), and blood samples for analyses of plasma TAG, peptide YY (PYY), glucagon-like peptide-1 (GLP-1), ghrelin, leptin, glucose-dependent insulinotropic polypeptide, insulin, and glucose were collected. Changes from baseline and incremental area under the curve (iAUC) values were analyzed by repeated-measures ANOVA.

Results: TAG responses did not differ significantly. The gastric antrum area decreased faster (P ≤ 0.01) after treatment with the acid-unstable emulsions (SU and LU), and satiety VAS ratings and plasma endpoints differed between treatments. After LS treatment, participants had 65% and 59% lower 3-h iAUC values for hunger (P = 0.021) and desire to eat (P = 0.031), respectively, compared to after SU treatment. LS treatment resulted in higher 6-h iAUC values for ghrelin (141%; P = 0.023) and PYY (150%; P = 0.043) compared to SU treatment, and LS treatment also resulted in higher GLP-1 values compared to SU (38%; P = 0.016) and LU (76%; P = 0.001) treatment.

Conclusion: Emulsion acid colloidal stability, independent of TAG physical state, delayed GE, and satiety was enhanced after consuming acid stable emulsions containing TAG in the liquid state. The study was registered at as NCT03990246.
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May 2021

Effect of pH and heat treatment conditions on physicochemical and acid gelation properties of liquid milk protein concentrate.

J Dairy Sci 2021 Jun 25;104(6):6609-6619. Epub 2021 Mar 25.

Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada N1G 2W1.

Milk protein concentrates (MPC) are typically dried high-protein powders with functional and nutritional properties that can be tailored through modification of processing conditions, including temperature, pH, filtration, and drying. However, the effects of processing conditions on the structure-function properties of liquid MPC (fluid ultrafiltered milk), specifically, are understudied. In this report, the pH of liquid MPC [13% protein (70% protein DM basis), pH 6.7] was adjusted to 6.5 or 6.9, and samples at pH 6.5, 6.7, and 6.9 were subjected to heat treatment at either 85°C for 5 min or 125°C for 15 s. Sodium dodecyl sulfate PAGE was used to determine the distribution of caseins and denatured whey proteins in the soluble and micellar phases, and HPLC was used to quantify native whey proteins as a measure of denaturation, based on the processing conditions. Both heat treatments resulted in substantial whey protein denaturation at each pH, with β-lactoglobulin denatured more extensively than α-lactalbumin. Changes in liquid MPC physicochemical properties were monitored at d 1, 5, and 8 during storage at 4°C. Viscosity increased after heat treatment and also over time, regardless of pH and heating conditions, suggesting the role of whey protein denaturation and aggregation, and their interactions with casein micelles. The MPC samples processed at pH 6.9 had a significantly higher viscosity than those heated at pH 6.5 or 6.7, for both temperature and time conditions; and samples processed at 85°C for 5 min had higher viscosity than those heated at 125°C for 15 s. Particle size analysis indicated the presence of larger particles after 5 and 8 d of MPC storage after heating at pH 6.9. Acid-induced gelation of the liquid MPC led to significantly higher gel firmness after processing at 85°C for 5 min, compared with 125°C for 15 s. Also, gels made from MPC adjusted to pH 6.5 had higher storage moduli, with both time and temperature combinations, demonstrating the role of pH-dependent association of denatured whey proteins with casein micelles in gel network formation. These findings enable a better understanding of the processing factors contributing to structural and functional properties of liquid MPC and can be helpful in tailoring milk protein ingredient functionality for a variety of food products.
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June 2021