Effect of microwave-vacuum drying on the physicochemical properties of a functional tomato snack bar.

BACKGROUND: Tomato is an indispensable ingredient of the Mediterranean diet. Reformulation of traditional Mediterranean products to increase the adherence of consumers is becoming popular. In this study, a tomato snack bar enriched with olive powder and pea protein was developed by using microwave-vacuum drying. Formulations also included tomato powder (TP) and low-methoxylated pectin (LMP) as a structuring agent. RESULTS: The moisture content of microwave-vacuum-dried samples varied in the range 13.6-19.8% and water activity (aw ) values were ~0.6. LMP and TP concentrations affected the color of microwave-vacuum-dried samples. However, the color mainly changed in conventionally dried samples due to browning. In microwave-vacuum-dried samples, lycopene content decreased with increasing LMP, but increased with increasing TP. Textural properties of microwave-vacuum-dried snack bars increased with increasing LMP and TP. CONCLUSION: Both texture and Fourier transform infrared spectroscopy results indicated that there was a network formation due to the contribution of protein and pectin; however, the type of interaction was highly dependent on the drying mechanism. Nuclear magnetic resonance relaxometry data showed that microwave-vacuum-dried samples had a more uniform water distribution. Besides its time and energy efficiency, microwave-vacuum drying improved the color and textural properties of tomato snack bars compared to conventionally dried ones. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The effects of pectin and wax on the characteristics of oil-in-water (O/W) emulsions.

The study was aimed to investigate characteristics of emulsion containing pectin, wax, maltodextrin, and carotenoid enriched flaxseed oil by means of stability, rheology, particle size, and low-resolution of time domain nuclear magnetic resonance (NMR) relaxometry measurements. Emulsions were prepared with different carotenoid enriched-flaxseed oil concentrations (6%, 9%, 12%, and 15% w/w) and ratios of maltodextrin/(pectin+wax) (3:1, 6:1, 9:1, and 12:1 g/g). Percentage separation of 12% oil 12:1 ratio of maltodextrin/(pectin+wax) (g/g), 15% oil 9:1, and 12:1 ratios of maltodextrin/(pectin+wax) (g/g) of emulsions was determined as 2.0 ± 0.5%, 4.0 ± 0.5%, and 8.0 ± 0.5%, respectively. No separation was observed in other emulsions. The rheological behavior of emulsions was best described by the power law model. When the concentration of pectin+wax in the emulsion decreased, the n values of the emulsions were close to 1, indicating that the fluid behavior approaches Newtonian behavior. Moreover, the emulsion viscosity was observed to increase when pectin and wax concentrations in the emulsion increased. The increase in pectin and wax concentration in emulsions with oil contents of 6% and 9% resulted in a reduction in the average particle size. However, if the oil concentration in the emulsions was 12% or more, the increase in the ratio of maltodextrin/(pectin+wax) (g/g) led to a decrease in the average particle size. NMR transverse relaxation times (T2 ) of emulsions were measured and results showed that T2 values for almost all formulations decreased when the ratio of maltodextrin/(pectin+wax) reduced. PRACTICAL APPLICATION: Study results demonstrated that the combination of pectin and wax together with maltodextrin as a filling material could be an alternative way to improve emulsion stability. Findings of this study provided useful guidance for the future studies about the potential use of pectin, wax, and maltodextrin as wall material in encapsulation of oils or in producing edible films.

Physical characterization of high methoxyl pectin and sunflower oil wax emulsions: A low-field 1 H NMR relaxometry study.

Pectin-wax-based emulsion systems could be used to form edible films and coatings with desired water permeability characteristics. Pectin is often used in food industry due to its gelling and viscosity increasing properties. Physical properties of pectin are highly dependent on its esterification degree. Waxes are commonly used as edible coatings to enhance the water barrier properties of food products. This study focuses on preparing emulsions with sunflower oil wax (SFW) and high methoxyl pectin (HMP) at different concentrations for any possible edible film or coating formulations. Sunflower oil (SFO) was added as the dispersed oil phase to these emulsions. Characterization of the emulsions was performed by using particle size, rheology, and time domain nuclear magnetic resonance (NMR) relaxometry measurements. Effects of HMP concentration and the presence of SFO in the emulsion formulations were explored. Mean particle size values were recorded between 1 and 3 µm. Rheology measurements showed that increasing HMP concentrations and presence of SFO in emulsions resulted in more pseudoplastic behavior. NMR transverse relaxation times (T2 ) were measured to detect the differences between the emulsions. Relaxation spectrum analysis was also conducted for a detailed understanding of the transverse relaxations. Addition of SFO and higher HMP concentrations decreased the T 2 values of the emulsion systems (P < 0.05). However, T2 decreasing effect of SFO was compensated at 10% (w/w) HMP concentration showing that SFO was well dispersed in this particular emulsion formulation. Changes in the rheological behavior and relaxation times provided insight on the formation and stability of the emulsions. PRACTICAL APPLICATION: Findings of this study can be utilized and integrated to produce edible films and coatings with different water permeability characteristics. This study showed that NMR relaxometry parameters were also effective in monitoring and determining the physical characteristics of the pectin-wax-based emulsion systems as other conventional techniques including rheology and particle size measurements. Our NMR relaxometry findings were in correlation with the flow behavior and particle size results of the investigated emulsion systems.

In vitro digestion of polysaccharide including whey protein isolate hydrogels.

Hydrogels are great systems for bioactive agent encapsulation and delivery. In this study, polysaccharide blended whey protein isolate (WPI) based hydrogels were loaded with black carrot (Daucus carota) concentrate (BC) and in vitro gastrointestinal release measurements were performed. Prior to 6 h digestion in simulated intestinal fluid (SIF), all hydrogels were exposed to simulated gastric fluid (SGF) for 2 h. Pectin (PC), gum tragacanth (GT) and xanthan gum (XG) were the polysaccharides used with WPI to manipulate the release behavior. Physico-chemical changes of the hydrogels throughout the digestion were evaluated by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) relaxometry measurements. Each polysaccharide induced different physico-chemical interactions within the hydrogels due to their distinct structural characteristics. Polysaccharide blending to hydrogels also retarded the release rates in all samples in SIF (p < 0.05). Moreover, microstructural differences between hydrogels were evaluated by scanning electron microscope (SEM) images.

Physico-Chemical Changes of Composite Whey Protein Hydrogels in Simulated Gastric Fluid Conditions.

Polysaccharide blended whey protein isolate (WPI) hydrogels were developed for the delivery of black carrot ( Daucus carota) concentrate as bioactive agent in simulated gastric fluid (SGF). Pectin (PC), gum tragacanth (GT), and xanthan gum (XG) were blended as additional polymers to modulate the release characteristics of the WPI hydrogels. Experiments showed that sole whey protein (C), XG, and GT blended hydrogels possessed restricted release profiles 67%, 61%, and 67%, respectively, whereas PC samples attained higher release rates (83%) ( p < 0.05). Interactions between polymers and aqueous medium were analyzed by nuclear magnetic resonance relaxometry. C (82 ms) and GT (84 ms) hydrogels attained higher T2 values than PC (74 ms) and XG (73 ms) samples in SGF. Hardness of only XG hydrogels increased from 1.9 to 4.1 N after gastric treatment. Physicochemical changes within hydrogels during release were also investigated, and hydrogels were proved to be appropriate for desired delivery purposes.