ABSTRACT
In the last decade, research has focused on examining the fundamental interactions occurring in triglycerides, aiming to comprehend the self-assembly of crystalline nanoplatelets (CNPs) and their role in forming larger hierarchical structures essential for fat functionality. Microscopy research on CNPs frequently requires disruptive preparatory techniques, such as deoiling and sonication, to achieve quantitative outcomes. Conversely, X-ray scattering has proven to be an advantageous method for studying triglycerides, as little sample is needed to quantify the system's hierarchical structures. Specifically, ultra-small-angle X-ray scattering (USAXS) has emerged as a fitting technique for studying CNPs, owing to its length scale range falling between 25 nm and 3.49 µm. In this study, we characterized four different 30% fat dilutions of stearic acid-based fats in triolein, with various purities and preparation protocols. Samples were characterized by combining diverse microscopy techniques (cryo-SEM, TEM, polarized light and phase contrast microscopy) with synchrotron-radiation X-ray scattering (WAXS, SAXS, and USAXS). A shape-dependent model for the interpretation of USAXS data is proposed, overcoming some of the drawbacks linked to previously utilized models. CNPs are modeled as polydisperse parallelepipeds, and the aggregates are characterized by fractal dimensionality. This model offers novel insights into CNP cross-section, as well as aggregation. In the long run, we hope that the model will increase our understanding of CNP conformation and interactions, helping us design new fat systems on the mesoscale.
ABSTRACT
Palm oil (PO), a semi-solid fat at room temperature, is a popular food ingredient. To steer the fat functionality, sucrose esters (SEs) are often used as food additives. Many SEs exist, varying in their hydrophilic-to-lipophilic balance (HLB), making them suitable for various food and non-food applications. In this study, a stearic-palmitic sucrose ester with a moderate HLB (6) was studied. It was found that the SE exhibited a complex thermal behavior consistent with smectic liquid crystals (type A). Small-angle X-ray scattering revealed that the mono- and poly-esters of the SE have different packings, more specifically, double and single chain-length packing. The polymorphism encountered upon crystallization was repeatable during successive heating and cooling cycles. After studying the pure SE, it was added to palm oil, and the crystallization behavior of the mixture was compared to that of pure palm oil. The crystallization conditions were varied by applying cooling at 20 °C/min (fast) and 1 °C/min (slow) to 0 °C, 20 °C or 25 °C. The samples were followed for one hour of isothermal time. Differential scanning calorimetry (DSC) showed that nucleation and polymorphic transitions were accelerated. Wide-angle X-ray scattering (WAXS) unraveled that the α-to-ß' polymorphic transition remained present upon the addition of the SE. SAXS showed that the addition of the SE at 0.5 wt% did not significantly change the double chain-length packing of palm oil, but it decreased the domain size when cooling in a fast manner. Ultra-small-angle X-ray scattering (USAXS) revealed that the addition of the SE created smaller crystal nanoplatelets (CNPs). The microstructure of the fat crystal network was visualized by means of polarized light microscopy (PLM) and cryo-scanning electron microscopy (cryo-SEM). The addition of the SE created a finer and space-filling network without the visibility of separate floc structures.
ABSTRACT
Inducing the spontaneous aggregation from casein molecules (i.e. αs1, αs2, ß, and κ-casein) into re-assembled casein micelles (RCMs) through the addition of salts as an alternative to native casein micelles, has garnered increasing attention in recent years. In this investigation, re-assembled casein micelles were generated by adding varying amounts of calcium, phosphate, and citrate ions to a sodium caseinate dispersion. The formed micelles were further characterized in terms of particle size, optical density, and partitioning of calcium ions and caseins. Besides, their small-angle X-ray scattering (SAXS) profiles and renneting properties were evaluated. The observations revealed that the particle size and optical density of RCMs increased with the continuous addition of salts, while the micellar yield improved and could exceed 85 %. Moreover, the quantity of individual casein molecules that contributed to the creation of micelles was in concordance with their level of phosphorylation (i.e. αs2-casein > αs1-casein > ß-casein > κ-casein). Mineral analysis results and SAXS scattering profiles confirmed that the added calcium ions acted as cross-linkers and participated in the construction of calcium phosphate nanoclusters. The renneting ability of RCMs was primarily dependent upon the colloidal calcium content per gram of micellar casein.
Subject(s)
Caseins , Micelles , Caseins/analysis , Calcium , Salts , Scattering, Small Angle , X-Ray Diffraction , Calcium, Dietary , PhosphatesABSTRACT
INTRODUCTION: It is still unclear which green nature aspects can counteract psychosocial stress: the green color or rather the environmental content (=nature). Since stress is often stimulating excess/unhealthy food intake, we hypothesize that green nature also buffers stress-induced eating. This study analyzed the effects of green/nature pictures on restorativeness, stress reactivity/response and stress eating in the lab. METHODS: Before (5min) and after (8min) the Trier Social Stress Test, 81 participants (82% women, 19-30y) saw one of the four slideshows with nature or urban environments in green or black-white shades. Group differences were tested on Perceived Restorativeness Scale, five repeated measures of heart rate variability (HRV), salivary cortisol and mood, food wanting and snack buffet consumption. RESULTS: The four groups did not differ in background and baseline values. Reported restorative power was higher in the nature pictures than urban pictures with an even better attentional/happiness restoration capacity for green versus black-white nature, while green urban pictures might induce more stress feelings than black-white urban pictures. The stress time patterns confirmed successful stress induction. Most consistent during stress induction was a higher happiness recovery in the green nature group. Nature overall was somewhat beneficial compared to urban pictures by lower HRV and negative emotions reactivity, although this might be due to unfavorable effects of green urban pictures. In food intake or wanting, no differences existed. CONCLUSION: Nature pictures were estimated higher in restorative power and green nature pictures had a positive effect on happiness recovery. Thus for prevention, the environmental content (=nature) as such seems important while just a green color seemed not enough. Future research should examine the effect of green nature in realistic indoor settings and consider influence on fruit/vegetable intake instead of solely snacks.
