Mechanical properties of cocoa butter in relation to its crystallization behavior and microstructure

Effect of temperature on the rheological, textural, and sensory properties of butters from New Zealand market

Texture and sensory studies at various temperatures are important in evaluating and improving the functionality of butter. While literature is scarce, we evaluated and compared the effect of temperature (5-25°C) on the texture, rheological and sensory properties of commercial butter samples (salted, unsalted, cultured, and spreadable) from the New Zealand market. In addition, the instrumental analyses were compared with the sensory evaluation, to understand the possibility of using instrumental analysis to evaluate consumer liking for different butters. Butter type, temperature, and their type-temperature interaction exhibited significant differences for all instrumental textural parameters. As expected, higher temperature produced softer butter that was more spreadable, liquid-like, less adhesive, less cohesive, had lower storage modulus (G') and lower loss modulus (G″) with the melting of milk fat crystals; however, the rate of change varied for the different butter samples. We have established meltability as the parameter for evaluating butter selection for different applications. The spreadable butter sample exhibited the lowest hardness and G', and highest spreadability (p < .05) at all temperatures, owing to its low solid fat content and the abundance of low-melting triglycerides. The cultured butter sample had the highest melting point, owing to compositional differences. The instrumental and sensory texture analyses were highly correlated, indicating the comparative effectiveness of both approaches for studying the effects of different temperatures on butter textural properties. Overall, our findings provide detailed reference to the dairy industry for butter manufacture, considering variation in fatty acid composition, texture analysis, rheology, and sensory analysis, over the range of storage/usage temperatures.

Comparative Study on Mixing Behavior of Binary Mixtures of Cocoa Butter/Tristearin (CB/TS) and Cocoa Butter/Coconut Oil (CB/CO)

The comparative study between the mixing behavior of two binary mixtures of cocoa butter (CB)/tristearin (TS) and cocoa butter (CB)/coconut oil (CO) was investigated by using differential scanning calorimetry (DSC). The DSC profile for CB/TS blends resulted in a monotectic temperature–concentration (T–X) phase diagram, whereas a phase diagram of eutectic type was observed for CB/CO blends at 65 wt % of CO and 35 wt % CB; this suggests that the eutectic crystal can be formed when the saturated fat (blue = CO) is smaller in size compared to monounsaturated fat (orange = CB), whereas, for similar and larger size (red = TS) to CB, phase separation under crystallization is likely to occur (as shown in the graphical abstract). In order to understand the interaction between the binary systems, the profile of the phase diagram was fitted with Bragg–Williams approximation for estimation of the nonideality mixing parameter. Moreover, the morphology of the two different systems by polarized light microscopy (PLM) also depicted the variations in phase behavior by showing a significant change in CB morphology from spherulitic, grainy to granular and needlelike after the addition of TS and CO, respectively. Our findings emphasize the fundamental understanding of the interaction of bulk fat/fat and fat/oil system.

Interesterified blend-based and physical blend-based special fats: storage stability under fluctuating temperatures

BACKGROUND

Temperatures that special fat faces in a real environment fluctuate, thus, understanding the property changes of special fats under fluctuating temperatures will be helpful in guiding how to keep its high quality in the production and application process. Therefore, a comparative study was carried out on the storage stability of physical blend-based and interesterified blend-based special fats (PBSFs and IBSFs) and their oxidative stability, crystallization and physical properties were studied under fluctuating temperatures.

RESULTS

The peroxide values of IBSFs and PBSFs were less than 10.0 mmol kg^-1 after 4 weeks of storage, and IBSFs had better oxidative stability. There was little change in the solid fat content, and the hardness decreased when IBSFs and PBSFs were stored for 4 weeks. X-ray diffraction results indicated that PBSFs had only β-crystal, but IBSFs had β- and β'-crystal after storage. Moreover, in IBSFs, the transformation from β'- to β-form in PS:RO-IBSF was more obvious than that in PS:SO-IBSF (PS, palm stearin; SO, soybean oil; RO, rapeseed oil) after 4 weeks of storage, and the good integrity of crystalline network in fast-frozen special fats during fluctuating temperature storage followed the order: IBSF > PBSF, PS:RO-PBSF > PS:SO-PBSF.

CONCLUSION

The results suggest IBSF can better maintain its quality during fluctuating temperature storage than PBSF. © 2019 Society of Chemical Industry.

Storage stability studies on interesterified blend-based fast-frozen special fats for oxidative stability, crystallization characteristics and physical properties

The storage stability of two kinds of interesterified blend-based fast-frozen special fats (PS:SO-IBSF, PS:RO-IBSF) with varied triacylglycerols (TAGs) compositions under different temperatures for 4 weeks was investigated. Rancimat and peroxide values experiments indicated that both IBSFs display good oxidation stability throughout a 4-week storage. As for the physical properties of both IBSFs, the solid fat content and hardness decreased with the increase of storage temperature, and IBSFs still exhibited a viscoelastic solid-like behavior. X-ray diffraction results showed that crystal transformation from β'- to β-form was more serious when stored at 25 °C. The more content of ECN 50-type TAGs in PS:RO-IBSF is helpful to reduce its crystal transformation from β'-to β-form compared to PS:SO-IBSF. On the other hand, storage at 4 °C was beneficial for both IBSFs to keep their crystal network integrity, and the PS:RO-IBSF maintained better quality under the same storage conditions.

Global Small-Angle X-ray Scattering Data Analysis of Triacylglycerols in the Molten State (Part I)

The study of triacylglycerols (TAGs) in their molten state is of fundamental importance for a deeper understanding of the TAG crystallization processes, being highly relevant for both manufacturing and medical applications. Although different models have been proposed to explain the nanostructured nature of the fluid state of TAGs, none of them are fully satisfactory. In this paper, we propose a new model consisting of positionally uncorrelated lamellar TAG assemblies embedded in an isotropic medium that assist as prenucleating structures. This model was validated by applying a novel global fitting method, resulting in an excellent agreement with the small-angle X-ray scattering data. A deeper analysis of the scattering patterns at different temperatures, both in cooling and heating directions, allowed us further to detect the crystalline traces of TAGs even after heating to 40 °C and record, on cooling, the onset of crystallization at 30-25 °C. The application of the presented novel model not only explains the outstandingly structured fluid of molten TAGs, but also lays the basis for analyzing first the crystallization steps in greater detail, which is outlined in our follow-up paper "Global Small-Angle X-ray Scattering Data Analysis of Triacylglycerols in the α-Phase (Part II)".

Physicochemical, rheological and functional properties of fats and oils in relation to cookie quality: a review

Sincere efforts of researchers are underway to understand the functionality of different fats and oils in relation to cookie quality. The quality of cookie primarily relies upon the functionality of fats and oils in cookie system which ultimately is combined result of their physical, chemical, and rheological properties. Effects of some major fats and oils such as butter, bakery fat, hydrogenated fat, lard, margarine, palm oil, sunflower oil, coconut oil, and soybean oil on the physical and sensory characteristics of cookie have been studied. Previous studies reported that fats and oils had radical contribution in cookie quality and most authors agree on the fact that different fats and oils affect the cookie quality to different extent. Furthermore, it was observed by many researchers that with oils, dough was softer and cookie spread was higher as compared with that of fats. It is important to understand the molecular basis of the difference in technological changes in cookies properties with different fats and oils. This review focuses on the current knowledge of quality determining physical, chemical, thermal, microstructural, and functional properties of fats and oils in relation to cookie dough rheology and cookie quality.

Effect of high pressure microfluidization on the crystallization behavior of palm stearin - palm olein blends

Moderate and high microfluidization pressures (60 and 120 MPa) and different treatment times (once and twice) were used to investigate the effect of high-pressure microfluidization (HPM) treatment on the crystallization behavior and physical properties of binary mixtures of palm stearin (PS) and palm olein (PO). The polarized light microscopy (PLM), texture analyzer, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques were applied to analyze the changes in crystal network structure, hardness, polymorphism and thermal property of the control and treated blends. PLM results showed that HPM caused significant reductions in maximum crystal diameter in all treated blends, and thus led to changes in the crystal network structure, and finally caused higher hardness in than the control blends. The XRD study demonstrated that HPM altered crystalline polymorphism. The HPM-treated blends showed a predominance of the more stable β' form, which is of more interest for food applications, while the control blend had more α- and β-form. This result was further confirmed by DSC observations. These changes in crystallization behavior indicated that HPM treatment was more likely to modify the crystallization processes and nucleation mechanisms.

Storage related changes in ghee-based low-fat spread

In order to assess the shelf life of a low fat spread (LFS) based on ghee, the product with (PS) and without (CS) added 0.05 % (w/w) preservative potassium sorbate and packaged in 200 g polystyrene tubs was stored at 5 °C and evaluated for changes in sensory, physico-chemical and microbiological properties. On the basis of flavour score, the PS spread could be stored for 10 weeks without appreciable loss in quality as against the CS spread which could be stored only for 5 weeks. From the point of view of spreadability, body and texture and colour, the CS product was acceptable even after 11 weeks of storage. Use of preservative had an inhibitory effect on the development of free fatty acids (FFA) and thiobarbituric acid (TBA) reactive substances. While both the products showed an increasing tendency to whey off during storage, CS wheyed off more than PS. The two spreads showed similar oiling off, which increased slightly during the storage. Microbiologically, the ghee-based low fat spreads with and without preservative was stable for 9 and 3 weeks, respectively, from the view point of yeast and mould growth; but the preservative had little effect on the total viable count. Coliforms were absent in all the samples in fresh and during storage.

Stability and dynamic rheological characterization of spread developed based on pistachio oil

This study investigated the influence of formulation variables (pistachio oil (PO, 7.5 and 15%, w/w), Cocoa butter (CB, 7.5 and 15%, w/w), xanthan gum (XG, 0 and 0.3%, w/w), and distillated monoglyceride (DMG, 0.5 and 1%, w/w)) on the rheological properties and emulsion stability of spreads. Power law and Herschel-Bulkley models were used for modeling shear-thinning behavior of samples. The power law model was found to describe the flow behavior of spreads better than Herschel-Bulkley model. All the rheological properties were increased by adding XG to the spreads whereas increasing PO content caused to decrease them. The DMG had positive effect on apparent viscosity and elastic behavior but had negative effect on viscose behavior. Apparent viscosity was increased by adding CB while rheological modules were not significantly (p < 0.05) affected. The XG and DMG improved stability of emulsion. The best spread formulation with optimum rheological properties was 15% PO, 7.5% CB, 0.3% XG and 1% DMG.

Relationship between crystallization behavior, microstructure, and macroscopic properties in trans-containing and trans-free filling fats and fillings

The objective of this study is to investigate the architecture to feature physical functionality of filling fats. This means an investigation of the different structure levels (crystallization, microstructure, macrostructure, etc.) that lead to good technological functionality. The isothermal crystallization behavior of two filling fats (one trans-containing and one trans-free) was examined by differential scanning calorimetry and microscopy. Furthermore, the hardness of the samples was examined after cooling in a water bath at two different temperatures and at three different storage times. The trans-containing filling fat crystallized faster and in smaller crystals as compared to the trans-free filling fat. The crystallization behavior of the trans-free filling fat was more complex, with the formation of different polymorphic forms. The hardness of the fillings was not only governed by the amount of solid fat present in the network but also by the structure of this network. The filling matrix components seem to have a pronounced influence on the microstructure and thus on the macroscopic properties.

Relationship between crystallization behavior, microstructure, and macroscopic properties in trans containing and trans free coating fats and coatings

The objective of this study is to gain further understanding into the relationship between crystallization behavior, microstructure, and macroscopic properties in coating fats. The isothermal crystallization behavior of two coating fats (one trans containing and one trans free) was examined, both as pure fats and in coatings, by DSC and microscopy. Furthermore, the hardness of the samples was examined after cooling in a water bath at two different temperatures and at three different storage times. Both fats seemed to show an alpha-mediated beta' crystallization at lower temperatures and a direct beta' crystallization at higher temperatures. The trans free coating fat clearly crystallized faster and in smaller crystals. The hardness was governed not only by the amount of solid fat present in the network but also by the structure of this network. The coating matrix components seem to have a pronounced influence on the microstructure and thus on the macroscopic properties.