Temperature dependent Raman and X-ray diffraction studies of anhydrous milk fat

Application of in-line Raman spectroscopy to monitor crystallization and melting processes in milk fat

Anhydrous milk fat (AMF) and its fractions are used as ingredients in a wide range of food applications. Obtaining the appropriate solid fat content (SFC) is essential to achieve the desired product texture. At present, in-line monitoring techniques to control milk fat crystallization and melting are largely unavailable. The thermal behaviour of milk fat (AMF and four of its fractions) was monitored in a temperature-controlled vessel using an in-line Raman analyser and compared with thermograms generated using differential scanning calorimetry (DSC). The major stages of milk fat crystallization and melting were identified using the in-line Raman analyser. Thermal data from DSC showed excellent linear correlations with Raman spectral data (R2 value of 0.97 for the onset of milk fat crystallisation). Partial least squares regression (PLSR) models were developed using Raman spectra to predict SFC with coefficient of determination (R2Cs) from 0.929 to 0.992 and root mean standard error of calibration (RMSECs) ranging from 3.20 to 10.36%. Results demonstrated Raman spectroscopy has significant potential as a way of monitoring milk fat crystallization and melting processes.

Palmitic acid at high concentration modifies the nanoscale structure of anhydrous milk fat

We performed a nanoscale study based on X-ray scattering to understand the impact of a promotor of crystallization, palmitic acid (PA), at high concentration, on the networks of triacylglycerols (TAGs) in anhydrous milk fat (AMF). Melted blends containing 10 wt% PA were quenched at 25 °C. X-ray scattering data were compared with those obtained for pure AMF, pure PA, and AMF containing 1 wt% PA. While PA at low concentration did not modify the nanostructure of TAG crystals (direct crystallization in the β'-2L form), a high concentration of this promotor favored the formation of polymorphic forms suggesting that PA first crystallizes and then directs crystallization of AMF TAGs towards α and β forms.

Comparative study of interfacial properties and thermal behaviour of milk fat globules and membrane prepared from ultrasonicated bovine milk

Milk fat globules or milk fat globule membranes (MFGs/MFGM) have been added to the infant formula to fortify the phospholipids and narrow the nutritional gap from breast milk. The main aim of this study was to profile the interfacial and thermal properties of MFGs/MFGM prepared from ultrasonicated bovine milk. Bovine milk was sonicated at ultrasonic intensities of 20 kHz and 40 kHz independently or synchronously with the duration time of 0 min (control), 5 min, 10 min, and 15 min (work/rest cycles = 5 s: 3 s). Ultrasonic treatments at 20 kHz/ 5 min and 20 + 40 kHz/ 5 min improved the volume density (%) of smaller particles (1-10 µm) while significantly decreasing the surface hydrophobicity (H0) (p < 0.05). 40 kHz/5 min samples showed significantly higher ζ- potential than the other samples (p < 0.05), which might be because more negative charges were detected. In comparison with control samples, ultrasonic treatments decreased the interfacial tension (π) between the air and MFGs/MFGM liquid phase. 20 kHz ultra-sonicated treatments decreased the diffusion rate (k diff) of MFGs/MFGM interfacial compositions significantly as the duration prolonged from 5 min to 15 min (p < 0.05) but did not affect the adsorption or penetration rate (k a) (p > 0.05). X-ray diffraction (XRD) results showed that α-crystal peaks only existed in control and ultrasonicated 5 min samples but disappeared in all 15 min samples. According to the different scanning calorimetry (DSC), one or two new exothermic events (in the range of 17.29 - 18.81 ℃ and 22.14 - 25.21 ℃) appeared after ultrasonic treatments, which, however, were not found in control samples. Ultrasonic treatments resulted in the low-melting fractions (LMF) (TM1) peaks undetectable in MFGs/MFGM samples in which only peaks of medium-melting fractions (MMF) (TM2) and high-melting fractions (HMF) (TM3) were detected. Compared with the control, both enthalpies of crystallisation (ΔHC) and melting (ΔHM) decreased in ultrasonicated samples. In conclusion, ultrasonic treatment affects the interfacial and thermal properties of MFGs/MFGM.

Application of small angle scattering (SAS) in structural characterisation of casein and casein-based products during digestion

In recent years, small and ultra-small angle scattering techniques, collectively known as small angle scattering (SAS) have been used to study various food structures during the digestion process. These techniques play an important role in structural characterisation due to the non-destructive nature (especially when using neutrons), various in situ capabilities and a large length scale (of 1 nm to ∼20 μm) they cover. The application of these techniques in the structural characterisation of dairy products has expanded significantly in recent years. Casein, a major dairy protein, forms the basis of a wide range of gel structures at different length scales. These gel structures have been extensively researched utilising scattering techniques to obtain structural information at the nano and micron scale that complements electron and confocal microscopy. Especially, neutrons have provided opportunity to study these gels in their natural environment by using various in situ options. One such example is understanding changes in casein gel structures during digestion in the gastrointestinal tract, which is essential for designing personalised food structures for a wide range of food-related diseases and improve health outcomes. In this review, we present an overview of casein gels investigated using small angle and ultra-small angle scattering techniques. We also reviewed their digestion using newly built setups recently employed in various research. To gain a greater understanding of micro and nano-scale structural changes during digestion, such as the effect of digestive juices and mechanical breakdown on structure, new setups for semi-solid food materials are needed to be optimised.

Effect of stearic and oleic acid-based lipophilic emulsifiers on the crystallization of the fat blend and the stability of whipped cream

Effect of stearic acid-based lipophilic emulsifiers (sorbitan monostearate (Span-60), sucrose ester S-170, and lactic acid esters of monoglycerides (LACTEM)) and oleic acid-based lipophilic emulsifiers (sorbitan monooleate (Span-80) and sucrose ester O-170) on the crystallization of fat blend and the stability of whipped cream were studied. Span-60 and S-170 possessed strong nucleation inducing ability and good emulsifying properties. Thus, tiny and uniform crystals were formed in fat blends, small and ordered fat globules were distributed in emulsions, and air bubbles were effectively wrapped in firmly foam structures. The crystallization of the fat blend and the stability of whipped cream were slightly modified by LACTEM due to its poor nucleation inducing ability and moderate emulsifying characteristic. Span-80 and O-170 had weak nucleation inducing ability and poor emulsifying properties, therefore, loose crystals were formed in fat blends and some big fat globules were separated in emulsions, thereby decreasing the stability of whipped creams.

Structural and Vibrational Investigations of Mixtures of Cocoa Butter (CB), Cocoa Butter Equivalent (CBE) and Anhydrous Milk Fat (AMF) to Understand Fat Bloom Process

Some studies found that the proportions of cocoa butter (CB), cocoa butter equivalent (CBE) and milk fatty acid (AMF) tend to influence the blooming delay when mixing them. The goal of our research is to determine the effects of the proportion of CB, CBE and AMF on the structural organization of the final mixtures. X-ray, DSC, MIR and Raman spectroscopy were used to analyze the structural features and the vibrational modes of four mixtures: CB + 0.5AMF, CB + AMF, CB + 0.5AMF + CBE and CB + AMF + CBE. At room temperature, the triglycerides are ingredients of CB, and CBE and AMF do not fully exhibit the known crystalline forms V or VI, unlike a recent CB sample. Part of these triglycerides is in the form IV instead. The presence of the latter seems to be a key parameter that favors the deceleration of the transformation to the form VI, which is responsible for the development of fat bloom.

Monitoring the ripening attributes of Turkish white cheese using miniaturized vibrational spectrometers

Monitoring the ripening process by prevalent analytic methods is laborious, expensive, and time consuming. Our objective was to develop a rapid and simple method based on vibrational spectroscopic techniques to understand the biochemical changes occurring during the ripening process of Turkish white cheese and to generate predictive algorithms for the determination of the content of key cheese quality and ripening indicator compounds. Turkish white cheese samples were produced in a pilot plant scale and ripened for 100 d, and samples were analyzed at 20 d intervals during storage. The collected spectra (Fourier-transform infrared, Raman, and near-infrared) correlated with major composition characteristics (fat, protein, and moisture) and primary products of the ripening process and analyzed by pattern recognition to generate prediction (partial least squares regression) and classification (soft independent analysis of class analogy) models. The soft independent analysis of class analogy models classified cheese samples based on the unique biochemical changes taking place during the ripening process. partial least squares regression models showed good correlation (R_Pre = 0.87 to 0.98) between the predicted values by vibrational spectroscopy and the reference values, giving low standard errors of prediction (0.01 to 0.57). Portable and handheld vibrational spectroscopy units can be used as a rapid, simple, and in situ technique for monitoring the quality of cheese during aging and provide real-time tools for addressing deviations in manufacturing.

Isothermal crystallization of anhydrous milk fat in presence of free fatty acids and their esters: From nanostructure to textural properties

We performed a multiscale study to understand the impact of pure exogenous compounds at low concentration on the crystallization of triacylglycerols (TAGs) in anhydrous milk fat (AMF). We selected butyric acid, an inhibitor of crystallization, and palmitic acid, a promotor, to investigate the influence of the chain length. Tripalmitin was also used as a promotor to assess the impact of fatty acid esterification. Melted blends containing the additives (1 wt%) were quenched at 25 °C. X-ray scattering data showed that AMF TAGs crystallized directly in the β'-2L form. The presence of additives did not modify the nanostructure of TAG crystals. However, they significantly altered the microstructure of AMF, as revealed by polarized light microscopy and rheology. This study emphasizes the interest of a multiscale approach to gain knowledge about the behavior of complex fat blends and of the use of modulators at low concentration to monitor their textural properties.

Physicochemical characteristics of anhydrous milk fat mixed with fully hydrogenated soybean oil

There is a growing demand for fats that confer structure, control the crystallization behavior, and maintain the polymorphic stability of lipid matrices in foods. In this context, milk fat has the potential to meet this demand due to its unique physicochemical properties. However, its use is limited at temperatures above 34 °C when thermal and mechanical resistance are desired. The addition of vegetable oil hard fats to milk fat can alter its physicochemical properties and increase its technological potential. This study evaluated the chemical composition and the physical properties of lipid bases made with anhydrous milk fat (AMF) and fully hydrogenated soybean oil (FHSBO) at the proportions of 90:10; 80:20; 70:30; 60:40; and 50:50 (% w/w). The increased in FHSBO concentration resulted in blends with higher melting point, which the addition of 10% of FHSBO increase the melting point in 12 °C of the lipid base. Also, FHSBO contributed for a higher thermal resistance conferred by the coexistence of polymorphs β' and β, which remained stable for 90 days. Co-crystallization was observed for all blends due to the total compatibility of milk fat with the fully hydrogenated soybean oil. The results suggest a potential of all blends for various technological applications, makes milk fat more appropriate to confer structure, and improve the polymorph stability in foods. The blends presenting singular characteristics according to the desired thermal stability, melting point, and polymorphic habit.

Evaluation of the quality of local butters: A new approach based on Raman spectroscopy and supported by the classical pycnometer method

In this study, the quality of the local Romanian butters was investigated using the classical pycnometer and optic microscopy methods, combined with Raman spectroscopy. We used a pool of 10 samples with different characteristics, and analyzed them by the three aforementioned methods. Pycnometric measurements showed a direct correlation between the fat content and the density values of the samples. Raman spectroscopy validated the results from the pycnometric measurements and the optical microscopy and indicated several other properties, such as protein content, hydration, saturation level of the polycarbonate chains, as well as the total cis isomer content and the type of arrangement preferred by the aliphatic chains (polymorphic transition). The methods employed in the present study have a strong potential to become analytical tools for the food industry and food safety agencies in order to assess the quality of butters and margarines, in a fast and cost-effective manner.