Tuyen Truong

Effects of emulsion droplet sizes on the crystallisation of milk fat.

The crystallisation properties of milk fat emulsions containing dairy-based ingredients as functions of emulsion droplet size, cooling rate, and emulsifier type were investigated using a differential scanning calorimeter (DSC). Anhydrous milk fat and its fractions (stearin and olein) were emulsified with whey protein concentrate, sodium caseinate, and Tween80 by homogenisation to produce emulsions in various size ranges (0.13-3.10 μm). Particle size, cooling rate, and types of emulsifier all had an influence on the crystallisation properties of fat in the emulsions. In general, the crystallisation temperature of emulsified fats decreased with decreasing average droplet size and was of an exponent function of size, indicating that the influence of particle size on crystallisation temperature is more pronounced in the sub-micron range. This particle size effect was also verified by electron microscopy.

Changes in Cracking Behavior and Milling Quality of Selected Australian Rice Varieties Due to Postdrying Annealing and Subsequent Storage

This study investigated the effect of drying temperatures, annealing regimes, and storage conditions on the level of rice kernel fissuring, mechanical strength, and head rice yield of three Australian-grown rice varieties, namely, Kyeema (long grain), Amaroo, and Reiziq (medium grains). Paddy samples were dried at 40, 60, and 80°C and then annealed for 0, 40, 80, and 120 min at the same drying temperature. It was found that annealing slightly improved the head rice yield with an increase in stiffness of rice kernels. The number of fissured kernels decreased with prolonged annealing duration of 80–120 min. During the storage period of up to 4 months at 4, 20, and 38°C, all measured parameters, such as percentage of fissured kernels, hardness, stiffness, head rice yield, and pasting properties, also showed increasing trends. A relatively rapid change in these physical properties of all rice samples was observed during storage at 38°C. A significant increase in stiffness of rice during storage at 38°C suggested that physical aging occurs during storage of rice below its glass transition temperature (55°C).

Effect of solubilised carbon dioxide at low partial pressure on crystallisation behaviour, microstructure and texture of anhydrous milk fat

The crystallisation and melting behaviour, fat polymorphs, microstructure and texture of anhydrous milk fat (AMF) was investigated in the presence of dissolved CO2 (0-2000ppm) under two crystallising conditions (non-isothermal versus isothermal). CO2 was found to induce higher onset crystallisation temperature during cooling from 35 to 5°C at 0.5°Cmin-1. X-ray scattering analysis showed that, in the presence of dissolved CO2, this rapid crystallisation caused the formation of unstable, α polymorph fat crystals. For milk fat crystallised under isothermal condition at 25°C for 48h, dissolved CO2 improved solid fat content, slightly depressed melting temperature and exhibited a sharper melting peak. Microstructure of AMF visualised by Polarised light microscopy of crystallised AMF showed that increasing dissolved CO2 concentration was associated with smaller crystal size and greater crystal number. The bulk properties of the fat appeared to mirror the microstructural differences, in that the texture of CO2-treated AMF was harder under isothermal condition but became softer than untreated AMF under cooling condition. The results of this study are of significance in understanding how CO2 treatment might be used to modulate the crystallisation behaviour of milkfat and thereby the structural development and physical functionality of fat-containing dairy products.

Effect of Milk Fat Globule Size on the Physical Functionality of Dairy Products

Effect of Milk Fat Globule Size on the Physical Functionality of Dairy Products provides a comprehensive overview of techniques utilized to vary milk fat globule size in fat-structured dairy products. The text aims to highlight the importance of both native and emulsified milk fat globule size in the processing and functionality of these products. Both herd managements strategies and fractionation techniques utilized to vary milk fat globule size are covered thoroughly, as are the effects of mechanical sheer processing. The influence of different size fat globules on aspects such as TAG composition, physical stability, viscosity, crystallization properties and electric conductivity are studied, as are the influences on processability and function. This Brief aims to highlight the importance of milk fat as a determinant of the microstructural, rheological and sensorial properties of fat-containing dairy products such as milk, cream, yogurt, ice cream, cheese, butter and milk chocolate. Since milk fat globules have a widely varied size distribution, controlling their size is of major importance in processing. In comprehensively covering the various methods used to vary milk fat globule size, this text serves as an important resource for those involved in dairy product processing.

Crystallization and melting properties of mixtures of milk fat stearin and omega-3 rich oils

Solid milk fat stearin (S25) can be a promising oxidation retarder due to its capacity to entrap liquid oils, especially for incorporating omega-3 (ω-3) rich oils into dairy products. Thermal properties of S25/ω-3 rich oil mixtures are necessary for such application. The effects of S25 on the crystallization and melting behaviours of ω-3 rich oils, namely fish oil (FO), linseed oil (LO) and krill oil (KO), were investigated by differential scanning calorimetry (DSC). Thermograms showed that with S25 concentration increasing, transitions of FO and LO shifted to lower and largely to higher temperatures, respectively, while crystallization temperature of KO slightly decreased. Negative, positive and low values of interaction enthalpy (ΔHint) suggested the adverse, beneficial and limited effect of S25 on the crystallization of S25/FO, S25/LO and S25/KO mixtures, respectively. LO could have the best oxidative stability upon the addition of S25 since their interactions facilitated earlier and stronger crystallization.

Methods to characterize the structure of food powders-a review

Food powders can exist in amorphous, crystalline or mixed structure depending on the order of molecular arrangement in the powder particle matrices. In food production, the structure of powders has a greatly effect on their stability, functionality, and applicability. The undesirable structure of powders can be accidentally formed during production. Therefore, characterization of powder structure as well as quantification of amorphous–crystalline proportions presenting in the powders are essential to control the quality of products during storage and further processing. For these purposes, many analytical techniques with large differences in the degree of selectivity and sensitivity have been developed. In this review, differences in the structure of food powders are described with a focus being placed on applications of amorphous powders. Essentially, applicability of common analytical techniques including X-ray, microscopic, vapor adsorption, thermal, and spectroscopic approaches for quantitative and qualitative structural characterization of food powders is also discussed. The common techniques to quantitatively and qualitatively characterize the structure (amorphous and crystallize) of food powders.

Spray-drying and non-equilibrium states/glass transition

In this chapter, the fundamental characteristics of spray drying are described with regards to its applications to alter the structure of food powders (crystalline or amorphous). Unlike amorphous powders which are in thermodynamically non-equilibrium state and tend to experience many phase transitions to obtain the lowest energy state, crystalline powders are stable and an alteration of its structure using spray drying involves two steps, disruption of the molecular order in crystal lattice and fast solidification to prevent molecules from orderly arrangement. As compared to other approaches, spray drying is the most effective technique to prepare amorphous powders due to its unique characteristics (fast and continuous process, diversity in capacity and designs, and ability to control crystallinity of produced powders). In the last part, differences about characteristics of crystalline and spray-dried amorphous alpha-cyclodextrin powders are shown as a case study of application of spray drying to change powder structure.

Changes in physicochemical properties of rice in response to high-temperature fluidized bed drying and tempering

ABSTRACT The effects of high-temperature fluidized bed drying and tempering on pasting, gelatinization, crystalline and microstructural properties of long-grain Vietnamese rice cultivar A10 were examined. The freshly harvest paddy (33% wet basis) was dried at two drying temperatures (80 and 90°C) and two drying durations (2.5 and 3.0 min) using a custom-made lab-scale batch fluidized bed dryer. The dried rice was immediately tempered in sealed containers at 75 and 86°C for various tempering durations (0, 30, 40, and 60 min), followed by thin-layer drying at 35°C to reduce moisture level to 14% wet basis. Characterization of pasting, gelatinization, crystallinity, and microstructure of the dried rice was undertaken using rapid visco analyzer, differential scanning calorimetry, X-ray diffraction (XRD), and environmental scanning electron microscopy (ESEM), respectively. Pasting properties and gelatinization enthalpy decreased with higher drying temperature and longer tempering time while pasting and gelatinization temperatures increased. Degree of crystallinity changed slightly, however, a shift from A-type to A+V-type XRD pattern was observed. ESEM observation demonstrated some degree of collapse of the rice microstructure. The kernel integrity appeared to be enhanced by the gel network formed during partial gelatinization of starch, corroborating with the changes in pasting and gelatinization properties of the fluidized bed dried and tempered rice.

Glass transition and crystallization in foods

The glass transition and crystallization are two of the major transitions in food which could affect the food physical properties significantly. The glass transition behavior and the crystallization phenomenon of food, as well as their interactions, are reviewed in this chapter. The major connection between glass transition and crystallization in a certain food or food component is the temperature. It has been reported that crystallization could hardly happen, if not impossible, below the glass transition temperature of food. And the temperature difference above or below the glass transition temperature (T − Tg) is an important indicator for food crystallization. Other factors, such as moisture content and molecular weight, also contribute to the interaction of glass transition and crystallization in foods. As examples the glass transition and crystallization of sugars, especially lactose and sucrose, which have been studied extensively in literature, are presented in this chapter. Other major food components are also summarized on their thermal transitions, including polyols, protein, and polysaccharides.

Effect of fat globule size on the churnability of dairy cream

The churnability of commercial dairy cream as a function of fat globule size from micron to nanometric range (0.17-3.50μm) was investigated. To achieve the lower fat globule size with increased interfacial area various amounts of sodium caseinate (NaCN) (0.15-4.9wt%) or Tween 80 (0.25-1wt%) were added to the cream. Under similar microfluidization and churning conditions, both fat globule size and emulsifier type had a significant influence on the churning time and proportion of fat in buttermilk. In general, churning time and buttermilk fat content were increased above 3.5min and 4.4% fat (for untreated fat globule size), respectively with decreasing average fat globule size irrespective of the type of emulsifier used. The addition of Tween 80 reduced the churning time significantly and also decreased the fat content of buttermilk as compared to NaCN added cream.