The influence of protein concentration on key quality attributes of chickpea-based alternatives to cheese.

In response to consumer demands, plant protein ingredients are increasingly being used in the formulation of plant-based alternatives to cheese. The aim of this study was to determine the influence of protein concentration on key quality attributes of chickpea-based alternatives to cheese. Moreover, the age-induced changes in such attributes were assessed, with samples analysed after 1 month of storage. After characterisation of the ingredients, the chickpea-based formulations were prepared by blending chickpea flour and protein concentrate in different proportions to obtain four samples of increasing protein content (i.e., 8.68-21.5%). Formulations were developed at pH ∼4.5, and a moisture content of 50%, with shea butter used to obtain 15% fat content. The differential scanning calorimetry thermograms of the samples showed a main peak around 30 °C, corresponding to transition of the shea butter, and a smaller peak around 70 °C related to starch gelatinisation. Analysis of microstructure showed formation of a protein matrix with more extensive protein structure at high protein concentration. Furthermore, none of the chickpea-based samples melted under the testing conditions and all samples showed increasing values for adhesiveness, springiness and cohesiveness with increasing protein content. However, hardness was the highest for the sample with the lowest protein content, likely due to starch retrogradation. After storage, hardness increased further for all samples. This work improves our understanding of the role of chickpea protein in developing plant-based alternatives to cheese and the challenges therein.

Effects of lipids on the water sorption, glass transition and structural strength of carbohydrate-protein systems.

Encapsulant systems are gaining wide practical interest due to their functional and nutritional properties. This paper was focusing on understanding structural relaxations in that systems near glass transition temperature. Freeze-dried trehalose-whey protein isolate-sunflower oil systems with various ratios of the last were used as a carbohydrate-protein-lipid food model. The Guggenheim-Anderson-de Boer (GAB) water sorption relationship was used as a tool to model water sorption isotherms. The glass transition temperature was obtained by differential scanning calorimetry (DSC). Structural α-relaxation temperatures were measured by dynamical mechanical analyses (DMA), dielectric analysis (DEA) and combined to cover a broad range for strength assessment. The microstructure was characterized by optical light microscopy, confocal laser scanning microscopy and scanning electron microscopy. The C1 and C2 constants for Williams-Landel-Ferry (WLF) equation and structural strength parameter were calculated for each system. The effect of sunflower oil and water contents on strength of carbohydrate-protein system was analyzed. Strength shows decreasing with increasing of lipid concentration in the mixtures and more complex dependence on the water content in a system.

Structural strength analysis of amorphous trehalose-maltodextrin systems.

Fundamental knowledge of physical state of materials gives practically important information for food, biological and pharmaceutical industry. Based on Williams-Landel-Ferry (WLF) equation, the strength concept was introduced. This concept provides a simple parameter, S, to express resistance of solids to flow above the glass transition temperature. To develop this approach, miscible trehalose-maltodextrin (0:100; 20:80; 40:60; 60:40; 80:20 and 100:0) systems with different ratios of components were used in the present study. Such systems represent various food products including infant formula and many nutritional formulations. Amorphous solids were prepared from 20% solids in water solutions by freeze-drying. Fractional water sorption analysis of trehalose-maltodextrin miscible systems allows control of water content at high water activities. Glass transition temperatures were measured by DSC. DMA and DEA in a multi-frequency mode allowed determination of corresponding α-relaxation temperatures at various structural relaxation times. Volume rheology gives structural relaxation time - temperature dependence for high water content systems. The strength showed linear dependence on maltodextrin concentration and its value decreased significantly with increasing water content in miscible systems.

Use and application of gelatin as potential biodegradable packaging materials for food products.

The manufacture and potential application of biodegradable films for food application has gained increased interest as alternatives to conventional food packaging polymers due to the sustainable nature associated with their availability, broad and abundant source range, compostability, environmentally-friendly image, compatibility with foodstuffs and food application, etc. Gelatin is one such material and is a unique and popularly used hydrocolloid by the food industry today due to its inherent characteristics, thereby potentially offering a wide range of further and unique industrial applications. Gelatin from different sources have different physical and chemical properties as they contain different amino acid contents which are responsible for the varying characteristics observed upon utilization in food systems and when being utilized more specifically, in the manufacture of films. Packaging films can be successfully produced from all gelatin sources and the behaviour and characteristics of gelatin-based films can be altered through the incorporation of other food ingredients to produce composite films possessing enhanced physical and mechanical properties. This review will present the current situation with respect to gelatin usage as a packaging source material and the challenges that remain in order to move the manufacture of gelatin-based films nearer to commercial reality.

State transitions and physicochemical aspects of cryoprotection and stabilization in freeze-drying of Lactobacillus rhamnosus GG (LGG).

AIMS: The frozen and dehydrated state transitions of lactose and trehalose were determined and studied as factors affecting the stability of probiotic bacteria to understand physicochemical aspects of protection against freezing and dehydration of probiotic cultures. METHODS AND RESULTS: Lactobacillus rhamnosus GG was frozen (-22 or -43 degrees C), freeze-dried and stored under controlled water vapour pressure (0%, 11%, 23% and 33% relative vapour pressure) conditions. Lactose, trehalose and their mixture (1 : 1) were used as protective media. These systems were confirmed to exhibit relatively similar state transition and water plasticization behaviour in freeze-concentrated and dehydrated states as determined by differential scanning calorimetry. Ice formation and dehydrated materials were studied using cold-stage microscopy and scanning electron microscopy. Trehalose and lactose-trehalose gave the most effective protection of cell viability as observed from colony forming units after freezing, dehydration and storage. Enhanced cell viability was observed when the freezing temperature was -43 degrees C. CONCLUSIONS: State transitions of protective media affect ice formation and cell viability in freeze-drying and storage. Formation of a maximally freeze-concentrated matrix with entrapped microbial cells is essential in freezing prior to freeze-drying. Freeze-drying must retain a solid amorphous state of protectant matrices. Freeze-dried matrices contain cells entrapped in the protective matrices in the freezing process. The retention of viability during storage seems to be controlled by water plasticization of the protectant matrix and possibly interactions of water with the dehydrated cells. Highest cell viability was obtained in glassy protective media. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows that physicochemical properties of protective media affect the stability of dehydrated cultures. Trehalose and lactose may be used in combination, which is particularly important for the stabilization of probiotic bacteria in dairy systems.

Invited review: spray-dried dairy and dairy-like emulsions--compositional considerations.

Milk constituents [caseins, whey proteins (WP), lactose, and anhydrous milk fat] are used widely in the manufacture of dehydrated dairy and dairy-like emulsions. When sodium caseinate- (NaCas) and WP-stabilized emulsions with an oil-to-protein ratio ranging from 0.25 to 5 are dehydrated, NaCas is a more effective encapsulant than WP because of its superior emulsifying properties and resistance to heat denaturation. Denaturation degree of WP during drying has been associated with increased powder surface fat and larger droplet size after reconstitution. Encapsulation of NaCas-stabilized emulsions improves in the presence of lactose; powder surface fat was reduced from 30 to <5% when lactose was added at a 1:1 ratio to NaCas in an emulsion containing 30% (wt/wt) oil. This has been related to the ability of lactose to form solid-like (or glassy) capsules during sudden dehydration. Encapsulation of WP-stabilized emulsions is not improved by addition of lactose, although there are conflicting reports in the literature. Storage stability of dehydrated dairy-like emulsions is strongly linked to lactose crystallization as release of encapsulated material occurs during storage at high relative humidities (e.g., 75%). The use of alternative carbohydrates as "matrix-forming" materials (such as maltodextrins or gum arabic) improves storage stability but compromises the emulsion droplet size after reconstitution. The composition of the powder surface has been recognized as a key parameter in dehydrated emulsion quality. It is the chemical composition of the powder surface that dictates the behavior of the bulk in terms of wettability, flowability, and stability. Analyses, using electron spectroscopy for chemical analysis of the surface of industrial milk powders and dehydrated emulsions that mimicked the composition of milk, showed that powder surface is covered mainly by fat, even when the fat content is very low (18 and 99% surface fat coverage for skim milk and whole milk powders, respectively). The functional properties of milk constituents during emulsion dehydration are far from being thoroughly understood; future research needs include a) the encapsulation properties of pure micellar casein; b) a deeper understanding of colloidal phenomena (such as changes in the oil-water and air-oil interfaces) that occur before, during, and after dehydration, which ultimately define emulsion stability after drying; and c) reconciliation of the current different views on powder surface composition.

Glass transition and water effects on sucrose inversion by invertase in a lactose-sucrose system.

Enzymatic changes are often detrimental to quality of low-moisture foods. In the present study, effects of glass transition and water on sucrose inversion in a lactose-sucrose food model were investigated. Amorphous samples were produced by freeze-drying lactose-sucrose (2:1)-invertase (20 mg invertase/49.4 g of carbohydrate) dissolved in distilled water. Sorption isotherms were determined gravimetrically at 24 degrees C. Sucrose hydrolysis was determined by monitoring glucose content using a test kit and the amounts of fructose, glucose, and sucrose using HPLC. The glass transition temperatures, T(g), at various water contents were measured using differential scanning calorimetry (DSC). The BET and the GAB sorption models were fitted to experimental data up to a(w) 0.444 and 0.538, respectively. Water sorption and DSC results suggested time-dependent crystallization of sugars at a(w) 0.444 and above. Significant sucrose hydrolysis occurred only above T(g), concomitantly with crystallization. Sucrose hydrolysis and crystallization were not likely in glassy materials.

Crystallization and X-ray diffraction of crystals formed in water-plasticized amorphous lactose.

Effects of storage time and relative humidity on crystallization and crystal forms produced from amorphous lactose were investigated. Crystallization was observed from time-dependent loss of sorbed water and increasing intensities of peaks in X-ray diffraction patterns. The rate of crystallization increased with increasing storage relative humidity. Lactose crystallized mainly as alpha-lactose monohydrate and anhydrous crystals with alpha- and beta-lactose in a molar ratio of 5:3. The results suggested that the crystal form was defined by the early nucleation process. The crystallization data are important in modeling of crystallization phenomena and prediction of stability of lactose-containing food and pharmaceutical materials.