Glass transition and caking of spray-dried lactose

Simple test methods to determine the onset temperatures of viscous flow and caking of spray-dried amorphous lactose are described. The extent of viscous flow was measured as an increase in the density of lactose plugs within a cylindrical aluminium compaction apparatus after incubation for 3h at a specified temperature. Caking was characterized by an increase in the hardness of the lactose plugs formed. The onset temperature of viscous flow decreased with increasing water activity, A_w, and corresponded to the onset temperature of glass transition, T_g1. Glass transition temperatures were determined using both differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR) spin relaxation. The results suggest that elevation of the powder temperature above T_g1 promotes viscous flow and increases the potential for caking of amorphous food powders.     

Flavor release from spray-dried maltodextrin/gum arabic or soy matrices as a function of storage relative humidity

The microencapsulation of emulsified ethyl butyrate by spray drying and its release from the spray-dried powder was investigated. Retention of emulsified ethyl butyrate during spray was dependent on the concentration of maltodextrin and the type of emulsifier. The rate of release of the encapsulated ethyl butyrate during storage was not only dependent on the relative humidity of storage, but also on the type of the emulsifier. The rate of release of ethyl butyrate was analyzed using Avrami's equation. The addition of 1% gelatin in the feed liquid had a pronounced influence in increasing the retention of ethyl butyrate during spray drying, and also in controlling the release rate of the encapsulated ethyl butyrate.     

Investigation of breakage behavior and its effects on spray-dried agglomerated whey protein-lactose powders: Effect of protein and lactose contents

Particle breakage of dairy powders occurs easily during many processes, reducing the powder functionality. The characteristics of particles and the applied stress from processing conditions on the particles are 2 main factors that can be manipulated to reduce breakage. In this study, we explored the effect of whey protein and lactose contents on dynamic breakage in agglomerated whey protein-lactose powders to provide useful information, in terms of particle characteristics, for controlling unwanted dairy powder breakage. A series of model agglomerates with different whey protein:lactose ratios were produced under the same spray-drying conditions, through a pilot plant trial. We evaluated physical characteristics, composition, and structure of samples; analyzed dynamic breakage under different mechanical stresses; and investigated the rehydration and water adsorption properties of model powders before and after breakage. The particle size and irregularity of agglomerates with more lactose was significantly higher than of samples that contained more protein. This resulted in higher particle breakage during dynamic breakage for samples with more lactose. The breakage of agglomerates was affected by the moisture content of powders and fatigue, where particle breakage happens when mechanical loads, lower than the strength of particles, occur multiple times. Breakage changed the morphology and surface composition of particles and decreased particle size. It also decreased the dispersibility of powders and increased the wetting time of wettable samples but decreased the wetting time of powders with poor wettability. Breakage accelerated time-dependent crystallization and decreased the crystallization temperature but did not affect the glass transition temperature of samples. Thus, under the same drying conditions, composition of powders significantly affected breakage, mainly by altering the physical properties of their particles, which resulted in deteriorated functionality.     

Effect of fat content on flavour release from sausages

The influence of fat content (5%, 10% and 15%) of sausage on the release of 10 volatile compounds with different physicochemical properties (log P and log ρL ranged between 1.01 and 4.23, and −0.66 and 1.69, respectively) was studied under static headspace (raw and cooked sausages) and in-mouth conditions (cooked sausages). Increasing fat content caused a general increase in the volatile compound concentrations of the sausages (fat acted as a reservoir) but a decrease in the compound concentration in the headspace and in the nosespace. The opposite effect was found for 3-methylbutanal and ethyl-2-methylbutanoate, which are more polar (low values for log P) and volatile (large values for log ρL) than the other compounds. Static headspace data revealed that the effect of fat content was larger in the raw samples than in the cooked sausages. The time to reach the maximum response for the compounds in the nosespace during mastication was not affected by fat content.     

Structural strength and crystallization of amorphous lactose in food model solids at various water activities

Freeze-dried lactose and lactose/whey protein isolate (WPI) mixtures were used as amorphous food models at various a_w, and the effects of temperature and water and WPI contents on physical state were analyzed. Thermal behavior and mechanical properties were studied and Williams-Landel-Ferry (WLF) model was fitted to structural relaxation times (τ). The WLF-analysis gave a strength parameter (S) that was used to describe structural strength of the food solids. Our results showed that lactose and WPI in mixtures exhibited fractional water sorption. Thermal properties and structural strength of the solids were affected by water and WPI while T_g measured for the lactose/WPI systems followed that of the lactose component and showed phase separation of lactose and proteins. A relationship between S and water content was established, whereas the crystallization of amorphous lactose was more rapid in systems with a smaller S. Therefore, S provided a simple and convenient measure of τ controlling structure formation in food processing as well as to control lactose crystallization.Industrial relevanceSugars are common ingredients and often used as a mixture with other components, e.g., proteins, in the food and pharmaceutical industries. Thus, understanding the physical state and thermal behavior of sugar containing food materials has a great importance in the development of processing and shelf life control procedures for such ingredients and relevant products. This study provides physicochemical information about thermal and mechanical properties of freeze-dried lactose/whey protein systems used as food models at various water activities. Data on water sorption, time-dependent lactose crystallization, calorimetric glass transition and crystallization temperatures, and structural relaxation times can be used to understand and predict structural changes during processing and storage of relevant foods. Moreover, the structural strength concept, described in this study, allows of the control of crystallization behavior as a physical state and time-dependent phenomenon, and therefore, stability of food and pharmaceutical materials     

Original article: Encapsulation of ascorbic acid in amorphous maltodextrin employing extrusion as affected by matrix/core ratio and water content

Ascorbic acid (AA) was encapsulated in glassy low‐dextrose equivalent maltodextrin matrix by extrusion. The effects of formulation parameters, i.e., core/matrix ratio and water content were mainly investigated on T_g of extrudate. The AA yield, AA content and water content of the products together with extrusion parameters were also determined and compared for different formulations. The T_g of extrudates containing water content from 7.860% to 10.430% ranged from 43.17 to 27.48 °C, and the T_g of extrudates which core to matrix from 1:4 to 1:8 ranged from 35.79 to 41.64 °C. AA yield of all extrudates is above 96%, and with increasing water content, there was a slight decrease in the AA yield. The increased water level and core/matrix ratio reduce specific mechanical energy and die head pressure. X‐ray diffraction and scanning electron microscopy suggested that AA was most likely molecularly dispersed within the maltodextrin indicating the miscibility of AA and maltodextrin.     

Effect of lactose content on dielectric properties of whole milk and skim milk

Dielectric properties (dielectric constant ε′ and dielectric loss factor ε′′) of whole milk and skim milk with the lactose content of 4.56–6.44% and 4.57–6.47%, respectively, were measured over the frequency range of 20–4500 MHz at 25 °C using a vector network analyzer. The results showed that ε′ decreased with increasing frequency, and ε′′ changed with V shape and its minimum was noted at about 2000 MHz. Whole milk had lower dielectric properties than skim milk at almost same lactose content and a given frequency. ε′ had weak positive linear relationship with lactose content for whole milk, but had negative linear relationship for skim milk. No matter for which milk, ε′′ had very good negative linear relationship with lactose content below 1000 MHz and had good positive linear relationship above 2300 MHz. The study provides information on developing rapid lactose detector for milk in future.     

Impact of amorphous and crystalline lactose on milk chocolate properties

Chocolate mass of low viscosity is preferred for most applications. Milk powder influences processing behaviour, flow properties and taste of milk chocolate. The project aimed to investigate influences of skim milk powders containing amorphous or crystalline lactose on flow properties after producing samples by roller milling and conching or alternatively by ball milling. For the first case, it was found that mass consistency before roller milling is strongly influenced by lactose type; producers must specify it and adapt initial mass fat content. Little impact on final products was found after processing milk powders at equilibrium moisture. If predried powders are used for reducing conching time, crystalline lactose leads to chocolate with slightly lower viscosity. At ball mill processing, crystalline lactose resulted in significantly lower viscosity, for example 15% at 40 s^?1; thus, for this process, it can be recommended to use special milk powders high in crystalline lactose content.     

Flavor release from salad dressing varying in fat and garlic flavor

Nine Ranch salad dressing samples varying in added canola oil (0, 6.75 and 13.5% w/v) and resoleum garlic (0.12, 0.36 and 0.6% w/v) were evaluated for garlic, pepper and sourness intensities by time–intensity profiling. Increased fat caused lower maximum intensity, total duration and area under the TI curve of garlic and pepper flavors (but not duration), and delayed sourness perception. Both molecular interactions between flavors and the food matrix, and physical properties of the food matrix may account for these effects of fat on flavor release.     

Effect of water uptake on amorphous inulin properties

Physical property changes of amorphous spray-dried inulin were investigated during water uptake at 20 °C. Modulated Differential Scanning Calorimetry (MDSC) and Wide Angle X-ray Scattering (WAXS) were used to investigate the evolution of the glass transition temperature (T_g) and the crystallinity index, respectively. The water content, crystallization and thermal properties relationship enabled the identification of three zones in the T_g–water content state diagram. Zone I delimited inulin in a glassy amorphous state, while zone II characterized inulin in a liquid amorphous state. Inulin crystallized and caked when T_g was below the storage temperature of 20 °C, but crystallization (zone III) was not spontaneous and was delayed by the defined zone II. The crystallization led to thermograms with an endotherm close to T_g. Temperature-Resolved WAXS allowed to correctly ascertain the MDSC endothermic peak as a melting peak because the crystallinity index was maximal at onset temperature of the transition, and dropped to zero at the endset temperature.     

Effect of water loss from apples during cool storage on the water content of the fruit

Apples which were stored in air of different relative humidities had different rates of water loss from the fruit but the water content of the fruit remained the same. It is suggested that water lost by evaporation is partly replaced by the water liberated from increased esterification of acids and alcohols in the fruit.     

Glass transition and water plasticization effects on crispness of a snack food extrudate

Abstract

A crispy snack model, composed of maltodextrin, wheat flour, salt, and water, with a clearly measurable glass transition was designed and produced by extrusion. The material was used to investigate effects of glass transition and water plasticization on mechanical properties and sensory crispness. Water sorption and the glass transition temperature range were determined gravimetrically and using differential scanning calorimetry (DSC) for samples stored at 0 to 85% relative humidity (RH), respectively. Mechanical properties were determined for extradates rehumidified at 0 to 76% RH. Three sensory panels evaluated crispness intensities of extrudates rehumidified at 33 to 76% RH by either breaking samples with fingers (Finger Task), biting using the incisor teeth (Bite Task), or biting and chewing (Bite‐and‐Chew Task). The extrudate was plasticized by water, as observed from a typical decrease of Tg with increasing water content. Changes in mechanical properties and loss of crispness occurred at an intermediate water activity level coinciding with the extent of plasticization depressing the Tg to below ambient temperature. The changes in mechanical properties and sensory crispness intensities with increasing water activity had sigmoid shapes following the Fermi's model. Loss of crispness as a result of water plasticization is likely to apply to a number of low‐moisture food materials, although various mechanical and sensory properties do not necessarily change in unison as the materials undergo a glass transition.     

The effect of temperature on the development of browning of amorphous and crystalline lactose

When lactose crystals are dried in industrial driers the temperatures used can, when exposure time is too long, cause the crystals to undergo non-enzymatic browning. This leads to a defect in the final product. Understanding the kinetics allows driers to be designed to avoid this. To examine the non-enzymatic browning kinetics of amorphous and crystalline lactose, samples were heat treated for 2–120 min at 110 °C, 120 °C, 130 °C, 140 °C and 150 °C. The evolution of colour was followed by spectrophotometry at 420 nm and colorimetry (L* a* b*). The absorbance and the b* values increased while L* value decreased with time and temperature. A first order reaction model with Arrhenius temperature dependence provided a good fit to the data. A difference was seen between crystalline and amorphous lactose, with the latter having more intensive browning under the same conditions due to the increased surface area available.     

Properties of spray-dried food flavours microencapsulated with two-layered membranes: Roles of interfacial interactions and water

Engineering the interface of oil-in-water emulsion droplets with biopolymers that modify its permeability could provide a novel technique to improve flavour retention in dry powders. The objective of this study was to determine if volatile compounds were more retained in dry emulsions stabilized by pea protein isolate (PPI)/pectin complex than that stabilized by PPI alone. The retention of ethyl esters during spray-drying increased with decreasing volatility of the encapsulated compound and ranged from 28% to 40%. The addition of pectin to feed emulsions was quite effective in markedly improving the retention of the three studied flavour compounds. In our previous work (Gharsallaoui et al., 2010), we showed that pectin was able to improve physical integrity of emulsion oil droplets during spray-drying. However, the pectin positive effect on both the droplet stability and the flavour retention at the time of spray-drying can also be explained by a protein molecular structure protective effect. Indeed, the obtained FTIR results showed that pectin was able to preserve the β-sheet secondary structure of pea protein when pea globulins/pectin complexes are heated. The study of the release characteristics of a flavour compound from dried powders showed that pectin addition did not affect the release profile mainly accomplished by the diffusion mechanism.     

水分对涂抹型再制干酪的影响

水分是影响涂抹型再制干酪感官、质构和微观结构的重要因素.通过测定涂抹型再制干酪的pH、融化性、质构性质(TPA),并结合微观结构观察的分析方法,确定水分对涂抹型再制干酪品质的影响.结果表明,水分的增大使样品中pH增大,但对pH的影响不显著,融化性显著增强(P<0.05),对硬度、黏着性和涂抹功影响极显著(P<0.01).48%、54.3%和60%含水量时的微观结构明显不同,水分增大使酪蛋白网络结构由致密变得松散,同时脂肪球不断增大并聚集.     

Effect of water and salt content on protein solubility and water retention of meat preblends

Different preblend water contents at a constant ionic strength were investigated to determine if increasing water availability would increase protein solubility and water retention in meat preblends. Four salt levels (0, 2, 4 and 8%) and four water levels (0, 20, 40 and 80% formulation water) were used with ground bovine semimembranosus muscle that had been frozen once. Ground muscle was mixed with either NaCl alone (0% formulation water) or NaCl and brine (20, 40 and 80% formulation water) for the 2, 4 and 8% NaCl treatments. Distilled water was used for the 0% NaCl treatment. The mixtures were stored at 5°C for 12 h. Following storage, the water/brine content was standardized, and protein solubility and water retention were measured. Elevating the water content of preblends, in which the salt concentration had been standardized, increased the water retained during centrifugation (P < 0·05). Although not statistically significant, a similar trend was observed for protein solubility. Four percent NaCl produced the greatest protein dissolution and water retention.     

水分含量及添加剂对面团流变学性能的影响

利用质构仪分析了水分含量和单甘酯、明胶、食盐、海藻糖、抗坏血酸等五种添加剂对面团流变学特性的影响。结果表明:水分的多少直接影响到面筋网络的形成,水分含量在40%～42%时,面团的综合流变学性能比较好。单甘酯和明胶对面团的抗穿刺能力提高比较明显,且明胶优于单甘脂,二者最佳添加量约为3%。NaCl、海藻糖、抗坏血酸能明显提高面团的抗拉伸能力,抗坏血酸的最佳添加量约为0.2%,海藻糖的最佳添加量约为1.5%。      

Enzymatic synthesis of galacto-oligosaccharides and other lactose derivatives (hetero-oligosaccharides) from lactose

Non-digestible oligosaccharides are applied as functional food ingredients to replace sucrose and to exploit specific biological functions, particularly low cariogenicity, low caloric content, prebiotic activity, and their ability to prevent adhesion of pathogens and toxins to eukaryotic cells. Oligosaccharides derived through enzymatic synthesis from lactose, i.e., galacto-oligosaccharides, lactulose and lactosucrose, account for a major part of the annual oligosaccharide production. Enzymatic production of oligosaccharides employs lactose as galactosyl-donor to transfer the galactosyl-moiety of lactose to suitable acceptor carbohydrates through the activity of β-galactosidases, or employs lactose as a galactosyl-, glucosyl- or fructosyl-acceptor through the activity of β-galactosidases, glucansucrases and fructansucrases. This communication provides an overview on the structural diversity of galacto-oligosaccharides and hetero-oligosaccharides that are produced by enzymatic conversion of lactose, and reviews the strategies used to optimize enzymatic transglycosylation with lactose as glycosyl donor or glycosyl acceptor.     

Effect of protein concentration on the surface composition,water sorption and glass transition temperature of spray-dried skim milk powders

The effects of dilution of protein content in skim milk (34–8.5% protein content), by lactose addition, on the surface composition, water sorption property and glass transition temperatures of spray-dried powders were investigated. The X-ray photoelectron spectroscopy (XPS) study of spray-dried powders showed preferential migration of proteins toward the surface of the milk particles whereas the lactose remained in the bulk. Sorption studies showed that the lower protein concentration in milk powders is linked to an increased water adsorption property and lowering of water activity (a_w) for lactose crystallization. Analysis of glass transition temperature (T_g) of the powders sorbed at different humidities showed no distinct change in T_g values, indicating the dominant effect of lactose on the glass transition temperature of all the powders.