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Konjac glucomannan (KGM) is a dietary fibre with potential to be used as a fat-replacer in Mozzarella cheese. The functional properties (texture, free oil, meltability and stretch performance) of full-fat cheese control (FFC), low-fat cheese control (LFC), skimmed cheese control (SKC), low-fat cheese with KGM (LF-KGM) and skimmed cheese with KGM (SK-KGM) after 0, 7, 14, 21 and 28 days of storage at 4 °C were measured. The pizza bake properties (appearance for pizza bake and browning) and microstructure were evaluated. Generally, LF-KGM and SK-KGM had lower firmness but higher meltability than LFC and SKC, respectively. The firmness and meltability of LF-KGM were similar to those of FFC. Both the stickiness and free oil content of LF-KGM and SK-KGM were similar to LFC and SKC, respectively. The LF-KGM and SK-KGM showed more complete shred melt, less scorching and lower browning (higher L* value after baking) on the cheese surface than LFC and SKC, respectively, when they were baked as a pizza topping. Microstructure of FFC, LFC and SKC showed that fat globules filled the serum pores/channels in the protein matrix. LF-KGM and SK-KGM showed more dense protein matrix with more coalesced fat globules distributed in the matrix. The stickiness, free oil content and meltability of all the cheeses increased but firmness decreased during storage. We show that KGM may be useful as a fat replacer in manufacturing fat-reduced Mozzarella cheeses to improve functionality and pizza bake characteristics.

Core-shell structural capsules can encapsulate various food ingredients (e.g., nutrients), thus being highly potential for the design of many food products. This work reports how the gum (xanthan, locust bean or gellan) inclusion tailors the practical features of agar/konjac glucomannan (KGM) system for fabricating the core-shell structural capsules. The rheological and textural analyses revealed that xanthan gum inclusion could simultaneously increase the sol-gel transition point and gel strength (ca. 1.6 times higher) of agar/KGM system. The composite gels were dehydrated to generate shell materials. The materials including xanthan or locust bean gum showed stronger chain interactions than did that including gellan gum, accompanied by weakened crystalline features for the different shell materials. Again, compared to the agar/KGM counterpart, the shell materials including xanthan gum could display a similar tensile strength (close to 50 MPa) but an evidently increased elongation at break (ca. 2.5 times higher). Then, these agar/KGM based systems were used to prepare core-shell structural capsules. The capsules based on agar/KGM/xanthan gum materials exhibited the highest roundness and breaking stress. Regarding this, the increased sol-gel point reduced the time required for droplet hardening (to generate core-shell gel balls); such fact, together with the higher gel strength, weakened the deformation of gel balls and thus increased the roundness and breaking stress of capsules (resulting from drying of gel balls).

Limonene is a kind of widely used flavor oil, susceptible to degradation with the loss of lemon-like odors and the formation of off-flavors. This study aimed to develop a novel structurally well defined zein-based core-shell microencapsules loaded with limonene for limonene protection and controllable release. The microencapsules were fabricated using a two-step heterogeneous precipitation process, with the shell being formed by direct zein precipitation on the oil-water interface and growing along with the water addition driven by hydrophobic interaction. The formation of core-shell microencapsules occurred at the limonene/zein ratio around 2.0 with D4,3 close to 10 μm and shell thickness about 25 nm, while the smaller self-assembled zein particles could be formed at the ratio of 0.1 and 5.0, suggesting that the mass ratio of core to shell affected the formation of encapsulation and the shell thickness could be controlled. An interior rough and porous shell of the microencapsules was also observed. Sodium caseinate (SC) was adsorbed onto hydrophobic zein surface by electrostatic interaction, contributing to a hydrophilic interface and improving the re-dispersibility of the freeze-dried powder in water. The release rate of limonene in the burst release phase from zein-SC microencapsules was significantly lower than that of whey protein isolate (WPI)-stabilized emulsion, and tended to be gradual in the sustained phase, followed the zero order kinetics. The limonene retention rate of the microencapsules was higher than that of the WPI-stabilized emulsion during an acceleration storage condition, attributing to the solid barrier of the zein-SC shell of the microencapsules. High linear relationship (R2 > 0.96) between limonene retention rate and storage time in both microencapsules and WPI-stabilized emulsion was observed, suggesting potential controllability of limonene degradation. The ability to design the natural biopolymer-based colloidal microcapsules with slow-release and oxidation prevention of the unstable flavor oils opens a new opportunity in a stable dispersions in aqueous foods.

An improved preparation method of konjac glucomannan-ethyl cellulose (KGM-EC) composite film was adopted to allow hydrophobic contents (EC) varying from 0% to 85.7% in the films, and may be explained by emulsification effect of both KGM and EC. Scanning electron microscopy images supported that all blend films had homogenous microstructures without phase separation. Moisture adsorption, water contact angle, swelling test, water vapor transmission, and mechanical tests were performed to evaluate the hydrophilicity-hydrophobicity and related properties of the films. Results indicated that EC addition significantly decreased the values of moisture adsorption, swelling, water vapor transmission, and mechanical strength of the films, and increased the contact angle. For composite films, linear relationships (most R2 > 0.9) were found between ingredient proportion and results of moisture isotherms, and water contact angle, indicating controllable hydrophilicity-hydrophobicity. Ingredient proportion was also found to correlate linearly with film tensile strength (TS) and elongation ratio (R2 = 0.7502 and 0.8974, respectively), and after immersion in water, TS still correlated linearly with ingredient ratio (R2 = 0.9767). These results support the hydrophilicity-hydrophobicity and related properties of KGM-EC film could be controllable through ingredient proportion, and this also offers the potential of the film to have unique property changes (e.g. linear) in response to different relative humidity or aw equilibrium condition under certain ingredient proportion.

Lipid digestion is the process of enzymatic hydrolysis at the interface, and the interfacial structure play an important role in the lipid digestion. Non-ionic surfactant Tween80 (T80) presented a significant impact on the lipid digestion of gum Arabic (GA) stabilized oil-in-water emulsion. The interfacial structure of GA-T80 emulsion droplets has been investigated by using gel permeation chromatography-multiangle laser light scattering, interfacial measurement and atomic force microscope. With addition of T80, the surface loading of GA decreased until a plateau value reached. About 15% of GA still remained on the interface when T80 concentration increased to ∼4%. Addition of T80 contributed to a stiffening of the network formed at the droplets interface. The kinetics of lipid digestion exhibited a biphasic rate under this certain interface, shown as an induction period followed by a speeding up process. It probably resulted from the adsorption behavior of lipase on the emulsion interface during the lipolysis process. In was found that the accumulation of lipase on the emulsion droplets interface contributed to the lag period of the free fatty acids release. The biphasic rate of lipid digestion was mainly caused by the rate of lipase adsorption, which was highly dependent on the interface structure of emulsion droplets.

Konjac glucomannan (KGM) has potential to contribute functional properties to dairy products, but mixtures containing a sufficient amount of KGM and milk may show undesirable appearance because of incompatibility between the polymers. Thus, the effects of KGM solution (with concentration of 0.1, 0.5, 1.0, 1.5, 2.0 and 2.5%) on the stability and phase behavior of KGM-milk mixtures were investigated. The phase separation diagram showed that only a low level of KGM (0.2%, w/v) was sufficient to induce phase separation in KGM-milk mixtures. KGM and milk appear to undergo segregative phase separation. The turbidity of the supernatant after centrifugation, precipitation percentages, particle size and zeta potential of the mixtures were measured to investigate the stability of the systems. The stability of the KGM-milk mixtures was related to both the concentration of KGM solution and the percentage of milk. In general, the stability of the mixtures was enhanced with increase in milk percentage and decrease in concentration of KGM solution. Confocal laser scanning microscopy was carried out to study the microstructures of the KGM-milk mixtures. When the concentration of KGM solution was higher than 0.5%, aggregate structures could be observed in the mixtures, and with increase in milk percentage, coarsening of the structures occurred. The microstructures also indicated that some KGM-milk mixtures were in metastable state even though no phase separation was observed in the mixtures after standing for 4 h at 22 °C.

This study aimed to investigate molecular aggregation of curdlan on heating in water through atomic force microscopy (AFM), transmission electron microscopy (TEM), turbidity, and rheology tests. With improved sample preparation methods, AFM and TEM analysis revealed that curdlan morphologies changed with heating temperatures. Bundles of curdlan triple-stranded helixes had mainly hydration and swollen process at 40 °C, and bundled triple-stranded helixes were driven to separate from each other at 50 °C. These triple-stranded helixes would dissociate into partially opened triple-helical chains and single-helical chains at 60and 70 °C, and finally large amounts of dissociated single-helical chain were presented at 80 and 90 °C. Accordingly, structures of curdlan at temperatures ranging from 25 to 90 °C were proposed, and the turbidity and rheology results could be well explained with proposed structures. This research may provide new insights on revealing the behaviour of curdlan water dispersions on heating in water alone.

Design and fabrication of iron fortifier is very essential in the prevention or improvement of iron-deficiency anemia in food industry. In this study whey protein isolate (WPI) and gum arabic (GA) loaded with ferric ions was expected to be self-assembled to form stable nanoparticles by heating at 85 °C for 15 min at pH 4.0. It is illustrated that WPI/GAFe3+ nanoparticles were more uniformly dispersed in comparison with the easily aggregative GAFe3+ complex. The tightly binding of ferric ions was confirmed by FTIR and XPS. During formation of WPI/GAFe3+ aggregates induced by heating, the disulfide bond was formed and the surface hydrophobicity was significantly enhanced. The ferric ions release rate of WPI/GAFe3+ nanoparticles was significantly slower than that of GAFe3+ complex in simulated gastric juice due to the fact that the assembled structure exhibited a delayed effect on the hydrolysis of peptides catalyzed by pepsin during its internal diffusion into nanoparticles. WPI/GAFe3+ nanoparticles contributed to a good adsorption activity on oil-water interface between WPI and GAFe3+ complex because of its high steric hindrance. The decrease of interfacial tension with sequential adsorption demonstrated that WPI/GAFe3+ nanoparticles could be electrostatically adsorbed onto positively charged sodium caseinate interface, or co-adsorbed onto non-ionic Tween 80 interface, forming a more stable interface with higher steric hindrance and lower interfacial energy. Thus, the self-assembled WPI/GAFe3+ nanoparticles would have great potential in the application for iron fortification especially in food emulsion system.

The gelation of β-lactoglobulin (BLG) and its fibrils was investigated in the presence of dithiothreitol (DTT) and transglutaminase (TGase). BLG fibrils were prepared by heating BLG at 80 °C and pH 2 for 10 h and then adjusting to pH 7. The structure of fibrils was observed by atomic force microscopy. The small and large amplitude oscillatory measurements were done to examine the gelation process and to get more insight into gel properties. It was shown that TGase alone could induce gelation for fibrillar BLG although it could not for non-fibrillar BLG. TGase could cross-link BLG fibrils to form a gel at very low protein concentration in comparison with other protein gels, and enhance the network formation of both non-fibrillar and fibrillar BLG in the presence of DTT. The scanning electron microscopic observation revealed that TGase increased the network density for non-fibrillar gels while it made network strands thicker for fibrillar gels.

Conjugated linoleic acid (CLA) is a dietary supplement due to its multiple health benefits. However, significant loss of biologically active CLA could occur due to oxidation. Oil-in-water emulsion is supposed to be an effective protection system. In a previous study (Yao et al., 2013), physical and chemical stabilities of CLA emulsion stabilized with gum Arabic were investigated, and the optimal gum concentration was identified as 5 wt%. The present study dealt with the interfacial adsorption of three gum Arabic samples (one conventional gum, GA; two matured gums, EM2 and EM10) at the CLA-water interface, in relation to their emulsifying properties. With increasing gum Arabic concentration, particle size ( D [3,2]) of CLA emulsion decreased and slowly leveled off, which was accompanied with a gradual saturation of gum Arabic adsorbed at the emulsion interface. Nevertheless, surface load of gum Arabic at the emulsion interface ( Γ , mg/m 2 ) reached maximum at a gum concentration of 5 wt%. This could reasonably explain the optimal emulsion stability observed at this gum concentration, as revealed by particle size distribution of fresh emulsions and by acceleration test at 60 °C. Among the three gums, EM10 exhibited the highest emulsifying activity and conferred the best emulsion stability, despite of its lowest surface load. This is presumably due to a larger tendency of the AGP fraction in EM10 toward aggregation at the CLA-water interface.

Konjac glucomannan (KGM)/ethyl cellulose (EC) blend films were prepared at different blend ratios (KGM/EC = 10/0, 9/1, 8/2, 7/3, 6/4, and 0/10, w/w) in the presence of dibutyl sebacate at 25% (w/w) of total solids content. Hydrogen bond interactions between KGM and EC occurred. An ethyl cellulose phase consisting of oval-shaped particles was uniformly embedded in the KGM continuous phase. The maximum values of tensile strength and elongation at break of blend films were respectively 48 MPa and 12.7% when the ratio of KGM and EC was 7/3 (w/w). Compared to KGM film, the moisture resistance, thermal stability, tensile strength, and elongation at break of blend films were increased. In addition, water vapor transmission was decreased, but the oxygen permeability was increased by blending. Applications of the blend film of KGM and EC for food packaging are suggested.

Sugar beet pectin (SBP) was enzymatically modified by crosslinking ferulic acid groups using horseradish peroxidase (HRP). The purpose of the modification was to achieve maximum molecular weight while retaining reasonably good solubility of the SBP. Reaction conditions were optimized in terms of pH (5.0–7.0), H2O2 concentration (0.25–1.0 mM) and HRP dose (0.0017–0.0083 U/mL). A maximum molecular weight of 1.86 × 106 Da was obtained at pH = 6.5, H2O2 = 1.0 mM and HRP = 0.005 U/mL while also remaining good solubility. The emulsifying properties of the SBPs before and after modification were evaluated. The emulsion prepared using the modified SBP and medium chain triglyceride (MCT) showed improved stability during acceleration test at 60 °C for a period of 10 days, in comparison with the emulsion prepared with control SBP. The volume-weighted mean diameter D4, 3 after 10-day acceleration was 12.1 and 20.6 μm for emulsions stabilized with modified and control SBPs, respectively.

Emulsification/internal gelation is an effective encapsulation method to protect probiotics from adverse environment. In this paper, microcapsules of Lactobacillus acidophilus CGMCC1.2686 were prepared by emulsification and gelation of alginate solutions with slow release of Ca2+ ions from calcium carbonate (CaCO3) and calcium disodium ethylenediaminetetraacetate (Ca-EDTA). Physical characterization of the two types of microcapsules showed that alginate-Ca-EDTA microcapsule was more uniform in size than alginate-CaCO3, with a span factor of 0.96 and 1.20, respectively. Mechanical measurements demonstrated that alginate-CaCO3 microcapsule was more robust and elastic, which was supported by its denser structure as observed by electron scanning microscopy. Bacteria encapsulation yields in the two microcapsules were similar, 37.9% for alginate-CaCO3 and 36.9% for alginate-Ca-EDTA. However, alginate-CaCO3 microcapsule exhibited much higher cell survivals in both simulated gastric juice and bile salts solution (22.2% and 2.6*10−2%, respectively) than alginate-Ca-EDTA (7.1% and 0%, respectively), indicating a more effective protection of L. acidophilus CGMCC1.2686. The protection efficiency was discussed in relation to the mechanical properties of the microcapsules and the calcium sources used.

The bioavailability of lipids from an emulsion can be controlled and regulated by the property of the stabilizing interfacial layer. Here we evaluate how low-molecular weight surfactants including hexadecyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and Tween 80 (T80) influence the interfacial behavior of lipase and bile extract on the surface of lipid droplets stabilized with gum arabic (GA). The lipolysis behavior was influenced by surfactant type and concentration. The results showed that anionic SDS could completely displace GA from droplet surface. Cationic CTAB might either adsorb onto existing GA layers or displace GA, whereas non-ionic T80 could co-adsorb with GA on the interface. When the concentration of surfactants was much higher than the critical micelle concentration (CMC), all the surfactants would form a dense adsorption layer on the droplet interface to prevent lipase from the direct contact with lipids. A considerable amount of surfactant in the aqueous phase may also compete with the bile salt and lipase, thus leading to suppressed digestion of lipids. Ionic surfactants would denature the lipase resulting in reduced enzyme activity, and T80 micelles may interact with the lipase, hindering their adsorption onto the droplet interface as well. These results were confirmed both by the digestion model and interfacial techniques. The results provided guidance for the development of emulsion-based delivery systems for functional lipid foods.

Moisture retaining materials are widely used in the food, cosmetic and tobacco industries. Conventional materials, for example, glycerin and propylene glycol have reasonable moisture absorption abilities, but poor moisture retention. Konjac glucomannan (KGM) is a heteropolysaccharide made up of glucose and mannose, linked with β-1,4 glycosidic bonds. Konjac superabsorbent polymer (KSAP) is a derivative containing hydrophilic groups and a network structure prepared by grafting sodium acrylate on to KGM. Previous work has shown that KGM and KSAP have properties which can lower water activity (aw). The objective of this paper is to consider the mechanism of this process. Filter-paper is used as a model fiber instead of tobacco, where this effect is practically important. Moisture absorption and retention of KGM and KSAP are compared with glycerin and propylene glycol. Moisture desorption isotherms have been determined and fitted to the GAB model. The results show that the moisture retention of KGM and KSAP are better than propylene glycol and glycerol. At a given moisture content, aw of filter-paper containing KSAP was the lowest. The monolayer moisture content and net isosteric heat of desorption of filter-paper containing KGM and KSAP were greater than that of the control groups. This study demonstrated that KGM and KSAP have the potential to be used as moisture retaining ingredients.