Gel Firmness Research Articles

Effect of Lactobacillus rhamnosus on Physicochemical Properties of Fermented Plant-Based Raw Materials.

To overcome texture and flavor challenges in fermented plant-based product development, the potential of microorganisms is generating great interest in the food industry. This study examines the effect of Lactobacillus rhamnosus on physicochemical properties of fermented soy, oat, and coconut. L. rhamnosus was combined with different lactic acid bacteria strains and Bifidobacterium. Acidification, titratable acidity, and viability of L. rhamnosus and Bifidobacterium were evaluated. Oscillation and flow tests were performed to characterize rheological properties of fermented samples. Targeted and untargeted volatile organic compounds in fermented samples were assessed, and sensory evaluation with a trained panel was conducted. L. rhamnosus reduced fermentation time in soy, oat, and coconut. L. rhamnosus and Bifidobacterium grew in all fermented raw materials above 107 CFU/g. No significant effect on rheological behavior was observed when L. rhamnosus was present in fermented samples. Acetoin levels increased and acetaldehyde content decreased in the presence of L. rhamnosus in all three bases. Diacetyl levels increased in fermented oat and coconut samples when L. rhamnosus was combined with a starter culture containing Streptococcus thermophilus and with another starter culture containing S. thermophilus, L. bulgaricus and Bifidobacterium. In all fermented oat samples, L. rhamnosus significantly enhanced fermented flavor notes, such as sourness, lemon, and fruity taste, which in turn led to reduced perception of base-related attributes. In fermented coconut samples, gel firmness perception was significantly improved with L. rhamnosus. The findings suggest that L. rhamnosus can improve fermentation time and sensory perception of fermented plant-based products.

Acylation modification and/or guar gum conjugation enhanced functional properties of pea protein isolate

There has been an increasing demand for diverse and more functional plant-based protein ingredients for food uses. This study aims to improve the functional properties of pea protein isolate through acylation and/or conjugation with guar gum and investigate the physicochemical characteristics of the modified proteins. Acylated pea proteins were prepared by reacting with acetic anhydride (AA) or succinic anhydride (SA) at 0.3 or 0.6 g of AA or SA per g protein, respectively. Guar gum-pea protein conjugates were prepared by incubating the mixture at a mass ratio of 1:20 and 1:40 at 60 °C for 24 h, respectively. Acylated-guar gum-conjugated pea proteins were also prepared to investigate their synergistic effects. Both conjugated and acylated pea proteins showed significantly improved oil holding capacity of up to 2.20 ± 0.05 and 2.09 ± 0.03 g oil/g protein, respectively, compared to the unmodified protein (1.03 ± 0.02 g oil/g). The acylated pea protein also had greater water holding capacity of up to 7.01 ± 0.31 g water/g protein compared to the unmodified protein (3.57 ± 0.05 g water/g). Emulsion capacity and stability were improved up to 96–100% and 95–100%, respectively, for the modified proteins (e.g., 1:20 conj., SA0.3/0.6, AA 0.3/0.6 conj., SA 0.3/0.6 conj.). The suspensions prepared with 9% acetylated pea protein formed firm gels. Sequential acylation and conjugation of pea proteins demonstrated more beneficial and synergistic effects on the water holding capacity and emulsifying properties. However, the in vitro gastrointestinal digestibility of the modified pea proteins decreased compared to that of the control pea protein. Overall, the acylated and conjugated pea proteins possessed superior functional properties that could be used as novel food ingredients in meat alternative or beverage applications.

Physicochemical characteristics of surimi-like material made from the muscle tissues of freshwater mussels (Sinanodonta woodiana Lea, 1834)

The aim of the study was to determine selected characteristics of surimi-like material (SLM) made from the muscle tissues of Sinanodonta woodiana (Lea, 1834) freshwater mussels. The research material consisted of unwashed mussel muscle homogenate as the control sample—C, mussel muscle tissue twice washed with water (SLM-W) and sample washed with NaCl at a concentration of 0.169 mol/L as well as water (SLM–S). A raw control sample and surimi like-materials were analysed using the SDS-PAGE technique. They were also tested using the DMTA method (dynamic mechanical thermal analysis) while heating the samples up to 80 °C and cooling to 20 °C. The thermal drip and texture of gels after heating (75 °C, 30 min) were also determined. The washing procedure had a significant impact on the protein composition of the SLMs. A significantly (p < 0.05) higher percentage of proteins with molecular weights of 270–273 kDa and 105–110 kDa (corresponding to specific filamin isoforms), as well as 42–43 kDa (corresponding to actin), were found in the SLMs compared to sample C. Ccorrelation analysis confirmed a strong positive relationship between the percentage share of the above proteins and the values of the elasticity modulus (r ≥ 0.84) and firmness (r ≥ 0.88) of SLM gels. The SLM-S sample was characterised by the lowest significant (p < 0.05) thermal drip values. During heating, the rheological traits of all samples changed at two stages: from 20 to 50 °C and over 50 °C. The highest dynamics of variation in the elasticity modulus (G′) value were noticed at temperatures exceeding 50 °C in all samples. The G′ values in the SLM samples were significantly greater than the values in sample C. The analysis revealed a strong correlation (r ≥ 0.81) between the determinants of the texture of the SLM samples and their rheological parameters. Sample SLM-W was the one with the highest firmness and elasticity values. The analysis showed that the textural properties of the SLM samples mainly resulted from the reaction of spatial matrices to mechanical interactions.

Pulsed electric fields (PEF) treatment to enhance starch 3D printing application: Effect on structure, properties, and functionality of wheat and cassava starches

This work evaluated the impact of PEF on the structure, properties, and functionality of wheat and cassava starches focusing on 3D printing application. Aqueous starch suspensions were PEF-treated using three different combinations of field strength and total specific energy input (T1:15 kV/cm;25 kJ/kg; T2:25 kV/cm;25 kJ/kg; and T3:25 kV/cm;50 kJ/kg). The three conditions had the same effect on cassava starch (no damage on granules surface, reduction of peak apparent viscosity, firmer gels), while T3 promoted a greater effect on wheat starch (fractures on granules surface, reduction in peak apparent viscosity, and firmer gels). T3 condition was selected for further evaluation, revealing depolymerization, reduction of relative crystallinity, and gelatinization enthalpy, but no changes in functional groups. PEF-treated wheat starch resulted in 3D printing with a smoother surface and different texture, while PEF-treated cassava starch showed the same performance of native starch. Therefore, PEF affects differently each source, potentially enhancing 3D printing applications.

Influence of Gum Arabic from &amp;lt;i&amp;gt;Acacia Senegal&amp;lt;/i&amp;gt; var. &amp;lt;i&amp;gt;kerensis&amp;lt;/i&amp;gt; on the Modifications of Pasting and Textural Properties of Cassava and Corn Starches

The use of hydrocolloids to modify the properties of native starches has been on the rise in the recent times due to the market demand for natural, safe and economical food ingredients. The objective of this study was to investigate the effect of gum Arabic from Acacia senegal var. kerensis to modify pasting and textural properties of corn and cassava starches, as an alternative to chemical and enzymatic modification. Blends were prepared by substituting the starches with gum at different levels (0%, 0.5%, 2.0%, 4.0%, 6.0% and 8.0%), whereas native corn and cassava starches were used as control. The pasting properties of the starch-gum mixed systems were determined using the Brabender viscograph while the textural properties (firmness, consistency, cohesiveness and work of cohesion) were determined using Texture Analyzer. Results showed that the gum Arabic significantly decreased all the viscosity parameters (peak viscosity, final viscosity, break down and setback values) of both starches at all levels of substitution. However, there was no significant effect of gum Arabic on the pasting temperature (72.05°C - 71.85°C) for corn starch and (68.90°C - 68.65°C) for cassava starch. The degree of gel firmness and consistency was higher in corn starch than in cassava starch and the effect of gum addition differed with each starch. The findings from this study indicate that gum Arabic significantly modified the pasting and textural properties of corn and cassava starches due to strong interaction between the gum and the starches. Hence, this property of gum Arabic could be useful in controlling starch retrogradation and determining starch end use functionality.

In silico-screened cationic dipeptides from scallop with synergistic gelation effect on ι-carrageenan.

In this paper, some cationic dipeptides from scallop (Patinopecten yessoensis) male gonads (SMGs), which can synergistically gel with ι-carrageenan (ι-C), were screened by the in silico approach. Fourteen protein sequences of SMGs were obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and nano liquid chromatography-mass spectrometry/mass spectrometry (nanoLC-MS/MS) analysis and were then hydrolyzed via in silicosimulation. A total of 414 sequences were obtained with 56 duplicates, half of which were positively charged at pH 7. Among the cation sequences, 171 had good water solubility, including two amino acids (Lys and Arg). The molecular weight analysis of the cationic water-soluble sequences showed that 0.2-0.3 kDa accounted for the highest proportion. Based on the obvious synergistic effect of Lys and ι-C, 11 Lys-containing dipeptides, including Ser-Lys (SK), Thr-Lys (TK), Trp-Lys (WK), Ala-Lys (AK), Leu-Lys (LK), Gly-Lys (GK), Val-Lys (VK), Cys-Lys (CK), Asn-Lys (NK), Phe-Lys (FK), and Met-Lys (MK), were finally screened out to study gelation with ι-C. It was found that the dipeptides/ι-C formed firm gels except WK/ι-C. The values of the storage modulus (G') of 11 dipeptides/ι-C were investigated by a rheometer. The G' of 8 dipeptides/ι-C was higher than 1000 Pa. These results indicated that the in silico-screened dipeptides from SMGs can form composite gels with ι-C, which can be used for the design and development of functional hydrogels.

Evaluation of rennet-induced gelation under different conditions as a potential method for 3D food printing of dairy-based high-protein formulations

The rennet-induced gelation of milk proteins was evaluated as a potential method for the formation of 3D printed food structures. The effects of pH, [Ca2+], and temperature on the rennet gelation properties of milk protein dispersion with 15% (w/w) protein content were assessed using low amplitude strain oscillation rheometry. A cycled-temperature ramp (heating-holding-cooling) during rheological measurements was suitable to evaluate gel firmness development, as an imitation of the temperature profile in the 3D printing process. A factorial design considering two levels of pH (6.0 and 6.4), [Ca2+] (1.5 and 5.7 mM), and temperature (31 and 40 °C), showed that the pH, temperature, and its interaction were the main factors enhancing gel formation and the strength of the resultant gel. At pH 6.0 and temperature ramped to 40 °C followed by cooling to 15 °C, a very high gel strength (~8–9 kPa) was obtained. These results showed that rennet-induced gelation could be manipulated for developing printable dairy formulations.

Biochemical diversity of cardoon flowers (Cynara cardunculus L.): Predicting PDO Mediterranean cheese textures

Cardoon flower extract is a vegetable coagulant used in the manufacture of some highly appreciated Mediterranean Protected Designation of Origin (PDO) sheep cheeses, due to their typical flavor and smooth texture. Flowers from 6 cardoon plants (1M–6M), selected on the basis of the total and specific A0, A and B cardosin concentrations were characterized using chromatographic and electrophoretic analysis. Extracts of these flowers were used to investigate the relationship between the biochemical profile and the proteolytic activity on caseins, coagulation properties and cheese texture. Milk-clotting activity and coagulation were measured using an Optigraph. Cheese making trials were done using the traditional protocol of Serra da Estrela PDO cheese manufacture. A multivariate exploratory PCA analysis showed that plants 4M, 5M and 6M with the highest total concentration of cardosins, the prevalence of cardosin A, proteolytic action with Ƙ-casein, and the lowest time of coagulation yielded cheeses with a firmer paste. Plants 1M, 2M and 3M, without the presence of cardosin A, were negatively influenced by the proteolytic action with β-casein, starting flocculation and gel consistency. Plant 3M showed a slow micellar aggregation rate and low gel firmness during milk coagulation, which was reflected in the smooth texture of the cheese. The specific characterization of natural biochemical diversity of cardoon flowers and their influence on cheese texture may help producers to choose the appropriated cardoon flowers to obtain a desired texture.

Relationships between cheese-processing conditions and curd and cheese properties to improve the yield of Idiazabal cheese made in small artisan dairies: A multivariate approach

Very diverse cutting and cooking intensity processes are currently used in small artisan dairies to manufacture Idiazabal cheese. The combination of the technical settings used during cheese manufacturing is known to affect cheese composition and yield, as well as whey losses. However, the information regarding the effect on microstructure and texture of cheese is scarce, especially in commercial productions. Therefore, the effect of moderate- and high-intensity cutting and cooking processes on whey losses, curd-grain characteristics, microstructure and cheese properties, and yield were analyzed. Three trials were monitored in each of 2 different small dairies during the cheesemaking of Idiazabal cheese, which is a semihard cheese made from raw sheep milk. The role and know-how of the cheesemakers are crucial in these productions because they determine the cutting point and handle semi-automatic vats. The 2 dairies studied used the following settings: dairy A used moderate-intensity cutting and cooking conditions, and dairy B used high-intensity cutting and cooking settings. Multiple relationships between cheese-processing conditions and curd, whey, and cheese properties as well as yield were obtained from a partial least square regression analysis. An increased amount of fat and casein losses were generated due to a combination of an excessively firm gel at cutting point together with high-intensity cutting and cooking processes. The microstructural analysis revealed that the porosity of the protein matrix of curd grains after cooking and cheese after pressing was the main feature affected, developing a less porous structure with a more intense process. Moderate-intensity cutting and cooking processes were associated with a higher cheese yield, regardless of the longer pressing process applied. No significant differences were observed in cheese composition. After 1 mo of ripening, however, the cheese was more brittle and adhesive when the high-intensity cutting and cooking process was applied. This could be associated with the composition, characteristics, and size distribution of curd grains due to differences in the compaction degree during pressing. These results could help to modify specific conditions used in cheesemaking, especially improving the process in those small dairies where the role of the cheesemaker is crucial.

Effect of Non‐Starch Polysaccharides on the Pasting, Gel, and Gelation Properties of Taro (Colocasia esculenta) Starch

AbstractThis study aims to assess the influence of various non‐starch polysaccharides at different concentrations (0.2%, 0.4%, and 0.6%) on the physicochemical, pasting, and gel properties of taro starch. Guar and xanthan gum appear to reduce the swelling power at higher temperatures while CMC improves it. Least gelation studies show that xanthan and guar gums are effective in producing firm gel at 6 and 8% of starch concentration, respectively. All hydrocolloids are found to be effective in decreasing syneresis and increase the stability of starch gel against repeated freeze−thaw (FT) cycles. The pasting properties of taro starch are greatly affected by all hydrocolloids and it is observed that guar and xanthan gums improve its peak viscosity even at the lowest concentration. The initial pasting temperature of taro starch is found to increase with gum arabic concentration while a significant decrease is noted with both guar gum and CMC which is an indication of ease in gelatinization. Xanthan and arabic gums are effective in controlling the set back of taro starch paste. The results indicate that different ratios of taro starch and hydrocolloids mixtures can play an important role as a functional additive in order to improve the quality of various processed food products.

Removing surface proteins promote the retrogradation of wheat starch

The effect of starch surface proteins on retrogradation of wheat starches were evaluated by rheometer, RVA, XRD, DSC, and TPA. An increase of the storage modulus and setback viscosity of starch pastes was observed after SDS and NaOH treatments. XRD resulted exhibited that recrystallinity of NaOH-treated and SDS-treated starch gels was increased to 10.33% and 11.15%, respectively, higher than that of native starch gel. Retrogradation enthalpy was increased from 3.5 J/g to 5.3 J/g for SDS-treated starch gels after 14 days storage at 4 °C. This was in line with the pronounced changes in gel firmness which was increased to 357g for SDS-treated starch. It suggested that removal of starch surface proteins apparently influenced the water mobility in starch gels and accelerated the retrogradation process.

Gel texture and rheological properties of normal amylose and waxy potato starch blends with rice starches differing in amylose content

SummaryThis study characterised the textural and rheological behaviour of blends of rice (waxy, low‐ and high‐amylose) and potato (waxy and normal) starch. Blends of potato starch with rice starch in the ratios of 100:0, 80:20, 60:40, 40:60, 20:80 and 0:100 were tested. Addition of rice starch (except high‐amylose rice starch) greatly increased the swelling of rice–potato starch mixtures. Addition of rice starch decreased gel firmness for most starch mixtures and increased gel adhesiveness for blends containing waxy potato starch. For rheological measurements, storage modulus was much higher than loss modulus of blends, indicating solid‐like behaviour. Starch blends with 20%/40% proportion of rice starch showed a greater thickening effect, whereas with further increase in rice starch proportion, a pseudoplastic, shear‐thinning behaviour was observed. This study may provide a basis to develop blends of potato and rice starch for potato noodle production without use of chemical additives.

Effects of Oil Type on Sterol-Based Organogels and Emulsions

The present study investigates the effect of oil type on the formation, morphology and mechanical properties of phytosterol-based organogels. The formation of organogels can be satisfactorily predicted with a criterion based on Hansen Solubility Parameters (HSPs), provided that the sterol and sterol ester in these systems assemble as tubules. When structures other than tubules are formed, the predictability of the HSP-based criterion becomes void. In cases where organogelling occurred, the morphology and mechanical properties of the tubular network of the gels and water-in-oil emulsions were investigated. The findings revealed that the structure of the tubular network formed in oils with different compositions, could be grouped based on the dielectric constants of the oils. Curly and bundled tubules which formed networks, were observed in gels prepared with low dielectric constant oils (i.e. decane and limonene). For oils with a moderate dielectric constant (i.e. castor oil and sunflower oil), the tubules became less curly and straighter. Upon increasing the dielectric constant of the oil (eugenol), individual tubules were observed next to the bundled tubules. The results showed that straighter, bundled tubules are associated with firmer gels, whereas less straight (i.e. curly) tubules rendered weaker gels. The tubular network of the water-in-oil emulsions obtained for oils with a low dielectric constant appeared more open with straighter tubules. For oils with relatively high dielectric constant, the water-in-oil emulsions lost most of their tubular structure and only a few tubules could be observed. In the presence of emulsion droplets fewer tubules are formed, resulting in weaker networks.

Dry heating treatment: A potential tool to improve the wheat starch properties for 3D food printing application

The futuristic technology of three-dimensional (3D) printing is an additive manufacturing that allows obtaining creative and personalized food products. In this context, the study of food formulations (named as “inks”) to be processed through 3D printing is necessary. This work investigated the use of dry heating treatment (DHT), a simple and safe method, to improve the wheat starch properties aiming to produce hydrogels to be used as “inks” for 3D printing. Wheat starch was processed by dry heating for 2 (DHT_2h) and 4 h (DHT_4h) at 130 °C. Modified wheat starches showed an increase in granule size, but processing did not alter the granule’s shape nor surface, neither alter the molecular functional groups. On the other hand, DHT promoted slight molecular depolymerization, and reduction of starch crystallinity. Hydrogels “inks” based on the modified starches showed lower peak apparent viscosity during pasting, higher structural strength at rest, higher resistance to external stresses, higher gel firmness, and lower syneresis than hydrogels based on native starch. The hydrogels based on starch DHT_4h showed the best printability (greater ability to make a 3D-object by layer-by-layer deposition and to support its structure once printed) and this “ink” showed better reproducibility. Another point observed is that DHT extended the texture possibilities of printed samples based on wheat starch hydrogels. These results suggested that DHT is a relevant process to improve the properties of hydrogels based on wheat starch, making this ink suitable for 3D printing application.

Addition of calcium and magnesium chlorides as simple means of varying bound and precipitated minerals in casein micelle: Effect on enzymatic coagulation

In casein micelle (CM), Ca is either precipitated in the colloidal calcium phosphate (CCP) stabilized by clusters of phosphoserine (SEP) residues, or is directly bound to SEP (or glutamic and aspartic acids) of caseins without inorganic phosphate. However, it is currently not possible to titrate separately the different micellar Ca forms, making it difficult to assess their respective importance for CM properties and behavior. Both Ca2+ and Mg2+ have the same binding constants with SEP. Moreover, MgHPO4 is more soluble than CaHPO4, and its natural concentration in milk is lower. Thus, upon addition of MgCl2, Mg is mainly exchanged with CM in the bound form, whereas upon addition of CaCl2, Ca is mainly exchanged in the precipitated form. Our objective was to assess the role of the 2 forms of micellar cations (bound and precipitated) during the enzymatic coagulation of cow milk. Magnesium chloride, CaCl2, or KCl (10 mM) were added to milk and pH was adjusted to 6.6 after overnight equilibration. The KCl-supplemented milk was a positive control to assess the effect of the increased ionic strength after MgCl2 and CaCl2 addition. Mineral partition between soluble and colloidal phases after salt addition was assessed both experimentally and by using computer simulation. Enzymatic coagulation was proceeded at 30°C. Hydrolysis of κ-casein was followed by the quantitative determination of caseinomacropeptide released by RP-HPLC, aggregation of para-κ-casein micelles was measured through the evolution of backscattering properties of milk and the gel time and gel firming kinetics were determined using a Chymograph (Chr. Hansen, Horsholm, Denmark). The KCl addition did not affect mineral partition. As expected, CaCl2 addition mainly increased the CCP content, whereas the addition of MgCl2 mainly increased the bound divalent cations content. The kinetics of κ-casein hydrolysis was slowed down after CaCl2 and MgCl2 addition, and was negatively correlated with the concentration of divalent cations in the soluble phase of milk. Aggregation and gel firming curves plotted versus the progress of κ-casein hydrolysis were similar for both CaCl2- and MgCl2-supplemented milk. In view of the dual-binding model for CM assembly, this means that both Ca forms reduce electronegative repulsions between para-micelles by specific charge shielding. Inclusion of 2 Ca forms in structural models for CM allows a more detailed comprehension of how mineral equilibria affect CM properties.

Less is more: Limited fractionation yields stronger gels for pea proteins

Limited fractionation of yellow pea yielded functional protein fractions with higher gelling capacity. Pea protein concentrates were obtained by dispersing flour at unadjusted pH (~6.7) and at pH 8. An additional isoelectric precipitation step resulted in a protein-rich isolate and a protein-poor supernatant. Aqueous solutions of these pea fractions (up to 15 wt %) were heated from 20 to 95 and subsequently cooled to 20 °C, and their viscoelastic response was characterized by small and large amplitude oscillatory shear measurements (SAOS and LAOS, respectively). SAOS rheology showed that the limited fractionated protein concentrates formed significantly firmer gels per mass of protein after cooling, than the more extensively fractionated protein isolate, with elastic moduli of G’~103 Pa and G’~102 Pa, respectively. LAOS rheology showed an overall strain softening behaviour for all pea fractions and a transition from elastic to viscous behaviour at smaller strain for the protein isolate. Confocal and electron microscopic images were consistent with those observations, and revealed a more homogeneous network for the limited fractionated samples, and a more heterogenous network for the protein isolate. A number of experiments showed that there are different processing and compositional factors affecting gelling capacity. These are isoelectric precipitation, amount of sugars upon lyophilization and differences in ash content. Furthermore, differences in pre-aggregated state, as found in earlier research, may be partially responsible for the different gelling behaviour. In conclusion, we explain how fractionation affects pea proteins and found that limited fractionation yields pea proteins that form stronger gels.

Effect of Lactobacillus rhamnosus on Physicochemical Properties of Fermented Plant-Based Raw Materials.

Texture and flavor are currently the main challenges in the development of plant-based dairy alternatives. To overcome them, the potential of microorganisms for fermentation of plant-based raw materials is generating great interest in the food industry. This study examines the effect of Lactobacillus rhamnosus, LGG® (LGG® is a trademark of Chr. Hansen A/S) on the physicochemical properties of fermented soy, oat, and coconut. LGG® was combined with different lactic acid bacteria (LAB) strains and Bifidobacterium, BB-12® (BB-12® is a trademark of Chr. Hansen A/S). Acidification, titratable acidity, and growth of LGG® and BB-12® were evaluated. Oscillation and flow tests were performed to analyze the rheological properties of fermented samples. Acids, carbohydrates, and volatile organic compounds in fermented samples were identified, and a sensory evaluation with a trained panel was conducted. LGG® reduced fermentation time in all three bases. LGG® and BB-12® grew in all fermented raw materials above 107 CFU/g. LGG® had no significant effect on rheological behavior of the samples. Acetoin levels increased and acetaldehyde content decreased in the presence of LGG® in all three bases. Diacetyl levels increased in fermented oat and coconut samples when LGG® was combined with YOFLEX® YF-L01 and NU-TRISH® BY-01 (YOFLEX® and NU-TRISH® are trademarks of Chr. Hansen A/S). In all fermented oat samples, LGG® significantly enhanced fermented flavor notes, such as sourness, lemon, and fruity taste, which in turn led to reduced perception of the attributes related to the base. In fermented coconut samples, gel firmness perception was significantly improved in the presence of LGG®. These findings suggest supplementation of LAB cultures with LGG® to improve fermentation time and sensory perception of fermented plant-based products.

Effect of traditional and radiofrequency assisted thermal processing on the gel firmness of egg white powder

Radiofrequency (RF) assisted thermal processing is a novel and energy-efficient method used for pasteurization, which heats the product volumetrically as opposed to traditional hot room (HR) pasteurization. RF-assisted thermal processing accelerates the heating rate of egg white powder (EWP), which has a very low thermal conductivity and further affect its gelling properties. In EWP, solubility plays a significant role in the water holding capacity of proteins, which affects the functional properties. The effect of processing methods (RF and HR) due to pH and treatment temperature combination is monitored by subjecting neutral EWP (6.4 pH) to 70 and 80 °C and alkaline EWP (pH 9.9) samples to 70 °C over 0, 5, 10, 15 and 20 d. RF processing substantially improved gelling properties. At 80 °C, the gel firmness was 48.6% higher than HR on the 0th d, indicating RF could potentially improve the functionality as well as reduce the come-up time to less than a day as opposed to the traditional hot room processing used in the industry which takes 5–6 days. The treatment period also significantly affects the gel firmness and insoluble content. With increased treatment severity, the gel firmness substantially increased without changing the soluble protein contents, and insoluble contents.

Food protein network formation and gelation induced by conductive or microwave heating: A focus on hen egg white

Heat-induced protein polymerization, gelation and the associated molecular scale changes were investigated during conductive and microwave heating (CH and MH, respectively). Given identical temperature-time profiles, polymerization of bovine serum albumin, ovalbumin, egg white (EW) and wheat gluten protein occurred faster and to a greater extent with CH than with MH. Moreover, lanthionine cross-links were present in some MH but in none of the CH samples. Gelation of EW protein by CH or MH was studied in more detail. Differential scanning calorimetry and fluorescence spectroscopy indicated that EW proteins initially denatured to a larger extent with CH than with MH. Size exclusion high performance liquid chromatography demonstrated that CH resulted in more heavily cross-linked EW protein networks than MH. Homogeneous EW gels were obtained by 15 min CH at 80 °C while 120 min MH at this temperature still resulted in inhomogeneous (with liquid and solid zones) gels. This was affirmed by low resolution 1H nuclear magnetic resonance measurements which indicated more mobile water in MH than in CH samples. However, MH gels had higher firmness than the corresponding CH gels. Thus, MH here led to less covalent cross-linking than CH, but still resulted in firmer gels most likely because its protein network relied heavily on non-covalent interactions. Industrial relevanceThis study highlighted differences between microwave and conventional, conductive, heating of different protein materials. While literature is divided about the origin of differences noted between these different heating modes, it is clear from our data that heating mode, given identical temperature-time profiles, impacts the changes that proteins undergo during heating. The knowledge that microwave heating favors protein unfolding, aggregation and cross-linking to a lower extent than conductive heating can likely be exploited in industrial applications.

Influence of fat substitution by inulin on fermentation process and physical properties of set yoghurt evaluated by an optical sensor

Inulin is a natural product with beneficial effects for human health commonly used as a source of dietary fiber, bulking agent and fat substitute in products like cheese and yoghurt. There are some confusing or contradictory results in the literature about the water holding capacity of inulin and its effect on syneresis, coagulation kinetics, rheology and texture of yoghurt, so in this study those effects were evaluated. Yoghurt fermentation tests were conducted with three fat concentrations (0.4, 1.6 and 3.6%) and three inulin levels (0, 1.6 and 3.2%). The coagulation process was monitored for the first time using simultaneously an inline light backscatter sensor, inline potentiometry and a rheometer. The increase in milk fat concentration from 0 to 3.6% delayed the start of coagulation and increased time to pH=4.8 in 11min. 3.2% of inulin addition increased yoghurt acidification rate, reduced 12min the time to pH=4.8, and increased final storage modulus and gel firmness. It was also determined that 3.2% of inulin addition increased 32% the spontaneous syneresis and had no effect on the water holding capacity of set yoghurt.