Freeze-thaw Treatment Research Articles

Effects of pH and incubation temperature on properties of konjac glucomannan and zein composites with or without freeze-thaw treatment

This work investigated the effect of pH and incubation temperature on the morphology and properties of konjac glucomannan (KGM)-zein composites with or without freeze-thaw treatment. When the incubation temperature was 90 °C, the composites prepared in the pH range of 10.5–11.5 were concentrated polymer solutions, while the composites prepared in the pH range of 12.0–13.0 were gels. The pH of 12.5 was found to form the composites with the most dense microstructure, the highest storage modulus and crystallinity, and the greatest ability to resist plastic deformation during compression. The composites tended to form gels with the increase of incubation temperature from 40 °C to 90 °C at pH = 12.5. The temperature of 90 °C was found to form the composites with the most dense microstructure, the greatest ability to resist plastic deformation during compression, and the highest crystallinity and frequency stability. The composite prepared at an incubation temperature of 70 °C and a pH = 12.5 had similar microstructure, rheological properties, and texture properties to that prepared at an incubation temperature of 80 °C and a pH = 12.0. The freeze-thaw treatment caused a slight increase in storage modulus (G′) and crystallinity when the composites were concentrated polymer solutions. When the composites were gels, the freeze-thaw treatment caused a rough and inhomogeneous microstructure, increased the G′ and the ability to resist plastic deformation during compression, decreased the springiness, and altered the internal water mobility. pH and incubation temperature play important roles in the morphology and properties of KGM-zein composites. • The composites were concentrated polymer solutions prepared at 80 °C and pH ≤ 11.5. • The composites were gels prepared at 40 °C–80 °C and pH = 12.5. • 70 °C and pH = 12.5 endowed the composite with similar properties to 80 °C and pH = 12.0. • Freeze-thaw treatment had different effects on gel and concentrated polymer solution.

Effect of Hofmeister series anions on freeze-thaw stability of emulsion stabilized with whey protein isolates

The effect of Hofmeister series anions at different concentrations on the freeze-thaw (FT) stability of emulsions stabilized with whey protein isolate (WPI) and its possible mechanism were studied. The emulsions prepared from WPI added with kosmotropic ions (Cl − and Br − ) presented good freeze-thaw stability, whereas those without NaCl were destabilized after freeze-thawing. In addition, the adsorbed protein (AP) percentage, protein load (τ), apparent viscosity, and mechanical moduli of emulsions added with Cl − and Br − were increased with the salt addition, thus facilitating the formation of elastic gel network structure in the emulsion system. WPI added with NaCl exhibited high interfacial pressure (π) and diffusion rate ( K diff ), indicating that its interfacial behavior promoted the stability of oil-water interface. During the adsorption process, the relative abundance of transferrin (TRF) and immunoglobulin (Ig) of WPI was increased, suggesting their higher interfacial affinity at the interface. After three FT cycles of the emulsion prepared from WPI added with Cl − , the proteins with low molecular weight (LMW) presented better emulsification activity. The decreased relative abundance of TRF and Ig due to the extrusion of the ice crystals would be responsible for the instability of the WPI-stabilized emulsion by freeze-thaw treatment. • WPI emulsions with Cl − and Br − addition exhibited good freeze-thaw (FT) stability. • The addition of kosmotropic ions increased the surface hydrophobicity of protein. • The surface hydrophobicity of protein with chaotropic ions was decreased. • Relative abundance of low-molecular-weight protein increased after three FT cycles. • Proteins with more quantities at the interface suggested the preferential adsorption.

Impact of ultra-shear technology on quality attributes of model dairy-pea protein dispersions with different fat levels

This study investigated the impact of ultra-shear technology (UST) processing on dairy-pea protein dispersions with different fat levels. Raw milk, skim milk, and cream, as well as model dispersions with combinations of dairy products and pea protein (i.e., raw milk with pea protein, skim milk with pea protein, and cream with pea protein) were employed as test samples. UST experiments were conducted at a pressure of 400 MPa and 70 °C shear valve exit temperature. The UST treatment increased the viscosity of the dispersions and the increases depended on the fat level. Dairy-pea protein dispersions from raw milk and skim milk were shear thinning and mathematically described by the power-law model defined by the consistency coefficient, K (Pa·sn) and the flow behavior index, n. UST treated cream + pea protein dispersions produced structures with gel-like characteristics. Microstructure and particle size analysis determined by laser scanning microscope revealed a reduction in particle size after UST treatment in raw milk + pea protein and skim milk + pea protein dispersions up to 7.55 and 8.30 μm, respectively. In contrast, the particle mean diameter of cream + pea protein dispersions increased up to 77.20 μm after the UST treatment. Thus, the effect of UST on the particle size and rheological behavior of the dispersions depended on the fat level. UST-treated dispersions were stable with no visible phase separation or sedimentation upon centrifugation at 4000×g for 30 min (4 °C). Heat treatment and freeze–thaw treatment of UST-treated samples showed stable blends immediately after the treatments, but subsequent centrifugation showed solid separation. Results from the study suggest that UST is a potential technology to produce stable dairy + pea protein liquids foods with different rheological characteristics for diverse applications.

New laterite-based geopolymer foam resistance under drastic conditions: A comparative study with a metakaolin model

The valorization of local materials in public building construction in emerging countries is a necessity from a sustainable development perspective. In Cameroon, laterite is an abundant and easily accessible local resource that can be used for the development of light and insulating materials, which until now have been made from metakaolin. Moreover, since metakaolin is not easily accessible in Cameroon, it would be interesting to compare to a model mixture based on metakaolin and hematite. The objective of this study is related to the feasibility and characterization of geopolymer foams based on laterite or on a model mixture (metakaolin-hematite) in different drastic conditions, such as fire resistance and freeze‒thaw cycles. The geopolymer foams were synthesized from a calcined laterite or metakaolin-hematite mixture, an alkaline silicate solution, a surfactant and metallic aluminum powder and then placed in an oven at 70 °C for 24 h. Structural data (X-ray diffraction) as well as determination of thermal conductivity and mechanical strength data of the foams were evaluated. The results show that the laterite and metakaolin-hematite mixture allows the elaboration of geopolymer foam, which is characterized by a low thermal conductivity (90 mW/(m. K)) and can be used as insulating materials. The freeze‒thaw treatment does not affect the thermal and mechanical properties. The treatment at 1175 °C slightly improves the mechanical strength and the thermal conductivity, leading to a good application of these materials.

Grayscale evolution characterization of the strain field and precursor identification in sandstone containing multiple flaws after freeze–thaw treatment

Grayscale evolution characterization of the strain field and precursor identification in sandstone containing multiple flaws after freeze–thaw treatment

Structural characterization, interfacial and emulsifying properties of soy protein hydrolysate-tannic acid complexes

With increasing awareness of health and sustainable dietary pattern, plant-based proteins have shown a growing interest as substitutes for animal proteins. Meanwhile, the non-covalent interaction of protein with natural phenolic compounds can be used to develop functional ingredients. In this work, Alcalase hydrolysates of soy protein isolate (HSPI) were used to fabricate complexes with tannic acid (TA), and their physicochemical properties were investigated and compared with soy protein isolate (SPI) and sodium caseinate (SC) to get insights into the advantage of polyphenol modification. The complex solution showed reduced particle size, higher turbidity, and higher surface charge with increasing TA concentration. The interaction mainly occurred through hydrogen bond and hydrophobic interaction, leading to the unfolding of protein molecular structure. The complexes displayed lower interfacial adsorption activity and reduced interfacial viscoelastic modulus upon increasing TA concentration possibly because of the interference of TA on the diffusion and molecule interaction of protein hydrolysates to form elastic films. Nonetheless, the complex-based emulsion showed enhanced emulsifying stability with small droplet size, superior oxidation stability, high physical stability against heat and freeze-thaw treatment due to the higher surface charge and formation of particle-stabilized interfacial membrane. These findings provide insights for developing plant-based protein with excellent emulsifying properties, which show great potential for application as SC substitute in dairy-free emulsified products.

Effects of Concentration of Soybean Protein Isolate and Maltose and Oil Phase Volume Fraction on Freeze-Thaw Stability of Pickering Emulsion.

There is growing interest in enhancing the freeze-thaw stability of a Pickering emulsion to obtain a better taste in the frozen food field. A Pickering emulsion was prepared using a two-step homogenization method with soybean protein and maltose as raw materials. The outcomes showed that the freeze-thaw stability of the Pickering emulsion increased when prepared with an increase in soybean protein isolate (SPI) and maltose concentration. After three freeze-thaw treatments at 35 mg/mL, the Turbiscan Stability Index (TSI) value of the emulsion was the lowest. At this concentration, the surface hydrophobicity (H0) of the composite particles was 33.6 and the interfacial tension was 44.34 mN/m. Furthermore, the rheological nature of the emulsions proved that the apparent viscosity and viscoelasticity of Pickering emulsions grew with a growing oil phase volume fraction and concentration. The maximum value was reached in the case of the oil phase volume fraction of 50% at a concentration of 35 mg/mL, the apparent viscosity was 18 Pa·s, the storage modulus of the emulsion was 575 Pa, and the loss modulus was 152 Pa. This research is significant for the production of freeze-thaw resistant products, and improvement of protein-stabilized emulsion products with high freeze-thaw stability.

Influence of repeated freeze-thaw treatments on the oxidation and degradation of muscle proteins from mirror carp (Cyprinus carpio L.), based on myofibrillar protein structural changes

The effects of repeated freeze-thaw (F-T) treatments on the oxidation and degradation of muscle proteins from mirror carp (Cyprinus carpio L.) were investigated. The myofibrillar fragmentation index, trichloroacetic acid-soluble peptides, total volatile basic nitrogen, amino nitrogen, and carbonyl content of the samples significantly increased (P < 0.05). However, the samples showed a significant reduction in the fragmentation index, myofibrillar protein (MP) solubility, and total sulfhydryl content after five F-T cycles (P < 0.05). Moreover, the sodium dodecyl sulfate-polyacrylamide gel electrophoresis bands of the MP faded because of the oxidation and degradation of the protein with increasing F-T cycles. By the fifth F-T cycle, the α-helix and β-turn content significantly decreased by 10.41 % and 5.72 %, respectively (P < 0.05), whereas the β-sheet and random coil content significantly rose by 7.66 % and 8.47 %, respectively (P < 0.05). Furthermore, the intrinsic fluorescence of the MP showed a substantial decrease in intensity and a redshift. In summary, iterative F-T cycles destroyed the MP structure and caused the oxidation and degradation of muscle proteins from mirror carp.

Storage stability, heat stability, controlled release and antifungal activity of liposomes as alternative fungal preservation agents

The aim of this study was to investigate the characteristics of liposomes encapsulated ethanolic Cinnamomum verum, Curcuma longa, Zingiber officinale, Syzygium aromaticum and Laurus nobilis extract prepared using lipid phase containing phosphatidylcholine/extract mixture of 10:1. The antifungal activity, size, zeta (ζ) potential, morphology, physical stability, heat stability, release in in-vitro digestion, color and differential scanning calorimetry (DSC) were conducted to determine the characteristics of liposomes. All extract-loaded liposomes showed prominently antifungal activity against Aspergillus sp. and Penicillium sp. The encapsulation efficiency of all samples was 86.60%–92.87%. Curcuma longa loaded liposome had high encapsulation efficiency after freeze dry-rehydration (FD-RH), long-term and freeze-thaw (FT) storage treatment. The thermal stability of Syzygium aromaticum loaded liposomes was higher than the others. The highest release values in the in-vitro gastric and intestinal condition were detected in Laurus nobilis loaded liposome. DSC data of liposomes demonstrated to be the endothermic phase at three different temperature ranges: lipid bilayers transition from gel state to liquid crystal form (1.69–5.31 °C), the pre-phase transition temperature (102.16–133.10 °C) and the main phase transition temperature (116.47–165.22 °C).

Physicochemical properties and gluten structures of frozen steamed bread dough under freeze–thaw treatment affected by gamma-polyglutamic acid

Concerned to chemical structure, the viscous gamma-polyglutamic acid (γ-PGA) should have the similar characteristics with antifreeze hydrocolloids and polypeptides which have been broadly used in frozen foods. However, the cryoprotective functions of γ-PGA are little explored as compared to those of hydrocolloids and polypeptides. In this study, influences of γ-PGA addition on fermentative performance and rheological behavior of frozen steamed bread (SB) dough during frozen storage and freeze–thaw cycles were investigated, and the underlying mechanism governing these influences was clarified. Results showed the γ-PGA dispersed free water, remarkably reduced freezable water content, and restricted water migration, which facilitated the formation of smaller and more uniform ice crystals in frozen dough structure. In addition, γ-PGA interacted with gluten proteins through electrostatic attractions and hydrogen bonds, transforming the gluten protein conformation from loose coil structures to relatively compact β-structures. In these relatively compact structures, the free sulfhydryl (SH) groups, originally located far away in space, became closer and easier to be oxidized into disulfide bonds (SS) or be involved in SH–SS exchange reaction. This led to intensive protein aggregations and water–solid interplay, rendering the dough better resilience to cope with ice growth and recrystallization. Accordingly, the deterioration in frozen SB dough's fermentability and rheology was effectively alleviated, suggesting that γ-PGA has a great potential to serve as an effective cryoprotectant in frozen SB.

The textural properties of cooked convenience rice upon repeated freeze–thaw treatments are largely affected by water mobility at grain level

Brown rice (BR) is a promising source for convenience rice that are mostly stored frozen. However, freezing and thawing may cause deterioration in rice texture quality. To investigate how rice texture is influenced by freeze–thaw cycles, BR, the pretreated BR with partially ruptured bran layer (UER) and white rice (WR) were cooked and treated with repeated freeze–thaw cycles, with their textural properties, variations in moisture distribution and starch structure being measured. Results showed that the repeated freeze–thaw treatment induced a progressive reduction in hardness and stickiness of all cooked rice. The reduced hardness of rice could be explained by the enlarged pore size of starch inside rice under scanning electron microscopy. Moisture migration in WR was the fastest responding to multiply freeze–thaw cycles, followed by UER, while water mobility in BR was slowest. Moreover, WR, BR and UER resulted in a similar extent of amylopectin retrogradation and chains length distribution after repeated freeze–thaw cycles. It indicated similar and minor effect of starch variations on determining the texture of different rice samples against freeze-thawing. Water mobility tended to be a main factor leading to the textural difference of fully gelatinized rice samples. This study focused on the relationship between water distribution and starch retrogradation, providing a better understanding on influences of multiple freeze-thawing on textural quality of cooked rice maintaining different extents of surface layer.

Effects of Freezing–Thawing Processes on Net Nitrogen Mineralization in Salinized Farmland Soil

Nitrogen is an indispensable and limiting element for plant and microbial growth. To investigate the combined effects of salinity and freezing–thawing (FT) processes on soil inorganic nitrogen (SIN) transformation in seasonally freezing salinized farmland, laboratory incubation experiments were conducted under five soil salt content (SSC) treatments (0.08%, 0.25%, 0.35%, 0.50%, and 0.70%), four FT temperature treatments (C (5 °C), FT (−5 + 5 °C), FT (−10 + 5 °C), and FT (−15 + 5 °C)), and two soil water content (SWC) treatments (40% and 80% of maximum water holding capacity (WHC)). Ammonium (NH4+-N) and nitrate (NO3−-N) nitrogen were monitored at the first, second, fifth, and eighth incubation days. The FT processes increased relative NH4+-N content by 13%, 39%, and 77% with the decreasing of freezing temperature from −5 °C to −15 °C compared with C (5 °C) treatments, respectively. FT (−5 + 5 °C) and FT (−15 + 5 °C) treatments decreased the relative NO3--N contents by 4% and 6% compared with C (5 °C) treatments, respectively. Under FT treatments, the increment of relative NH4+-N content was higher in low-SSC treatments and lower in high-SSC treatments. The relationship between relative NO3–-N content and SSC gradually changed from a decrease in C (5 °C) to an increase in FT (−15+5 °C) treatments. SWC decreased NH4+-N content in high-SSC and low-freezing temperature treatments (SSC × freezing temperature &lt; −2.5%· °C), while NH4+-N increased in low-SSC and unfrozen treatments. The variations of SIN/Rmin (nitrogen mineralization rate) were mostly affected by NO3–-N/Rnit (net nitrification rate) and NH4+-N/Ra (net ammonification rate) in C (5 °C) and FT treatments, respectively. Overall, the results suggested that enhanced salinity inhibited the effects of freezing temperature on NH4+-N and NO3−-N formation, respectively. The increase in SWC weakened the NH4+-N formation induced by the decrease in freezing temperature, and this function increased with the increase in salinity.

Influence of sanxan on the quality of salt‐free frozen‐cooked wheat noodles during freeze–thaw cycles

SummaryDeveloping salt‐free frozen‐cooked wheat noodles (FCNs) has a promising future, and how to eliminate the deficiency of the absence of salt is key to enhance its quality. In this study, based on the unique ‘gel‐forming in cold water and gel strength‐strengthening during heating’ properties, sanxan was used to improve the quality of salt‐free FCNs and the underlying mechanism was initially explored. TPA analysis, colour profile, thermal stability analysis, determination of free sulfhydryl and disulphide bonds contents, scanning electron microscopy observation, confocal laser scanning microscopy observation were carried out. The results showed that adding 1.2% sanxan could minimise the decrease in hardness, springiness, maximum tensile strength and tensile fracture distance, and the increase in adhesiveness of salt‐free FCNs during freeze–thaw treatments (FTs). The chrominance and thermal stability of salt‐free FCNs during FTs were also improved by adding 1.2% sanxan. Adding sanxan could strengthen the gluten network of salt‐free FCNs by weakening the recrystallisation of ice crystals, inhibiting the breakage of SS and enhancing the cross‐linkage degree and continuity of gluten network during FTs. The current study could develop a new preparation strategy of salt‐free convenient noodles and provide theoretical basis for expanding the novel application of sanxan in frozen foods.

Physicochemical and Sensory Properties Colored Whey Protein-Cellulose Nanocrystal Edible Films after Freeze-Thaw Treatment

Balancing physicochemical properties and sensory properties is one of the key points in expanding edible packaging applications. The work consisted of two parts, one was to investigate the effects of cellulose nanocrystals (CNC) on the packaging-related properties of whey protein isolate films with natural colorants (curcumin, phycocyanin, and lycopene) under freeze-thaw (FT) conditions; the other was to test oral tactility and visual sensory properties of the edible films and their overall acceptability in packed ice cream. FT treatment reduced the mechanical strength and moisture content and increased the water vapor permeability of the films, as water-phase transformation not only disrupted hydrogen bonds but also the film network structure through physical stress. The oral tactility produced by CNC and the visual effect produced by colorants could affect participants' preference for edible films. This study provides a good reference for the consumer-driven product development of packaged low-temperature products.

Effect of small molecular surfactants on physical, turbidimetric, and rheological properties of Pickering nanoemulsions stabilized with whey protein isolate

In the present study, Pickering nanoemulsions (oil-in-water) co-stabilized with whey protein isolate (WPI) and three types of small molecular surfactants were prepared. Hexadecyltrimethylammonium (CTAB), sodium dodecyl sulfate (SDS), and Tween 20 were used as cationic, anionic, and nonionic surfactants, respectively. To investigate effects of small molecular surfactants on physical stability, turbidimetric, and rheological properties of protein-stabilized Pickering nanoemulsions, various treatments mimicking food processing including pH, heat, freeze-thaw, and salt were applied. Results revealed that the droplet size and polydispersity index of the nanoemulsion prepared with WPI alone were increased after heat treatment or at pH condition near the isoelectric point of WPI, indicating a low physical stability. However, nanoemulsions prepared with WPI-SDS or WPI-CTAB maintained their initial state even after heat treatment including autoclave. Furthermore, there was no significant change in the droplet size of the nanoemulsion prepared with WPI-Tween after freeze-thaw and salt treatments. Although Pickering nanoemulsion stabilized with both WPI and SDS had the highest viscosity, Turbiscan stability index (TSI) was the highest. However, the TSI of the nanoemulsions added with CTAB or Tween 20 was lower than that of the nanoemulsions prepared with WPI alone, confirming that the storage stability of protein-stabilized Pickering nanoemulsion was improved by adding small molecular surfactants.

Enhancing the stability of oil-in-water emulsions by non-covalent interaction between whey protein isolate and hyaluronic acid

This study aimed to investigate the effect of non-covalent interactions between different concentrations (0.1–1.2 %, w/v) of hyaluronic acid (HA) and 3 % (w/v) whey protein isolate (WPI) on the stability of oil-in-water emulsions. Non-covalent interactions between WPI and HA were detected using Fourier-transform infrared spectroscopy. The addition of HA increased the electrostatic repulsion between molecules and reduced the particle size of WPI. Circular dichroism spectroscopy results indicated that the addition of HA caused an increase in β-sheet content and a decrease in α-helix and random coil content in WPI. Moreover, HA increased the emulsion viscosity and strength of the interfacial network structure. Micrographs obtained using confocal laser scanning microscopy indicated that the emulsion with 0.8 % (w/v) HA exhibited good dispersion and homogeneity after storage for 14 d. Complexation with HA significantly altered the rheological and emulsifying properties of WPI, providing an emulsion with excellent stability under heating treatment, freeze-thawing treatment and centrifugation. The results provide a potential for HA application in emulsified foods.

A Polyvinyl Alcohol-Tannic Acid Gel with Exceptional Mechanical Properties and Ultraviolet Resistance.

Design and preparation of gels with excellent mechanical properties has garnered wide interest at present. In this paper, preparation of polyvinyl alcohol (PVA)-tannic acid (TA) gels with exceptional properties is documented. The crystallization zone and hydrogen bonding acted as physical crosslinkages fabricated by a combination of freeze-thaw treatment and a tannic acid compound. The effect of tannic acid on mechanical properties of prepared PVA-TA gels was investigated and analyzed. When the mass fraction of PVA was 20.0 wt% and soaking time was 12 h in tannic acid aqueous solution, tensile strength and the elongation at break of PVA-TA gel reached 5.97 MPa and 1450%, respectively. This PVA-TA gel was far superior to a pure 20.0 wt% PVA hydrogel treated only with the freeze-thaw process, as well as most previously reported PVA-TA gels. The toughness of a PVA-TA gel is about 14 times that of a pure PVA gel. In addition, transparent PVA-TA gels can effectively prevent ultraviolet-light-induced degradation. This study provides a novel strategy and reference for design and preparation of high-performance gels that are promising for practical application.

Improving freeze-thaw stability and 3D printing performance of soy protein isolate emulsion gel inks by guar & xanthan gums

Frozen storage of 3D printing inks could increase their shelf life. We improved freeze-thaw stability and 3D printing performance of soy protein isolate (SPI) emulsion gel inks by guar (GG) and xanthan gums (XG). Freeze-thawed inks led to higher storage modulus (G′), lower water holding capability (WHC) and poor printing performance compared to initial inks. An increase in gums content decreased oil droplet aggregation and protein flocculation in all freeze-thawed inks, hence reducing syneresis in the gel structure and preventing solid-liquid separation during 3D printing. The freeze-thaw stability of SPI-XG inks was consistently greater than that of SPI-GG inks at the same concentrations, resulting in superior 3D printing performance. The hardness of cylinders printed with SPI-XG0.5 freeze-thawed inks was lower than that of the cylinders printed by initial inks, in contrast to the results of G'. At the maximum strain amplitude (500%), Lissajous analysis indicated that the SPI-XG0.5 freeze-thawed inks retained less energy than the initial inks, resulting in a weaker gel. Overall, this study demonstrated that freeze-thaw treatment negatively affected the 3D printing performance of SPI emulsion gel inks, but that the 3D printing performance of freeze-thaw inks could be reinforced by modifying the formulation.

Effect of cyclic freeze–thaw treatments on the dynamic fracture characteristics of granite: Laboratory testing

In this study, the dynamic fracture toughness of freeze-thawed granite was studied. Different freeze–thaw (F-T) cycles were used to treat notched semicircular bending (NSCB) granite samples. The microstructure changes of samples treated with different numbers of F-T cycles were measured by a nuclear magnetic resonance (NMR) testing system. The dynamic fracture toughness was obtained by dynamic testing with split Hopkinson pressure bar (SHPB) equipment. In addition, the roughness of the rock fracture surface was studied using fractal geometry, and the F-T damage was defined using fractal dimensions. On this basis, a dynamic fracture toughness prediction model is proposed. The influence of the F-T cycle and loading rate on fracture toughness are discussed.

Effects of natural freeze-thaw treatment on structural, functional, and rheological characteristics of starches isolated from three bitter potato cultivars from the Andean region

Three cultivars of bitter potatoes ( Cuchi jipilla, Ocucuri negra, and Pala ), grown in the Andean region of Peru (3862 m above sea level), and their “Tuntas” were used for starch isolation. “Tunta” is obtained from the natural freeze-thaw (F/T) treatment of these bitter potatoes. The structural, functional, and rheological characteristics of starches from bitter potatoes (PS) and their “Tuntas” (TS) were determined to evaluate the effect of F/T treatment. Among the results, TS showed lower apparent amylose content, lower gelatinization enthalpies, and higher syneresis values in refrigeration than PS. Scanning electron microscope (SEM) micrographs did not exhibit differences on PS and TS granules surfaces. The mean size D[4,3] of the starch granules from bitter potatoes and “Tuntas” ranged between 36.3 and 43.1 μm. FT-IR analysis showed that the chemical structure of starch granules from “Tunta” was not significantly affected by the natural F/T treatment. Pasting profiles of PS exhibited higher properties than TS. All starch gels showed a pseudoplastic behavior (0.48 ≤ η ≤ 0.53) which the Herschel-Bulkley model well described. In addition, PS and TS gels showed an elastic behavior ( G’ > G’’ ). The results suggest that PS and TS exhibited significant differences in their structural, functional, and rheological characteristics, which make them feasible for food and non-food applications. • PS and TS showed differences on their functional and structural characteristics. • Enthalpy values of TS were slightly lower than PS. • Natural F/T treatment affected pasting properties and syneresis of TS. • TS showed higher decomposition temperature (DTGA) than PS. • Crystallinity for CJ-TS and PL-TS decreased by natural F/T treatment.