Evaluation of Long-term colour resistance of composite materials used in aligner treatments: A comparative study

AIM

The aim of this study is to evaluate the discolouration resistance of attachments made of composites having different physical properties, filler ratios and viscosity through the simulated environment and conditions.

MATERIALS AND METHODS

Seventy-two extracted human teeth were aligned to simulate upper and lower dental arches. The attachments were prepared according to the guides determined by ClearCorrect. Three different composite groups were used for attachments preparation: Aligner Connect, G-Aenial Universal Injectable, and Tetric Prime and Tetric Evoflow combination. Dental models and aligners were kept in artificial saliva throughout the experiment of 96 weeks. The aligners were also subjected to 2308 thermal cycles and insertion and removing procedures 840 times for each period of 12 weeks. Afterwards, the models were kept in coffee and red wine solutions. Colour measurements were made with Vita Easy Shade 4.0 at 12th, 24th, 48th and 96th simulated weeks.

RESULTS

No significant difference in discolouration was observed during thermal cycle application of 12th and 24th week experimental periods. In the later periods, discolouration was observed in the composite materials, and G-Aenial Universal Injectable was less coloured than the other samples. The composite samples were more coloured in proportion to their residence time. The G-Aenial Universal Injectable was more affected by wine solution, and Tetric Prime and Tetric Evoflow combination were more affected by coffee solution.

CONCLUSIONS

Viscosity, resin matrix content and nature of inorganic filler particles of the composite materials significantly affect the colour changing properties of them due to the long-term ageing and exposure to colouring agents.

Method development and validation for analysis of microencapsulated cyanidin-3-O-rutinoside in dairy samples containing juçara palm fruit by high-performance liquid chromatography

Euterpe edulis is a plant native of Brazil and popularly known as juçara. The aim of this study was to develop and validate an analytical method using high-performance liquid chromatography (HPLC) of juçara crude extracts (JCEs) and to evaluate dairy products containing free and microencapsulated extracts. The validated analytical method for JCE was performed using cyanidin-3-O-rutinoside (C3R - isolated and identified as major component from JCE) as a reference: linearity was obtained using ten concentrations between 25 and 250 μg mL-1 (R2  = 0.994); limits of detection and quantification were 19.04 μg mL-1 and 57.7 μg mL-1 respectively; accuracy (relative standard deviation) was <5%; recovery was 104.85 μg mL-1 ; and the method is robust. Physicochemical analyses of the dairy products were evaluated using colour, pH, and concentration of anthocyanins using HPLC calculated as C3R over 21 days of storage. The pH remained stable until the end of the test. The colour and the concentration of anthocyanins remained stable for 9 days. C3R was isolated, the HPLC method was developed and validated, and the colour stability was not altered until 9 days. © 2023 Society of Chemical Industry.

Color Stability of Pediatric Restorative Material Over Pediatric Drug Formulation

AIM

 To investigate the color stability of light-cured (LC) restorative material in different pediatric drug formulations.

METHOD

 Two distinct restorative materials, specifically LC resin and LC glass ionomer cement (GIC), were employed to create 88 disc-shaped specimens. These comprised 44 specimens fabricated from each material. Each specimen had a diameter of 5 mm and a height of 3 mm. To conduct the experiment, specimens were randomly allocated into four experimental groups, each containing 11 specimens made of each material. This division was accomplished through the use of a stratified random sampling method. The five experimental groups and their respective liquid medications were as follows: Group 1 - montelukast sodium and levocetirizine dihydrochloride syrup, Group 2 - cefixime, Group 3 - sodium valproate, and Group 4 - metronidazole. To ensure thorough exposure to the medications, all samples underwent a two-minute agitation cycle, which was repeated every 12 h over the course of one week. Following the immersion period, the color stability of all specimens was assessed using a spectrophotometer. The data obtained from the color stability measurements were subjected to statistical analysis using one-way analysis of variance (ANOVA), followed by a post hoc test. The aim was to determine whether significant differences in color stability were observed among the groups studied.

RESULTS

 The mean values and standard deviations of ΔE were calculated. The highest values of ΔE were observed in Group 3 (4.70 ± 1.89), followed by Group 4 (4.04 ± 2.10). Conversely, the lowest ΔE values were observed in Group 2 (3.23 ± 2.02) and Group 1 (3.24 ± 2.31). The calculated p-value was 0.298, and the F-value was 1.269.

CONCLUSION

 This study concludes that both restorative materials, LC composite and LC GIC, are susceptible to discoloration. Sodium valproate exhibited the greatest staining effect on both materials. Conversely, cefixime had the least impact on the color of the LC composite, whereas montelukast had the least effect on the color of LC GIC.

Colour Stability of Two Commercially Available Maxillofacial Prosthetic Elastomers after Outdoor Weathering in Al Jouf Province

Facial prostheses are created from special elastomers modified for their specific physical and mechanical properties; however, they also show two common major clinical problems: gradual discolouration of the prosthesis over time in service environment and deterioration of static, dynamic, and physical properties. As a result of external environmental factors, facial prostheses may become discoloured and discolour by changing colour from intrinsic and extrinsic colouring, and this is associated with the intrinsic colour stability of elastomers and colourants. Thus, in this in vitro study, a comparative evaluation of the effect of outdoor weathering on the colour stability of A-103 and A-2000 room-temperature vulcanised silicones used for maxillofacial prosthesis was conducted. To accomplish this study, a total of 80 samples were fabricated, 40 samples of each material were grouped as clear (20) and pigmented (20). These samples were mounted on wooden board and the assembly was placed on the roof of the dental school from October 2021 to March 2022. To maximise the amount of sunlight on the specimens, the exposure rack was set on five 68° angles from horizontal and also to prevent standing water. The specimens were left uncovered during exposure. The testing of samples was conducted with the help of a spectrophotometer. The colour values were recorded in the CIELAB colour system. It describes the three colour coordinates (colour values) x, y, and z in three new reference values of L, a, and b, aiding in numerically classifying colour differences. After 2, 4, and 6 months of weathering, testing was conducted using a spectrophotometer and the colour change (ΔE) was calculated. The A-103 RTV silicone group with pigmentation showed the maximum change in colour after six months of environmental conditioning. The data for colour difference within groups were analysed using a one-way ANOVA test. Tukey's post hoc test assessed the pairwise mean comparison's contribution to the overall significant difference. The nonpigmented A-2000 RTV silicone group showed the maximum change in colour after six months of environmental conditioning. After 2, 4, and 6 months of environmental conditioning, pigmented A-2000 RTV silicone showed better colour stability than A-103 RTV silicone. The patients requiring facial prosthesis do need to work on outdoor fields, and thus weathering will have deleterious effects on such prosthesis. Hence, the selection of appropriate silicone material with respect to the Al Jouf province region is crucial, which includes economic, durable, and colour stability.

Cytotoxicity, Colour Stability and Dimensional Accuracy of 3D Printing Resin with Three Different Photoinitiators

Biocompatibility is important for the 3D printing of resins used in medical devices and can be affected by photoinitiators, one of the key additives used in the 3D printing process. The choice of ingredients must be considered, as the toxicity varies depending on the photoinitiator, and unreacted photoinitiator may leach out of the polymerized resin. In this study, the use of ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate (TPO-L) as a photoinitiator for the 3D printing of resin was considered for application in medical device production, where the cytotoxicity, colour stability, dimensional accuracy, degree of conversion, and mechanical/physical properties were evaluated. Along with TPO-L, two conventional photoinitiators, phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide (BAPO) and diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO), were considered. A total of 0.1 mol% of each photoinitiator was mixed with the resin matrix to prepare a resin mixture for 3D printing. The specimens were printed using a direct light processing (DLP) type 3D printer. The 3D-printed specimens were postprocessed and evaluated for cytotoxicity, colour stability, dimensional accuracy, degree of conversion, and mechanical properties in accordance with international standards and the methods described in previous studies. The TPO-L photoinitiator showed excellent biocompatibility and colour stability and possessed with an acceptable dimensional accuracy for use in the 3D printing of resins. Therefore, the TPO-L photoinitiator can be sufficiently used as a photoinitiator for dental 3D-printed resin.

Retail Packaging Affects Colour, Water Holding Capacity, Texture and Oxidation of Sheep Meat more than Breed and Finishing Feed

This study investigated the CIELab colour, water holding capacity, texture and oxidative stability of sheep meat from different breeds, finishing feeds, and retail packaging methods. Leg primal cuts from a subset of Composite wether lambs (n = 21) and Merino wether yearlings (n = 21) finished on a standard diet containing grain and cereal hay, a standard diet with camelina forage, or a standard diet with camelina meal, were used in this study. Semimembranosus and Vastus lateralis were packaged in vacuum skin packaging (VSP), or modified atmosphere packaging with 80% O₂ and 20% CO₂ (HioxMAP), or with 50% O₂, 30% N₂, and 20% CO₂ (TrigasMAP). Packaging had a greater effect (p < 0.001) on L*, a*, b*, hue, and chroma than the effects from breed and finishing feed. Purge loss was affected by packaging. Cooking loss was affected by breed for Semimembranosus and packaging for both muscle types. HioxMAP and TrigasMAP increased WBSF and Texture Profile Analysis hardness of the meat compared to VSP. Lipid oxidation, assessed by TBARS, were lower in camelina forage or camelina meal supplemented diets and TrigasMAP compared to standard diet and HioxMAP, respectively. Total carbonyl and free thiol content were lower in VSP. Thus, supplementing feed with camelina forage or meal and lowering oxygen content in retail packaging by TrigasMAP or VSP are recommended to ensure optimal sheep meat quality.

Influence different polishing systems on roughness and colour stability of chairside CAD/CAM blocks with laminate veneer thickness

OBJECTIVE

The aim of this study was to evaluate the effect of different polishing systems on the colour stability of different laminate veneer blocks for chair-side CAD-CAM after ultraviolet (UV) ageing.

METHODS

About 240 sample (13 × 13 × 0.7) were prepared from four different CAD-CAM blocks IPS e.max CAD (IP), IPS Empress CAD (IE), Mark II (M) and Lava Ultimate (LU)) with A1 shade. Each group was divided into five subgroups (n = 12) according to the control (C) and four different polishing system: Sof-Lex (S), Edenta (E), Identoflex (I) and Zircon Brite (Z). Surface roughnesses (Ra) were measured by a profilometer before and after polishing. The baseline colour values were recorded according to the CIELab system. The colour coordinates (L*, a* and b*) of the samples were measured before and after UV ageing, and colour differences (ΔE₀₀) were calculated by using the CIEDE2000 colour difference formula. A two-way ANOVA and Tukey test methods were used to analyse the data (α = 0.05).

RESULTS

A significant interaction was observed between CAD-CAM blocks and polishing system (p < 0.001). The higher Ra and colour difference was calculated in LU in the Z group after polished and the lower Ra and colour difference was calculated in the IP in the S group after polished. For the IP group, the glazing procedure showed higher Ra and ΔE values with Z group than polished S system, whereas there is no statistical differences.

CONCLUSION

It is concluded that polishing with the Sof-Lex system improves significantly smoothness and colour stability. However, there is no success in using the Zircon Brite polishing system.

A comparative evaluation of colour stability of different resin cements and its influence on the final shade of All-Ceramic Restorations: An in-vitro Study

Introduction

Colour changes of the luting material can become clinically visible affecting the aesthetic appearance of thin ceramic veneers. Therefore, unfortunately, the long-term success of veneers is tied to the colour stability of the luting agent used to cement them.

Aim

To compare the colour stability of different resin cements and its influence on the final shade of overlying ceramic using two different thicknesses of ceramic.

Material and Methodology

Sixty disc-shaped specimens of high translucency (HT) A2 shade of two thicknesses (0.5 mm & 1 mm) were prepared from lithium disilicate glass-ceramic. The discs of each thickness were further divided into three groups randomly depending upon the resin cements used. Group A - light cure resin cement - Variolink N LC by Ivoclar Vivadent in clear shade, Group B - base paste of dual-cure resin cement - Variolink N by Ivoclar Vivadent in transparent shade and Group C dual-cure resin cement - Clearfil esthetic cement EX by Kuraray in clear shade were used to compare their colour stability. A spectrophotometer was used for the colour measurements of the specimens before and after accelerated ageing. The colour stability was determined by colour differences (ΔE) using the coordinates L*, a* and b* in the pre and post accelerated ageing. Results: On comparing the three resin cements, Group A showed the lowest ΔE, whereas the highest ΔE was observed in Group B. This finding was constant for discs of both thicknesses.

Conclusion

Even though statistically significant results were observed between the groups, they were not visibly differentiable.

Effect of Cleansers on the Colour Stability of Zirconia Impregnated PMMA Bio-Nanocomposite

Exposure of denture base acrylic resins to the oral environment and storage media for extended periods of time results in colour change due to changes in the properties of the material. The purpose of this in vitro study was to assess the colour stability of high-impact heat-polymerized denture base acrylic resin (HI PMMA) impregnated with zirconia nanoparticles after storage in distilled water (DW) and denture cleaners such as Steradent (STD) and Milton (MIL) for 180 days. Ninety specimens of PMMA + Zirconia nanocomposite with varying nanoparticle concentrations (1.5 wt.%, 3.0 wt.%, 5.0 wt.%, 7.0 wt.% and 10 wt.%) were prepared with a diameter and thickness of 25 ± 1.0 mm × 2 ± 0.1 mm and divided into six groups, while each group was further divided into three subgroups: storage in DW (control), STD and MIL. Colour changes were measured with a Minolta Chroma Meter (Minolta, Osaka, Japan), and assessed using the CIE L*a*b* colorimetric system. Data were statistically analysed for colour change with Friedman's Two-way and Kruskal-Wallis tests at a pre-set alpha value level of 0.05. The colour change (ΔΕ) exhibiting significant differences were found among all groups immersed in denture cleaners, and all values increased with time. According to the National Bureau of Standards, the control group displayed the lowest colour change value (ΔΕ = 1.22), and the highest value was for 10 wt.% ZrO₂ while stored in MIL (ΔΕ = 6.07). The values of colour change for storage in water ranged from 0.49 (control) to 1.82 (10 wt.% ZrO₂). The colour change value for the composite group containing 3 wt.% zirconia was clinically acceptable. However, high concentrations of denture cleaners should be avoided, and the shortest cleaning time is recommended to improve the clinical life of the nanocomposite denture base.

Effect of Hydrothermal Aging and Beverages on Color Stability of Lithium Disilicate and Zirconia Based Ceramics

Background and Objectives: All-ceramic prosthesis is widely used in modern dental practice because of its improved physico-mechanical and optical properties. These restorations are exposed to coloring agents from various nutrition and beverages in the oral cavity. Long-term color stability is critical for the success of these restorative materials. The purpose of this in vitro study was to assess the effect of common beverages and mouthwash on the color stability of lithium disilicate (LD), monolithic zirconia (MZ) and bilayer zirconia (BZ) surfaces. Materials and Method: Thirty disc-shaped specimens from each material were fabricated; each group was subdivided (n = 10) according to coffee, green tea and chlorhexidine immersion solutions. The baseline color of ceramic discs was recorded according to the CIE L*a*b* system with a portable spectrophotometer. The second measurement was recorded after 3000 thermocycling and immersion in coloring agents for 7 days. The mean color difference was calculated and data were compared with Kruskal-Wallis and Mann-Whitney post hoc tests (0.05). Results: ΔE values for LD with the immersion of coffee, tea, and Chlorhexidine gluconate (CHG) were 1.78, 2.241 and 1.58, respectively. Corresponding ΔE values for MZ were 5.60, 5.19, and 4.86; marginally higher than the clinically acceptable level of 3.5. Meanwhile, BZ showed better color stability compared to MZ with ΔE values of 4.22, 2.11 and 1.43. Conclusions: Among the ceramics evaluated, LD ceramic was found to be more color stable, while MZ ceramics displayed a higher susceptibility to discoloration. MZ and BZ ceramic colors were significantly altered with coffee immersion, while LD ceramics were more affected by green tea.

Effects of Killing Methods on Lipid Oxidation, Colour and Microbial Load of Black Soldier Fly (Hermetia illucens) Larvae

Black soldier fly (BSF) larvae represent a promising alternative ingredient for animal feed. Post-production processing can, however, affect their quality. This project aimed to optimize larval killing by comparing the effects on the nutritional and microbiological quality of 10 methods, i.e., blanching (B = 40 s), desiccation (D = 60 °C, 30 min), freezing (F20 = -20 °C, 1 h; F40 = -40 °C, 1 h; N = liquid nitrogen, 40 s), high hydrostatic pressure (HHP = 3 min, 600 MPa), grinding (G = 2 min) and asphyxiation (CO2 = 120 h; N2 = 144 h; vacuum conditioning, V = 120 h). Some methods affected the pH (B, asphyxiation), total moisture (B, asphyxiation and D) and ash contents (B, p < 0.001). The lipid content (asphyxiation) and their oxidation levels (B, asphyxiation and D) were also affected (p < 0.001). Killing methods altered the larvae colour during freeze-drying and in the final product. Blanching appears to be the most appropriate strategy since it minimizes lipid oxidation (primary = 4.6 ± 0.7 mg cumen hydroperoxide (CHP) equivalents/kg; secondary = 1.0 ± 0.1 mg malondialdehyde/kg), reduces microbial contamination and initiates dehydration (water content = 78.1 ± 1.0%). We propose herein, an optimized protocol to kill BSF that meet the Canadian regulatory requirements of the insect production and processing industry.

Colour stability of dental restorative materials submitted to conditions of burial and drowning, for forensic purposes

The aim of this study was to evaluate the effect of earth and water on the colour stability of tooth-coloured dental restorative materials: composite resin (CR) and glass ionomer cement (GIC). Aiming to distinguish between one and another tooth-coloured material and to estimate the period in which they could be submitted to the factors earth and water, the proposed method may contribute to the proceedings of human identification of victims of burial and submersion in water. Forty bovine incisors were prepared (6 x 6 x 2mm) and restored with CR FiltekTM Z250 XT (3M ESPETM) and GIC KetacTM Fil Plus (3M ESPETM). After initial colour read-outs (VITATM Easyshade spectrophotometer), the samples were separated into two groups (n=10), according to the conditions to which they were submitted: simulations of burying and submersion in water, for periods of 1, 3, 6 and 12 months, when new read-outs were taken. The values of colour change (ΔE, ΔL*, Δa*, and Δb*) were subjected to 3-way ANOVA statistical analysis, repeated measures, Bonferroni (p<.05), and it was verified that both factors produced colour changes in the restorative materials, which were higher for glass ionomer cement (p<.05) after 12 months of burial, and 6 months of submersion in water. The authors concluded that the analysis of colour change in the material contributed to the forensic odontology casework depending on the time during which the victim was submitted to the condition of burial or submersion in water.

Inclusion complexes of yellow bell pepper pigments with β-cyclodextrin: preparation, characterisation and application as food natural colorant

BACKGROUND

This work aimed to prepare inclusion complexes using yellow bell pepper pigments and β-cyclodextrin by two different procedures (method A, ultrasonic homogenisation; method B, kneading), to characterise them and evaluate their colour stability in an isotonic beverage model. The extract/β-cyclodextrin ratio was 1:2 for both inclusion methodologies evaluated. The formed extract-β-cyclodextrin complexes and a physical mixture of extract and β-cyclodextrin were evaluated by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR).

RESULTS

Both methodologies resulted in good complex yield and inclusion efficiency. The colour indices L* (lightness), a* (green/red) and b* (blue/yellow) of isotonic drinks added with the complexes were measured during storage under irradiance (1400 lx) and in the absence of light at temperatures between 25 and 31 °C for 21 days.

CONCLUSION

The complex obtained by inclusion method B promoted better colour protection for the beverage compared with the use of the crude extract, showing that the molecular inclusion of yellow bell pepper carotenoids can provide good results for that purpose. © 2017 Society of Chemical Industry.

Green tea extract as an anti-browning agent for cloudy apple juice

BACKGROUND

Enzymatic browning of fruits and vegetables and their products is an important factor worsening their quality. The influence of five green tea extracts at the concentrations of 1 g L^-1 , 2 g L^-1 and 3 g L^-1 on polyphenol oxidase (PPO) activity in fresh cloudy apple juice was investigated. Moreover, PPO inhibition by tea extract and colour stability of juice during short-time refrigerated storage was studied. The changes of juice colour during storage was expressed as the total colour differences (ΔE*), browning index (BI), yellowness index (YI), and the absorbance at 420 nm (A₄₂₀ ).

RESULTS

All extracts inhibited PPO activity in fresh apple juice in concentration-dependent manner. PPO activity in pure apple juice decreased by 7% after 48 h, whereas PPO activity in samples with 1 g L^-1 , 2 g L^-1 and 3 g L^-1 tea extract decreased by 53%, 74%, and 96%, respectively. Browning of apple juice during storage decreased with increased concentration of green tea extract. After 48 h, extract at 1 g L^-1 , 2 g L^-1 and 3 g L^-1 inhibited browning of juice expressed as BI by 48%, 60%, and 86%, respectively, comparing to pure apple juice.

CONCLUSION

Green tea extract may be an effective anti-browning agent for short-time stored cloudy apple juices. © 2016 Society of Chemical Industry.

Supra-nutritional levels of α-tocopherol maintain the oxidative stability of n-3 long-chain fatty acid enriched subcutaneous fat and frozen loin, but not of dry fermented sausage

BACKGROUND

Meat products enriched with n-3 fatty acids are more prone to oxidation. The aim was to investigate whether supra-nutritional levels of α-tocopherol can enhance the colour and lipid oxidative stability of n-3 fatty acids enriched dry fermented sausages, frozen loins and subcutaneous fat. Pigs were fed a diet supplemented with 18 g kg(-1) fish oil and 50, 150 or 300 mg kg(-1) α-tocopheryl acetate. The control group received 12 g kg(-1) soy oil and 150 mg kg(-1) α-tocopheryl acetate.

RESULTS

α-Tocopherol levels of the frozen loin, dry fermented sausage and subcutaneous fat were elevated as a result of the dietary α-tocopherol supplementation. Lipid oxidation occurred to the same extend in the n-3 fatty acid enriched frozen loins when compared to the control group. In the subcutaneous fat enriched with n-3 fatty acids reduced lipid oxidation was found when comparing 50 mg kg(-1) versus 150 and 300 mg kg(-1) . However, in the dry fermented sausages no such effect was observed and higher TBARS values were found in the n-3 fatty acid enriched sausages compared to the control group. Colour parameters of the loin and subcutaneous fat were not affected, whereas some significant differences in the dry fermented sausages were found. The colour stability of the frozen loins was not affected by the dietary treatments.

CONCLUSION

Supra-nutritional levels of α-tocopherol maintain the oxidative stability of n-3 fatty acid enriched frozen loins and subcutaneous fat, but not of dry fermented sausages. © 2016 Society of Chemical Industry.

Influence of carbon monoxide on the colour stability of defrosted yellowfin tuna (Thunnus albacares) muscle stored under aerobic and anaerobic conditions

BACKGROUND

The use of carbon monoxide (CO) and various packaging types has been suggested to improve/stabilise the colour and oxidative processes of red meats, thereby improving the retail value and revenue. The main aim of this study was to investigate the influence of packaging type and CO treatment on the colour and oxidative stability of tuna.

RESULTS

The addition of CO significantly increased the redness (a(*) ) of the tuna steaks but the redness was not equally stable for all treatments. The aerobically packaged steaks showed a temporal decrease in redness while the redness of anaerobically packaged steaks remained relatively stable. The addition of CO did not significantly affect (P >0.05) the brownness (b(*) ) (with one exception) and lightness (L(*) ) of the steaks. The anaerobically packaged steaks showed a significant difference (P <0.05) in the b(*) values. No significant differences (P >0.05) in lipid or protein oxidation were observed between treatments. The aerobically packaged steaks had a significant temporal increase (P <0.05) in lipid oxidation while no such trend was apparent in the anaerobically packaged steaks. Protein oxidation remained relatively stable over time for both aerobically and anaerobically packaged steaks.

CONCLUSION

Storing CO treated tuna steaks in anaerobic packaging can improve the oxidative and colour stability of tuna. Such treatment can reduce spoilage and wastage thereby potentially increasing revenue.

Colour evaluation of a phycobiliprotein-rich extract obtained from Nostoc PCC9205 in acidic solutions and yogurt

BACKGROUND

Phycobiliproteins are coloured proteins produced by cyanobacteria, which have several applications because of their colour properties. However, there is no available information about the colour stability of phycobiliproteins from Nostoc sp. in food systems. The aim of this work was to study the colour stability of a purple-coloured phycobiliprotein-rich extract from the cyanobacterium Nostoc PCC9205 in acidic solutions and yogurt.

RESULTS

Variations of pH for Nostoc PCC9205 extract have shown stability for the L* (lightness) and a* (redness) indexes in the range 1.0-7.0. The b* index (blueness), however, increased at pH values below 4.0, indicating loss of the blue colour. The Nostoc PCC9205 extract was used as colorant in yogurt (pH 4.17) stored for 60 days. Instrumental colour analysis showed no changes for the L* and a* indexes during storage, whereas the b* index changed after 20 days of storage. A multiple comparison test showed colour instability after 20 days of storage. A hedonic scale test performed on the 60th day of storage showed acceptability of the product.

CONCLUSIONS

The red component of the phycobiliprotein-rich extract from Nostoc PCC9205 presented an improved stability in acidic media and yogurt compared with the blue component of this extract.