Natural color pigments: oxidative stability and degradation kinetics during storage in thermally pasteurized vegetable purees

A review on improving the sensitivity and color stability of naturally sourced pH-sensitive indicator films

Naturally sourced pH-sensitive indicator films are of interest for real-time monitoring of food freshness through color changes because of their safety. Therefore, natural pigments for indicator films are required. However, pigment stability is affected by environmental factors, which can in turn affect the sensitivity and color stability of the pH-sensitive indicator film. First, natural pigments (anthocyanin, betalain, curcumin, alizarin, and shikonin) commonly used in pH-sensitive indicator films are presented. Subsequently, the mechanisms behind the change in pigment color under different pH environments and their applications in monitoring food freshness are also described. Third, influence factors, such as the sources, types, and pH sensitivity of pigments, as well as environmental parameters (light, temperature, humidity, and oxygen) of sensitivity and color stability, are analyzed. Finally, methods for improving the pH-sensitive indicator film are explored, encapsulation of natural pigments, incorporation of a hydrophobic film-forming matrix or function material, and protective layer have been shown to enhance the color stability of indicator films, the addition of copigments or mental ions, blending of different natural pigments, and the utilization of electrospinning have been proved to increase the color sensitivity of indicator films. This review could provide theoretical support for the development of naturally sourced pH-sensitive indicator films with high stability and sensitivity and facilitate the development in the field of monitoring food freshness.

Biopolymer-based intelligent packaging integrated with natural colourimetric sensors for food safety and sustainability

Increasing concerns about global food safety and security demands innovative solutions, particularly in food packaging technologies. This review paper investigates the advanced integration of natural colourimetric sensors with biopolymer-based packaging materials, with a focus on developments over the past 5 years. These sensors change colour in response to environmental stimuli such as oxygen, temperature, pH and relative humidity, intuitively indicating food freshness and safety. The paper emphasizes the recent advancements in using natural colourants, such as alizarin, anthocyanins, betacyanins, chlorophyll, curcumin and shikonin. When combined with either natural or synthetic biopolymers, these colourants contribute to a sustainable and eco-friendly approach to food packaging. Such technological advances could notably decrease the incidence of foodborne illnesses by signaling potential spoilage or contamination, while also addressing food wastage by providing clear indications of edibility. Although challenges remain in sensor longevity and widespread adoption, the prospects for biopolymer-based food packaging with embedded natural colourimetric sensors are promising.

A critical review on the stability of natural food pigments and stabilization techniques

This comprehensive review article delves into the complex world of natural edible pigments, with a primary focus on their stability and the factors that influence them. The study primarily explores four classes of pigments: anthocyanins, betalains, chlorophylls and carotenoids by investigating both their intrinsic and extrinsic stability factors. The review examines factors affecting the stability of anthocyanins which act as intrinsic factors like their structure, intermolecular and intramolecular interactions, copigmentation, and self-association as well as extrinsic factors such as temperature, light exposure, metal ions, and enzymatic activities. The scrutiny extends to betalains which are nitrogen-based pigments, and delves into intrinsic factors like chemical composition and glycosylation, as well as extrinsic factors like temperature, light exposure, and oxygen levels affecting for their stability. Carotenoids are analyzed concerning their intrinsic and extrinsic stability factors. The article emphasizes the role of chemical structure, isomerization, and copigmentation as intrinsic factors and discusses how light, temperature, oxygen, and moisture levels influence carotenoid stability. The impacts of food processing methods on carotenoid preservation are explored by offering guidance on maximizing retention and nutritional value. Chlorophyll is examined for its sensitivity to external factors like light, temperature, oxygen exposure, pH, metal ions, enzymatic actions, and the food matrix composition. In conclusion, this review article provides a comprehensive exploration of the stability of natural edible pigments, highlighting the intricate interplay of intrinsic and extrinsic factors. In addition, it is important to note that all the references cited in this review article are within the past five years, ensuring the most up-to-date and relevant sources have been considered in the analysis.

Microbial Pigments: Major Groups and Industrial Applications

Microbial pigments have many structures and functions with excellent characteristics, such as being biodegradable, non-toxic, and ecologically friendly, constituting an important source of pigments. Industrial production presents a bottleneck in production cost that restricts large-scale commercialization. However, microbial pigments are progressively gaining popularity because of their health advantages. The development of metabolic engineering and cost reduction of the bioprocess using industry by-products opened possibilities for cost and quality improvements in all production phases. We are thus addressing several points related to microbial pigments, including the major classes and structures found, the advantages of use, the biotechnological applications in different industrial sectors, their characteristics, and their impacts on the environment and society.

Exploring the Potential of Roselle Calyx and Sappan Heartwood Extracts as Natural Colorants in Poly(butylene Succinate) for Biodegradable Packaging Films

Recently, there has been a growing concern among consumers regarding the safety of packaging products, particularly due to the presence of potentially harmful substances like synthetic pigments and inorganic dyes. These substances, which are often used to attract consumer attention, can migrate and contaminate products over extended shelf storage periods. To address this issue, the focus of this research was the development of a biodegradable packaging film using poly(butylene succinate) (PBS) incorporated with natural colorants extracted from roselle (RS) and sappan heartwood (SP). RS and SP serve as non-toxic and alternative pigments when compared to synthetic colorants. The biodegradable packaging films were prepared using blown film extrusion, encompassing different weight percentages of RS and SP (0.1%, 0.2%, and 0.3%). The films exhibited distinct colors, with RS films appearing pink to purple and SP films exhibiting an orange hue. The water vapor transmission rate slightly decreased with an increasing content of RS and SP extracts, indicating improved barrier properties. Additionally, the films showed reduced light transmittance, as evidenced by the UV-Vis light barrier results. The degree of crystallinity in the films was enhanced, as confirmed by X-ray diffraction and differential scanning calorimetry techniques. Regarding mechanical properties, the PBS/RS and PBS/SP films exhibited slight increases in tensile strength and elongation compared to neat PBS films. Moreover, the blended films demonstrated higher stability after undergoing an aging test, further highlighting their potential for use in biodegradable packaging applications. The key advantages of these films lie in their non-toxicity, biodegradability, and overall environmental friendliness.

Production and characterization of nanofibrillated cellulose gels simultaneously exhibiting thermally stable green color and oil-in-water emulsion stabilizing capability from Centella asiatica

Nanofibrillated cellulose (NFC) gels simultaneously exhibiting Pickering stabilizing capability and thermally stable green color were developed for use as food additive in thermally processed food emulsion requiring the expression of color. Chopped Centella asiatica plant was mixed with zinc amino acid chelate solution and subject to autoclaving at 130°C for 2 h to form zinc-chlorophylls complex and to remove noncellulosic components. Autoclaved sample was high-shear homogenized at 26,000 rpm for 15 min and microfluidized at either 80, 120, or 160 MPa for 5 passes. An increase in microfluidization pressure resulted in a decrease in NFC diameters; microfluidization at 160 MPa did not nevertheless yield any further reduction in the diameters when compared with that at 120 MPa. From energy consumption point of view, microfluidization at 120 MPa for 5 passes was then noted as optimal condition for preparation of NFC coloring gel; NFC with diameters of 8-42 nm and crystallinity index of 35% was obtained. Freshly prepared gel exhibited gel-like behavior and dark green color. Heating at 121°C for 1 h did not affect diameters, viscoelasticity, and color of the gel. Addition of the gel at 0.9% or 1.2% (w/w) into soybean oil-in-water emulsion, in combination with high-shear homogenization at 18,000 rpm for 5 min, resulted in adequate emulsion stability. The emulsion exhibited stable dark green color and no phase separation after heating at 121°C for 1 h and during storage for 8 weeks. PRACTICAL APPLICATIONS: Information presented here can serve as a guideline for further development of a multifunctional food ingredient exhibiting thermally stable green color and oil-in-water emulsion stabilizing capability. In other words, one simple ingredient can serve at the same time as both natural food colorant and emulsion stabilizer.

The Stability of Phenolic Compounds in Fruit, Berry, and Vegetable Purees Based on Accelerated Shelf-Life Testing Methodology

Evaluating the stability of polyphenols in fruit, berry, and vegetable purees helps to assess the quality of these products during storage. This study aimed to (1) monitor the stability of total phenolic content (TPC) in four-grain puree with banana and blueberry (FGBB), mango-carrot-sea buckthorn puree (MCB), and fruit and yogurt puree with biscuit (FYB); (2) study the effect of aluminum-layered vs. aluminum-free packaging on the changes in TPC; and (3) assess the suitability of accelerated shelf-life testing (ASLT) methodology to evaluate the stability of polyphenols. The samples were stored at 23 °C for 182, 274, 365, and 427 days. The corresponding time points during ASLT at 40 °C were 28, 42, 56, and 66 days, calculated using Q₁₀ = 3. The TPC was determined with Folin-Ciocalteu method. The results revealed that the biggest decrease in TPC took place with high-pH FGBB, which contained fewer ingredients with bioactive compounds. Minor changes were seen in FYB and MCB, which had lower pH values, and contained a larger amount of ingredients that include polyphenols. In addition, the choice of packaging material did not affect the TPC decrease in each puree. Finally, it was concluded that the ASLT methodology is suitable for studying the TPC changes in such purees, but the corresponding Q₁₀ factors may vary and should be determined based on the chemical profile and ingredient list of the product.

EFFECTS OF COLD PLASMA ON CHLOROPHYLLS, CAROTENOIDS, ANTHOCYANINS, AND BETALAINS

Plasma is considered by several researchers to be the fourth state of matter. Cold plasma has been highlighted as an alternative to thermal treatments because heat induces less degradation of thermolabile bioactive compounds, such as natural pigments. In this review, we provide a compilation of the current information about the effects of cold plasma on natural pigments, such as the changes caused by plasma to the molecules of chlorophylls, carotenoids, anthocyanins, and betalains. As a result of the literature review, it is noted that can degrade cell membrane and promote damage to pigment storage sites; thereby releasing pigments and increasing their content in the extracellular space. However, the reactive species contained in the cold plasma can cause degradation of the pigments. Cold plasma is a promising technology for extracting pigments; however, case-by-case optimization of the extraction process is required.

pH-dependent color response of cellulose-based time-temperature indicators impregnated with red cabbage extract

Color-based time-temperature indicators (TTIs) can show the time and temperature changes of an environment with a visually recognizable color change. Made from natural dyes, these TTIs are simple, inexpensive and sustainable. In this study, cellulose-based TTI labels were prepared with red cabbage extract of pH2, pH7 and pH9 to determine how pH alter the response of the labels to time and temperature changes. This study also aimed to determine the relationship between color change and time at different temperatures. The color responses of the labels were followed spectrophotometrically by measuring the CIE Lab color coordinates and by giving the total color difference at 4 °C, 23 °C, 40 °C, 80 and 100 °C after increments of time. The best fitting linear or nonlinear regression models of the CIE Lab coordinates, total color difference and time data as a function of temperature were also determined. The labels prepared with red cabbage extract at different pH behaved differently. Opposite to expectations, the acidic, pink colored labels did not have the highest color stability. Our finding was, that the label prepared with the acidic red cabbage extract is the most suitable as time-temperature label for indicating long-term temperature storage and the label prepared with the neutral red cabbage extract is the most suitable as time-temperature label for indicating short-term storage by color change. According to the results the color changes of the labels are predictable with the fitted models with a correlation coefficient between 0.96 and 1.

Survival Analysis to Predict How Color Influences the Shelf Life of Strawberry Leather

Color change of fruit-based products during storage is an important quality parameter to determine their shelf life. In this study, a combination of relative humidity (RH) and illumination was evaluated on the stability of strawberry leathers. Samples were conditioned at 25 °C, in chambers with RH of 22.5% and 52.3% and under two levels of illumination (no illumination and with a light-emitting diode (LED) illumination at 1010 lx). Samples were analyzed during storage by instrumental color measurements, total anthocyanin content, and consumers’ acceptance/rejection of the product color. Current-status survival analysis was performed to estimate the sensory-based shelf-life of the strawberry leather. The chromatic parameters (a* and ΔE* values) and anthocyanin content changed with increasing storage time and RH, fitting a first-order fractional conversion model. Samples conditioned at the higher RH showed a higher reduction of a* values and anthocyanins losses when stored under LED illumination than those without illumination. The increase of RH resulted in a faster increase of the consumer rejection probability and a shorter shelf life of the strawberry leather. For 50% of consumers’ rejection, the sensory shelf life of the strawberry leather equilibrated at 22.5% RH was estimated as at least 54 days, while it was reduced to approximately 2 days at 52.3% RH. The red chromatic parameter (a* value) strongly correlated to the percentage of consumer rejection in all storage conditions, suggesting that this analytical parameter can be useful as a predictor of strawberry leather’s shelf life. Therefore, the results of this study show the applicability of an approach that integrates instrumental and sensory data to acquire faster information on color changes during the storage of strawberry leather and product shelf-life prediction.

Effect of Oxidative Stress on Physicochemical Quality of Taiwanese Seagrape (Caulerpa lentillifera) with the Application of Alternating Current Electric Field (ACEF) during Post-Harvest Storage

This study aims to determine the physicochemical quality of seagrape (Caulerpa lentillifera) as a freshness label for products cultivated in different seasons. The applied post-harvest storage experiments compared between, within and without seawater that led to oxidative stress conditions. Water content, malondialdehyde (MDA) compound, total phenolic content (TPC), and chlorophyll content were observed at 0, 3, 6, and 9 days of storage. The storage without seawater showed sharper quality reductions by reaching 20–40% of water loss, 70–90% of MDA production, 15–25% of TPC reduction, and 40–60% of total chlorophyll degradation. The storage within seawater showed lower quality reductions due to the specific growth rates still reaching 5–10%. This study found that the greater the physicochemical quality, the slower the decomposition rates of the stored seagrape during storage. Therefore, the seagrapes’ obvious discoloration occurred earlier in winter, followed by summer and spring. Kinetics of chlorophyll degradation on seagrape in different seasons meet different order-reactions during storage. Furthermore, alternating current electric field (ACEF) treatment with 125 kV/m of intensity for 60 min can lower the spring seagrapes’ physicochemical quality by reaching 10–30% of inhibition, resulting in the shelf-life extension for up to 12 days of post-harvest storage.

Betacyanins and Betaxanthins in Cultivated Varieties of Beta vulgaris L. Compared to Weed Beets

There are 11 different varieties of Beta vulgaris L. that are used in the food industry, including sugar beets, beetroots, Swiss chard, and fodder beets. The typical red coloration of their tissues is caused by the indole-derived glycosides known as betalains that were analyzed in hypocotyl extracts by UV/Vis spectrophotometry to determine the content of betacyanins (betanin) and of betaxanthins (vulgaxanthin I) as constituents of the total betalain content. Fields of beet crops use to be also infested by wild beets, hybrids related to B. vulgaris subsp. maritima or B. macrocarpa Guss., which significantly decrease the quality and quantity of sugar beet yield; additionally, these plants produce betalains at an early stage. All tested B. vulgaris varieties could be distinguished from weed beets according to betacyanins, betaxanthins or total betalain content. The highest values of betacyanins were found in beetroots ‘Monorubra’ (9.69 mg/100 mL) and ‘Libero’ (8.42 mg/100 mL). Other beet varieties contained less betacyanins: Sugar beet ‘Labonita’ 0.11 mg/100 mL; Swiss chard ‘Lucullus,’ 0.09 mg/100 mL; fodder beet ‘Monro’ 0.15 mg/100 mL. In contrast with weed beets and beetroots, these varieties have a ratio of betacyanins to betaxanthins under 1.0, but the betaxanthin content was higher in beetcrops than in wild beet and can be used as an alternative to non-red varieties. Stability tests of selected varieties showed that storage at 22 °C for 6 h, or at 7 °C for 24 h, did not significantly reduce the betalain content in the samples.

Characterization of the sensory, chemical, and microbial quality of microwave-assisted, thermally pasteurized fried rice during storage

Companies producing ready-to-eat (RTE) meals are looking for processing alternatives that allow them to gain presence in the supermarket chill section. Microwave-assisted pasteurization systems (MAPS) offer the potential to produce safe, high-quality foods. This research examined sensory, physical, chemical, and microbial changes in fried rice processed with MAPS and stored at 7 °C over a 6-week storage period. Additional fried rice samples (cooked but not MAPS-processed) were stored at -31 °C and were used as the control. Randomly selected trays of each type of rice were analyzed at 1, 4, and 6 weeks of storage. Aroma, appearance, taste/flavor, texture, mouthfeel, and aftertaste were evaluated by a semitrained sensory panel with rate-all-that-apply questions. The type of rice treatment (MAPS or control) significantly influenced sensory attributes (P < 0.05), with firm texture attribute of the egg being more intense in the MAPS-rice compared to the control. In addition, storage time affected the sensory modalities of both rice samples, including aroma, appearance, and taste/flavor (P < 0.05). No spoilage-associated sensory attributes were detected in the MAPS-rice during storage. At each examination point, various physical, chemical, and microbial analyses were conducted for the MAPS- and control rice. From the physical and chemical perspective, the MAPS-rice did not present relevant changes over the period tested. Microbial growth was the main cause of spoilage of the MAPS-rice; however, MAPS was able to extend the regular 5-day shelf life of a chilled fried rice meal to 6 weeks, demonstrating the potential of this technology for the RTE industry. PRACTICAL APPLICATION: The findings of this study indicate that, by applying microwave technology to RTE fried rice, the shelf life can be extended from 5 to 7 days up to 42 days (6 weeks) when stored at 7 °C. This temperature closely mimics that of consumers' refrigerators in the United States. This study also shows the potential of working with a semitrained panel and RATA questions when characterizing sensory changes during storage.