Color change kinetics of lac dye as influenced by some food spoilage metabolites: validation for spoilage monitoring of strawberries (original) (raw)
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Pigment & Resin Technology
Purpose This paper aims to study the color change kinetics of lac dye in response to pH and food spoilage metabolites (ammonia, lactic acid and tyramine) for its potential application in intelligent food packaging. Design/methodology/approach UV-Vis spectroscopy was used to study the color change of dye solution. Ratio of absorbance of dye solution at 528 nm (peak of ionized form) to absorbance at 488 nm (peak of unionized form) was used to study the color change. Color change kinetics was studied in terms of change in absorbance ratio (A528/A488) with time using zero- and first-order reaction kinetics. An indicator was prepared by incorporating lac dye in agarose membrane to validate the result of study for monitoring quality of raw milk. Findings Dye was orange-red in acidic medium (pH: 2 to 5) and exhibited absorbance peak at 488 nm. It turned purple in alkaline medium (pH: 7 to10) and exhibited absorbance peak at 528 nm. The change in absorbance ratio with pH followed zero-order...
Colour Measurement and Analysis in Fresh and Processed Foods: A Review
Colour is an important quality attribute in the food and bioprocess industries, and it influences consumer’s choice and preferences. Food colour is governed by the chemical, biochemical, microbial and physical changes which occur during growth, maturation, postharvest handling and processing. Colour measurement of food products has been used as an indirect measure of other quality attributes such as flavour and contents of pigments because it is simpler, faster and correlates well with other physicochemical properties. This review discusses the techniques and procedures for the measurement and analysis of colour in food and other biomaterial materials. It focuses on the instrumental (objective) and visual (subjective) measurements for quantifying colour attributes and highlights the range of primary and derived objective colour indices used to characterise the maturity and quality of a wide range of food products and beverages. Different approaches applied to model food colour are described, including reaction mechanisms, response surface methodology and others based on probabilistic and non-isothermal kinetics. Colour is one of the most widely measured product quality attributes in postharvest handling and in the food processing research and industry. Apart from differences in instrumentation, colour measurements are often reported based on different colour indices even for the same product, making it difficult to compare results in the literature. There is a need for standardisation to improve the traceability and transferability of measurements. The correlation between colour and other sensory quality attributes is well established, but future prospects exist in the application of objective non-destructive colour measurement in predictive modelling of the nutritional quality of fresh and processed food products.
Tracking bioactive compounds with colour changes in foods – A review
Dyes and Pigments, 2013
Colour is one of the major attributes that affect the consumer perception of food quality. Several pigments in foods, measurable by colourimetric instrumentation, possess biological activity. The present work is a review of studies that assessed the colour changes (by the CIELAB parameters) and the bioactive compound content, analysing statistically their correlation in a broad spectrum of foods. An emphasis was placed on the contribution of phenolics, carotenoids, chlorophylls and betalains on the food colour characteristics during different processing and storage conditions. The correlation between these compounds and the colour changes of some foods had r-values higher than 0.72, according to the Pearson correlation analysis. This suggests that colour instrumentation may be an efficient and practical technique to indirectly estimate the presence of bioactive components. This approach potentially facilitates the real-time quality control of biological compounds during the food industry processes.
Image analysis of oxidation induced food colour changes
Journal of the Serbian …, 2010
Colour evaluation, by means of multivariate image analysis was applied on colour lightness changes corresponding to oxidative browning of minimally-processed basil-based food emulsions. We have analysed the influence of metal-chelating protein lactoferrin on browning of emulsions (atributed to enzymaic and non-enzymatic oxidation). The colourgram of digitalized images, taken during oxidation of the samples, was evaluated, both by colour analysis and by PCA analysis. The basic colour information was derived from frequency colour distribution for RGB and HSV colour system, while the PCA analysis was carried out by evaluating covariance matrix, for raw, mean centered and autoscaled matrix of the basic R, G, B colour information, and the evaluation of eigenvalues and eigenvectors for all three numeric models. The resulting colourgram information is one-dimensional signal, which consists of 4900 elements, and describes colour properties of the image. The changes in material due to oxidation was observed by the changes in lightness frequency distribution (L).
Postharvest Biology and Technology
The study aimed to develop an intelligent real-time freshness indicator for white button mushrooms by immobilizing the lac dye, a natural anthraquinone dye on filter paper. The indicator was characterized for its pH responsiveness; structural, mechanical, thermal properties; and color stability. During the freshness test, mushrooms were packed in punnet with an indicator placed in the package headspace and stored at two different temperatures (4 • C and 25 • C). Mushroom spoilage was monitored concurrently by indicator's color change, physicochemical indices, and volatile organic compounds (VOC) generated during storage. The FTIR results revealed that dye was immobilized on matrix via hydrogen bonding. A slight reduction in matrix crystallinity post dye immobilization was observed. However, the thermal and mechanical properties remained unaffected. Indicator showed good color stability during one month storage at 4 • C and 25 • C. The indicator changed its color from orange-red (at acidic pH) to purple (at alkaline pH) due to the inherent properties of lac dye. In the freshness test, the visual color change of indicator distinguished mushrooms into three stages: ' fresh', 'medium fresh', and 'spoiled'. Principle Component Analysis (PCA) validated the synchronization between color change of indicator and quality parameters. Partial Least Square (PLS) regression models derived from indicator's color parameter data successfully predicted the physicochemical indices of mushrooms stored at 4 • C. The lac dyebased indicators emerged as a novel and potential solution for non-destructive freshness monitoring of white button mushrooms.
Detection and identification of natural water-soluble colouring matters in foods
Zeitschrift f�r Lebensmittel-Untersuchung und -Forschung, 1977
Isolierung und Identifizierung wasserl6slicher Naturfarbstoffe in Lebensmitteln Zusammenfassung. Bei der DurchfiJhrung des Benzalkonium-Verfahrens zur Isolierung ktinstlicher Farbstoffe aus Lebensmitteln k6nnen auch die Naturfarbstoffe isoliert und identifiziert werden. Anthocyanine, Carmins~iure, Betanin, Caramel und Lactoflavin werden yon den ktinstlichen Farbstoffen abgetrennt. Car-mins~iure kann yon den Anthocyaninen durch Oxydation oder Chromatographie unterschieden werden. Summary. The natural colouring matters of foods can be isolated and identified simultaneously with the synthetic dyes by the benzalkonium method. In the course of isolation anthocyanins, carmine, betanin, caramel and riboflavin are separated from synthetic dyes, as well as from one another, with the exception of first two, which are separated from one another by chromatography or distinguished by oxidation.
Effect of concentration and drying processes on color change of grape juice and leather (pestil)
Journal of Food Engineering, 2002
The Hunter color parameters ðL; a; bÞ of grape juice during boiling, cooking and of pestil samples (1.53 mm) during drying were investigated. It was found that most of the color changes occurred during grape juice boiling. However, during hot air or sun drying only the Hunter a-value changed. The reaction associated with color change followed zero-order reaction kinetics. The temperature dependence of the reaction rate constant was described by an Arrhenius-type equation. Ó
Polysaccharides
Food that is still fit for consumption is wasted in the domestic environment every day, so food packaging technologies are being developed that will monitor the quality of the products in real time. Highly perishable milk is currently one of the products that suffers most from this waste, due to its short shelf life. Active use-by date (AUBD) indicators have been shown to discriminate between fresh and spoiled milk. Colorimetric indicators undergo characteristic changes in their chemical structure, causing abrupt color changes. Among the polymeric materials studied that may function as solid support are cellulose acetate (CA) and agar-agar (AA). The AA colorimetric indicator proved to be more suitable as a solid support due to its ability to maintain the color change properties of the anthocyanin and its high colorimetric performance. The technique was shown to be capable of indicating, in real time, changes in milk quality.
Journal of Chemometrics, 2019
Colorants are widely used in food industry to improve appearance of edible products. This work present a method for the determination of two colorants, tartrazine and allura red, with UV-Vis spectrophotometry and MCR-ALS using only five standards for calibration and the correlation constraint. MCR-ALS is usually applied in second-order data but it rarely has been used for first order data, for which is more usual the use of PLS. In this case, MCR-ALS applied to first order data can show some advantages like interference identification and the use of a reduced calibration matrix. Using this methodology, the relative errors obtained are below 0.28%, correlation coefficients are above 0.99 and the calculated LOD and LOQ are 0.26 and 0.80 mg L-1 for allura red and 0.70 and 2.11 mg L-1 for tartrazine respectively. The procedure has been successfully applied to some food dyes and other liquid commercial products and, compared to HPLC analysis, no significant differences were found in the results. Recovery values obtained at two spiked levels were between 92.0% and 106.7% except for a sample.