GREEN COLOR DEGRADATION of BLANCHED BROCCOLI (BRASSICA OLERACEA) DUE to ACID and MICROBIAL GROWTH

Influence of steaming duration, chlorophyll-a and -b content and ratio, and pH on the color of green tea processed from multiple tea (Camellia sinensis L.) cultivars

BACKGROUND

The color of green tea is an important quality indicator. In recent years, shading of tea (Camellia sinensis L.) plants has been widely adopted for green tea production to enhance its green color and umami taste. In this study, we identified factors that influence green tea color by (i) examining variation in the chlorophyll content of fresh new tea shoots among cultivars, cropping seasons, and the degree of shading, (ii) investigating the rate of conversion of chlorophyll to pheophytin during the tea manufacturing process, specifically with steaming duration, and (iii) analyzing the effects of the new tea shoot properties and the steaming process on colorimetric values of the steamed new tea shoots.

RESULTS

Multiple regression analysis revealed that three factors contributed to the rate of conversion of each chlorophyll type to pheophytin in steamed new tea shoots (ranked by importance): steaming duration > each chlorophyll type (chlorophyll-a and chlorophyll-b) content of fresh new tea shoots > pH. The colorimetric hue angle (h) value of steamed new tea shoots was influenced by four factors (ranked by importance): steaming duration > total chlorophyll (chlorophyll-a + chlorophyll-b) content in fresh new tea shoots > pH > chlorophyll-a/chlorophyll-b ratio in fresh new tea shoots.

CONCLUSION

Differences in the color of new tea shoots can be explained by the aforementioned four factors. The findings will be useful for cultivar selection, and determining the appropriate degree of shading and steaming duration, to produce high-quality green teas with a good appearance. © 2024 Society of Chemical Industry.

Characterization of complex photosynthetic pigment profiles in European deciduous tree leaves by sequential extraction and reversed-phase high-performance liquid chromatography

Leaf pigments, including chlorophylls and carotenoids, are important biochemical indicators of plant photosynthesis and photoprotection. In this study, we developed, optimized, and validated a sequential extraction and liquid chromatography-diode array detection method allowing for the simultaneous quantification of the main photosynthetic pigments, including chlorophyll a, chlorophyll b, β-carotene, lutein, neoxanthin, and the xanthophyll cycle (VAZ), as well as the characterization of plant pigment derivatives. Chromatographic separation was accomplished with the newest generation of core-shell columns revealing numerous pigment derivatives. The sequential extraction allowed for a better recovery of the main pigments (+25 % chlorophyll a, +30 % chlorophyll b, +42 % β-carotene, and 61% xanthophylls), and the characterization of ca. 5.3 times more pigment derivatives (i.e., up to 62 chlorophyll and carotenoid derivatives including isomers) than with a single-step extraction. A broad working range of concentrations (300-2,000 ng.mL^-1) was achieved for most pigments and their derivatives and the limit of detection was as low as a few nanograms per milliliter. The method also showed adequate trueness (RSD < 1%) and intermediate precision (RSD < 5%). The method was developed and validated with spinach leaves and their extracts. The method was successfully performed on leaf pigment extracts of European deciduous tree species. Within a case study using Fagus sylvatica L. leaves, pigment derivatives revealed a high within-individual tree variability throughout the growing season that could not be detected using the main photosynthetic pigments alone, eventually showing that the method allowed for the monitoring of pigment dynamics at unprecedented detail.

Magnesium sulfate as a potential dye additive for chlorophyll-based organic sensitiser of the dye-sensitised solar cell (DSSC)

In this work, a new chlorophyll dye-sensitiser derived from mitragyna speciosa (MS) leaves, also known as Kratom, was employed for dye-sensitised solar cells (DSSCs). The influence of magnesium sulfate (MgSO₄), a low-cost dye additive, and suitable extraction solvents on the performance of DSSCs were examined. Here, the optical properties were investigated using UV-Visible spectroscopy and the functional anchoring group were investigated by FTIR spectroscopy. Meanwhile, the photovoltaic parameters were investigated by I-V measurements. The highest conversion efficiency is obtained when using a dye extracted from methanol solvent in combination with MgSO₄ additive, namely methanolic magnesium sulfate (MMSO). This higher power conversion efficiency is mainly attributed to the enhancement of the hydroxyl group in the MMSO dye solutions, which promotes higher dye adsorption and provides an organic dye passivation layer that reduces back-recombination in the cell. Furthermore, MgSO₄ aids in the replenishment of magnesium lost in the chlorophyll porphyrin ring during the degradation process. These combined effects have contributed to the overall conversion efficiency of the MMSO cell at 0.26 %, followed by 0.24 % for ethanolic magnesium sulfate (EMSO), respectively.

Development of a colorless Centella asiatica (L.) Urb. extract using a natural deep eutectic solvent (NADES) and microwave-assisted extraction (MAE) optimized by response surface methodology

This study outlines a green process for Centella asiatica (L.) Urb. (CA) extraction. Natural deep eutectic solvents (NADESs) and microwave-assisted extraction (MAE) were combined to provide a high bioactive compound yield and high antioxidant activity. Among the NADESs evaluated, the combination of acetylcholine chloride : malic acid : water (1 : 2 : 2): water (40 : 60) was the best for extraction. These conditions provide high madecassoside (MS) (21.7 mg g-1 dry weight) and asiaticoside (AS) (12.7 mg g-1 dry weight) yields, with greater than 80% (v/v) EtOH (13.3 mg g-1 MS and 7.80 mg g-1 AS). In addition, the extracts from this process showed higher antioxidant activity (IC50 = 0.26 mg mL-1) than the CA aqueous EtOH and water extracts. Moreover, the color of the extract products was less green than that of the extracts prepared using EtOH and aqueous EtOH as solvents, which are suitable for cosmeceutical products. Response surface methodology (RSM) was used for MAE optimization. The ANOVA data from the central composition design (CCD) of RSM were fitted with quadratic models yielding acceptable R 2 (>0.93), adjusted R 2 (>0.87), predicted R 2 (>0.81), and nonsignificant lack of fit (p  > 0.05) values. The quadratic model was validated using optimal conditions (30 s, power 300 W, and a liquid to solid ratio 20 mL g-1), and the model validation showed more than 80% accuracy in both MS and AS yields. This research presented an effective green process for CA extraction, which resulted in an environmentally friendly CA extract requiring little energy consumption and no organic solvents.

Effect of processing temperature on dynamic rheological properties and color degradation kinetics of bael fruit pulp

BACKGROUND

A lack of knowledge about the dynamic rheological properties and color degradation of bael fruit pulp gives rise to many problems during thermal processing for the preparation of bael fruit products. In this research, the effects of processing temperature (30-75 °C) on dynamic rheology and color degradation kinetics of bael fruit pulp were studied and analyzed.

RESULTS

Bael fruit pulp showed more elastic behavior than viscous behavior by analyzing the storage modulus, loss modulus and phase angle over oscillatory frequency range 0.06-300 rad s^-1 . The dynamic rheological study classified the bael fruit pulp as a weak gel (G' > G″). The values of first-order degradation rate constant (k) were determined to be 0.07, 0.011, 0.018 and 0.023 for 30, 45, 60 and 75 °C, respectively. The first-order color degradation kinetics of bael fruit pulp has given a higher value of activation energy (E_a = 23.83 kJ mol^-1 ) with coefficient of determination (R² ) of 0.99, which indicated a higher sensitivity for treatment temperature and time during processing.

CONCLUSIONS

The results obtained would allow simplification of processes for easier formulation of quality products from bael fruit pulp. This study has the potential to increase the processing ability of bael fruit, which will encourage a greater production of bael fruits. © 2020 Society of Chemical Industry.

Optimizing Thermal Processing of Broccoli: Model Development, Numerical Simulation, Experimental Validation

Kinetic models describing the thermal inactivation of peroxidase and degradation of broccoli (Brassica Oleracea var. Italica) color were coupled with heat transfer equation (2D conductive heat transfer in cylindrical packed broccoli samples), and their simultaneous numerical simulation followed by experimental validation was carried out. Obtained results revealed that modeling the rate constants of the reactions with log logistic equation provides a better prediction in comparison with the most popular Arrhenius equation. It was observed that processing at temperatures lower than 80 °C is not recommended for processing of broccoli due to its adverse effect on the color of samples and considerable longer process time needed for assuring sufficient inactivation of enzyme at the cold spot. Temperatures above 80 °C were suitable for this purpose because the process time needed for inactivating peroxidase at the cold spot of sample not only affected the green color of samples negatively, but oppositely it resulted in a higher greenness than the original value.

Effect of varying fermentation conditions with ensiling period and inoculum on photosynthetic pigments and phytol content in Italian ryegrass (Lolium multiflorum Lam.) silage

This study aimed to investigate the effect of an ensiling period (Experiment 1) and adding lactic acid bacteria (LAB, Experiment 2) on the changes in carotenoid, chlorophyll, and phytol in ensiled Italian ryegrass (IR, Lolium multiflorum Lam.). In Experiment 1, the IR herbage ensiled into plastic bags was analyzed for the contents of photosynthetic pigments and phytol over a 5-week period. During the ensiling process, the β-carotene content decreased (p < .05), whereas the lutein content did not change. Although the chlorophyll content decreased (p < .05) after ensiling, the phytol content barely changed until week 5. In Experiment 2, IR herbage was ensiled without additive, as a Control, or with LAB for 60 days. The pH was lower (p < .05) and lactic acid content was higher (p < .05) for the LAB silage than for the Control. The chlorophyll content in silage was not affected by the LAB; however, the β-carotene content was higher (p < .05) for the LAB silage than for the Control. Phytol and lutein contents in the herbage did not change after ensiling. These results indicate that phytol and lutein in IR herbage can be preserved well in silage, irrespective of their fermentation condition.

Effect of Moist Cooking Blanching on Colour, Phenolic Metabolites and Glucosinolate Content in Chinese Cabbage (Brassica rapa L. subsp. chinensis)

Non-heading Chinese cabbage (Brassica rapa L. subsp. chinensis) is a widely consumed leafy vegetable by the rural people in South Africa. Traditional blanching methods (5%, 10% or 20% lemon juice solutions in steam, microwave treatments and hot water bath at 95 °C) on the changes of colour properties, phenolic metabolites, glucosinolates and antioxidant properties were investigated in this study. Blanching at 95 °C in 5% lemon juice solution maintained the chlorophyll content, reduced the difference in colour change ∆E, and increased the total phenolic content and the antioxidant activities (ferric reducing-antioxidant power assay (FRAP) and Trolox equivalent antioxidant capacity (TEAC) assay). The highest concentration of kaempferol-dihexoside, kaempferol-sophoroside, kaempferol hexoside, and ferulic acid was noted in samples blanched in 5% lemon juice, at 95 °C. However, concentrations of kaempferol O-sophoroside-O-hexoside was highest in raw leaf samples. Supervised Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA) and the UPLC-MS and chemometric approach showed the acid protocatechuoyl hexose unique marker identified responsible for the separation of the blanching treatments (5% lemon juice at 95° C) and raw leaves. However, other unidentified markers are also responsible for the separation of the two groups (the raw leaves and the hot water moist blanched samples) and these need to be identified. Blanching at 95 °C in 10% lemon solution significantly increased the glucosinolate sinigrin content. Overall blanching at 95 °C in 5% lemon juice solution can be recommended to preserve the functional compounds in Nightshade leaves.

Enhancement of the stability of chlorophyll using chlorophyll-encapsulated polycaprolactone microparticles based on droplet microfluidics

Chlorophyll is a valuable bioactive compound, which is used as a natural food coloring agent and a photosensitizer for photodynamic therapy because of its antioxidant properties, antimutagenic ability, and near-infrared fluorescence. However, chlorophyll is unstable when it comes to retaining its antioxidant activity, when exposed to oxygen, high temperature, or light environments. To enhance the stability of chlorophyll, a polymer encapsulation method was proposed. Polycaprolactone (PCL) was employed to encapsulate the chlorophyll, and the particles size of the composites was controlled through droplet microfluidics. The composites (chlorophyll-encapsulated PCL particles) were characterized through UV-VIS spectrometry, SEM, optical microscopy, and light exposure. The particles were spherical, with diameters adjustable from 68 to 247 μm. Additionally, the chlorophyll-encapsulated PCL particles exhibited considerably prolonged chlorophyll stability. The solid microparticle is more convenient for storage and transportation, and have great potential for application in the food industry.

Recovery of chlorophylls from spent biomass of Arthrospira platensis obtained after extraction of phycobiliproteins

Extraction of chlorophylls has received scant attention or priority over phycobiliproteins from Arthrospira platensis. In fact extraction of chlorophylls from spent biomass (left after extraction of phycobiliproteins which goes as waste or underutilized) on drying, will improve the economics of the overall downstream processing. Ethanol (yield 5.75 mg/g, db), being a food grade solvent, was preferred over acetone and dimethyl sulfoxide in spite of their slightly better yields (5.85 mg/g, db). The best conditions were 100% concentration of ethanol, 1:8 S/L ratio, pH 6, 50 °C temperature and 1 h extraction time. An increase of 125% in yield besides reduction of 83.3% in extraction time (from 6 to 1 h) could be achieved at standardized conditions. Low-Humidity drying was observed to be a possible alternative to freeze drying for drying of spent biomass. Ultrasonication as pre-treatment and ethanol as solvent were found effective for extraction of chlorophylls from dry spent biomass.

Stability of Chlorophyll as Natural Colorant: A Review for Suji (Dracaena angustifolia (Medik.) Roxb.) Leaves’ Case

Suji (Dracaena angustifolia (Medik.) Roxb.) leaves are famous chlorophyll source used as food colorant in Indonesia and other south-east Asian countries. Its chlorophyll has unique characteristics which can degrade through enzymatic and non-enzymatic reactions. This article summarizes traditional application of Suji leaves, the characteristics of Suji leaf chlorophyll, postharvest stability, and several ways to retain its green color. Potential development of Suji leaf extract as food colorant or food ingredients are also discussed.

Change in the color of heat-treated, vacuum-packed broccoli stems and florets during storage: effects of process conditions and modeling by an artificial neural network

BACKGROUND

Vacuum-packed broccoli stems and florets were subjected to heat treatment (60-99 °C) for various time intervals. The activity of peroxidase was measured after processing. Thermally processed samples were then stored at 4 °C for 35 days, and the color of the samples was measured every 7 days. Effects of parameters (heating temperature and duration, storage time) on the color of broccoli were modeled and simulated by an artificial neural network (ANN).

RESULTS

Simulations confirmed that stems were predicted to be more prone to changes than florets. More color loss was observed with longer processing or storage combinations. The simulations also confirmed that higher temperatures during heat processing could retard color changes during storage. For stems treated at 80 °C for short durations, color loss was more predominant than both 65 and 99 °C, probably due to the incomplete inactivation of enzymes besides more tissue damage, with increased enzyme access to the substrate.

CONCLUSION

The greenness of both stems and florets during storage can be better preserved at higher temperatures (99 °C) and short times. The simulation results revealed that the ANN method could be used as an effective tool for predicting and analyzing the color values of heat-treated broccoli. © 2018 Society of Chemical Industry.

Influence of heat and moisture treatment on carotenoids, phenolic content, and antioxidant capacity of orange maize flour

The aim of this work was to study the effect of heat and moisture treatment (HMT) on carotenoids, phenolic content and antioxidant capacity of ground, orange maize. Total carotenoid content (TCC) of untreated sample (53.39 mg/kg) was 2.2 times higher than measured in treated orange maize f (24.61 mg/kg). The rates of degradation with HMT were in the following order: β-carotene > β-cryptoxanthin > zeaxanthin > lutein. There was a significant interaction between longer heating time and higher moisture content on carotenoid degradation (p < .05). Total phenolic content (TPC) in raw sample (1664.74 mg/kg) was two-fold higher than in treated orange maize (827.89 mg/kg). Ferulic acid was the most abundant and stable phenolic acid in raw and treated orange maize. The antioxidant capacity of orange maize was higher in methanol than in butanol extracts. The highest correlation (0.924) was observed between TPC and ABTS+ scavenging capacity of methanol extracts.

Influence of different blanching methods on colour, ascorbic acid and phenolics content of broccoli

Lack of nutrients in cooking water, high energetic costs, high water consumption and recycling are some drawbacks of vegetable blanching. Those disadvantages could be bypassed using microwave blanching. Three blanching methods (microwave, boiling water and steaming) were compared in this study in order to determine their effects on some functional properties of broccoli. In addition, the thermal damage on broccoli colour was evaluated. The effectiveness of each blanching process was performed measuring the lost of peroxidase activity, that results more rapidly in microwaves and steam treatments (50 and 60 s respectively) than in boiling water treatment (120 s). The colour indexes did not allow to discriminate a significant difference among treatments. The increase of treatment time caused a vitamin C decrease in samples blanched by boiling water and steam; this trend was not observed in microwaved samples. The phenols content did not significantly vary depending both on type and on time of treatment.

Regulation of light harvesting in the green alga Chlamydomonas reinhardtii: the C-terminus of LHCSR is the knob of a dimmer switch

Feedback mechanisms that dissipate excess photoexcitations in light-harvesting complexes (LHCs) are necessary to avoid detrimental oxidative stress in most photosynthetic eukaryotes. Here we demonstrate the unique ability of LHCSR, a stress-related LHC from the model organism Chlamydomonas reinhardtii, to sense pH variations, reversibly tuning its conformation from a light-harvesting state to a dissipative one. This conformational change is induced exclusively by the acidification of the environment, and the magnitude of quenching is correlated to the degree of acidification of the environment. We show that this ability to respond to different pH values is missing in the related major LHCII, despite high structural homology. Via mutagenesis and spectroscopic characterization, we show that LHCSR's uniqueness relies on its peculiar C-terminus subdomain, which acts as a sensor of the lumenal pH, able to tune the quenching level of the complex.

Stability of hydroperoxide lyase activity from Amaranthus tricolor (Amaranthus mangostanus L.) leaves: influence of selected additives

BACKGROUND

Hydroperoxide lyase (HPL) has potential value for the flavour additive industry. Currently, the production and application of HPL suffer from stability problems. The objective of this study was to investigate the stabilisation of HPL preparation from Amaranthus tricolor leaves by the addition of selected chemical additives.

RESULTS

Amaranthus tricolor leaves were identified as a particularly rich source of 13-HPL activity. The addition of 100 g L(-1) sucrose and trehalose to microsomal HPL prior to lyophilisation could retain nearly 100% enzymatic activity, compared to only 20% for the lyophilised control. The lyophilised microsomal HPL containing sucrose maintained full activity for even 40 days storage at -20 degrees C. For HPL solution, glycerol was effective for long-term stability at -20 degrees C. Moreover, poyols (sucrose and trehalose) and amino acid (glycine) enhanced the thermostability of HPL, while KCl and polyol mannitol decreased the thermostability of HPL.

CONCLUSION

The flavour-producing enzyme HPL, found in the leaves of Amaranthus tricolor, was stabilised by the addition of chemical additives.

Combined effect of mild heat and acetic acid treatment for inactivating Escherichia coli O157:H7, Listeria monocytogenes and Salmonella typhimurium in an asparagus puree

AIMS

This study was conducted to validate combined heat and acid treatments for inactivating Escherichia coli O157:H7, Listeria monocytogenes and Salmonella typhimurium in an acidified brine containing, or pickled, asparagus model food.

METHODS AND RESULTS

A mixture of three strains of E. coli O157:H7, L. monocytogenes and S. typhimurium were inoculated onto pickled asparagus samples. Combinations of various concentrations of acetic acid [0%, 0.25%, 0.5%, 0.75%, 1%, 1.5% and 2% (v/v)] and various temperatures (40 degrees C, 50 degrees C, 60 degrees C and 75 degrees C) were investigated. Following treatment, asparagus samples were stored at room temperature and enumerated at 0, 0.5, 1, 2 and 3 days. Heat and acetic acid treatments were synergistic. The inhibitory effects of these combined treatments on the tested foodborne pathogens were also effective during storage. Loss of green colour in the pickled asparagus significantly increased with increasing concentrations of acetic acid.

CONCLUSIONS

Using a combination of mild heat and acetic acid treatments can successfully control E. coli O157:H7, L. monocytogenes and S. typhimurium in pickled asparagus, combinations of heat and acid are synergistic and effective treatments can be selected to reduce adverse effect on colour which occur during product storage.

SIGNIFICANCE AND IMPACT OF THE STUDY

Mild heating plus acetic acid treatment are synergistic, so combined treatments can be developed, which would lower the temperature and amount of acetic acid required for minimally processed vegetables while maintaining pathogen control.