Juice Color Research Articles

Effect of cold plasma on blueberry juice quality

This work focusses on the effects of cold plasma, a novel, non-thermal technology, on the quality of blueberry juice, such as inactivation of Bacillus, anthocyanins, phenolics, vitamin C, antioxidant activity and color change. Oxygen concentration (0, 0.5% and 1%) of ionized gas was firstly confirmed to be the main factors for CP treatment, besides treatment time (2, 4 and 6 min). The increment of treatment time and oxygen concentration significantly promoted an increasing trend of death for Bacillus. Compared with thermal treatment, the content of phenolics was significantly increased by CP treatment, and also CP treatment could better keep the original color of blueberry juice. In terms of anthocyanin and vitamin C, relatively shorter exposure time to CP was more suggested. In antioxidant tests, increment of oxygen concentration resulted in the increasing trends of antioxidant activity in DPPH and ABTS assays.

Synergistic effect of ohmic heating and UV-C irradiation for inactivation of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes in buffered peptone water and tomato juice

Hurdle technology, in which preservation techniques are combined, has been of interest to scientists aiming to ensure microbiological food safety. We investigated the synergistic effect of UV-C irradiation and ohmic heating on the inactivation of foodborne pathogens. UV-C irradiation and ohmic heating were applied to buffered peptone water and tomato juice inoculated with pathogens simultaneously or sequentially. A synergistic bactericidal effect of the simultaneous treatment was observed against Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes. For example, the reductions (log CFU/ml) in E. coli O157:H7 by UV-C irradiation, ohmic heating and simultaneous treatment in tomato juice were 0.48, 1.84 and 3.83, respectively. Additive effect was observed for cell membrane damage and lipid oxidation values with the simultaneous treatment Therefore, the proposed synergistic bactericidal mechanism by the simultaneous treatment consists of an acceleration of lipid oxidation, which results in an additive effect on cell membrane pore formation. Sequential treatment of UV-C irradiation after ohmic heating showed the least antibacterial effect in buffered peptone water. On the other hand, the reductions levels of all three pathogens in tomato juice were not significantly different between the two treatments regardless of the sequence. The color and lycopene content of tomato juice were not significantly deteriorated by either ohmic heating or the simultaneous treatment. Therefore, the combination treatment of UV-C irradiation and ohmic heating including simultaneous and sequential treatments, and regardless of treatment sequence, can be used as an effective hurdle technology ensuring microbiological safety in juice products.

Effect of thermal, high hydrostatic pressure, and ultraviolet‐C processing on the microbial inactivation, vitamins, chlorophyll, antioxidants, enzyme activity, and color of wheatgrass juice

AbstractThe comparative study determined the fate of vitamin C, chlorophyll, antioxidants, enzymes (polyphenol oxidase [PPO], peroxidase [POD]) and effect on color of wheatgrass juice processed by thermal, high hydrostatic pressure (HHP), or ultraviolet‐C light (254 nm; UV‐C) to inactivate Escherichia coli P36, Listeria innocua ATCC 51742, and Salmonella Typhimurium WG49. A thermal treatment at 75°C for 15 s, HHP at 500 MPa for 60 s, and UV‐C fluence of 69.2 mJ cm−2 was required to achieve the target 5 log CFU reduction of the test bacteria. Thermal treatment resulted in a significant (p < 0.05) loss of enzyme activities (75.3% POD and 40.0% PPO), total phenolic content (TPC; 36.0%), vitamin C (27.4%), chlorophyll (12.4%), and negatively impacted the juice color. UV‐C treatment significantly (p < 0.05) decreased the TPC of the juice and resulted in a 20.0% decrease in PPO activity. In comparison, HHP significantly (p < 0.05) increased the chlorophyll content by 9.0% with negligible impact on the nutritive content, and PPO and POD levels. HHP would be preferentially selected over UV‐C and thermal treatment for wheatgrass juice based on changes induced by processing.Practical applicationsWheatgrass juice is a low‐acid health beverage that is marketed with the claims of high content of chlorophyll, antioxidants (phenolics and vitamin C), and enzymes (polyphenol oxidase and peroxidase) and distributed in frozen state. As a risk prevention control, a pasteurization step is required to achieve a 5 log CFU reduction of relevant pathogens. The study illustrated that HHP is the preferred treatment method for wheatgrass juice based on the negligible impact on product quality parameters and retention of nutritive composition while delivering the required microbial reduction. Although, the current study focused on wheatgrass juice the same equivalent treatments approach can be undertaken with other beverages when selecting the appropriate processing method to retain the raw characteristics of juices.

Application of gas phase surface discharge plasma with a spray reactor for Zygosaccharomyces rouxii LB inactivation in apple juice

Abstract The effects of the gas phase surface discharge plasma system with a spray reactor on yeast in 12, 36, and 60°Brix apple juice were evaluated. Results indicated that the number of Zygosaccharomyces rouxii LB cells in 0.5 L of 12°Brix apple juice was reduced by 5.60 log10 after discharge plasma treatment for 30 min. When the soluble solids content increased from 12 to 60°Brix, yeast inactivation was decreased by 2.55 log10. After treatment, the pH level of the apple juice only slightly increased, and the titratable acidity and concentration of reducing sugars remained unchanged. The total color differences between the plasma-treated and untreated samples in 12, 36, and 60°Brix apple juice were 9.53, 7.97, and 3.86. Meanwhile, the concentrations of alcohols, esters, aldehydes, and ketones—the main components of volatile compounds showed no significant change (p Industrial relevance Inactivation of microorganisms using nonthermal plasma technology can reduce food costs and minimize changes in food products and is therefore an alternative to heat-based technology. The proposed research showed that the gas phase surface discharge plasma treatment with a spray reactor can effectively reduce Zygosaccharomyces rouxii in apple juice. In addition, the effect of plasma treatment on the color and volatile compounds of the apple juice were determined. This study provided a technical support for the application of plasma technology in apple juice processing.

Изучение влияния пектина на изменение вязкости и окраски напитков на основе натуральных красителей в процессе хранения

Production of functional foods containing such functional ingredients as pectin and anthocyanins is particularly important nowadays. The goal of the given research was to study the effect of high esterified pectin obtained from apples at a dosage of 0.3% on the changes of viscosity and color of drinks based on cherry juice and anthocyanin colourant obtained from black carrot, apple juice and sugar color IV during storage in a dark place at 22 ± 3 °C for 180 days. Optical density was measured using spectrophotometric method at a wavelength of 350 to 700 nm. Mass fraction of solid matter was adjusted using sucrose to reach 10.1 ± 0.7 %, pH for drinks based on cherry juice and anthocyanin colourant obtained from black carrot was adjusted to reach 3.0, and for drinks based on apple juice and sugar color IV – to reach 3.5 in the prepared beverages. The author shows that pectin does not have any significant effect on colour retention in drinks based on cherry juice and anthocyanin obtained from black carrot, and that anthocyanin colourant from black carrots is more stable during storage than the colourant that cherry juice contains. The color of the drinks based on apple juice and sugar color IV without pectin remains almost the same during storage. In the visible spectrum region they have a monotonous graph of the change in optical density, and pectin makes a significant contribution to the final color. It is established that for 180 days of storage kinematic viscosity of the beverages with pectin decreased not more than 12%, that indicates a high level of pectin preservation. According to the results of the research, the author makes a conclusion that the use of pectin to preserve the color of beverages with natural colourants is not practical. It makes sense to use pectin in order to give the beverages functional properties, as well as to increase their viscosity and stability.

JUS BUAH BERBASIS BIT MERAH (Beta vulgaris) PENAMBAHAN NANAS SMOOTH CAYENNE (Ananas comosus (L) merr.) SEBAGAI PANGAN FUNGSIONAL BAGI PENDERITA HIPERTENSI

Hypertension is an increase in systolic blood pressure, the height of which depends on the age of the individual affected. Red beet (Beta vulgaris) is one of the vegetables rich in inorganic nitrate, betalain, folic acid, riboflavin and potassium antioxidant compounds. Potassium and folic acid play an important role in the process of regulating blood pressure. The addition of pineapple aims to reduce the smell of the soil in red beets. In addition, pineapple also contains potassium and vitamin C which can help lower blood pressure. The purpose of this study was to determine the organoleptic quality, potassium levels and antioxidant activity of red beet juice (Beta vulgaris) by adding smooth cayenne pineapple (Ananas comosus (L) merr.) To patients with hypertension. This research is a RAL study (Completely Randomized Design) with three levels of treatment, namely the ratio of red bits to pineapple, P1 (100: 37.5), P2 (100: 50) and P3 (100: 62.5). Organoleptic quality analysis descriptively and Kruskal Wallis with Mann Whitney follow-up. Potassium test using the Spectometry test and the antioxidant activity test using DPPH Spectometry and converted to IC50. Chemical quality analysis using One-way ANOVA with Duncan's Multiple Range Test. The results showed that the addition of smooth cayenne pineapple had a significant influence on the quality of organoleptic juices. The panelists' acceptance of organoleptic quality of juice (smell, taste and color) tends to be favored. The level of potassium juice increased by an average of 468-1128 mg/ 100ml, the antioxidant juice activity on average was weak to moderate (166.9-101.4 µg/ml). The best treatment level is P3. Further research is needed on the use of pineapple humps, to increase antioxidant levels, and the addition of pineapple or other types of fruit is needed to increase the acceptability of juice.

Enzymatic polyphenoloxidase inactivation with temperature and ozone in sugarcane variety RB 92579 to produce lower color sugar

Abstract Some sugarcane varieties have high activity of polyphenoloxidase enzyme, impairing the production of lower color sugar. Polyphenoloxidase (PPO) is an enzyme from the oxidoreductases group and it is present in a greater or lesser amount depending on the sugarcane variety, climatic conditions, age, culture treatment, harvest and processing conditions. The presence of this enzyme has great impact in the food industry, as it is the main enzyme involved in the undesirable darkening of fruits and vegetables during processing and storage. It is of great importance for the food industry to study inactivation methods for this enzyme. The aim of this work was to evaluate the effect of ozone gas associated (replacement of the conventional sulphitation process), whose concentrations were 150, 300 and 450 mg/L, at the inactivation temperature of polyphenoloxidase enzyme of sugarcane variety RB 92579 for the production of lower color sugar. Treatment with ozone concentration of 150 mg·L-1 at 105 °C showed direct correlation between juice color reduction and enzyme inactivation, resulting in the production of lower color sugar.

New evidence of anthocyanins reduction in fruit juices on Pt electrode, and separate investigation of their oxidized and reduced forms

The deterioration of colour of juices containing anthocyanins when antioxidant (ascorbic acid) is added, shows that the approach to the improvement of antioxidant properties of juices containing anthocyanins should be re-evaluated. Despite the importance of the characterization of content of reduced forms of anthocyanins in a redox system, there are no data about separate investigations of oxidized and reduced forms of redox substances in fruits and fruit products. In this article, new evidence of separate determination of oxidized and reduced forms of anthocyanins in fruit juices on Pt electrode, has been demonstrated. For the first time, electrochemical parameters and mechanism of reduction conversion of oxidized anthocyanins of fruit juices on Pt electrode have been substantiated. It has been established that redox reactions of anthocyanidins of fruit juices under acidic conditions include the transition of electrons in a single reaction, followed by the disproportionation reaction. The treatment of aronia juice on Pt cathode for 20 min allowed for conversion of 44% of oxidized forms of anthocyanins into reduced forms without deterioration of organoleptic properties. The content of anthocyanins, calculated as the content of cyanidin–galactoside, was 250.3 mg per 100 mL FW of aronia juice, including 76.3 mg of reduced forms. Therefore, the electrochemical method allows for separate determination of anthocyanins in fruit juices. It can be seen that electrochemical reduction on Pt electrode is useful for improving antioxidant properties of anthocyanins in fruit juices.

Storage Temperature Impacts on Anthocyanins Degradation, Color Changes and Haze Development in Juice of "Merlot" and "Ruby" Grapes (Vitis vinifera).

This study evaluated the degradation kinetics of selected anthocyanins and the change in polymeric color, browning index, and haze development of grape juices from “Merlot” and “Ruby” grape cultivars stored at 5, 25, and 35°C for up to 360 days. Five major anthocyanins namely malvidin-3-O-glucoside (M3G), delphinidin-3-O-glucoside (D3G), petunidin-3-O-glucoside (Pt3G), peonidin-3-O-glucoside (Pn3G), and cyanidin-3-O-glucoside (C3G) were identified. Juice from “Merlot” had significantly higher (p < 0.05) content of all individual anthocyanins as compared to “Ruby.” During the long-term storage, total, and individual anthocyanins from both cultivars degraded following first-order reaction kinetics at the rate strongly dependent on temperature. At the end of the storage, noticeably higher loss of anthocyanins (95–99.9%) was observed at 25 and 35°C as compared to storage at 5°C [50–60% (“Merlot”); 74–81% (“Ruby”)]. Considerably lower rate of decay was observed at 5°C (k = 0.01–0.04) as compared to 25 (k = 0.04–0.14) and 35°C (k = 0.05–0.14) storage temperatures. The most temperature sensitive anthocyanin compounds were C3G (Ea = 66.5 kJ/mol) and D3G (Ea = 63.3 kJ/mol). At higher storage temperatures, significant (p < 0.05) and strong negative correlations were observed between anthocyanin concentrations and the levels of haze, polymeric and brown color development during storage. Storing grape juice, at lower temperature conditions could reduce the continuous loss of biologically active anthocyanins as well as the development of haze and brown color.

Quality changes in high hydrostatic pressure and thermal pasteurized grapefruit juice during cold storage.

This study evaluated the effects of high hydrostatic pressure (HHP) and thermal pasteurization (TP) on microbial counts, physicochemical properties, antioxidant characteristics, naringin and naringenin contents, and naringinase activity of grapefruit juice during 21 days cold storage period. Results showed that HHP and TP significantly decreased the total microbial, coliform, and yeast counts. No significant differences between HHP-treated grapefruit juice (600MPa/5min) and untreated fruit juice with respect to physicochemical properties such as total titratable acidity, pH, and total soluble solids was observed after 21 days of storage. Although HHP affected the colour and antioxidant characteristics of grapefruit juice, the extent of effect was significantly lower than that for TP-treated fruit juice. This demonstrated that HHP could better maintain the original flavour and quality of grapefruit juice compared to TP. In addition, 92% naringinase activity was maintained in HHP-600 group on Day 21, which increased the degradation of bitter naringin into non-bitter naringenin during the cold storage of grapefruit juice. In summary, HHP can simultaneously maintain the microbiological safety of grapefruit juice along with its original quality characteristics. HHP can effectively extend the storage period and safety during cold chain transport, and hence highly applicable in the grapefruit juice industry.

A study on processing conditions of fermented acerola juice

This study investigated some key processing steps of fermented acerola juice, including variety, maturity, enzyme treatment, sugar concentration and fermentation and pasteurization conditions. One or two-factor experiments were randomly designed to determine the most suitable processing variables based on the investigated parameters, including the content of vitamin C, sensory quality and physicochemical properties of the resultant juice. The results showed that the Brazil variety (Malpiphia emarginata D.C) had highest vitamin C content (1567.9 mg/100 g), followed by sour variety (Malpiphia glabra L.) (882.9 mg/100 g) and sweet variety (Malpiphia punicifolia L.) (630.4 mg/100 g). However, according to sensory evaluation results, the sour acerola juice after fermentation had the highest overall score, indicating to be the most suitable for processing. The fermented juice of sour acerola variety at 100% maturity had the highest sensory score and vitamin C content compared to other levels of maturity. In order to enhance the clarity of acerola juice, the addition of 0.15% pectinase enzyme (Pectinex ultra SPL, Novozymes) was the most effective compared to 0.05 and 0.1% (w/w) enzyme concentrations. The fermentation at 15oC in 48 hours with 22% sugar concentration and 0.1% commercial yeast (Saf-instant, France) obtained the highest quality fermented juice. The fermented product was pasteurized at 80oC for 10 minutes to stop fermentation process as well as to retain the color and taste of the fermented juice. The good quality of the fermented acerola juice, in terms of physicochemical, sensory and microbiological properties could be maintained for at least 6 months.

Physicochemical, Antioxidant and Microbial Properties of Fresh Black Stem Sugarcane Juice with Addition of Calamansi Juice

This study was designed to determine the physicochemical, antioxidant and microbial properties of fresh sugarcane juice with calamansi juice addition. The sugarcane that was used in the experiments was the black cane variety (Saccharum officinarum). Sugarcane pressed with and without their peel was juiced and added with calamansi juice before analysis was carried out. Standard method was used to analyse physicochemical properties such as pH, total soluble solids, acidity and colour of sugarcane juice. Total phenolic content (TPC), DPPH and FRAP assay were conducted for antioxidant properties. Total plate count and yeast and mould count were carried out for the microbiological analyses. Two way analysis of variance (ANOVA) shows significant (p 0.05) difference shown for pH, acidity and total soluble solids of sugarcane juice pressed with and without peel. Sugarcane juice pressed with peel produced higher antioxidant value compared to sugarcane pressed without peel. However, sugarcane juice pressed without peeled showed a lower microbial count compared to sugarcane juice pressed with peel. The addition of calamansi juice proved to have significant (p<0.05) effect on colour, antioxidant and microbial count of the sugarcane juices.

Effect of thermosonication and thermal treatments on phytochemical stability of barberry juice copigmented with ferulic acid and licorice extract

Abstract This study was designed to compare the effect of thermosonication and thermal treatment on color and anthocyanins stability of natural and copigmented barberry juice during processing and storage. Addition of copigments significantly induced the hyperchromic effect and increased the total phenolic and antioxidant activity of barberry juice. Copigmentation especially at 1:2 M ratio, markedly enhanced the color and anthocyanin stability of barberry juice during processing. Thermal treatment negatively affected the phytochemical compounds, whereas thermosonication especially at low amplitude showed no significant changes. A similar trend in the degradation of anthocyanins and color instability of samples was observed during storage. Copigmentation, especially with licorice extract, considerably increased the half-life of anthocyanins and well preserved pelargonidin 3-glucoside and the color parameters of the juice during storage. The results indicate that licorice extract can be a good alternative to synthetic copigments and the application of thermosonication maintains the effectiveness of copigmentation reaction. Industrial relevance Barberry (Berberis vulgaris) is one of the most important medicinal plants which is mainly cultivated in Iran. Barberry fruits are used in preparing sauces, jellies, candies, marmalades and especially juice drinks. Like other berry fruits, barberry contains high amounts of anthocyanins. Due to the highly instability of these pigments, the preservation of these nutrients during industrial processing and storage of barberry juice is very important. Intermolecular copigmentation of anthocyanins with phenolic compounds, especially with phenolic extract from various plant species, is an efficient method to stabilize these compounds. Moreover, because of the adverse effect of thermal treatment on the copigmentation reaction and the degradation of nutritive compounds of fruit juice, there is a need for non-thermal processing techniques like sonication or high pressure to preserve the nutritional and sensory properties of juices. Therefore, in this study, for the first time, the simultaneous use of thermosonication and copigmentation with ferulic acid and licorice extract on the stability of color and anthocyanins of barberry juice was evaluated. The results of our study revealed that licorice extract due to having various flavonoid compounds such as liquiritin and isoliquiritin can be a good alternative to synthetic copigments. Furthermore, the application of thermosonication in comparison with thermal treatment maintains the effectiveness of copigmentation reaction.

Comparative Diminution of Patulin Content in Apple Juice With Food-Grade Additives Sodium Bicarbonate, Vinegar, Mixture of Sodium Bicarbonate and Vinegar, Citric Acid, Baking Powder, and Ultraviolet Irradiation.

This study aimed to determine an optimal method for patulin (PAT) reduction for application in apple juice production. PAT levels in spiked apple juice (100 μg/L) were measured after treatment with citric acid, sodium bicarbonate, vinegar, mixture of sodium bicarbonate and vinegar, baking powder, and ultraviolet (UV) irradiation. Treatments with sodium bicarbonate and UV irradiation were most effective in reducing PAT; however, UV irradiation reduced the yellowness (b∗) of apple juice. However, sodium bicarbonate treatment affected quality attributes including soluble solids, pH, and color of apple juice. The color and odor of apple juice treated with sodium bicarbonate could be recovered via addition of citric acid. The present results suggest that sodium bicarbonate could be considered an additive in apple juice for PAT reduction.

Effects of glow plasma technology on some bioactive compounds of acerola juice

This work examines the influence of glow plasma technology on vitamins, carotenoids, phenolic content, antioxidant capacity, and color of acerola juice. The effects of nitrogen plasma treatment were observed at different operation conditions: flowrates (from 10 to 20 mL/min) and processing times (5 to 15 min). The study explored the suitability of glow plasma on 40 mL samples, which is considered a large sample of current plasma technology studies. Nitrogen glow plasma increased the content of vitamin A and carotenoids in acerola juice under specific processing conditions. The highest increase of vitamin A and carotenoids was found at gas flow rate of 10 mL/min and 10 min of treatment time. The effect of glow plasma on vitamin C (main vitamin in acerola juice) was not significant, maintaining the retention of vitamin C above 95% under all operating conditions that were studied. The phenolics content reduced by 30% due to reaction with reactive nitrogen species when the juice was treated at the most severe condition (gas flow rate of 20 mL/min and 15 min of treatment time). The antioxidant capacity was little affected by the reactive nitrogen species formed by N2 glow plasma, which remained relatively constant at high plasma flow rate (20 mL/min) but reduced when lower gas flow rates were used (10 mL/min). The typical orange color of the juice improved due to the increase in free carotenoid content. In summary, this study showed that the operating conditions of glow plasma treatment could be adjusted to have a positive influence on vitamin A, carotenoids and color of acerola juice.

Effects of biennial cropping and controlled shoot density on yield performance and fruit quality in red raspberry (Rubus idaeus L.)

ABSTRACTEffects of annual versus biennial cropping with varying shoot densities on plant structure, berry yield and quality were studied in ‘Glen Ample’ raspberry over a period of four seasons (two cropping years). In the vegetative phase, primocane height and internode length were larger in the annual than in the biennial cropping system. These parameters as well as Botrytis infestation increased with increasing shoot density. In both cropping years, berry yields per unit area were about 20% higher in the biennial cropping system, whereas yields per shoot were not significantly different in the two systems. In both cropping systems, yields per shoot strongly declined with increasing shoot density, while yields per metre row increased slightly. Regardless of cropping system, yields per metre row did not increase with increasing shoot density beyond eight shoots per metre. The concentrations of dry matter, soluble solids, titratable acidity and ascorbic acid as well as the intensity of juice colour all declined with increasing shoot density. We conclude that under controlled shoot density conditions, there is little scope for biennial yield increases that fully compensates for the lost crops every second year. However, the system greatly facilitates berry harvest and eases plant disease pressure.

Influence of different pectinolytic enzymes on bioactive compound content, antioxidant potency, colour and turbidity of chokeberry juice

The aim of this study was to investigate the influence of addition of pectinolytic enzymes to chokeberry juice on the content of polyphenolic compounds analysed by UPLC-PDA-FL, antioxidant potency measured by ABTS and FRAP assay, turbidity, precipitation, and sugar composition analysed by HPLC-ELSD and colour parameters determined by the CIEL*a*b* system. UPLC-PDA-FL analysis identified 30 polyphenolic compounds belonging to hydroxycinnamic acids, anthocyanins, flavonones, flavonols, and flavan-3-ols. High content of bioactive compounds, high antioxidant capacity and low values of turbidity and precipitation were obtained in juice with addition of Panzym YELD MASH, Pectinex YELD MASH and Opti EYXL. The colour of chokeberry juice with these enzymes was intensely red, attractive, and without browning before or after storage. These pectinolytic enzymes influenced the stability of parameters such as chemical, physical and bioactive potency in the chokeberry juice after 5 months of storage at 5 °C.

Effect of UV–Vis processing on enzymatic activity and the physicochemical properties of peach juices from different varieties

Abstract This work evaluated the effect of ultraviolet and visible light (UV–Vis) processing on the enzymatic activity (polyphenol oxidase and peroxidase) and physicochemical characteristics (pH, °Brix, acidity, formol index, phenolics, ascorbic acid, sugars and colour) of peach juices from three different varieties (Baby Gold, Calanda and Planet Top). Irradiation was performed for 120 min, at 25 and 45 °C, using a multi-wavelength emission lamp which provided a radiation power of 4.49 · 10−2 W·cm−2 at the liquid surface. After the treatments, no significant changes were observed in the pH value, acidity, vitamin C content, sugar content, or lightness. The phenolic content was reduced for the Planet Top juices, while the formol index decreased for the Calanda variety. a* and b* CIELab parameters decreased with processing time, contrary to that reported for thermal treatments. In most cases, UV–Vis irradiation was effective at inactivating polyphenol oxidase (PPO) and peroxidase (POD), although sometimes an initial activation was observed. The inactivation stage was described by a first-order model. At 45 °C, PPO was almost totally inactivated for the three juices studied, while reductions in POD of up to 60% were registered. Further experiments are suggested to improve the effectiveness of this technology for inactivating enzymes in peach juices.

Degradation kinetics of anthocyanins and polyphenols during storage of red apple juice produced from red-fleshed apples

The aim of this study was to determine the stability of various anthocyanins in red-coloured apple juice for the development of a new attractive beverage. Red-coloured apple juice was generated from red-fleshed apples of cultivar “Maggy” to analyse the composition of anthocyanins and the effect of storage at various temperatures. Cyanidin-3-galactoside (cy-3-gal) was identified as the main component of the anthocyanin profile, next to 5-carboxypyranocyanidin-3-hexoside, tentatively carboxypyranocyanidin-3-galactoside, and two cyanidin-3-pentosides. In addition, we found cyanidin-3-glucoside, another 5-carboxypyranocyanidin-3-hexoside, probably 5-carboxypyranocyanidin-3-glucoside, one 5-carboxypyranocyanidin-3-pentoside, two unknown anthocyanins, and another cyanidin-3-pentoside. The loss of anthocyanins during storage can be described as a first-order reaction as it is the case also for other red-coloured fruit juices. The T1/2 value of cyanidin-3-galactoside varied between 53 and 84 days after storage at 4 °C, and between 15 and 13 days at 20 °C. Storage at 37 °C reduced the T1/2 values from 7 to 6 days. A much longer half-life was observed for 5-carboxypyranocyanidin-3-galactoside. The T1/2 values at 4 °C were 250–315 days and 50–112 days at 20 °C. At 37 °C, T1/2 decreased from 23 to 25 days. The antioxidant capacity (TEAC) was constant during storage for at least 1 year. The colour of red apple juice, however, is less stable than in aronia, black currant and red grape juices, for example. Taken together, red apple juice, generated of the cultivar “Maggy”, is an attractive new fruit juice, but other cultivars of red-fleshed apples with higher anthocyanin concentrations would achieve a more colour-intense product.

Influence of different sterilization treatments on the color and anthocyanin contents of mulberry juice during refrigerated storage

Abstract The color stability of mulberry juice is affected during its processing and storage. This study investigates changes in the color of mulberry juice processed by four different sterilization treatments during 30 days of storage at 4 °C: high pressure processing (HPP at 400 MPa/5 min, 400 MPa/10 min, 500 MPa/5 min, and 500 MPa/10 min), thermal processing (TP at 70 °C/10 min, and 75 °C/10 min), high temperature short time (HTST), and membrane filtration (MF). After 30 days of storage, the retention rates of total anthocyanin, cyanidin-3-glucoside and cyanidin-3-rutinoside in juice samples treated by different sterilization methods were found to be significantly higher than those of the control group. Among these treatments, the retention rates of total anthocyanin, cyanidin-3-glucoside and cyanidin-3-rutinoside were highest in HPP (400 MPa/5 min) at 84.70%, 80.20% and 98.61%, respectively. Both TP (70 °C/10 min) and HTST treatments also showed significantly higher anthocyanin retention rates, at 83.19% and 84.27%, respectively. These results indicate that HPP (400 MPa/5 min), TP (70 °C/10 min) and HTST treatments are most suitable for the sterilization of mulberry juice. Industrial relevance The distinct color of mulberry juice is one of the foremost qualities that imprints on consumers' senses, but it is extremely unstable in processing and storage. However, the color protection of mulberry juice was not studied previously. In this study, the protective effects of different sterilization treatments on the color-preservation and anthocyanin contents of mulberry juice were investigated for the first time. We found that the high-pressure processing treatment (HPP, 400 MPa/5 min) had the most powerful color-preserving effect. The study is of great significance as a guide to improving the color stability of mulberry juice, thereby also improving and promoting the development of the mulberry deep processing industry.