Effects of condensed tannins on anthocyanins and colour of authentic pomegranate (Punica granatum L.) juices

Effects of juicing methods on the bioactive compounds and flavor quality of 'Black-seed' pomegranate from three producing areas

BACKGROUND

Color, nutrients and flavor are the key characteristics of pomegranate juice, but they are susceptible to processing methods and raw materials. In this study, the effects of aril juicing and whole fruit juicing methods on the composition of 'Black-seed' pomegranate juice from three producing areas were studied, including physicochemical parameters, color attributes, organic acids, sugars, phenolic compounds, and volatile compounds.

RESULTS

The whole fruit juicing method resulted in higher juice yields of pomegranate fruit with 69.01-72.59%, hue angle values were 5.95-6.45°, and the juice remained red. The highest level of citric acid (21.21 g L-1 ), total acids (24.78 g L-1 ), and total anthocyanin content (435.59 mg L-1 ) were found in whole fruit juice, and seven tannins were detected. The most abundant volatile compounds were (Z)-3-hexen-1-ol and 1-hexanol in all juice samples, with alcohol content increased and aldehydes content decreased by whole fruit juicing. Principal component analysis revealed that the 24 indexes (variable important in projection >1) clearly distinguished juice samples obtained by two juicing methods, with ellagic acid hexoside, (E)-2-heptenal, (+)-catechin, and octanoic acid having the best discriminatory potential.

CONCLUSION

Overall, the effects of juicing method on 'Black-seed' pomegranate juice were greater than those of raw-material-producing areas. These results confirmed the potential for using the whole 'Black-seed' pomegranate for processing, and also provided a theoretical basis for the healthy product development and utilization of dark-color pomegranate varieties. © 2023 Society of Chemical Industry.

Increase in colour stability of pomegranate juice against 5-hydroxymethylfurfural (HMF) through copigmentation with phenolic acids

BACKGROUND

Anthocyanins are responsible for both attractive colour of pomegranate juice (PJ) and its health-promoting effects against cancer and coronary heart disease. However, 5-hydroxymethylfurfural (HMF) at some concentrations causes anthocyanin degradation. The present study aimed to reduce the degradation of PJ anthocyanins as a result of HMF at various concentrations (0-20 mg L-1 ) through phenolic acid [PA; ferulic (FA), gallic (GA) and caffeic acids (CA)] copigmentation during storage at 20 °C.

RESULTS

A strong correlation (r = 0.872) was found between anthocyanin degradation rate and HMF concentration in PJ without PA addition. An increase in HMF concentration during storage caused faster (< 32%) anthocyanin degradation. However, PA addition reduced (< 60 times) the HMF formation rate. The lowest HMF formation rates (0.07-0.28 day-1 ) were determined in PJ with added GA. Although GA caused an important increase in content of cyanidin-3-glucoside (16-42%), which is major PJ anthocyanin, against HMF at all concentrations, CA (15%) and FA (28%) increased cyanidin-3-glucoside content against 10 mg of HMF L-1 . FA maintained its protection effect against the highest HMF concentration (20 mg of HMF L-1 ), but CA lost its protection effect. Generally, FA increased stabilities of hyperchromic effect (HE) (9.6-27.7%) and colour density (CD) (57.1-74.3%) at all HMF concentrations, although CA increased HE stability (19.8-37.7%) in the presence of 10 and 20 mg of HMF L-1 . Interactions of 'all individual anthocyanins-FA' and 'delphinidin-based anthocyanins-GA/CA' resulted in copigmentation.

CONCLUSION

FA addition was recommended to increase CD and HE for PJ containing HMF between 3.1-5.6 mg L-1 , whereas the addition of GA was recommended to increase anthocyanin stability for PJ containing 12.0 mg of HMF L-1 . © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Dietary polyglycosylated anthocyanins, the smart option? A comprehensive review on their health benefits and technological applications

Over the years, anthocyanins have emerged as one of the most enthralling groups of natural phenolic compounds and more than 700 distinct structures have already been identified, illustrating the exceptional variety spread in nature. The interest raised around anthocyanins goes way beyond their visually appealing colors and their acknowledged structural and biological properties have fueled intensive research toward their application in different contexts. However, the high susceptibility of monoglycosylated anthocyanins to degradation under certain external conditions might compromise their application. In that regard, polyglycosylated anthocyanins (PGA) might offer an alternative to overcome this issue, owing to their peculiar structure and consequent less predisposition to degradation. The most recent scientific and technological findings concerning PGA and their food sources are thoroughly described and discussed in this comprehensive review. Different issues, including their physical-chemical characteristics, consumption, bioavailability, and biological relevance in the context of different pathologies, are covered in detail, along with the most relevant prospective technological applications. Due to their complex structure and acyl groups, most of the PGA exhibit an overall higher stability than the monoglycosylated ones. Their versatility allows them to act in a wide range of pathologies, either by acting directly in molecular pathways or by modulating the disease environment attributing an added value to their food sources. Their recent usage for technological applications has also been particularly successful in different industry fields including food and smart packaging or in solar energy production systems. Altogether, this review aims to put into perspective the current state and future research on PGA and their food sources.

Coloration mechanisms of fresh sugarcane juice: Investigating the critical components and enzyme activity

The color of sugarcane juice has a great influence on the preferences of consumers. The contents of pigments, sugars, free amino acids, organic acids, phenolic compounds, enzyme activities, antioxidant activities, and color differences among juices produced from four sugarcane varieties were investigated in this study. The data suggested that variety played an important role in the color and chemicophysical properties of sugarcane juice. The color of four varieties of sugarcane juice varied from greenish yellow to light brown. Bamboo cane juice and black rind sugarcane juice presented similar color properties and both had high contents of phenolic compounds and strong antioxidant activities. Yellow rind sugarcane juice with higher value of L* (26.10) and more pigment contents than the other varieties was attractive. Sucrose, glucose, β-alanine, chlorogenic acid, p-hydroxybenzoic acid, isochlorogenic acid, DPPH, and polyphenol oxidase activity had positive correlations with a* value. The effects of organic acids on color were limited. PRACTICAL APPLICATION: This study demonstrated the relationships between color parameters and contents of pigments, sugars, free amino acids, organic acids, phenolics, enzyme activities, and antioxidant activities of sugarcane juice. This could help to find out the coloration mechanisms of sugarcane juice. Our manuscript created a paradigm for future studies on color control during juice processing and storage.

Analysis of coloration characteristics of Tunisian soft-seed pomegranate arils based on transcriptome and metabolome

In this study, combining metabolome and transcriptome, color related attributes and phenolic compositions of Tunisian pomegranate arils from 7 Chinese regions at same developing stage were studied. The total anthocyanin (TAC), flavonoids, and percent polymeric color (PPC) were ranged at 8.93-28.41 mg/100 g arils, 37.55-69.72 mg/100 g arils, and 3.38-21.96%, respectively. In total, 51 phenolic compounds were characterized, most of which were markedly higher in reddish-purple pomegranate arils than those levels in reddish pomegranate arils. In contrast, the accumulation of tannins was significantly higher in reddish pomegranate arils. Among the 49 differentially expressed genes, 8 and 5 genes were matched to β-glucosidase and peroxidase, respectively. Correlation analysis showed that PPC was negatively correlated with 10 phenolic metabolites and TAC, positively correlated with L*, polymeric color, and 1 gene (|r| > 0.7, p < 0.01). Our results provide new insights for understanding the difference in coloration of pomegranate arils.

Influence of amino acid addition on the thermal stability of anthocyanins in pomegranate (Punica granatum L., cv. Hicaznar) and orange (Citrus sinensis L. Osbeck, cv. Valencia) juice blend

This is the first study revealing effects of aspartic acid (AA), proline and valine as well as ascorbic acid on individual anthocyanins in pomegranate and orange juice blend (POJB) during heating at 90-150 ℃. Effect of amino acids on colour and anthocyanin stability varied depending on heating temperature. At 90 ℃ (3 h), AA, proline and valine increased (up to 4.7 times) contents of cyanidin-3-glucoside and total anthocyanin, and cyanidin-3,5-diglucoside stability. At 105 ℃ (2 h), AA and valine caused the highest absorbance value at maximum wavelength (A_max) and high anthocyanin stability, which pointed out copigmentation. At 150 ℃ (0.5 h), AA and valine increased (up to 11%) stabilities of cyanidin-3-glucoside, cyanidin-3,5-diglucoside and delphinidin-3,5-diglucoside, and caused the highest A_max. Owing to copigmentation by hydrophobic interactions/hydrogen bond, degradative effect of ascorbic acid on anthocyanins was slowed down. Thus, these three amino acids might have a high potential for copigmentation in products containing anthocyanins and ascorbic acid at high concentration.

Effects of various clarification treatments on anthocyanins, color, phenolics and antioxidant activity of red grape juice

Low turbidity and low discolouration is targeted in clear red grape juice (RGJ) production. Depending on type of clarification agents, substantial discolouration may occur. Therefore, this study was undertaken to show effects of various clarification treatments (bentonite and chitosan, and combinations of "bentonite + gelatin (B + G)," "bentonite + casein (B + CA)," "bentonite + albumin (B + A)" and "bentonite + chitosan (B + CTS)" on turbidity, color (ACNs, color density-CD and polymeric color-PC), phenolics and antioxidant activity (AOA) during RGJ clarification. Casein alone (4.0 NTU and 9.1% ACN loss) and in combination with bentonite (4.4 NTU and 12.3% ACN loss), followed by B + A (5.7 NTU and 12.3% ACN loss) resulted in best clarity and was associated with least change in ACNs. These clarifications also resulted in high CD (intensive red color) and low PC (low browning). At all dosages, gelatin and albumin were associated with highest ACN losses, while casein in greatest retention. "Bentonite + casein," followed by "bentonite + albumin," achieved the best clarification of RGJ.

Recovery of Bioactive Compounds from Pomegranate (Punica granatum L.) Peel Using Pressurized Liquid Extraction

Pressurized liquid extraction (PLE) is a clean and environmentally friendly alternative for the recovery of bioactive compounds from fruit by-products. Herein we focused on PLE for the extraction of bioactive compounds from pomegranate peel using a combination of pressurized water and ethanol. The main aim was to determine the optimal PLE conditions, i.e., ethanol percentage and process temperature, to obtain a pomegranate peel extract (PPE) with maximum total phenolic content (TPC), punicalagin content, and antimicrobial activity (AMA). The experimental design was conducted using a central composite design with axial points. Response surface methodology was applied to optimize the response variables using the desirability function. Multiple response optimization indicated a process temperature of 200 °C and ethanol of 77% as optimal conditions. The TPC and the punicalagin content of PPE-PLE obtained under optimal conditions were 164.3 ± 10.7 mg GAE/g DW and 17 ± 3.6 mg/g DW, respectively. Our findings support the efficacy of PLE on TPC recovery but not in punicalagin recovery. The AMA against S. aureus was 14 mm. The efficacy of PPE-PLE in food applications must continue to be studied in order to achieve adequate information on its potential for developing new food additives.

Anthocyanins, Vibrant Color Pigments, and Their Role in Skin Cancer Prevention

Until today, numerous studies evaluated the topic of anthocyanins and various types of cancer, regarding the anthocyanins' preventative and inhibitory effects, underlying molecular mechanisms, and such. However, there is no targeted review available regarding the anticarcinogenic effects of dietary anthocyanins on skin cancers. If diagnosed at the early stages, the survival rate of skin cancer is quite high. Nevertheless, the metastatic form has a short prognosis. In fact, the incidence of melanoma skin cancer, the type with high mortality, has increased exponentially over the last 30 years, causing the majority of skin cancer deaths. Malignant melanoma is considered a highly destructive type of skin cancer due to its particular capacity to grow and spread faster than any other type of cancers. Plants, in general, have been used in disease treatment for a long time, and medicinal plants are commonly a part of anticancer drugs on the market. Accordingly, this work primarily aims to emphasize the most recent improvements on the anticarcinogenic effects of anthocyanins from different plant sources, with an in-depth emphasis on melanoma skin cancer. We also briefly summarized the anthocyanin chemistry, their rich dietary sources in flowers, fruits, and vegetables, as well as their associated potential health benefits. Additionally, the importance of anthocyanins in topical applications such as their use in cosmetics is also given.

Pomegranate Fruit and Juice (cv. Mollar), Rich in Ellagitannins and Anthocyanins, Also Provide a Significant Content of a Wide Range of Proanthocyanidins

Proanthocyanidins (PAs) were characterized in husk, membranes, arils, and seeds of 'Mollar de Elche' pomegranate cultivar using liquid chromatography-electrospray ionization-ion-trap tandem mass spectrometry after acid catalysis in the presence of phloroglucinol (phloroglucinolysis). PAs were also evaluated in commercial juice and in the juice made in the laboratory by pressing fresh arils. Pomegranate PAs were composed of a very rich mixture of flavan-3-ols: catechin, epicatechin, gallocatechin, epigallocatechin, epigallocatechin gallate, and epicatechin gallate. Catechins and gallocatechins were the most abundant units, while galloylated flavanols were detected at lower concentrations. The highest PA content was found in husk (1840.5 μg/g), followed by seeds (316.2 μg/g) and membranes (51.4 μg/g). With regard to the pomegranate edible parts, arils showed concentrations of 34.4 μg/g and pressed aril juice of 21.3 mg/L, lower than those found in other traditional PA-containing food and beverages, such as apple, grapes, chocolate, red wine, or tea. Higher concentrations similar to those found in red wine were observed in commercial whole fruit pressed pomegranate juice (146.9 mg/L). These PA concentrations represented between 0.1 and 7% of the total polyphenol content in the different pomegranate samples, which were richer in ellagitannins and anthocyanins. The mean degree of polymerization (1.2-2.1) revealed that PAs in Mollar pomegranate samples are constituted mainly of monomers and dimers, which may influence in better absorption and bioavailability of these compounds.

A Critical Overview of Labeling Information of Pomegranate Juice-Based Drinks: Phytochemicals Content and Health Claims

Punicalagin is responsible for over 50% of the antioxidant activity of pomegranate, but ellagic acid (EA) and total polyphenol content (TPC) are also key parameters regarding pomegranate bioactivity. Many juices and other drinks based on pomegranate take advantage from the widespread healthy image of this fruit, whereas their real content of bioactive phytochemicals is low. For that reason, the objective of this study was to compare the labelling information with the real phytochemical contents (TPC, punicalagin [Pn] [isomers α, β], and EA). Titratable acidity (TA), color density (CD), polymeric color (PC), and sensory profiles (trained panel) were assessed. The experimental ranges of TPC and Pn contents were 2.75 to 70.9 mg/g and traces to 3.18 mg/g, respectively. The percentage of pomegranate juice was highly correlated with the intensity of the pomegranate ID attribute (R = 0.85; p < 0.001), Pn content (R = 0.71; p < 0.001), and EA content (R = 0.36; p < 0.001). The experimental results showed a high variability in the content of bioactive compounds and the need to urge food companies to optimize processes and storage conditions. Although no health claim for pomegranate has been authorized so far at the European Union, significant mismatches among labelling and bioactive compounds content are misleading consumers. PRACTICAL APPLICATION: Pomegranate juice and nectar producers need to evaluate the real content of bioactive Pn, EA, and TPC in their products to optimize formulation, heat treatment, packaging and storage conditions to guarantee high levels of bioactive compounds during shelf life. Producers' organizations may benefit from harmonizing Pom products labelling, so they may fulfill consumer expectations and may be ready if health claims are finally authorized for these products. The development of a new sensory quality marker will be an interesting option.

Influence of deficit irrigation and crop load on the yield and fruit quality in Wonderful and Mollar de Elche pomegranates

BACKGROUND

The working hypothesis of the present study was that, by proper simultaneous control of irrigation (hydroSOStainable products) and crop load (thinning), it is possible to promote the accumulation of bioactive compounds and improve fruit appearance (size and weight). The effects of (i) irrigation status [T0, 120% ETc (estimated crop evapotranspiration); T1, 60% ETc during fruit growth and ripening] and (ii) crop load (A0, no thinning; A1, thinning) on yield and fruit quality were evaluated in two pomegranate cultivars (Wonderful, Wond and Mollar de Elche, ME).

RESULTS

Thinning was effective in increasing the size and weight of fruits. Unfortunately, neither punicalagin, nor total polyphenolic content were positively affected by irrigation and thinning. T1A1 Wond fruits were characterized by high sugar content (glucose and fructose), together with high fruit size and weight. Furthermore, T1A1 ME fruits were characterized by high contents of alcohols and monoterpenoids (providing vegetal and citric flavor notes) and key sensory attributes (color, fruity and fresh pomegranate).

CONCLUSION

The final recommendation was to use the treatment T1A1 [simultaneous combination of deficit irrigation during fruit growth and ripening (T1) and thinning (A1)], although the positive results were cultivar-dependent. © 2017 Society of Chemical Industry.

Influence of Tannin Extract and Yeast Extract on Color Preservation and Anthocyanin Content of Mulberry Wine

The color of mulberry wine is extremely unstable in processing and aging. This paper investigates the effects of tannin extract and yeast extract on the color and color-preserving characteristics of mulberry wine made from the Dashi cultivar. The results showed that the maximum absorption wavelength in both tannin extract and yeast extract groups changed generating the red shift effect. The color of the tannin extract maintained a good gloss in the first 4 months, while the yeast extract group showed remarkable color preservation for the first 3 months. The total anthocyanin and cyanidin-3-rutinoside contents in both experiment groups were significantly higher than that of the control group, thus proving that tannin extract and yeast extract both exert a remarkably positive effect on preserving the color of mulberry wine during its aging. Moreover, sensory analysis indicated that the quality of mulberry wine treated with tannin extract was significantly higher than that of the control.

PRACTICAL APPLICATION

The distinct color of mulberry wine is one of the foremost qualities that imprints on consumers' senses, but it is extremely unstable in processing and aging. However, the color protection of mulberry wine was not studied previously. In this study, we found that tannin extract and yeast extract both exert a remarkably positive effect on preserving the color of mulberry wine during aging. The study is of great significance as a guide to improving the color stability of mulberry wine, thereby also improving and promoting the development of the mulberry deep processing industry.

Gallic acid as a protective antioxidant against anthocyanin degradation and color loss in vitamin-C fortified cranberry juice

The objective of this study was to evaluate different antioxidants for anthocyanin (ACY) retention in vitamin C fortified cranberry juice and assess its quality. Cranberry juice was fortified with 40-80mg/100mL vitamin C and added hesperidin, catechin, and gallic acid at different concentrations. Juice was pasteurized at 85°C for 1min and stored at 23°C for 16days. ACYs, vitamin C, color intensity, and browning index (BI) were evaluated at 2-day intervals. Gallic acid was found to be the most effective antioxidant against ACYs degradation and significantly (p<0.05) increased red color intensity by 37% and ACY concentration by 41%, compared to the control. After 16-day storage, the BI of gallic acid-added juice was significantly lower (0.80 vs 1.00) than the control juice. The outcome of this research provided a potential solution of using gallic acid to preserve a health-beneficial component (ACYs), and endogenous red color in cranberry juice.