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.

Clarification of pomegranate and strawberry juices: Effects of various clarification agents on turbidity, anthocyanins, colour, phenolics and antioxidant activity.

Effects of clarification on turbidity, anthocyanins (ACNs), colour, phenolics, ascorbic acid and antioxidant activity (AA) of pomegranate (PJ) and strawberry juices (SJ) were investigated. Cold-clarification was applied to PJ using only gelatine. For hot-clarification of both juices, bentonite, gelatine and kieselsol were used. Moreover, pectolytic enzyme was added to SJ that contains pectin. Depectinization caused an increase in colour density of SJ and bentonite treatment resulted in low turbidity (9.5 NTU). However, gelatine and kieselsol significantly reduced ACN content (15%) and increased turbidity (70.1 NTU). In PJ, no step during hot-clarification provided low turbidity (93.2-162.0 NTU), while relatively low turbidity (28.7 NTU) and anthocyanin loss (9.8%) was achieved during cold-clarification. Hot-clarification of SJ showed no effect on AA and phenolics, while cold-clarification of PJ reduced both to a limited extent. Therefore, depectinization and bentonite treatment are recommended for hot-clarification of SJ and gelatine for cold-clarification of PJ.

Increase in thermal stability of strawberry anthocyanins with amino acid copigmentation.

Copigmentation effects of aspartic acid, proline and valine on individual anthocyanins in strawberry juice (SJ) were investigated during heating at 90, 105 and 150 °C. Aspartic acid increased (4.5-45.6%) total anthocyanin stability at all temperatures, while proline and valine had no effect at 90 °C but reduced (2.2-19.4%) stability at 150 °C. At 90 °C, aspartic acid and valine caused the highest Amax. Evaluating changes in individual anthocyanin contents, Amax, colour density and polymeric colour of SJs together revealed that aspartic acid had copigmentation effects on pelargonidin-3-glucoside and pelargonidin-3-rutinoside, whereas valine on pelargonidin-3-glucoside and cyanidin-3-glucoside. At 105 °C, all amino acids increased (7.9-33.1%) stabilities of pelargonidin-3-glucoside, pelargonidin-3-rutinoside, Amax and colour density all of which together pointed out the copigmentation. At 150 °C, interactions between "aspartic acid-pelargonidin-3-glucoside," "proline-pelargonidin-3-rutinoside" and "valine-pelargonidin-3-rutinoside" resulted in high colour density. Thus, among these amino acids, selection should be based on the heating temperature and anthocyanin profile of the product.

Effects of fermentation time and pH on quality of black carrot juice fermented by kefir culture during storage.

BACKGROUND: The effects of fermentation time (17-48 h) and pH (3.37-4.50) on qualities of fermented beverages (FBs) produced from black carrot juice (BCJ) were monitored during storage at 4 °C for 20 weeks. RESULTS: Fermentation and adjusting the pH level provided significant increases (up to 22%) in anthocyanin content and the absorbance value at λmax (Amax ). Moreover, the stability of anthocyanins, color density, and Amax in FBs was somewhat higher than those in BCJ. Lactic acid showed a co-pigmentation effect on cyanidin-3-galactoside-xyloside-glucoside-sinapic acid and cyanidin-3-galactoside-xyloside-glucoside-ferulic acid. Sucrose was degraded much faster at pH 4.50 (17 h) and 4.35 (48 h) than at lower pH levels. During storage, pH 4.35 caused a balanced distribution between counts of lactic acid bacteria (LAB) and yeasts, and antioxidant activity of all FBs increased. Fermented beverages at 4.35 and 3.90 were found to be more palatable by panelists. CONCLUSION: We recommend FB production at pH 4.35 after 48 h fermentation due to the balanced distribution of probiotics, high color enhancement, and consumer preference. © 2021 Society of Chemical Industry.

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 â„ƒ. Effect of amino acids on colour and anthocyanin stability varied depending on heating temperature. At 90 â„ƒ (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 â„ƒ (2 h), AA and valine caused the highest absorbance value at maximum wavelength (Amax) and high anthocyanin stability, which pointed out copigmentation. At 150 â„ƒ (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 Amax. 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 pasteurization and storage on turbidity and copigmentation in pomegranate juices clarified with various hydrocolloid combinations.

Success of clarification treatment in pomegranate juice is related to prevention of after-bottling haze formation and high anthocyanin content after pasteurization and during storage. Therefore, this study was conducted to achieve these targets with hydrocolloid [albumin (A), casein (C), chitosan (CH) and xanthan gum (XG)] combinations. While C, "A + XG" and "A + C" resulted in the greatest clarity after pasteurization, "A + C" and "A + C + CH" were associated with the greatest clarity during storage. In comparison with "A + C + CH" (k = 0.053 week-1), "A + C" (k = 0.065 week-1) was associated with more rapid improvement in clarity (23%). Greater clarity of "A + C" was associated with reductions in contents of punicalagins (r = -0.963), gallic (r = -0.936), chlorogenic (r = -0.995) and ellagic (r = -0.989) acids. However, "A + C + CH" clarity was associated with fewer proteins. Since copigmentation occurred between anthocyanins and phenolics, "A + C" enhanced colour density stability better (1.1 times) than "A + C + CH." Therefore, "A + C" is recommended producing pomegranate juice with high clarity and colour density after pasteurization and during storage.

Changes in the quality of kefir fortified with anthocyanin-rich juices during storage.

Changes in sensorial, chemical and microbiological qualities of kefirs fortified with black carrot (KBCJ), black mulberry (KBMJ), pomegranate (KPJ), and strawberry (KSJ) juices at different concentrations (10, 25 and 50%, w/w) were monitored throughout storage at 4 °C for 12 weeks. The most preferred kefirs by the sensorial panel were KSJ and KPJ, followed by KBMJ and KBCJ. KBMJ was associated with the highest anthocyanin stability, followed by KPJ, KSJ, and KBCJ. Lactic acid [r = (-0.688)-(-0.970)], glucose [r = (-0.563)-(-0.793)] and microorganisms [r = (-0.633)-(-0.961)] in kefirs had significant effect on anthocyanin stability and colour (p < 0.05). Copigmentation between lactic acid and anthocyanins were observed. Fortification with 25% juices led to an increase (1.8-4.8 times) in antioxidant activity (AA). Shelf-lives of samples, except for KPJ, ended after 12 weeks of storage, due to low sensorial scores. Additions of SJ, PJ and BMJ at 25% concentration are recommended for the production of more palatable kefir with high AA.

Color and stability of anthocyanins in strawberry nectars containing various co-pigment sources and sweeteners.

Effects of various co-pigment sources [gallic acid (GA) and the extracts of rose leaf (RLE), cherry stem (CSE), pomegranate rind (PRE) and sour cherry stem (SCSE)] on anthocyanins and colour in strawberry nectars (SNs), sweetened with sucrose (SNS), maltose syrup (SNM) and honey (SNH), were investigated during storage at 20 °C. Honey elicited the highest stabilities of anthocyanins, hyperchromic and bathochromic effects in SNs containing all co-pigment sources, except for PRE. PRE co-pigments were composed of mainly tannins which could interact with SNs proteins and honey proline. As a result of these interactions, PRE co-pigments could not show significant contribution to protection of SN anthocyanins and colour. Among co-pigment sources, SCSE caused the highest stabilities of anthocyanins, hyperchromic effect and colour density, regardless of sweetener used. Interactions between SCSE phenolic acids, and pelargonidin-3-glucoside and pelargonidin-3-rutinoside resulted in the most stable co-pigmentation effect. Thus, SCSE should be preferred in beverages containing pelargonidin-based anthocyanins.

Effects of natural copigment sources in combination with sweeteners on the stability of anthocyanins in sour cherry nectars.

Effects of various co-pigment sources [gallic acid (GA), rose leaf extract (RLE), cherry stem extract (CSE), pomegranate rind extract (PRE) and green tea extract (GTE)] on anthocyanin content, colour, and turbidity in sour cherry nectar (SCN), sweetened with sucrose (SCNS), maltose syrup (SCNM) or honey (SCNH), were investigated during storage at 20 °C. Co-pigment sources were associated with increases in λmax (up to 4.1 nm), colour density (up to 22%), and polymeric colour (up to 1.7 times). Among the co-pigment sources, GA and PRE were associated with the greater anthocyanin stabilities in SCNS and SCNH. Moreover, the lowest turbidity, at the beginning of storage, and turbidity formation rate, throughout storage, were observed in SCNS, SCNM and SCNH containing PRE. When the changes in Amax, λmax, polymeric colour, colour density, and turbidity were considered together, PRE was the best co-pigment source, regardless of the sweetener used.

Effects of sucrose and copigment sources on the major anthocyanins isolated from sour cherries.

Cyanidin-3-O-glucosylrutinoside and cyanidin-3-O-rutinoside were isolated from sour cherry juice concentrate (SCJC). Sucrose and copigments [gallic acid (GA), cherry stem extract (CSE) and pomegranate rind extract (PRE)] were added to these anthocyanins. Effects of sucrose and copigments on the isolated anthocyanins were studied during storage at 20 °C for 140 days. All copigment sources provided protection against degradation effect of sucrose on the isolated anthocyanins before storage. Although GA increased the stabilities of both isolated anthocyanins, only CSE had copigmentation effect on both isolated anthocyanins. Copigmentation effect on cyanidin-3-O-glucosylrutinoside continued throughout storage. However, this effect on cyanidin-3-O-rutinoside continued for only 56 days of storage. Cyanidin-3-O-glucosylrutinoside containing three sugar moieties was more prone to copigmentation than cyanidine-3-rutinoside containing two sugar moieties. Results showed that the presence of more than one anthocyanin in a media changed stability of copigmentation. We recommend CSE for enhancement in colour density, but GA for enhancement in anthocyanin stability.

Effect of sweeteners on anthocyanin stability and colour properties of sour cherry and strawberry nectars during storage.

Effects of various sweeteners (sucrose, maltose syrup and honey) on individual anthocyanins, colour and turbidity in sour cherry (SCN) and strawberry nectars (SN) were investigated during 168 and 42 days of storage at 20 °C, respectively. In SCN, major anthocyanin was cyanidin-3-glucosylrutinoside (cyd-3-glu-rut), followed by cyanidin-3-rutinoside (cyd-3-rut), cyanidin-3-glucoside (cyd-3-glu) and cyanidin-3-sophoroside (cyd-3-soph). Maltose syrup increased stabilities of cyd-3-glu-rut (8%) and cyd-3-rut (4%), while honey reduced stabilities of all anthocyanins in SCN. Due to higher anthocyanin stability, maltose syrup for SCN was recommended. In SN, the major anthocyanin was pelargonidin-3-glucoside (pg-3-glu), followed by pelargonidin-3-rutinoside (pg-3-rut) and cyd-3-glu. Stabilities of anthocyanins (46-51%) and colour density (6-7%) in SN sweetened with honey were higher than that sweetened with sucrose and maltose syrup. Considering maximum wavelength (λmax), absorbance value at λmax (Amax), polymeric colour and colour density values together, copigmentation of anthocyanins occurred in SN sweetened with honey. This study is the first study showing copigmentation of anthocyanins with honey.

Effect of SO2 on sugars, indicators of Maillard reaction, and browning in dried apricots during storage.

BACKGROUND: The effect of sulfur dioxide (SO2 ) concentration was determined on sugars and indicators in the Maillard reaction (MR), and on browning, in sulfured, dried apricots (SDAs) during storage at 4, 20 and 30 °C for 379 days. RESULTS: As SO2 concentration increased, the content of reducing sugars involved in the MR also increased. The preventive effect of SO2 on the MR could not result from the binding of SO2 to reducing sugars. Before storage, furosine was detected in the non-SDAs but 5-hydroxymethylfurfural (HMF) was not detected. Even the lowest SO2 concentration (451 mg kg-1 ) was sufficient to prevent the formation of furosine and HMF during drying of apricots. CONCLUSION: Formation of furosine and HMF in all samples during storage at 20 and 30 °C for 379 days indicated that SO2 could not prevent the first and intermediate stages of MR in SDAs during storage. Thus, the main prevention effect of SO2 on browning in SDAs occurred during drying, not storage. © 2018 Society of Chemical Industry.

Changes in polyphenol profile of dried apricots containing SO2 at various concentrations during storage.

BACKGROUND: Changes in polyphenols have important effects on the quality (especially color) and health benefits of dried apricots. SO2 concentration, storage and the activities of polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) were factors which had significant effects on polyphenols. Polyphenol profile and activities of PPO and PAL in sulfured dried apricots (SDAs, 0, 451, 832, 2112 and 3241 mg SO2 kg-1 ) were monitored during storage at 4, 20 and 30 °C for 379 days for the first time. RESULTS: Even the lowest SO2 concentration (451 mg kg-1 ) was sufficient to inactivate PPO during the entire storage period. However, while SO2 led to the increase in PAL activity of the samples (r = 0.767) before storage, PAL activities of SDAs decreased during storage. After 90 days of storage, PAL activity was determined in only non-sulfured dried apricots (NSDAs) and dried apricots containing 451 mg SO2 kg-1 . Although the major polyphenol in NSDAs was epicatechin (611.4 mg kg-1 ), that in SDAs was chlorogenic acid (455-1508 mg kg-1 ), followed by epicatechin (0-426.8 mg kg-1 ), rutin (148.9-477.3 mg kg-1 ), ferulic acid (23.3-55.3 mg kg-1 ) and gallic acid (2.4-43.6 mg kg-1 ). After storage at 30 °C for 379 days, the major polyphenol in SDAs was gallic acid (706-2324 mg kg-1 ). However, the major polyphenol in NSDAs did not change after storage. The highest total polyphenol content was detected in SDAs containing 2112 mg SO2 kg-1 and stored at 30 °C. CONCLUSION: To produce dried apricots having high polyphenol content, ∼2000 mg SO2 kg-1 should be used. Low storage temperature (<30 °C) was not necessary for the protection of polyphenols. © 2017 Society of Chemical Industry.

Effects of sulfur dioxide concentration on organic acids and ß-carotene in dried apricots during storage.

The effects of various sulfur dioxide (SO2) concentrations (0, 451, 832, 1594, 2112 and 3241mg/kg) on the profiles and contents of organic acids (OAs) and ß-carotene in sulfured dried apricots (SDAs) were investigated during storage at 4, 20 and 30°C for 379days. In all samples, four OAs [malic acid (MA), citric acid (CA), succinic acid (SA) and oxalic acid (OXA)] were identified. SA (13.9-31.8g/kgdw) was the major OA in SDAs containing SO2 at lower than 1594mgSO2/kg, while MA (11.7-11.7g/kgdw) was the major OA in SDAs containing SO2 at higher than 1594mgSO2/kg. As SO2 concentration increased, CA and OXA contents increased whereas MA contents decreased. Moreover, the highest stabilities of ß-carotene, MA and SO2 were determined in SDAs containing 1594mgSO2/kg at 4°C. Therefore, we suggest using 1594mgSO2/kg and storing SDAs at 4°C to protect OAs and ß-carotene.

Colour stabilities of sour cherry juice concentrates enhanced with gallic acid and various plant extracts during storage.

Gallic acid (GA) and pomegranate rind extract (PRE), cherry stem extract (CSE) and green tea extract (GTE) were added to sour cherry juice concentrates (SCJCs) to enhance the colour. Effects of these copigment sources on anthocyanins, colour and turbidity were investigated during storage at -20, 4 and 20°C for 110 days. Cyanidin-3-glucosylrutinoside (cyd-3-glu-rut, 75%) was the major anthocyanin, followed by cyanidin-3-rutinoside (cyd-3-rut, 23%) and cyanidin-3-sophoroside (cyd-3-soph, 2%). While GA (37-53%), PRE (27-77%) and GTE (44-119%) increased the stabilities of cyd-3-rut and cyd-3-glu-rut, CSE reduced (12-24%) the stabilities of all anthocyanins. Polymeric colour and turbidity values increased after the addition of all extracts and GA. The lowest turbidity value after 110 days of storage at 20°C was determined in the SCJC enhanced with PRE. We recommend the addition of PRE to SCJC for the enhancement of anthocyanin stability and colour intensity, and the reduction in turbidity.

Effects of various protein- and polysaccharide-based clarification agents on antioxidative compounds and colour of pomegranate juice.

The effects of natural sedimentation and clarification agents [protein-based (albumin, casein and gelatin) and polysaccharide-based (chitosan and xanthan gum)] on total phenolics, hydrolysable tannins, anthocyanins and antioxidant activity of pomegranate juice were investigated. While protein-based agents led to higher reductions in the contents of total phenolics (7.2-17.2%), hydrolysable tannins (16.7-59.5%) and anthocyanins (11.7-23.7%) (p<0.05) than natural sedimentation, polysaccharide-based agents had similar effects on these compounds, like natural sedimentation (p>0.05). The stabilities of ß-punicalagin and α-punicalagin (the major hydrolysable tannins) against clarification were similar. Moreover, antioxidant activities of the samples clarified with polysaccharide-based agents were higher (2.4-26.6%) than those of the protein-based agents. For both high total phenolic, hydrolysable tannin and anthocyanins contents, as well as high antioxidant activity, we suggest that polysaccharide-based agents be used for the clarification of pomegranate juice. In fact, chitosan is especially recommended for this purpose since chitosan (10.3NTU) led to lower turbidity as compared to xanthan gum (20.0 NTU).

Effects of different sorbic acid and moisture levels on chemical and microbial qualities of sun-dried apricots during storage.

Effects of different sorbic acid (SA) (0, 488-530 and 982-1087 mg/kg) and moisture [intermediate (271-278 g/kg) and high (341-344 g/kg)] levels on the chemical and microbiological qualities of sun-dried apricots during storage at different temperatures (4, 10, 20 and 30 °C) for 10 months were evaluated. Moisture content and SA concentration showed significant effect on brown colour formation, ß-carotene oxidation and microbial load (p < 0.05). As moisture content increased, brown colour formation decreased. Moreover, SA oxidation protected ß-carotene from oxidation. Although no microbial spoilage was observed in the samples with intermediate moisture content, control group with high moisture was spoiled by yeast and mould in 1-3 months of storage at all temperatures studied; 488 mg SA/kg was sufficient to prevent the spoilage. Regardless of moisture content, 500 mg SA/kg was found to be effective for the prevention of brown colour formation and inhibition of microbial growth.

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

This study was conducted to determine the effects of condensed tannins (CT) on anthocyanins (ACNs) and colour of pomegranate juice (PJ) samples obtained from nine registered varieties in Turkey. CT-catechins (CTCs) reactive to vanillin and phloroglucinol adducts of CT contents were determined. CTC and ACN contents of PJs highly depended on variety (p<0.01), and ranged from 31 to 155 mg/L juice and from 47 to 405 mg/L juice, respectively. As catechin-phloroglucinol content increased, ACN content also increased (r=0.866). Strong logarithmic correlation between the ratio of ACN contents to catechin-phloroglucinol contents and polymeric colour (PC) values of the samples was found (r=-0.822). When PC value of PJs was ⩾8% or ratio of ACN contents to catechin-phloroglucinol contents of PJs was ⩽2.82, ACN contents of the samples determined by spectrophotometric method were higher than those determined by HPLC.

Loss of sulfur dioxide and changes in some chemical properties of Malatya apricots (Prunus armeniaca L.) during sulfuring and drying.

BACKGROUND: This study was conducted to determine the differences in some analytical properties of four apricot cultivars and to determine the changes in these analytical properties during sulfuring and sun-drying. RESULTS: There were significant differences in the contents of polyphenols, carotenoids and organic acids (OA) as well as antioxidant activities (AOAs) of the cultivars (P < 0.05). After sulfuring and drying, considerable reductions were detected in the contents of total polyphenols (TPCs, 11-26%), OAs (4-32%) and ß-carotene (6-21%), and AOAs (2-21%) of the samples. Sun-drying resulted in 71-83% decreases in sulfur dioxide (SO2 ) contents of sulfured-dried apricots (SDAs) in comparison with apricots immediately after sulfuring. As the TPCs increased, the SO2 absorption by the samples also increased. In contrast, the OA contents had no effect on SO2 absorption, but an increase in OA content resulted in an increase in the browning values of the SDAs. As expected, increases in contents of ferulic acid (r = 0.932), chlorogenic acid (r = 0.850), epicatechin (r = 0.804) and quercetin (r = 0.750) led to an increase in browning values of the SDAs. CONCLUSION: There were significant effects of cultivar and processing on the physico-chemical properties investigated in the study, and with the absorption of SO2 and the formation of a brown colour in the samples.

Effects of various sulphuring methods and storage temperatures on the physical and chemical quality of dried apricots.

The effects of different sulphuring methods, i.e. sulphuring by "burning the elemental sulphites (BES)," "SO2 gas from liquified SO2 tank (SG)" and "dipping into sodium metabisulphite solution (DSM)" on the colour (brown colour formation and carotenoid degradation) and the loss of SO2 in apricots from Hacihaliloglu and Kabaasi varieties stored at 5, 20 and 30 °C for a year were investigated. There were significant effects of variety, sulphuring method and especially storage at 30 °C on the brown colour formation and loss of SO2 (P<0.05). As storage temperature-time increased, ß-carotene content decreased. Sulphuring methods and variety did not show significant effect on ß-carotene content (P>0.05). The changes in L(*), b(*) and C(*) values were directly associated with ß-carotene content and browning values. The most suitable method for all samples, except for Hacihaliloglu variety stored at 30 °C (BES), is SG, because the samples retained their attractive golden yellow colour during storage.