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.

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 pressing programs and yields on the antioxidant activity, antimicrobial activity, phenolic content and colour of pomegranate juices.

Pomegranate juice (PJ) samples were produced with three different pressing programs: (1) 1.2-4.8 bar for 25 min, (2) 1.2-2.4 bar for 15 min and (3) 1.2-1.8 bar for 5.5 min. Respective juice yields were 39.2%, 33.2% and 27.2%. Effects of pressing pressure-time and yield on total phenolic (TP) content, condensed tannin (CT) content, monomeric anthocyanin (MA) content, antioxidant activity (AOA) and antimicrobial activity (AMA) of the samples were determined. Strong positive linear correlations were found between the pressing pressure with AOA (r=0.973) and TP content (r=0.979), while negative logarithmic correlations were found between pressing pressure with the contents of CT (r=-0.778) and MA (r=-0.955). Among 12 microorganisms tested, Bacillus megaterium, Bacillus subtilis, Staphyloccocus aureus and Pseudomonas sp. were found to be sensitive to juice samples. However, increasing pressing pressure and yield did not lead to a significant change on the AMAs of the juices.