Yazar "Ozkan, Mehmet" seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • [ X ]
    Öğe
    Degradation kinetics of bioactive compounds and antioxidant activity in strawberry juice concentrate stored at high and low temperatures
    (Springer, 2020) Menevseoglu, Ahmed; Diblan, Sevgin; Turkyilmaz, Meltem; Ozkan, Mehmet
    In this study, changes in ascorbic acid (AA), phenolics, anthocyanins (ACNs) and antioxidant activity (AOA) were monitored during storage at - 25, 4, 10 and 20 degrees C to observe the stability of bioactive compound in strawberry juice concentrates (SJCs). Half-life periods (t(1/2)) for ACN and AA degradations were 7.9 and 50 days at 20 degrees C, respectively. On the contrary, much higher t(1/2)values were found for the reduction in AOA and phenolics, i.e. 251 and 430 days at 20 degrees C, respectively. AOA and phenolics were more stable during storage than AA and ACNs.p-Coumaric acid was the major phenolic identified in SJC.p-coumaric acid (33.8%), catechin (23.1%), vanilic acid (18.6%) and epicatechin (16.1%), which constituted 91.6% of phenolics in SJC, followed by chlorogenic acid (4.9%) and caffeic acid (3.2%). Chlorogenic acid was the least stable phenolic in SJC stored at 20 degrees C. Strong correlations were found between AOA and ACNs (r = 0.99), phenolics (r = 0.94) and AA (r = 0.92) in SJC stored at 20 degrees C. Significant ACN and AA degradations occurred at storage temperature as low as 4 degrees C. Therefore, storage at - 25 celcius was suggested for SJC to maximize the stabilities of especially ACNs and AA in SJC.
  • [ X ]
    Öğe
    Effects of various clarification treatments on anthocyanins, color, phenolics and antioxidant activity of red grape juice
    (Elsevier Sci Ltd, 2021) Diblan, Sevgin; Ozkan, Mehmet
    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 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.