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    Activity and bioaccessibility of antioxidants in yoghurt enriched with black mulberry as affected by fermentation and stage of fruit addition
    (Elsevier Sci Ltd, 2021) Durmus, Nihal; Capanoglu, Esra; Kilic-Akyilmaz, Meral
    Pasteurised whole milk was acidified with bacterial culture or glucono-delta-lactone (GDL) to determine effects of fermentation and pH reduction on activity and in vitro bioaccessibility of antioxidants and physical properties of yoghurt with black mulberry. Both pH reduction and fermentation were found to influence activity and bioaccessibility of antioxidants in mulberry yoghurt. Total phenolic content of the sample prepared with bacterial culture was higher than that of the sample with GDL, while there was a similar level of reduction in both samples after three weeks of storage at 4 degrees C. Fermentation with the bacterial culture yielded lower copper reducing activity but higher DPPH scavenging activity compared with acidification with GDL. Bioaccessibility of the antioxidants in in vitro gastrointestinal system was less than 25% in all samples. Addition of fruit after acidification or fermentation of milk, rather than before, resulted in higher antioxidant activity, higher consistency coefficient and less serum separation. (C) 2021 Elsevier Ltd. All rights reserved.
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    Bioactivity of non-extractable phenolics from lemon peel obtained by enzyme and ultrasound assisted extractions
    (Elsevier, 2023) Durmus, Nihal; Kilic-Akyilmaz, Meral
    Lemon peel waste constitutes a natural resource for bioactive phenolics with antioxidant, antihypertensive and antidiabetic activities. Bioactivities of non-extractable phenolics from lemon peel obtained by conventional heat-, enzyme-, ultrasound-, and ultrasound-enzyme-assisted extractions were evaluated in comparison with those of extractable phenolics. The antioxidant, angiotensin-I-converting enzyme (ACE), and alpha-amylase inhibitory ac-tivities and phenolic profile of the phenolic fractions were analysed. While the extractable fraction had higher total phenolic content, ascorbic acid content, and antioxidant activity, phenolic profile analysis indicated that the non-extractable fraction contained higher concentrations of phenolics especially hesperidin and hesperetin. The concentrations of hesperidin and hesperetin in the non-extractable fraction were 270.9 mg/100 g dry weight and 415.9 mg/100 g dry weight, respectively, which were about two-fold higher than those present in the extractable fraction. Moreover, ACE and alpha-amylase inhibitory activities of non-extractable fraction were stronger than those of the extractable fraction. Total phenolic content, total flavonoid content, and antioxidant activity were increased by enzyme and ultrasound treatments compared to those by conventional heat treatment. However, ACE inhibitory activities of all non-extractable fractions were similar while alpha-amylase inhibitory activity was higher in ultrasound-and ultrasound-enzyme-treated fractions. While ultrasound-assisted extraction slightly improved the yield of non-extractable phenolics, enzyme-assisted extraction yielded two-to four-fold increases in the amounts of phenolic compounds compared to heat-assisted extraction. Non-extractable phenolic fraction from lemon peel was found to have a significant potential as an antihypertensive and antidiabetic agent.