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    EFFECT OF DIFFERENT DRYING TECHNIQUES ON THE BIOACTIVE, COLOR, ANTIBACTERIAL AND SENSORY FEATURES OF DATE PLUM FRUITS (DIOSPYROS LOTUS L.)
    (2023) Goktas, Hamza
    In this study, the effects of hot air drying (HD), vacuum drying (VD) and freeze drying (FD) processes on total phenolic (TPC) and flavonoid contents (TFC), antioxidant capacity (AC), color and antibacterial properties and sensory evaluation of date plum (DP) fruit were determined. Total phenolic, total flavonoid and antioxidant capacity values of dried and fresh samples were determined as 13.86-7.45 mg GAE/g, 7.17-4.09 mg CE/g and 86.60-54.98%, respectively. The highest inhibition levels against Bacillus cereus (24.50 mm) and Salmonella Typhimurium (24.67 mm), Yersinia enterocolitica (25.75 mm) and Staphylococcus aureus (25.17 mm) were determined for HD and VD, respectively. In terms of sensory evaluation, FD drying was scored similarly to fresh samples (P>0.05). Overall, FD drying could be applied for longer preservation of DP fruits in terms of bioactive properties, color and sensory evaluation.
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    Enrichment of antioxidant activity of ice cream samples with addition of rowanberry (Sorbus aucuparia L.) pulp and production of functional probiotic ice cream with using L. rhamnosus
    (Wiley, 2023) Goktas, Hamza
    Rowanberry fruit is rich in functional compounds, therefore, this work goaled to produce functional probiotic ice cream with addition of rowanberry pulp (2.5%, 5%, 10% and 20%) and Lacticaseibacillus rhamnosus. Using rowanberry pulp and probiotic decreased pH and brightness values of the ice creams and changed between 6.65-5.37 and 96.19-73.46, respectively (P <= 0.05). Consistency values (49.54-13.94 (Pa.s)) of the ice creams decreased with addition of rowanberry pulp and probiotic while hardness values (236.80-494.50 (g)) increased. Antioxidant capacity of ice creams increased with addition of rowanberry pulp (P <= 0.05) and the highest value were determined for D10 sample as 53.08 (%). After 120 days of storage, probiotic viability was higher than 8.24 log CFU g(-1) and survival rate of L. rhamnosus was preserved under in vitro digestion with addition of rowanberry pulp. Finally, sensorial scores showed that 5% rowanberry pulp can be used in the manufacturing of functional probiotic ice cream.
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    Multilocus sequence typing of L. bulgaricus and S. thermophilus strains from Turkish traditional yoghurts and characterisation of their techno-functional roles
    (Korean Society Food Science & Technology-Kosfost, 2024) Dikmen, Hilal; Goktas, Hamza; Demirbas, Fatmanur; Kayacan, Selma; Ispirli, Humeyra; Arici, Muhammet; Turker, Mustafa
    In this study, Streptococcus thermophilus and Lactobacillus bulgaricus strains from traditional Turkish yoghurts were isolated, identified by 16S rRNA sequencing and genotypically 14 S. thermophilus and 6 L. bulgaricus strains were obtained as distinct strains by MLST analysis. Lactic acid production levels of the L. bulgaricus strains were higher than S. thermophilus strains. HPLC analysis showed that EPS monosaccharide composition of the strains mainly consisted of glucose and galactose. In general, all strains were found to be susceptible for antibiotics, except some strains were resistance to gentamicin and kanamycin. Apart from two strains of S. thermophilus, all strains displayed strong auto-aggregation level greater than 95% at 24 h incubation. S. thermophilus strains showed higher cell surface hydrophobicity than L. bulgaricus strains. This study demonstrated the isolation, identification, genotypic discrimination and techno-functional features of wild type yoghurt starter cultures which can potentially find place in industrial applications.
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    Using paprika extract in chocolate spread and white compound chocolate: effects on color stability and bioavailability
    (Springer, 2023) Goktas, Hamza; Baycar, Abdullah; Konar, Nevzat; Yaman, Mustafa; Sagdic, Osman
    White compound chocolate (CC) and chocolate spread (CS) do not contain cocoa solids and thus they have deficiency of antioxidant activity. So, paprika extract (PE) was used to develop the visual and functional features of compound chocolate (CC) and chocolate spread (CS). Color stability of both chocolate samples was investigated for 12 weeks under accelerated shelf-life conditions and using PE significantly increased + a*, C*, and h degrees values of chocolate samples (P < 0.05). Also, at the end of shelf life, Delta E values were determined as > 2.83 and > 3.74 for CC and CS samples, respectively. Using PE in the production of CC and CS samples significantly increased antioxidant activity for pre-and post in vitro digestion, except for post digestion of S025 samples (P < 0.05). General acceptability of the CS samples decreased with increasing of PE ratios, for CC samples it was increased except for C100. The results showed that PE can be used in the production of functional chocolate with high antioxidant activity and as a natural coloring agent.