https://doi.org/10.17113/ftb.64.04.26.9425

Article in press

Changes in Physicochemical, Bioactive, Microbiological, and Sensory Properties of Yogurts with Fresh and Dried Grapes During Storage

Fatıma Çelikahmetoğlu^1* and Deren Tahmas-Kahyaoğlu^2*

¹Department of Food Engineering, Institute of Science, Kastamonu University, Orgeneral Atilla Ateş Paşa Street 19, 37150 Central District, Kastamonu, Türkiye

²Department of Food Engineering, Faculty of Engineering and Architecture, Kastamonu University, Orgeneral Atilla Ateş Paşa Street No: 19, 37150 Central District, Kastamonu, Türkiye

Copyright © 2026 This is a Diamond Open Access article published under CC-BY licence. Copyright remains with the authors, who grant third parties the unrestricted right to use, copy, distribute and reproduce the article as long as the original author(s) and source are acknowledged.

Food Technol. Biotechnol. 2026; 64(4).

Article history:

Received: 17 October 2025

Accepted: 2 November 2026

Keywords:

yogurt; grape; sultani; Vitis vinifera; antioxidant activity; functional food

Summary:

Research background. Growing consumer distrust of synthetic antioxidants has heightened the demand for natural alternatives. This study utilizes grapes-a rich natural source of antioxidants-to diversify less commonly consumed dairy products and encourage their consumption. Fresh and dried grapes sourced from Köprübaşı, Manisa, Türkiye were incorporated into the milk used in yogurt production.

Experimental approach. The study evaluated key properties of yogurts supplemented with fresh or dried grapes at concentrations of 6, 8 and 10 %, as well as a plain control yogurt, over a 21-day storage period (analyzed on days 1, 7, 14 and 21). Physicochemical, bioactive, microbiological, and sensory parameters were assessed across all formulations.

Results and conclusions. The incorporation of grapes increased dry matter, ash, titratable acidity, viscosity, mineral content, and bioactive properties, while decreasing fat content, protein levels, and pH. Syneresis increased in fresh grape yogurts but decreased in dried grape formulations. The highest concentrations of Al, Mn, Fe, Zn, Mg, and K were detected in yogurt containing 10 % dried grapes, whereas Na, Ca, and P peaked in the control sample. Antioxidant activity correlated positively with the fruit ratio. During storage, total aerobic mesophilic bacteria counts increased as grape concentrations rose, while lactic acid bacteria counts declined. Yeast and mold were detected exclusively in grape-supplemented samples on day 21 of storage. Coliform bacteria were absent in all treatments. Regarding overall acceptability, the control sample received the highest sensory scores, closely followed by the yogurt containing 8 % dried grapes.

Novelty and scientific contribution. Although fruit-supplemented yogurts are documented in the literature, no prior studies have investigated the combined physicochemical, bioactive, and sensory profile of yogurts formulation with fresh or dried grapes. This study contributes to the literature by adding value to regional grape crops and developing a novel functional dairy product to encourage yogurt consumption.