This study evaluated the effects of controlled heat treatment on the glycemic index (eGI), bile acid-binding capacity (BABC), total phenolics, antioxidant activity, and in vitro bioaccessibility of whole grain buckwheat (Fagopyrum esculentum), rye (Secale cereale L.), and oats (Avena sativa). Cereals were subjected to thermal processing at three temperatures (120, 150, and 180 °C) for 30 min. The eGI values increased in rye and oat following heat treatment but decreased in buckwheat at 150 and 180 °C. Thermal processing significantly affected BABC in all cereals (p ≤ 0.05), with the highest values observed at 180 °C for oats (6.56 µmol/g), buckwheat (6.65 µmol/g), and rye (5.77 µmol/g). The total phenolic content (TPC) increased with heat treatment. The highest TPC values were recorded at 180 °C for rye (9.33 mg GAE/g dw), 120 °C for buckwheat (15.39 mg GAE/g dw), and 150 °C for oats (10.04 mg GAE/g dw). Antioxidant capacities, measured using DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) assays, were enhanced in buckwheat and oats after thermal processing, while a significant decrease was observed in rye. The in vitro bioaccessibility of TPC significantly improved during the gastric phase for all samples except oat, with buckwheat showing the highest increase (86.56% at 180 °C). Oats maintained the highest bioaccessibility index (BI) for total antioxidant capacity (TAC) across all treatments, while rye peaked at 444.09% TAC during the intestinal phase at 120 °C. These findings underscore the influence of thermal processing on the functional and nutritional properties of these cereals, with notable variations based on their unique compositions. Overall, these findings demonstrate that controlled heat treatment can enhance the nutraceutical value and bioaccessibility of phenolics in whole grains, providing a promising strategy for developing minimally processed, functional cereal-based products with cardiometabolic and digestive health benefits. Graphical Abstract

Bu çalışmada en az işlem uygulanarak doğala en yakın şekilde üretilen tam tahıl çerezinin, pratik kahvaltıya bir alternatif olma potansiyeli araştırılmıştır. Bu kapsamda üretilen tam tahıl çerezi ile piyasadan temin edilen tam tahıllı kahvaltılık gevreğinin besinsel ve duyusal özellikleri karşılaştırılmıştır. Yulaf, çavdar ve karabuğdaydan oluşan tam tahıl çerezi; yulaf ve çavdar 180 °C’de 17 dakika ve karabuğday taneleri ise 180 °C’de 10 dakika kavrularak elde edilmiştir. Her iki örnekte besinsel özellikleri belirlemek için genel bileşim analizleri yapılmıştır. Duyusal özelliklerini belirlemek için tam tahıllı kahvaltılık gevrek ile tam tahıl çerezinde duyusal analiz yapılmıştır. Besinsel analiz sonuçlarına göre tam tahıl çerezinin, tam tahıllı kahvaltılık gevreğe göre besinsel açıdan daha zengin bir alternatif olduğu görülmüştür. Özellikle tam tahıl çerezinin, klasik tam tahıllı kahvaltılık gevreğe göre daha yüksek toplam diyet lifi içeriğine sahip olduğu belirlenmiştir. Duyusal açıdan ise dış görünüş, renk, çıtırlık ve tat parametrelerinden gevreğe göre daha düşük puan almış olsa da, doyuruculuk ve genel beğeni parametrelerinden istatistiksel açıdan kahvaltılık gevrekle aynı puanı almıştır. Elde edilen bu sonuçlara göre kahvaltıya bir alternatif olabileceği gibi, yeni geliştirilmiş tam tahıl çerezinin diyetetik bir ara öğün olarak rahatlıkla kullanılabileceğini göstermiştir.

This study characterized the pattern and timing of post-cooking quality deterioration in durum wheat held at 25, 35, and 45 °C by performing physicochemical, microbiological, and volatile compound analyses combined with a sensorially defined off-odor onset endpoint. The bulk moisture content remained high throughout holding at all temperatures. Titratable acidity increased from 1.49 to 2.15, and pH at off-odor onset decreased from 6.63 to 6.49 with increasing temperature. Off-odor was detected after 50, 45, and 34 h at 25, 35, and 45 °C, respectively. Microbial growth was fastest at 35 °C (μ_max = 0.0651 h⁻¹). Thiobarbituric acid reactive substances (TBARS) values were slightly lower at 45 °C than at 25 °C, despite the shorter holding duration, whereas lipid oxidation-derived volatile aldehydes declined more sharply over the same comparison. This pattern, together with the earliest off-odor onset occurring at 45 °C, suggests that non-lipid-derived volatiles increasingly drive off-odor perception as holding temperature increases. Gas chromatography–mass spectrometry (GC–MS)-based relative odor activity value (ROAV) analysis identified 2-methoxy-4-vinylphenol, 2,4-decadienal, 2-nonenal, 2,3-butanedione, nonanal and 2-methoxyphenol as the principal contributors to the aroma profile. These findings indicate that off-odor development during post-cooking holding results from a temperature-dependent interplay between microbial and chemical deterioration pathways and provide a basis for optimizing holding time and temperature to delay off-odor onset and limit quality losses in bulgur production.