Effects of storage on the oxidative stability of acorn oils extracted from three different Quercus species.

BACKGROUND: Acorn fruit and its components and by-products are receiving renewed interest due to their nutritional and phytochemical features. In particular, the oil extracted from acorns is recognized for having high nutritional quality and for being rich in bioactive compounds. Despite the growing interest, few papers are available that consider the evolution of acorn-oil characteristics during storage. Our aim was to investigate the storage-related changes in acorn oils extracted from three Quercus species grown in Algeria (Q. ilex, Q. suber, and Q. coccifera) 180 days after production, with a focus on polar and volatile compounds, not yet investigated. Basic quality parameters, phenolic content, antioxidant activity and induction time were also monitored. RESULTS: The oxidation markers (peroxide value and UV absorptions) increased during storage, whereas antioxidants decreased. A distinctive volatile profile was observed at the time of production, which underwent changes during storage. Polar compounds increased, whereas induction time decreased. The oil extracted from Quercus suber L. was the most affected by storage time. CONCLUSION: Floral and fruity volatile compounds detected in the oils' headspace could explain the pleasant flavor of acorn oils reported by other authors. As with other vegetable oils, storage depletes both volatiles and antioxidants and produces oxidation compounds, such as oxidized triacylglycerols. However, the acorn oils that were studied were quite stable under storage in the dark at room temperature for 6 months. © 2020 Society of Chemical Industry.

Effect of acorn flour on the physico-chemical and sensory properties of biscuits.

The aim of the work was to explore the feasibility of using acorn flour as a novel and healthy ingredient in biscuits. The physico-chemical characteristics of acorn flour obtained from three different Quercus species were compared. Acorns of Quercus coccifera L. were the most antioxidant and were therefore used for preparing biscuits at two levels of addition, 30 and 60 g 100 g-1 on wheat flour basis. The physico-chemical and sensory characteristics of the obtained biscuits were then assessed. Acorn-added biscuits showed significantly (p < 0.05) higher content of phenolics, antioxidant activity and oxidative stability than control biscuits, prepared without acorn flour. These features improved as the level of acorn flour increased. As for appearance, the acorn-added biscuits were darker, larger, more voluminous and more friable than control biscuits. Higher levels of fermentative alcohols and esters, as well as Maillard reaction volatile compounds (particularly furans), were observed in the acorn-added biscuits.

Antioxidant activity, tocopherols and polyphenols of acornoil obtained from Quercus species grown in Algeria.

Among the unusual vegetable fats, acorn oil has interesting nutritional and functional properties. Few studies are present in literature on acorn oil characterization and antioxidant activity evaluation while no studies are present regarding the analysis of the phenolic profile. The present study aims at investigating the content of hydrophilic and lipophilic phenolic compounds and pigments, as well as antioxidant properties and quality of the oil extracted from three Quercus species grown in Algeria. Oil yield, expressed as dry weight, was in the range 7.05-8.40%. Tocopherols contents were remarkable for the three species (539-676 mg kg-1), with (ß + γ)-tocopherols being the most abundant. Oils had also significant amounts of carotenoids (42-66 mg kg-1) and similar polyphenol patterns, but with a wide quantitative variability between species (195-436 mg kg-1). Twenty phenolic compounds were detected, 12 of which were tentatively identified. All of them were hydrolysable tannins derivatives (gallotannin or ellagitannin). Oils methanolic extracts had remarkable antioxidant activity; up to 3.34 and 3.79 µmol TE g-1 oil (DPPH and ABTS test, respectively). Quercus oil is a potential source of natural antioxidants, and it could be used as a new functional oil.