*3.2. Ozone Exposure*

Apparatus for the ozone treatment of plant material was fed with ozone generated by a TS 30 (Ozone Solution, Hull, MA, USA) ozone generator, and the ozone concentration was measured by a 106 M UV Ozone Solution detector (Ozone Solution, Hull, MA, USA), with the range of 0–1000 ppm [33]. The plant material was placed into the reactor chamber. Samples (500 g) of the sea buckthorn were exposed to ozone at the concentration of 10 ppm and 100 ppm for 10, 15, and 30 min respectively with the gas flow rate of 4 m<sup>3</sup> h <sup>−</sup><sup>1</sup> at room temperature (20 ◦C). The experiments were conducted in triplicate.

#### *3.3. Determination of the Moisture Content*

The moisture content in the plant material was determined using a SLW 115 SMART moisture analyzer (POL-EKO-APARATURA, Wodzisław Sl ˛aski Poland). The maximal ´ temperature during this procedure was 105 ◦C.

#### *3.4. Measurement of Mechanical Properties*

*Hippophae rhamnoides* L. samples were subjected to the puncture strength test with a pen puncture probe with a diameter of: a~8 mm, b~6 mm, using Zwick/ Roell Z010 machine (Zwick Roell Polska Sp. z o.o. Sp. K., Wrocław, Poland). Measurements of the mechanical properties were conducted at the preliminary power F = 1 N (initial force), and the speed of traverse of the beam load cell V = 0.3 mm·mins−<sup>1</sup> (crosshead return speed). The measurements were conducted in 36 repetitions for each of the analyzed varieties, on the fresh and the ozonated fruit after the first, the fourth, and the seventh day of storage at a temperature of 4 ◦C.

#### *3.5. Content of Bioactive Compounds*

The content of polyphenols in *Hippophae rhamnoides* L. fruit was measured in accordance with the methodology described by Matłok et al. [34] utilizing the Folin–Ciocalteu method. The total ascorbic acid content and the antioxidant activity DPPH were determined according to the methodology described by Oszmia ´nski et al. [35] and Piechowiak et al. [19]. The analysis was performed in three replicates.
