# Chemical Characterization of Cider Produced in Hardanger--From Juice to Finished Cider
## 2 Materials and Methods
### HPLC-UV/RI Analysis of Sugars, Acids, Ethanol, as Well as Titratable Acidity  
Chemicals for high-performance liquid chromatography (HPLC) coupled to ultraviolet (UV)/refractive index (RI) analysis: glucose (99%) (Acros Organics, Fair Lawn, NJ, USA), \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Producer** & **Variety** & **Year** & \
\begin{tabular}{c} **Sample Type** \\ **(juice-J, cider-C)** \\ \end{tabular} & **Production System and Production Volume (Litre of Cider)** \\ \hline Producer 1 & Summerred & 2019 & J and C & Hydropress, steel tank, production volume per year 10,000 L \\ \hline Producer 2 & Discovery & 2019 & J and C & Steel tank, added yeast, production volume per year 5000 L \\  & Gravenstein & 2019 & J and C & Steel tank, added yeast, production volume per year 5000 L \\  & Aroma & 2021 & C & \\ \hline Producer 3 & Summerred & 2019 & J and C & \\  & Gravenstein & 2019 & J & Belt press, steel tank, added yeast, production volume per year 2019 \\  & Aroma & 2019 & J and C & year 7000 L \\  & Aroma & 2021 & C & \\ \hline Producer 4 & Discovery & 2019 & J and C & \\  & Aroma & 2021 & J and C & \\  & Gravenstein/ciderapple & 2019 & J and C & Belt press, steel tank, spontaneous fermentation, production volume per year 12,000 L \\  & Gravenstein/Signe Tillisch & 2019 & J and C & \\  & Gul Gravenstein & 2021 & J and C & \\ \hline Producer 5 & Gravenstein/Elstar & 2021 & J and C &
\begin{tabular}{c} Belt press, steel tank, spontaneous fermentation, \\ centrifugation, production volume per year 150,000 L \\ \end{tabular} \\ \hline Producer 6 & Aroma & 2020 & J and C & \\  & Summerred & 2021 & J and C & Belt press, steel tank, added yeast and yeast nutrition, \\  & Discovery & 2021 & J and C & production volume per year 150,000 L \\  & Gravenstein & 2021 & J and C & \\  & Rubinstep & 2021 & J and C & \\ \hline Producer 7 & Aroma & 2020 & J and C & Pack cider press, steel tank with floating lid, spontaneous \\  & Gravenstein & 2020 & J and C & fermentation, production volume per year 4000 L \\ \hline Producer 8 & Summerred & 2020 & J and C & Belt press, steel tank, added yeast and nutrition, production \\  & Rubinstep & 2021 & J & volume per year 130,000 L \\ \hline Producer 10 & Gravenstein & 2020 & J & Belt press, steel tank, added yeast, production volume per year 60,000 L \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Overview of the 10 producers from Hardanger (Norway) and samples. fructose (99%) (Acros Organics, Fair Lawn, NJ, USA), sucrose (99.9%) (Acros Organics, NJ, USA), tartaric acid (Alfa Aesar, Karlsruhe, Germany), lactic acid (30%) (Sigma, Steinheim, Germany), D-L malic acid (99%) (Sigma-Aldrich, Steinheim, Germany), and citric acid (99.9%) (Sigma, Steinheim, Germany) as standards. Concentrated sulfuric acid (VI) was purchased from VWR Chemicals (Leuven, Belgium). HPLC-UV/RI analysis was performed using an Agilent 1100 series HPLC system (Agilent Technologies(r), Palo Alto, CA, USA) equipped with Agilent OpenLab CDS ChemStation 2.3.54 software, a UV detector (G1314A VWD) for the analysis of organic acids (detection at 210 nm) and a refractive index detector (model G7162A) for the analysis of sugars (fructose, glucose, and sucrose) and ethanol. Samples were filtered using polytetrafluoroethylene (PTFE) 0.45 \(\upmu\)m syringe filters (VWR(r) International, Radnor, PA, USA). The organic acids were determined using a reversed-phase HPLC-UV method [4]. Glucose, fructose, and sucrose determination was performed using the HPLC method based on hydrophilic interaction liquid chromatography [4], while the assessment of ethanol was performed on a Phenomenex ROA Organic Acid H\({}^{+}\) (8%) column with a size of 300 \(\times\) 7.8 mm with detailed method description published elsewhere [9]. All HPLC quantifications were performed with external calibration in the range of the expected values for the juice and cider samples [4].