## 2 Materials and Methods
### Method for Index Determination  
2.4.1. Total Soluble Solids (TSS)  
The PAL-BX/ACID2 sugar acidity meter was used to measure TSS in 20 \(\upmu\)L samples. Each sample was tested in triplicate, and the average value was recorded.  
2.4.2. Titratable Acidity (TA)  
A 20 \(\upmu\)L sample was extracted, diluted to 1000 \(\upmu\)L, and measured using the PAL-BX/ACID2 sugar acidity meter (Atago Co., Ltd., Tokyo, Japan). Each sample was tested in triplicate, and the average value was recorded.  
2.4.3. TSS/TA Ratio  
The TSS/TA ratio was calculated as the ratio of total soluble solids to TA.  
2.4.4. Turbidity  
Turbidity was measured using a WZS-188 turbidimeter (Wuhan Huaxing, Wuhan, China). Each sample was tested in triplicate, and the average value was recorded.  
2.4.5. Microbiological Indicator Detection  
The numbers of _E. coli_ were determined according to [PERSON]'s method [19]. From the dilutions made, 1 mL of sample was taken and inoculated on Petrifilm (3M, St. Paul, MN, USA), and then incubated at 37 \({}^{\circ}\)C for 24 h.  
The total number of germs was determined according to [PERSON] and [PERSON]'s method [19; 20], respectively. Thus, 1 mL sample was taken from each sample and 7 dilutions were made. From the last dilution, 1 mL was taken and inoculated on a Petri plate, using nutrient agar as a nutrient medium. The plates were inoculated at 35 \({}^{\circ}\)C for 24 h, and the colonies were counted.  
2.4.6. Colour  
Colour measurements were performed using a YS6060 desktop colourimeter (Yashica Co., Ltd., Tokyo, Japan), with values expressed as L, a, and b, according to the Commission Internationale de I'Eclairage (CIE) system. The total colour difference (\(\Delta\)E) was calculated using the formula: \(\Delta\)E = (\(\Delta\)L*2 + \(\Delta\)a*2 + \(\Delta\)b*2)1/2.  
2.4.7. Nutritional Quality Determination  
Betaine content was determined according to [PERSON]'s method [21]. The determination of \(\beta\)-carotene, polysaccharides, and total phenol content was based on [PERSON] [22], and other relevant literature.  
2.4.8. Determination of Volatile Components  
Volatile substances in both processed and unprocessed goji juice were analysed using gas chromatography-ion mobility spectrometry (GC-IMS). A 3.00 g sample of goji juice was placed in a 20 mL (2 cm \(\times\) 4 cm) headspace vial. Each experiment was repeated three  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & & & \\ \hline \multirow{2}{*}{**Level**} & **A. Homogenisation** & **B. Ultrasonication** & **C. Sterilisation** & **D. Sterilisation** \\  & **Time (min)** & **Time (min)** & **Temperature (\({}^{\circ}\)C)** & **Time (s)** \\ \hline \(-1\) & 2 & 1 & 90 & 60 \\
0 & 3 & 2 & 100 & 90 \\
1 & 4 & 3 & 110 & 120 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Levels of factors in response surface experiments.  
times. The sample was incubated at 40 \({}^{\circ}\)C for 10 min and then injected with 0.5 mL, with the injection needle at 45 \({}^{\circ}\)C and an incubation speed of 500 rpm. High-purity nitrogen (\(\geq\)99.999%) was used as the carrier gas. The chromatographic column was FS-SE-54-CB-0.5 15 m ID: 0.53 mm, with a column temperature of 45 \({}^{\circ}\)C. The analysis time was 20 min, with a program flow rate set to 2.00 mL/min for 10 min, linearly increasing to 20.00 mL/min over 5 min, then to 100.00 mL/min over 15 min, and maintained at 100.00 mL/min for 5 min.  
Standards of 2-pentanone, 2-hexanone, 2-heptanone, 2-octanone, and 2-nonanone were used to establish standard curves and determine the retention times of flavour substances in the samples.