Temperature changes will cause fluctuations in the visible near-infrared spectra of apples, which will affect the models’ robustness and accuracy in predicting the soluble solids content (SSC) of apples. By collecting the spectra and SSC data of apples at different temperatures, this study established common single temperature models, the mixed temperature model, and the models based on the external parameter orthogonalisation (EPO) algorithm. The results indicated that EPO algorithm can effectively eliminate the influence of temperature on the spectra, and does not affect the results of the characteristic wavelengths selection. Most of the selected characteristic wavelengths were distributed in the wavelength range of 700–900 nm. The models based on the EPO algorithm were employed to predict the samples at different temperatures. The concordance correlation coefficient (CCC) ranged between 0.865 and 0.882, and the ratio of performance of deviation (RPD) was in the range of 2.045–2.191. The models based on EPO algorithm achieved high prediction accuracy and were insensitive to temperature changes. The model established by using the spectral data in the 700–900 nm band processed by EPO algorithm had high prediction accuracy and low complexity. Finally, 60 samples were used to verify the performance of the model. It was found that there was no significant difference between the predicted values and the measured values (CCC = 0.892, RMSEP = 0.543 %, RPD = 2.173). The results of the study have practical implications for improving the economic efficiency of the apple industry, including the subsequent development of portable field testing equipment.
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