基于激光诱导荧光光谱的酸奶乳酸菌数快速检测

Rapid detection of lactic acid bacteria in yogurt based on laser induced fluorescence

以市售搅拌型酸奶为研究对象,利用自行搭建的激光诱导荧光(LIF)采集系统,获取不同乳酸菌数酸奶样品的荧光光谱,探讨酸奶中各种荧光物质的荧光峰强度随乳酸菌数变化的响应关系,结合光散射校正算法建立了酸奶中乳酸菌数定量预测模型.结果显示,不同乳酸菌数酸奶样品均在435、485和520 nm附近出现了荧光特征峰,且均随乳酸菌数的变化呈现规律性变化.利用4种光散射校正方法对酸奶原始荧光光谱进行了校正,其中,OPLEC+SR光散射校正算法能够有效消除与波长相关的基线漂移的影响,所建立的PLSR预测模型结果最优,其校正集、验证集相关系数R_(c)、R_(p)分别为0.9654和0.9533,均方根误差C_(RMSE)、P_(RMSE)分别为0.1525 logCFU/mL和0.2362 logCFU/mL.为验证模型的稳定性与可靠性,利用未参与建模的8个酸奶样品对最优模型进行外部验证,实测值与预测值线性拟合后的相关系数R可达到0.9510,拟合残差模为0.8606,说明所建预测模型可以实现酸奶中乳酸菌数的实时监测.

Taking the commercial mixed yogurt as research object,the fluorescence spectra of yogurt samples with different numbers of lactic acid bacteria were obtained by the self-developed laser induced fluorescence(LIF)system.The correlation between the peak of various fluorophore produced by lactic acid bacteria in yogurt and the number of lactic acid bacteria was discussed.The quantitative prediction model of the number of lactic acid bacteria in yogurt was established.The results show that the fluorescence peaks at about 435,485 and 520 nm can be identified,and the fluorescence peaks show regular changes with the variation of lactic acid bacteria.The original fluorescence spectrum of yogurt was corrected by four types of light scattering correction methods,and the lights cattering correction algorithm of OPLEC+SR can effectively eliminate the effect of baseline drift related to the wavelength with the optimal PLSR prediction model results.The correlation coefficients of correction set R_(c)and validation set R_(p)are respective 0.9654 and 0.9533,and the root mean square errors of C_(RMSE)and P_(RMSE)are respective 0.1525 logCFU/mL and 0.2362 logCFU/mL.According to the validation result of the proposed method with the independent set of 8 samples,the correlation coefficient R after linear fitting of the measured and predicted values can reach 0.9510 with the residual modulus of 0.8606,which demonstrates that the proposed LIF system can meet the requirements of real-time monitoring of the number of lactic acid bacteria in yogurt.