Analysis and discrimination of grape spoilage via volatiles: a comparison between long optical path Fourier-transform-infrared spectroscopy and sensor arrays

Abstract

Fruits release specific volatiles as vapors during spoilage that can provide information about the spoilage stages of fruits. We used long optical path Fourier Transform Infrared Spectroscopy (FTIR) and sensor arrays comprising carbon dioxide and ethanol sensors to study the grape spoilage process synchronously. The results revealed that specific volatiles, such as carbon dioxide, ethanol and esters, are released from grapes during spoilage. The presence and concentrations of these compounds gradually change with storage time. Through chemometric analysis, the infrared spectra of volatiles from different spoilage stages of grapes were successfully classified. As a simple form of instrumentation, the sensor arrays also have the ability to discriminate whether the grapes have decayed. We established a Soft Independent Modeling of Class Analogy (SIMCA) model to classify the grape samples into different spoilage stages, and the model according to different quantities of grapes is also discussed. This study demonstrates that it is possible to characterize grape spoilage by analyzing the released volatiles.

Chinese vinegar classification via volatiles using long-optical-path infrared spectroscopy and chemometrics

“…1(c)), which exhibited strong absorbance characteristics despite overlapping with the alcohol peaks. This feature was not present in the spectra of the vapors from Chinese spirits (Dong et al, 2014a(Dong et al, , 2014b. Previous studies also found many other components in the vapors from Chinese vinegars that were not observed in the current experiment (Li et al, 2005;Miao et al, 2010;Wang et al, 2012), which may be due to both the weak absorbance characteristics of these components and the overlap with other strong absorbance peaks.…”

“…As observed from Fig. 1 and our previous study, the infrared spectrum of the vapors from Chinese vinegar was similar to that from Chinese spirits (Dong et al, 2014a(Dong et al, , 2014b, which may be due to the similar raw materials and brewing processes used for both. In this study, we observed the spectral characteristics of some major compositions in Chinese vinegars, includes alcohols, acetic acid, furfural, esters and 2,3-butanedione.…”

“…In previous works, we used multi-reflecting mirrors to increase the optical path of a common FTIR (Fourier transform infrared spectroscopy) system, studied the volatiles released from grapes and strawberries and observed the spectral characteristics corresponding to alcohols, esters, etc. (Dong et al, 2013(Dong et al, , 2014a(Dong et al, , 2014bWenzhong et al, 2013). The results revealed that it is possible to classify fruit spoilage stages via their volatiles using infrared spectroscopy.…”

“…Absorbance spectra were calculated using the spectra in vacuum as a reference. The procedure of exhausting gases from the container to the gas cell was described in our previous publication (Dong et al, 2013(Dong et al, , 2014a(Dong et al, , 2014b.…”

Potential using of infrared thermal imaging to detect volatile compounds released from decayed grapes

“…Thus, the specific type of volatile compounds from fruit was proposed as a potential indicator for rapid detection of spoilage [5–7]. To date, gas chromatography-mass spectrometer (GC-MS) has been the most widely adopted method for precision analysis of volatile compounds from fruits [8–10]. More recently, other methods such as electronic nose (E-nose) and infrared spectroscopy have been developed as alternative means for quick analysis and to assess fruit freshness with high sensitivity [4, 10, 11].…”