Use of near infrared spectroscopy and chemometrics to evaluate the shelf-life of cloudy sonicated apple juice

Abstract

Fresh products, such as cloudy apple juice, could be preserved from early spoilage through the application of non-thermal processes such as sonication. However, shelf-life analyses based on microbiological and sensory evaluations are expensive and time consuming. Few studies have applied near infrared spectroscopy to evaluate the quality and decay of apple juices. Here, a feasibility trial was conducted to study the spectral behaviour at 1300-2500 nm combined with chemometric approaches. The shelf-life was monitored during two experiments, a challenge test with juices inoculated with spoilage yeasts (inoculated non-sonicated (INS)) and then submitted to sonication treatments (inoculated sonicated (IS)), and a storage test to evaluate the spoilage on non-inoculated juices (non-inoculated non-sonicated (NINS)) and sonicated noninoculated juices (non-inoculated sonicated (NIS)). These experiments were investigated at six different refrigeration times 7, 14, 21, 28 and 60 days. Two functions were modelled to describe the behaviours of the first principal component according to the storage time. In agreement with a previous chemical and sensory evaluation, this approach allowed us to highlight shelf-life end points of 7 and 14 days for non-sonicated and sonicated samples, respectively. Three different models were evaluated for classification purposes: (1) sonicated versus non-treated samples, (2) end-point shelf-life evaluation at seven days for the NINS and INS juices and (3) end-point shelf-life discrimination at 14 days for IS and NIS samples. A partial least square-discriminant analysis enabled a group classification with accuracy values ranging from 0.63 to 1.00. The application of a variable importance in projection index to interpret the wavelengths of the spectral features suggests a contribution of organic acids and lipids to the prediction of decay. A canonical discriminant analysis provided a clearer separation of samples according to the storage time, especially in relation to the two time thresholds of 7 and 14 days.

Chemometrics, NIRS-XRF and wet chemistry laboratory, and research Group – Department of Animal Medicine, Production and Health, University of Padova

“…34 Further research aims to evaluate the feasibility of NIR and UV-vis in the characterization of blue strains belonging to the Pseudomonas fluorescens group. 35 Recently, NIR technology has been employed to evaluate the quality of sonicated fruit juices 36 and chicken meat 37 along with their shelf life.…”

VIII Italian Symposium on Near Infrared Spectroscopy – NIRItalia 2018

“…Lorenzo Serva presented two studies with the first aimed at the authentication of the floral origin of honeys 13 and the second at evaluating the chemical and microbiological quality traits of cloudy apple juice treated with power ultrasound by using NIR spectroscopy. 14 Moreover, contributions in this session suggested the potential use of NIR spectroscopy for process monitoring, such as in the supply chain of the Annurca apple (IGP) 15 and in the coffee in capsules production process. 16 In this last study, the authors tried to identify the most suitable instrumentation to be used in the different production process steps capable of highlighting failures in the semi-finished production without waiting for the final control of the encapsulated product.…”