Kinetic Modeling of Food Quality: A Critical Review

Building kinetic models for determining vitamin C content in fresh jujube and predicting its shelf life based on near-infrared spectroscopy

Fresh jujube (Ziziphus jujube) is rich in vitamin C, which is an important quality index and generally decreases with storage time. The aim of this study was to build kinetic models for determining the vitamin C content, thus predicting the quality characteristics and shelf life of fresh jujube. The quality changes of the jujube stored at room temperature (20 °C) were analyzed using near-infrared spectroscopy. The significant spectra were determined and a calibration model for vitamin C content was developed. The results showed that vitamin C content could be described by the zero-order kinetics model based on the regressions. In addition, the shelf life of the jujube at room temperature was calculated according to the regression model.

Kinetics of furan formation from ascorbic acid during heating under reducing and oxidizing conditions

This study aimed to investigate the effect of oxidizing and reducing agents on the formation of furan through ascorbic acid (AA) degradation during heating at elevated temperatures (≥100 °C) under low moisture conditions. To obtain these conditions, oxidizing agent, ferric chloride (Fe), or reducing agent, cysteine (Cys), was added to reaction medium. Kinetic constants, estimated by multiresponse modeling, stated that adding Fe significantly increased furan formation rate constant, namely 369-fold higher than that of control model at 100 °C. Rate-limiting step of furan formation was found as the reversible reaction step between intermediate (Int) and diketogluconic acid (DKG). Additionally, Fe decreased activation energy of AA dehydration and furan formation steps by 28.6% and 60.9%, respectively. Results of this study are important for heated foods, fortified by ferric ions and vitamins, which targets specific consumers, e.g. infant formulations.

Potential application of quantitative microbiological risk assessment techniques to an aseptic-UHT process in the food industry

Aseptic ultra-high-temperature (UHT)-type processed food products (e.g., milk or soup) are ready to eat products which are consumed extensively globally due to a combination of their comparative high quality and long shelf life, with no cold chain or other preservation requirements. Due to the inherent microbial vulnerability of aseptic-UHT product formulations, the safety and stability-related performance objectives (POs) required at the end of the manufacturing process are the most demanding found in the food industry. The key determinants to achieving sterility, and which also differentiates aseptic-UHT from in-pack sterilised products, are the challenges associated with the processes of aseptic filling and sealing. This is a complex process that has traditionally been run using deterministic or empirical process settings. Quantifying the risk of microbial contamination and recontamination along the aseptic-UHT process, using the scientifically based process quantitative microbial risk assessment (QMRA), offers the possibility to improve on the currently tolerable sterility failure rate (i.e., 1 defect per 10,000 units). In addition, benefits of applying QMRA are (i) to implement process settings in a transparent and scientific manner; (ii) to develop a uniform common structure whatever the production line, leading to a harmonisation of these process settings, and; (iii) to bring elements of a cost-benefit analysis of the management measures. The objective of this article is to explore how QMRA techniques and risk management metrics may be applied to aseptic-UHT-type processed food products. In particular, the aseptic-UHT process should benefit from a number of novel mathematical and statistical concepts that have been developed in the field of QMRA. Probabilistic techniques such as Monte Carlo simulation, Bayesian inference and sensitivity analysis, should help in assessing the compliance with safety and stability-related POs set at the end of the manufacturing process. The understanding of aseptic-UHT process contamination will be extended beyond the current "as-low-as-reasonably-achievable" targets to a risk-based framework, through which current sterility performance and future process designs can be optimised.

Thermal degradation kinetics of neoxanthin, violaxanthin, and antheraxanthin in virgin olive oils

A first-order kinetic mechanism was appropriate for describing the thermal degradation of epoxy xanthophylls in virgin olive oil (VOO). Consecutive reactions that involve reorganization of 5,6-epoxide groups to 5,8-furanoxide groups and subsequent rupture of the polyene chain occurred in the degradation pathways. Thermal stability was significantly affected by changes in the chemical structure (epoxy to furanoid structure), being the greatest stability for neoxanthin. A true kinetic compensation effect was found in a series of similar reactions, that is, the degradation of 5,8-furanoxides into colorless products. An isokinetic study in different VOO matrices showed that the oily medium did not significantly affect the reaction mechanisms. Consequently, the kinetic parameters obtained as temperature functions according to the Arrhenius model can be used to develop a prediction mathematical model for 5,8-furanoxide xanthophylls in VOO over time. The potential usefulness of the parameter neoxanthin/neochrome ratio is discussed as a chemical marker of heat treatment in VOO.

Kinetic modeling of the thermal inactivation of bacteriocin-like inhibitory substance p34

Optimization of thermal processes relies on adequate degradation kinetic models to warrant food safety and quality. The knowledge on thermal inactivation kinetics of antimicrobial peptides is necessary to allow for their adequate use as natural biopreservatives in the food industry. In this work, thermal inactivation of the previously characterized bacteriocin-like inhibitory substance (BLIS) P34 was kinetically investigated within the temperature range of 90-120 degrees C. Listeria monocytogenes ATCC 7644 was used as the indicator microorganism for antimicrobial activity. Applicability of various inactivation models available in the literature was critically evaluated. The first-order model provided the best description of the kinetics of inactivation over the selected temperatures, with k values between 0.059 and 0.010 min(-1). D and k values decreased and increased, respectively, with increasing temperature, indicating a faster inactivation at higher temperatures. Results suggest that BLIS P34 is thermostable, with a z value of 37.74 degrees C and E(a) of 72 kJ mol(-1).