Identifying in silico how microstructural changes in cellular fruit affect the drying kinetics

Causal factors concerning the texture of French fries manufactured at industrial scale

In this paper, we review the physical/chemical phenomena, contributing to the final texture of French fries, as occurs in the whole industrial production chain of frozen par-fried fries. Our discussion is organized following a multiscale hierarchy of these causal factors, where we distinguish the molecular, cellular, microstructural, and product levels. Using the same multiscale framework, we also discuss currently available theoretical knowledge, and experimental methods probing the relevant physical/chemical phenomena. We have identified knowledge gaps, and experimental methods are evaluated in terms of the effort and value of their results. With our overviews, we hope to give promising research directions such to arrive at a multiscale model, encompassing all causal factors relevant to the final texture. This multiscale model is the ultimate tool to evaluate process innovations for effects on final textural quality, which can be balanced against the impacts on sustainability and economics.

Recent Advances in the Drying Process of Grains

Grain drying is a vital operation in preparing finished grain products such as flour, drinks, confectioneries and infant food. The grain drying kinetics is governed by the heat and mass transfer process between the grain and the environment. Incomplete, improper and over-drying are crucial to the grain quality and negatively influence the acceptance of the grain by the consumers. Dried grain moisture content is a critical factor for developing grain drying systems and selecting optimal performance by researchers and the grain processing industry. Many grain drying technologies such as fluidised bed dryers, fixed bed dryers, infrared dryers, microwave dryers, vacuum dryers and freeze dryers have been used in recent years. To improve the drying process of grain, researchers have combined some drying technologies such as microwave + hot air, infrared + hot air and microwave + a fluidised bed dryer. Also, they introduce some treatments such as ultrasound dielectric and dehumidification. These methods enhance the dryer performance, such as higher moisture removal, reduced processing time, higher energy efficiency and nutrient retention. Therefore, this review focused on the drying conditions, time, energy consumption, nutrient retention and cost associated with the reduction of moisture content in grain to a suitable safe level for further processing and storage.

Physics-Based Digital Twin Identifies Trade-Offs Between Drying Time, Fruit Quality, and Energy Use for Solar Drying

Solar drying is regarded as a less reliable process compared to continuous hot-air drying due to the intermittency of solar radiation. This problem is mitigated by equipping solar dryers with thermal storage, dehumidifier units, or auxiliary heating that enhances drying continuity during night time. In this study, we combine a mechanistic fruit drying model, quality models (vitamin C decay and browning reaction) and weather data to evaluate the drying characteristics and quality evolution of apple fruit with and without the aforementioned improvement strategies. By coupling to measured weather conditions, a digital twin of the drying fruit is established. The twin outputs drying times and final product quality for a specific fruit type and size, a particular dryer configuration, and specific weather conditions. The trade-offs between drying time, final product quality and energy use for the different improvement strategies of solar drying are documented. We found that solar drying may benefit from the slower drying due to the improvement of product quality. Compared to the other improvement strategies, dehumidification of the drying air is shown to be superior in retaining the vitamin C content and prohibiting the browning reaction. However, in general, drying with auxiliary heating is found to balance the trade-offs between drying time, final product quality and energy use since the weather-dependency of the process is mitigated. Additionally, we quantified the impact of a pre-treatment process that modifies the permeability of the fruit tissue by breaking the cell membrane. We found that inducing such lysis is more effective in decreasing the drying time when drying is conducted at low (room) temperature. This study shows that using the developed digital twin, future drying process and control strategies could be optimized in real-time for every single drying run.