Food Engineering Reviews

Intelligent packaging, in addition to acting as a food protection barrier, can emit a signal (electric, colorimetric, among others) in real time in response to any change in the initial packaging conditions and food quality. Packaging with pH indicators or pH sensors usually consists of two parts, a solid base and a dye sensitive to the pH change that makes up the colorimetric sensor. The dyes are extracted from various sources of fruits and vegetables or synthetics. At the beginning of the food deterioration process, alteration of the pH occurs; this change is one of the indicators of product quality. Packaging with a pH indicator is a measure that could indicate the quality of the food at the time of purchase or before consumption, making it safer for consumers. Research is being carried out with the aim of improving the characteristics and applicability of these indicators. This review paper presents research results on intelligent pH indicator packaging, with studies covering pigments, polymers, food and packaging solutions, as well as an overview of the materials/technologies used for the development, and the perspectives/challenges that involve this new technology.

Đông lạnh là một phương pháp được sử dụng rộng rãi để kéo dài thời gian bảo quản của thực phẩm. Tuy nhiên, các sản phẩm đông lạnh phải đối mặt với những biến đổi nhiệt độ trong quá trình bảo quản và vận chuyển, dẫn đến các hiện tượng như tái kết tinh của đá và di chuyển độ ẩm/mass, điều này làm giảm chất lượng thực phẩm. Bài báo này xem xét cơ chế hình thành tinh thể đá, sự phát triển và chuyển trạng thái kính, đồng thời trình bày kết quả thực nghiệm về tác động của chu kỳ đông - rã đông đến tái kết tinh của đá. Các mô hình toán học dự đoán thời gian đông lạnh và mô tả sự truyền nhiệt và khối lượng trong quá trình đông lạnh cũng được đề cập. Việc hình thành tinh thể và tính di động của độ ẩm/khoáng chất có những đặc điểm đa quy mô, trong khi mô hình truyền thống chỉ có thể mô tả hiệu ứng trung bình một quy mô duy nhất. Do đó, lý thuyết hỗn hợp lai (HMT), dựa trên các định luật cân bằng đa quy mô và bất bình đẳng entropy, cũng được thảo luận trong bối cảnh vấn đề đông lạnh nhằm dự đoán sự thay đổi pha, sự phát triển tinh thể và các hiệu ứng nhiệt cơ học.

This article overviews the technological evolution of residential refrigerators, key national and international regulations covering them, and summarizes the information available to estimate the quality and safety deterioration in foods and beverages stored in them. At present, the national and international government standardized performance tests used to assess residential refrigerators focus on energy consumption. Efforts by refrigerator manufacturers to consider the impact of temperature fluctuation, temperature recovery, extreme ambient temperature, door openings, and other factors affecting temperature control and, thus, food safety and quality need to be harmonized, validated, and implemented as official standardized tests. Published predictive models here summarized, and describing microbial growth and other product degradation mechanisms, could be combined with energy efficiency evaluations in future science-based regulations seeking a balance between energy consumption and food preservation. While numerous mathematical models are available, this review identified a serious lack of model parameter values to allow a combined assessment of energy consumption and food preservation in residential refrigerators. Much of past research has focused on temperature abuse effects and, thus, not applicable to estimating food preservation under the prevailing temperatures in residential refrigerators. Particularly urgent is the data on the microorganisms’ response at multiple temperature levels, allowing the development of secondary models to assess the temperature effect on the safety and quality of a diverse but representative pool of products. New standardized testing procedures could then be developed to guide the design of new residential refrigerators minimizing food waste and the frequency of foodborne diseases while meeting energy consumption requirements.

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.

A correction to this paper has been published: https://doi.org/10.1007/s12393-021-09287-8

This review aims to approach the secondary shelf life (SSL) issue by providing an overview of the studies currently available on the subject and suggesting a theoretical framework to model the dependence of the SSL on the residual shelf life (RSL), a new concept introduced in this study. As it will be discussed later, to date, there are no systemic approaches and no guidelines to predict the dependence of the SSL on the RSL, even though the SSL is closely related to RSL. The few articles on the topic available in the literature are limited to assess the SSL of food, and its dependence on packaging systems or storage conditions after the package opening. The new approach based on the RSL can give a valid tool to industrial and scientific operators in the food sector for a more appropriate prediction of SSL. The enhanced awareness about a correct SSL prediction might lead to lower food waste generation.

A dynamic (e.g., non-isothermal) kinetic model of microbial survival during a lethal process or growth under favorable conditions is either in the form of a differential rate equation from the start or obtained from an algebraic static model by derivation. Examples of the first kind are the original and modified versions of the logistic (Verhulst) equation and of the second the dynamic Weibull survival or Gompertz growth models. In the first-order inactivation kinetics, the isothermal logarithmic survival rate is a function of temperature only. Therefore, converting its static algebraic form into a dynamic differential rate equation, or vice versa, is straightforward. There is also no issue where both the static and dynamic versions of the survival or growth model are already in the form of a differential rate equation as in the logistic equation of growth. In contrast, converting the nonlinear static algebraic Weibull survival model or the Gompertz growth model into a dynamic differential rate equation, requires replacement of the nominal time t by t*, defined as the time which corresponds to the momentary static survival or growth ratio at the momentary temperature. This replacement of the nominal time in the rate equation with a term that contains the momentary survival or growth ratio eliminates inevitable inconsistencies and renders the resulting dynamic model truly predictive. The concept is demonstrated with simulated dynamic microbial survival patterns during a hypothetical thermal sterilization where the temperature fluctuates and with simulated dynamic microbial growth in storage where the temperature oscillates.

Food extrusion provides a great versatility for the development of low-cost, high-nutritive and convenient food products such as cereal-based snacks and food products. Extruded snacks are gaining importance nowadays due to their peculiar taste, texture and convenience. Extruded products contain low levels of protein, which makes it necessary to fortify them with protein-rich diets. One of the possible ways for alleviating this problem is to utilize fish and fish proteins to enrich cereal-based extruded products. Demand for fish meat and fish meat-based products is increasing day by day, and utilization of bycatch, low-cost and underutilized fish and shellfish is a major current issue. Utilizing fish meat and fish portions to develop extruded products will add value to the low-cost and underutilized fish and shellfish, thus promoting their utilization. The major factors during extrusion processing which affect the physical and chemical properties of the final product are high barrel temperature, feed moisture, composition of raw materials (protein and starch mainly) and the screw speed. Extrusion processing and changes in the ingredients will influence the system variables as well as product characteristics. In this view, the present article describes in detail about food extrusion process, application of food extrusion to develop fish meat-based extruded products, quality of fish-based extruded products and future prospects of the technology.

Large amounts of agri-food by-products, non-edible food, and waste are produced throughout the supply chain from the initial production to the final consumption stages. The valorization of this biomass to obtain high value-added compounds has been the focus of extensive research in the last decade. For this purpose, the use of green techniques is essential to reduce the negative impact on the health and the environment. In this review, we discuss the use of green solvents for the valorization of agri-food waste and by-products, and we consider their potential to replace conventional organic solvents in order to provide more environmentally friendly and sustainable processes. The use of supercritical fluids, neoteric (ionic liquids and deep eutectic solvents), bio-based, and supramolecular solvents is critically dicussed. Parameters affecting extraction efficiency are detailed for each type of solvent along with advantages and limitations for application at the industrial scale.