Challenges and solutions of extracting value-added ingredients from fruit and vegetable by-products: a review.

Every year, huge amounts of fruit and vegetable by-products in the food processing factories are produced. These by-products have great potential to be used for different targets especially the extraction of value-added ingredients. The target of this study is to review the challenges of extraction of value-added ingredients from fruit and vegetable by-products on the industrial scale and to describe current trends in solving these problems. In addition, some strategies such as multi-component extraction as well as application of fermentation before or after the extraction process, and production of biofuel, organic fertilizers, animal feeds, etc. on final residues after extraction of value-added ingredients are discussed in this review paper. In fact, simultaneous extraction of different value-added ingredients from fruit and vegetable by-products can increase the extraction efficiency and reduce the cost of value-added ingredients as well as the final volume of these by-products. After extraction of value-added ingredients, the residues can be used to produce biofuels, or they can be used to produce organic fertilizers, animal feeds, etc. Therefore, the application of several appropriate strategies to treat the fruit and vegetable by-products can increase their application, protect the environment, and improve the food economy.

Critical assessment of methods for measurement of temperature profiles and heat load history in microwave heating processes-A review.

Limitations of microwave processing due to inhomogeneities of power input and energy absorption have been widely described. Over- and underheated product areas influence reproducibility, product quality, and possibly safety. Although a broad range of methods is available for temperature measurement and evaluation of time/temperature effects, none of them is sufficiently able to detect temperature differences and thermally induced effects within the product caused by inhomogeneous heating. The purpose of this review is to critically assess different methods of temperature measurement for their suitability for different microwave applications, namely metallic temperature sensors, thermal imaging, pyrometer measurement, fiber optic sensors, microwave radiometry, magnetic resonance imaging, liquid crystal thermography, thermal paper, and biological and chemical time-temperature indicators. These methods are evaluated according to their advantages and limitations, method characteristics, and potential interference with the electric field. Special attention is given to spatial resolution, accuracy, handling, and purpose of measurement, that is, development work or online production control. Differences of methods and examples of practical application and failure in microwave-assisted food processing are discussed with a special focus on microwave pasteurization and microwave-assisted drying. Based on this assessment, it is suggested that infrared cameras for measuring temperature distribution at the product surface and partially inside the product in combination with a chemical time/temperature indicator (e.g., Maillard reaction, generating heat-induced color variations, depending on local energy absorption) appear to be the most appropriate system for future practical application in microwave food process control, microwave system development, and product design. Reliable detection of inhomogeneous heating is a prerequisite to counteracte inhomogeneity by a targeted adjustment of process and product parameters in microwave applications.

Enhancing textural properties in plant-based meat alternatives: The impact of hydrocolloids and salts on soy protein-based products.

Consumer studies suggest that the meat-like texture of plant-based meat alternatives is crucial for the market success of these products. Many meat analogues contain wheat gluten, because it is cost-effective and give rise to nice fibrous structures. However, individuals with celiac disease cannot consume products containing wheat gluten producing a fibrous structure. To provide meat-like textures, different hydrocolloids with appropriate salt concentrations could be used. Therefore, this study investigated the influence of different hydrocolloids, including high acyl gellan gum, low acyl gellan gum, high methoxyl pectin, low methoxyl pectin, and xanthan at 2%, as well as two types of salts (CaCl2 and NaCl) at three concentrations (0%, 0.5%, and 1%) on the macrostructure, microstructure, and mechanical properties of plant-based meat alternatives containing only soy protein isolate and without wheat gluten. The addition of hydrocolloids and salts increased the cross-link bonds and structural compactness at the microscopic level and enhanced the fibrous structure at the microscopic level at different extent. These findings provide insight into how the addition of salts and hydrocolloids can effect plant-based meat alternatives without wheat gluten, which have practical implications for the food industry and are important for their success in the market.

The role of plant age and leaf position on protein extraction and phenolic compounds removal from tomato (Solanum lycopersicum) leaves using food-grade solvents.

The large availability and considerable amount of proteins (approx. 30 % on dry matter) make tomato leaves attractive as a potential new protein source. In this study, the feasibility of extracting proteins and removing phenolic compounds from tomato leaves using food-grade solvents as function of plant age and leaf position was investigated. Water and 50-50 % ethanol-water were used. We found that most proteins (>70 mg/g leaf protein) remained in the pellet after extraction. The protein purity of the dry matter present in the supernatant did not exceed the original leaf protein content. Additionally, leaf position had stronger effect than plant age on the leaf protein content and extraction yield. Ethanol-water was more efficient in removing phenolic compounds than water. The most phenolic compounds was removed from the top leaves. For future processing, the diversity of leaves has to be considered when striving for full utilization of tomato plants (fruits and leaves).

Effect of Vertical and Horizontal Sample Orientations on Uniformity of Microwave Heating Produced by Magnetron and Solid-State Generators.

In this study, the effect of different horizontal and vertical orientations of a model sample (cuboid gellan gel samples containing Maillard reactants) on microwave heat processing was investigated in the solid-state and magnetron microwave systems. To achieve this target, seven orientations inside both microwave cavities were defined. Two of the investigated sample orientations were in a vertical position with and without turntable rotation, and five in a horizontal position. Furthermore, samples at horizontal orientations were put at an angle position without turntable rotation. To analyze the microwave heating patterns, infrared (IR) pictures and photographs of the gellan gel samples were taken after processing to document IR-based thermal and Maillard color changes, respectively. Three main factors for improvement of the heating homogeneity were identified: first, processing samples in the solid-state microwave system; second, position variation of the sample by turntable activated; and third, horizontal orientation. In addition, it was observed that placing the gellan gel samples in a vertical position in the magnetron microwave system resulted in considerably more absorbed power and a more uniform microwave heat processing compared to other horizontal orientations in this system. This indicated a non-uniform microwave field distribution. The results of this study can also confirm the importance of designing suitable food packaging: a vertical shape for more microwave energy absorbance and thus, more energy efficiency, and a horizontal shape for more uniform microwave heat processing.

Influence of applied time and power of ultrasonic pretreatment on convective drying of potato slices.

Ultrasound is a novel technology that can be applied as a pretreatment for the convective drying in order to reduce its undeniable shortcomings. The objectives of the present study are to ascertain the influence of sonication time (10, 20, and 30 min) and sonication power (100 and 300 W) on the performance of drying potato slices with regard to the drying kinetics and energy efficiency as well as the final product quality. The results showed that the application of ultrasound pretreatments significantly increased the drying rate of potato slices during the initial period of the drying process. Furthermore, ANOVA showed that the decrease in the sonication time and power gave rise to a significant reduction in drying time, specific energy consumption (SEC), and shear strength. In addition, compared to the control (pure convective drying), ultrasound pretreatments reduced the drying time, SEC, and the shear strength of dried potato slices.

Coating pretreatment of banana slices using carboxymethyl cellulose in an ultrasonic system before convective drying.

Drying is one of the oldest methods of food preservation. However, this method requires careful promotion and maintenance of the quality of the dried products. In this paper, Carboxymethyl cellulose (CMC) coating and sonication pretreatments were employed as a new approach to improve the efficiency of convective drying and produce dried banana slices with acceptable quality in a short period. To achieve these goals, the effects of ultrasonic power (at three levels of 0, 500, and 1000 W) and sample to CMC coating solution ratio (with three levels of 1:2, 1:3, and 1:4), as well as the mutual effect of these two independent variables, were evaluated. The results showed that increasing the ultrasonic power from 0 to 1000 W decreased the drying time (P ≤ 0.001), energy consumptions of the convective drier (P ≤ 0.001), total energy consumption (P ≤ 0.001), shrinkage (P ≤ 0.001), apparent density (P ≤ 0.001), shear stress (P ≤ 0.001), and the total color change (P ≤ 0.001); it also increased energy consumptions of the ultrasonic system (P ≤ 0.001), porosity (P ≤ 0.001), and TPC (P ≤ 0.001) of the dried banana slices significantly. Moreover, changing the sample to coating solution ratio from 1:2 to 1:4 reduced the shrinkage (P ≤ 0.001), apparent density (P ≤ 0.001), shear stress (P ≤ 0.001), and total color change (P ≤ 0.01); this also led to remarkable increase in the porosity (P ≤ 0.001) and TPC (P ≤ 0.05) of the dried samples. With respect to the cross-sectional scanning electron microscopy (SEM) images of the dried banana slices, it was found that the CMC coating pretreatment in an ultrasonic system, especially with an ultrasonic power of 1000 W and a sample to coating solution ratio of 1:4, enhanced the porosity of the dried banana slices. Overall, the combined application of ultrasonication and Carboxymethyl cellulose coating pretreatments could be considered as an effective approach to improve the quality of the dried products through convective drying.