Rheological and physicochemical properties of vegetable juices and concentrates: A review

Power ultrasound enhanced the flavor quality of tomato juice

BACKGROUND

The loss of flavor in modern tomato cultivars represents a great challenge for the food industry. This study investigated the potential of power ultrasound as an innovative approach to improve tomato juice flavor by releasing bound volatiles.

RESULTS

It was found that power ultrasound offered a more viable, environmentally friendly technique for enhancing the aroma of tomato juice compared with enzymatic or acid hydrolysis methods. There were significant differences in the released aromas among these three methods: Ultrasound primarily released alcohols and esters, with the characteristic volatiles being trans-2-hexenol and 6-methyl-5-hepten-2-one. Enzymatic hydrolysis primarily released glycosides such as alcohols and aldehydes, with the characteristic volatiles being hexanal, 6-methyl-5-hepten-2-one, β-damascenone, methyl salicylate and phenylethyl alcohol. Acid hydrolysis mainly released ketones and alkenes, with the characteristic volatiles being hexanal, 6-methyl-5-hepten-2-one, β-damascenone, methyl salicylate and trans-2-hexenol. Ultrasound parameters could be varied to improve the level of flavors of tomato juice with the optimal parameters being 40 °C, 10 min, 600 W L-1 ultrasound density and 50% duty cycle.

CONCLUSION

The present investigation will provide a reference for aroma-enhancing application of power ultrasound. © 2025 Society of Chemical Industry.

Heat transfer and friction factor analysis for tomato puree flowing in a concentric-tube heat exchanger

The heat and momentum transfer of tomato puree through a concentric-tube heat exchanger over a range of generalized Reynolds number (0.05 < Re < 66.5) was experimentally and numerically analyzed. Thermophysical and rheological properties of tomato puree (12°Brix) were measured from 20 to 60°C. The velocity, pressure, and temperature were calculated using the computational fluid dynamics (CFD) software FLUENTTM with temperature-dependent transport properties. The thermal operation of the concentric-tube exchanger was satisfactorily predicted using CFD, indicating accurate measurement of tomato puree properties with temperature variations. A concordance was found between the calculated Fanning friction factor and generalized Reynolds with the experimental correlation. A modified Sieder-Tate correlation was established, which allows properly expressing the Nusselt number as a function of the Peclet number. Simple correlations for the mechanical work and the heat transfer rate as a function of the volumetric flow rate were derived. The thermal efficiency was high at low puree flow rates but decreased with higher rates. However, at high flow rates, ceased its decline, instead showing a slight improvement. The analysis confirmed higher heat transfer rates in the concentric-tube heat exchanger compared to a plain tube at low puree flow rates. The results offer valuable insights for assessing diverse operational conditions in dairy, beverage, sauce, and concentrated food industries. Additionally, they also enhance the analysis and design of concentric-tube heat exchangers. PRACTICAL APPLICATION: The knowledge of the rheological and hydrodynamical behavior of fluids in concentric-tube heat exchangers allows to explore a set of different operating conditions to improve the yield and effectiveness on the system heating/cooling design.

Effects of ultra-high pressure, thermal pasteurization, and ultra-high temperature sterilization on color and nutritional components of freshly-squeezed lettuce juice

The aim of this study was to evaluate the effects of ultra-high pressure (UHP, 600 MPa/2 min), thermal pasteurization (TP, 95 °C/1 min) and ultra-high temperature (UHT, 115 °C/5 s) sterilization on the color, sensory evaluation, microorganisms, physicochemical characteristics and nutritional components of freshly-squeezed lettuce juice (FLJ). Results showed that three sterilization methods demonstrated desirable inactivation effects on total aerobic bacteria, yeast and mold, and there were no significant changes in the main nutritional components, including ash, protein, carbohydrate and total dietary fiber. However, UHT and TP significantly affected the color of FLJ from bright green to light brown and made chlorophyll, β-carotene and vitamins (VE, VC, VK1, VB6, VB12, and folic acid) contents markedly decreased. By contrast, UHP maintained the original color, fresh-like sensory qualities, vitamins, and carotene of FLJ to the greatest extent. Our results provide a promising application of UHP in the large-scale processing of FLJ.

Improving the colloidal stability of pectin-phycocyanin complexes by increasing the mixing ratio

In the food industry, the phycobiliprotein phycocyanin acts as a color pigment or the functional part of the superfood "Spirulina." It is industrially extracted from Arthrospira platensis. Current scientific research is focusing on finding complex partners with the potential to stabilize phycocyanin against its sensitivity toward heating and pH changes. Less attention is paid to the factors that influence complexation. This study focuses on the mixing ratio of phycocyanin with pectin. Phycocyanin concentration was fixed, and the mixing ratios ranged from 0.67 to 2.50 (pectin:phycocyanin). All samples were analyzed for their color, size, microscopic structure, zeta potential, and sedimentation stability before and after heating at 85°C. It was found that increasing the pectin content fostered the initial interactions with the protein and chromophore, resulting in a color shift from blue to turquoise. The size of the complexes decreased from several micrometers to nanometers with increasing pectin concentration. Those smaller complexes that were formed at a mixing ratio of 2.5 showed a higher colloidal stability over a period of ∼2 days. It is suggested that at a low mixing ratio (0.67), phycocyanin cannot be completely entrapped within the complexes and attaches to the complex surface as well. This results in aggregation and precipitation of the complexes upon heating. With increasing aggregation and consequently size as well as density of the complexes, sedimentation was accelerated. PRACTICAL APPLICATION: Under acidic conditions, as found in many foods and beverages (e.g., soft drinks, hard candy), phycocyanin tends to agglomerate and lose its color. Specifically heating, triggers denaturation, causing phycocyanin to aggregate and lose vital protein-chromophore interactions necessary to maintain a blue color. To prevent precipitation of the phycocyanin-pectin complexes, increasing the amount of pectin to a ratio of at least 2.0 is effective. This illustrates how adjusting the mixing ratio improves stability. Conversely, lower mixing ratios  induce color precipitation, valuable in purification processes. Thus, practical use of biopolymer-complexes, requires determination of the optimal mixing ratio for the desired effect.

Bio-yogurt with the inclusion of phytochemicals from carrots (Daucus carota): a strategy in the design of functional dairy beverage with probiotics

The development of yogurt with functional characteristics from bioactive compounds such as fiber, antioxidants, and probiotics represents a novel strategy in designing value-added dairy beverages. However, biotechnological challenges are present in these bioprocesses, such as the selection of probiotic strains, as well as the correlation with the physicochemical characteristics of the fermentative metabolism of probiotic microorganisms. Therefore, yogurt could be a vehicle for including probiotic bacteria, bioactive compounds, and phytochemicals that allow synergistic effects in the development of bioprocesses with potential benefits for the host's health. Therefore, this article aims to review the current conditions of bio-yogurt production, discuss the physicochemical and bioactive composition (sugars, fiber, vitamins), and include phytochemicals from carrots to establish synergistic relationships with probiotic microorganisms to obtain a functional dairy beverage.

Application of pulsed light technology for fruits and vegetables disinfection: A review

Non-thermal technologies can maintain fruit and vegetable products quality better than traditional thermal processing. Pulsed light (PL) is a non-thermal method for microbial inactivation (vegetative cells and spores) in fruits and vegetables. The PL treatment involves the application of intense and short-duration pulses of broad spectrum wavelengths ranging from UV to near-infrared (100-1100 nm). This review summarized application of PL technology to control microbial contamination and increasing shelf-life of some fruits and vegetables including apple, blueberries, grape, orange, strawberries, carrot, lettuce, spinach, and tomato. The microbial inactivation in very short treatment times, low energy used by this system, flexibility for solid or liquid samples, few residual compounds and no synthetic chemicals that cause environmental pollution or harm humans, is benefits of PL technique. The efficiency of PL disinfection is closely associated with the input voltage, fluence (energy dose), composition of the emitted light spectrum, number of lamps, the distance between samples and light source, and frequency and number of applied pulses. The PL treatments control pathogenic and spoilage microorganisms, so it facilitates the growth and development of the starter microorganisms affecting product quality.

Quality, physicochemical, and textural properties of dairy products containing fruits and vegetables: A review

Due to the high utilization rate of dairy products, enrichment of these products will successfully decrease or prevent diseases related with nutrition deficiencies. Fruits and vegetables in different forms (i.e., fresh, juices, powder, puree, and extract) are excellent sources for the enrichment of dairy products because of their desired taste, color, aroma, fibers, and vitamins content. So, this manuscript reviews the effect of some fruits and vegetables on the rheological behavior, physicochemical attributes, color parameters, sensorial and quality properties of dairy products including cheeses, ice creams, and yogurts. The physicochemical, color, texture, and sensorial properties of dairy products were affected with addition of fruits or vegetables. Also, the addition of these products contributes to the higher content of vitamins, natural colorants, minerals, polyphenols, crude fiber, and carotenoids. In addition, some fruits and vegetables are considered as potential dairy products stabilizing agent due to their desirable functional properties, such as water binding and holding, gelling and thickening ability. In summary, enrichment of cheeses, ice creams, and yogurts with fruits and vegetables increase the market share of these products due to the high demand for goods for an improved diet, rich in compounds with antioxidant activity and biological properties.