Nonthermal pasteurization of tender coconut water using a continuous flow coiled UV reactor

Effect of coil diameter on water disinfection efficiency in a helical photoreactor using ultraviolet-C light emitting diodes

This study investigated the disinfection efficiency of a photoreactor equipped with a helical water flow channel and ultraviolet-C (UV-C) light emitting diodes (LEDs). Theoretical simulations and biodosimetry tests were conducted to investigate the effects of coil diameter and flow rate on the reactor's performance in inactivating Escherichia coli. The interplay between hydrodynamics and UV radiation was analyzed to determine the UV fluence absorbed by the microbes. The simulations revealed that, primarily due to the specific radiation pattern of the UV LEDs, the coil diameter strongly influenced the distribution of irradiance in the water and the UV fluence received by microbes. The experimental results indicated that the photoreactor achieved the highest inactivation value of 2.8 log when the coil diameter was 48 mm for a flow rate of 40 mL/min; this log value was superior to those for coil diameters of 16, 32, 64, and 80 mm by approximately 1.9, 0.4, 0.5, and 0.7 log units, respectively. This optimal coil diameter leading to the maximal UV irradiance and the highest degree of irradiance uniformity along the flow channel. This study offers design guidelines for constructing a high-efficiency water disinfection reactor with a helical flow channel configuration.

Volatile aroma and physicochemical characteristics of freeze-dried coconut water using different encapsulating agents

This research studied how different types and concentrations of encapsulating agents impacted freeze-dried coconut water products. Volatile aroma and physicochemical product characteristics were evaluated. The encapsulating agents were maltodextrin 4-8% (w/v), polydextrose 4-8% (w/v) and xanthan gum 0.1-0.3% (w/v). A plate freezer and an air blast freezer were used to pre-freeze the coconut water before drying. Freezing time had no impact on moisture content and water activity. The flavor compounds of coconut water is composed of alkanes, aldehyde, ketones, organic acids and some other flavor substances. Encapsulating agents are the main factors affecting the flavor of coconut water. Optimal conditions for producing dried coconut water were adding polydextrose at a concentration of 8%. Volatile compounds were assessed under different conditions of SPME- GC-TOFMS. The composition of flavor compounds in coconut water is complex and mainly includes esters, aldehydes, and phenols. Results showed that encapsulating agents improved the volatile aroma of dried coconut water products.

A Rapid Method for Low Temperature Microencapsulation of Phase Change Materials (PCMs) Using a Coiled Tube Ultraviolet Reactor

Microencapsulation of phase change materials (PCMs) remain a suitable option within building materials, as they contribute to the thermal mass and provide an energy buffer, an added benefit. This paper presents a novel method for the rapid fabrication of microencapsulated phase change materials (PCMs) at ambient conditions in a perfluoroalkoxy (PFA) coiled tube ultraviolet (UV) reactor. The objective of this study was to optimize key parameters such as the product yield and quality of the as-prepared microcapsules. Rubitherm® RT-21™ PCM was microencapsulated within shells of poly-methyl-methacrylate (PMMA) through a suspension emulsion polymerization approach, where the crosslinking of polymers was driven by UV radiations with an appropriate photoinitiator. The characteristics of the resulting PCM microcapsules were found to be affected by the volumetric flow rate of the emulsion inside the coiled tube reactor. Higher volumetric flow rates led to higher PCM contents and higher microencapsulation efficiency, resulting in an average particle size of 6.5 µm. Furthermore, the effect of curing time on the PCM microcapsule properties was investigated. The optimum encapsulation yield, conversion, efficiency and PCM content were observed after 10 min of polymerization time. The thermal analysis indicated that the developed process had an efficiency of 85.8%, and the capsules were characterized with excellent thermal properties. Compared to the conventional thermal microencapsulation processes, the use of a coiled tube UV reactor with an appropriate photoinitiator enables the encapsulation of heat-sensitive PCMs at ambient conditions, and reduces the microencapsulation time dramatically. As a result, this novel microencapsulation approach can lead to a wider scope of PCM encapsulation and enable rapid, continuous and potentially large-scale industrial production of PCM microcapsules with low energy consumption.

Effects of variety and maturity stage of coconut on physicochemical and sensory characteristics of powdered coconut drink

Introduction. Coconut water is rich in nutrients and biologically-active compounds. However, it has a short shelf life that can be prolonged by freeze drying. The purpose of this study was to analyze the physicochemical and sensory characteristics of fresh and powdered coconut drinks. Study objects and methods. The experiments included eight samples, namely fresh and powdered coconut drinks obtained from coconuts of different varieties (tall and hybrid) and maturity stages (4 and 6 m.o.). The samples were analyzed for nutrient content (ash, protein, fat, total carbohydrate, and fibre), physicochemical properties (titratable acidity, pH, viscosity, total soluble solids, turbidity, water activity, and browning index), and sensory characteristics (color, aroma, taste, texture, and overall acceptance). Results and discussion. The results obtained showed that there were significant differences among the coconut drinks of different varieties and maturity stages. They differed in nutrient content, pH value, titratable acidity, viscosity, and water activity. Meanwhile, the aroma, taste, and overall acceptance scores of all the samples were not significantly different. The powdered drink from 6 m.o. hybrid coconut was selected as the optimal sample due to its good sensory and physicochemical attributes. These attributes were similar to those of the fresh coconut drink. Conclusion. The powdered drink from 6 m.o. hybrid coconut obtained by freeze drying could be considered as an alternative healthy drink with good quality characteristics.

Effects of UV-C Irradiation and Thermal Processing on the Microbial and Physicochemical Properties of Agave tequilana Weber var. azul Extracts at Various pH Values

The effects of UV-C irradiation (at doses of 8.16, 10.93, 16.17, and 33.29 mJ/cm2) on the physicochemical and microbiological properties of Agave tequilana Weber extracts at various pH values (4.5, 5.5, and 6.5) were evaluated. Thermal treatment (TT) was used as a control (85 °C for 30 s). Both processed (UV-C or TT) and unprocessed (UP) extracts were investigated. The UV-C dose and the pH significantly (p < 0.05) affected the inactivation of total coliforms (TC), total aerobic mesophiles (TAM), and yeasts and molds (YM). UV-C doses of 10.93 mJ/cm2 at pH 4.5 and 33.29 mJ/cm2 at any agave extract pH completely inactivated the native microbial load compared to TT. The total polyphenols (TP), antioxidant activity (AA), and sugar content did not change in the agave extracts at any dose, but the total flavonoid (TF) content decreased at doses > 16.17 mJ/cm2 at the evaluated pH values. Although the color of the agave extracts (L*, a*, and b*) was significantly affected, the total color difference (∆E) did not change after processing compared to the ∆E in the UP extracts. TT further reduced all the physicochemical properties of the agave extracts compared to UV-C processing. The results suggest that UV-C continuous flow technology can be used to stabilize agave extracts at doses of 10.93 mJ/cm2 and pH 4.5, while preserving their functional properties.

Use of coconut water (Cocus nucifera L) for the development of a symbiotic functional drink

Many studies suggest that probiotic, prebiotic and symbiotic foods may be beneficial in the prevention and management of nutrition and health, the objective of this work was to develop a symbiotic drink based on coconut water. Fermentation was performed using lyophilized Lactobacillus rhamnosus SP1 and inulin as a source of soluble fiber. Different formulations were developed, determining the concentrations of fiber and probiotics. The growth of the probiotic in MRS broth was evaluated, using the plate counting technique in different periods of time. The fermentation time of the drink was 8 h and the shelf life in refrigeration was 14 days evaluated by pH and hedonic scale. The pH of the final drink was 3.48 and the probiotic content was 82 × 10 ⁸ CFU/ml. It is concluded that coconut water can be processed by adding probiotic and prebiotic characteristics with sensory acceptance and adequate preservation characteristics.

Ultraviolet inactivation of bacteria and model viruses in coconut water using a collimated beam system

This study investigated the effect of ultraviolet-C irradiation on the inactivation of microorganisms in coconut water, a highly opaque liquid food (1.01 ± 0.018 absorption coefficient). Ultraviolet-C inactivation kinetics of two bacteriophages (MS2, T1UV) and three surrogate bacteria (Escherichia coli, Salmonella Typhimurium, Listeria monocytogenes) in 0.1% (w/v) peptone and coconut water were investigated. Ultraviolet-C irradiation at 254 nm was applied to stirred samples, using a collimated beam device. A series of known ultraviolet-C doses (0-40 mJ cm^-2) were applied for ultraviolet-C treatment except for MS2 where higher doses were delivered (100 mJ cm^-2). Inactivation levels of all organisms were proportional to ultraviolet-C dose. At the highest dose of 40 mJ cm^-2, three surrogates of pathogenic bacteria were inactivated by more than 5-log₁₀ (p < 0.05) in 0.1% (w/v) peptone and coconut water. Results showed that ultraviolet-C irradiation effectively inactivated bacteriophage and surrogate bacteria in highly opaque coconut water. The log reduction kinetics of microorganisms followed log-linear and exponential models with higher R² (>0.95) and low root mean square error values. The D₁₀ values of 3, 5.48, and 4.58 mJ cm^-2 were obtained from the inactivation of E. coli, S. Typhimurium, and L. monocytogenes, respectively. Models for predicting log reduction as a function of ultraviolet-C irradiation dose were found to be significant (p < 0.05). Fluid optics were the key controlling parameters for efficient microbial inactivation. Therefore, the ultraviolet-C dose must be calculated not only from the incident ultraviolet-C intensity but must also consider the attenuation in the samples. The results from this study imply that adequate log reduction of vegetative cells and model viruses is achievable in coconut water and suggested significant potential for ultraviolet-C treatment of other liquid foods.

Comparison of the quality attributes of coconut waters by high-pressure processing and high-temperature short time during the refrigerated storage

This study compared the shelf life and quality of high-pressure processing (HPP) and high-temperature short time (HTST)-treated coconut water at 4°C. HPP of 500 MPa (5 min) and HTST of 72°C (15 s) treatments could ensure microbial safety of coconut water during refrigerated storage of 25 and 15 days, respectively. At the end of 15 days of storage, loss of 51.54% amino acids and 32.37% protein, and retention of 65.0% total sugars, 64.51% ascorbic acid, and 74.34% total phenols were found in HTST group. More nutrient contents, 76.85% amino acids, 76.76% total protein, and 93.17% total phenols, were retained in HPP groups at the end of 25 days of storage. HPP-treated fresh-like product could provide an effective approach of extending shelf life of coconut water.