Thermal Pasteurization Research Articles

Effect of high-pressure processing of bovine colostrum on immunoglobulin G concentration, pathogens, viscosity, and transfer of passive immunity to calves.

This study aimed to determine the effects of high-pressure processing on the immunoglobulin concentration, microbial load, viscosity, and transfer of passive immunity to calves when applied to bovine colostrum as an alternative to thermal pasteurization. A pilot study using Staphylococcus aureus was conducted to determine which pressure-time treatments are most appropriate for use with bovine colostrum, with the goals of maximizing bacterial inactivation while minimizing IgG content and viscosity changes. Following the pilot study, an inoculation study was conducted in which first-milking colostrum samples from Holstein-Friesian cows were inoculated with known concentrations of various bacteria or viruses and pressure processed at either 300 MPa for up to 60min or at 400MPa for up to 30min. The recovery of total native aerobic bacteria, Escherichia coli, Salmonella enterica ssp. enterica serovar Dublin, Mycobacterium avium ssp. paratuberculosis, bovine herpesvirus type 1, and feline calicivirus were determined after processing. Colostrum IgG content was measured before and after pressure processing. Shear stress and viscosity for each treatment was determined over shear rates encompassing those found during calf feeding and at normal bovine body temperature (37.8°C). Following a calf trial, serum IgG concentration was measured in 14 calves fed 4 L of colostrum pressure processed at 400MPa for 15min. In the pilot study, S. aureus was effectively reduced with pressure treatment at 300 and 400MPa (0, 5, 10, 15, 30, and 45min), with 2 treatments at 400MPa (30, 45min) determined to be inappropriate for use with bovine colostrum due to viscosity and IgG changes. High-pressure processing at 300MPa (30, 45, and 60min) and 400MPa (10, 15, and 20min) was shown to effectively reduce total native aerobic bacteria, E. coli, Salmonella Dublin, bovine herpesvirus type 1, and feline calicivirus populations in bovine colostrum, but no decrease occurred in Mycobacterium avium ssp. paratuberculosis. All inoculation study pressure treatments insignificantly decreased IgG content of colostrum. Treatment of colostrum at 400MPa for 15min during the calf trial decreased IgG content of colostrum. Treatment at 400MPa for 15min increased colostrum viscosity, with 2 of 14 samples requiring dilution with water for calf feeding. Calves fed pressure-processed colostrum had similar serum IgG but lower efficiency of absorption than calves fed heat-treated colostrum. The results of this study suggest that high-pressure processing of bovine colostrum maintains an acceptable IgG level while decreasing bacterial and viral counts. Changes in viscosity sometimes made calf feeding more difficult, but still feasible. Additional research to optimize this technology for on-farm use is necessary.

Effects of the high pressure homogenization on the viability of yeast cell and volatile components in non-pasteurized rice wine.

This study investigated the effects of high pressure homogenization (HPH) to replace a thermal pasteurization on the yeast cell inactivation and the volatile components of rice wine (RW). By applying HPH (172 MPa with 5 passes), the yeast count was reduced over 4 log cycles. The inactivation of yeast cells by HPH and a thermal processing, i.e. Holder pasteurization (HP), was quantitatively analyzed. In terms of the inactivation of yeast cells, the HPH at 172 MPa with 5 passes was equivalent to the HP at 65°C for 3 min. In RW, 34 volatile components were identified, including 8 alcohols, 18 esters, 2 acids, 1 carbonyls, 3 hydrocarbons, and 2 miscellaneous. Fruity volatiles were found more in HPH samples while components having fatty and oily characters were more detected in HP treated samples.

Effects of high hydrostatic pressure processing and subsequent storage on phenolic contents and antioxidant activity in fruit and vegetable products

SummaryFresh fruits and vegetables have been reported to possess a variety of bioactivities partly due to their high abundance of phenolics. However, traditional thermal pasteurisation during fruit and vegetable processing typically induces a pronounced loss of phenolic compounds. In contrast, nonthermal pasteurisation techniques, especially high hydrostatic pressure (HHP) processing, are beneficial to the retention of phenolics. In addition to more effectively keeping original freshness, flavour and colour of fruit and vegetable products to the greatest extent, in most cases, HHP processing and subsequent storage more effectively sustain the levels of phenolic compounds and antioxidant activity in fruit and vegetable products compared with thermal pasteurisation. Therefore, HHP processing has a huge potential to preserve fruit and vegetable products rich in phenolic compounds.

Inactivation kinetics of Alicyclobacillus acidoterrestris in apple juice submitted to ultraviolet radiation

Ultraviolet-C radiation (UV-C) is widely used as an alternative strategy to control microorganism in food products. Alicyclobacillus acidoterrestris is a thermo-acidophilic, non-pathogenic and spore-forming bacterium, able to grow at low pH and high temperatures. It is a concern, particularly in apple juice thermal pasteurization, because it is responsible for quality degradation.The main objective of this work was to study the influence of UV-C radiation treatments with seven different intensities (0.34, 0.86, 2.59, 5.59, 8.45, 11.50 and 13.44 W/m2) on A. acidoterrestris inactivation in apple juices. Treatments were carried out in a camera (75 × 70 × 45 cm3) with four germicidal UV lamps with peak emission at 254 nm. Commercial juices were artificially inoculated with bacterium, with initial loads around 107 CFU/mL and then exposed to UV-C radiation and the treatment impact on microbial loads was assessed throughout exposure times. The UV transmittance at 254 nm of the juice was 58%. Results showed that the log-survival of A. acidoterrestris decreased linearly with treatment time, for all intensities tested. When the most severe intensity was used, the number of spores decreased drastically (around 5-log reduction) after 8 min of treatment. Overall it can be concluded that UV-C radiation is a promising treatment with a drastic impact on the loads of A. acidoterrestris in apple juices, especially when high intensities are used.

Change of microbial and quality attributes of mango juice treated by high pressure homogenization combined with moderate inlet temperatures during storage

Abstract The effects of high pressure homogenization (HPH) on microbial inactivation and quality attributes (physio-chemical properties, bioactive components and antioxidant capacity) of mango juice, as well as their changes during storage at 4 °C and room temperature were investigated. Pressure levels ranged from 40 to 190 MPa, the inlet temperature from 20 °C to 60 °C and the number of passes from 1 to 5. Complete inactivation of molds and yeasts was achieved by 1 and 3 passes at 190 MPa and 60 °C, while total plate count was below 2.0 log10 CFU/mL. No multiplication of microorganisms was observed in mango juice over 60 days of storage at 4 °C. HPH treatment could retain or even increase the carotenoids and total phenols by 11.8% and 21.4%, respectively, while significant reductions were found for heat treatment (HT) samples. During the storage of 60 days, HPH treatment also provided better preservation of color, bioactive components and antioxidant capacity of mango juice than HT. Industrial relevance High pressure homogenization (HPH) is a novel non-thermal technique, particularly suitable for continuous production of liquid foods limiting thermal damage and promoting “freshness”. Results showed that high pressure homogenization had the advantage of notably reducing the microbial load to levels equivalent to thermal pasteurization. Moreover, HPH treatment was superior to heat treatment with regard to post-treatment levels of bioactive.

Comparative Study on the Effect of Heat Treatment and Sonication on the Quality of Barberry (Berberis Vulgaris) Juice

Barberry (Berberis vulgaris) is an indigenous Iranian plant which its fruit is mainly consumed as fresh, dried and also used for juice production. The objective of this study was to compare the effect of thermal treatment and different sonication conditions on the characteristics of barberry juice. Additionally, the effect of both treatments on degradation kinetics of anthocyanins during refrigerated storage (at 4C) was also evaluated. Sonication and thermal treatments significantly (P < 0.05) reduced microbial counts. A significant increase in the total phenol content and antioxidant activity in all the sonicated juice samples was observed while the thermal treatment had adverse effect on these parameters. Sonication (especially in 70% amplitude) showed less effect on total anthocyanin and color of barberry juice compared to thermal treatment. The degradation kinetics of anthocyanins in all juice samples during refrigerated storage followed first-order kinetics. Half-life (t1/2) of anthocyanins was much shorter in thermal treatment sample (64.90 days) comparing with sonication samples (111.33–158.58 days). Practical Application In recent years, emerging non-thermal techniques, such as sonication, for inactivating microorganisms and improving the health related compounds and other quality parameters of fruit juices have been developed in food industry. Barberry (Berberis vulgaris) is a new source of anthocyanins and antioxidant compounds which can be used as natural pigments in the industry. In this study the effects of thermal pasteurization and sonication on microbial growth and some important quality parameters of barberry juice were compared. The information obtained in our study will be useful for successful application of sonication treatment of barberry juice for preserving the quality of this product.

Effects of high hydrostatic pressure on the quality and shelf-life of jujube (Ziziphus jujuba Mill.) pulp

This study evaluated the effects of high hydrostatic pressure (HHP) on the microbial counts, physicochemical properties, bioactive compounds, and antioxidant capacity of jujube pulp. Additionally, this study compared the shelf life of jujube pulp following HHP (600 MPa/20 min) and thermal treatment (100 °C/10 min) during 40 days of storage at 4 °C and 15 °C. The microbial count of HHP-treated jujube pulp (≥ 400 MPa/20 min) was below the detection limit. Total soluble solids and total sugars were not significantly affected by HHP processing, and > 90% ascorbic acid was retained in HHP-treated samples. HHP slightly reduced pH and browning degree and increased total phenolic content, flavonoid content, and antioxidant capacity. HHP can be used as an alternative to thermal pasteurization of freshly squeezed jujube pulp. Effects of high hydrostatic pressure (HHP) processing and thermal treatment (TT) on microbiological quality, physicochemical properties, bioactive compounds and antioxidant activity in jujube pulp were investigated. Greater inhibition of microorganisms and better retention of ascorbic acid, total phenolics, flavonoid and antioxidant capacity were observed after HHP-treatment. The available data could be used to design the HHP parameters for high quality jujube juice. Further, this research would provide a useful method for preservation of jujube products and potential technical support for jujube commercial production.

Nonthermal pasteurization of beer by high pressure processing: modelling the inactivation of saccharomyces cerevisiae ascospores in different alcohol beers

ABSTRACTThe industrial production of beer ends with a process of thermal pasteurization. In this research, the nonthermal pasteurization of beer by high pressure processing (HPP) was carried out. First, the effect of alcohol content on Saccharomyces cerevisiae ascospore inactivation at 400 MPa was studied. The number of ascospores in 0.0%, 4.8%, and 7.0% alc/vol beers for 10 min processing time decreased by 3.1, 4.9, and ≥ 6.0 log, respectively. The Weibull model fitted the ascospore inactivation by HPP in 0.0%, 4.8%, and 7.0% alc/vol beers. At 400 MPa, 7.2 s could ensure the minimum pasteurization of beers and for 600 MPa 5 s were enough for ≥ 7 log reductions. The overall flavour of HPP vs. untreated beers was evaluated for a lager and an ale, with no significant differences between the untreated and HPP beers. Thus, nonthermal HPP is a feasible technology to pasteurize beer with different alcohol contents without heat.

Fermented minced pepper by high pressure processing, high pressure processing with mild temperature and thermal pasteurization

Abstract High pressure processing (HPP) and thermal pasteurization (TP) of fermented minced pepper (FMP) were comparatively evaluated by examining their impacts on microbial load, titratable acid (TA), pH, aw, firmness, color, capsanthin, ascorbic acid (AA), and biogenic amines (BAs) after processing and during 12 weeks of storage at 25 and 37 °C. The total plate count (TPC) in FMP samples was reduced by 1.48, 0.12 and 1.58 log10 CFU/g after TP (83 °C/15 min), HPP1 (500 MPa/20 °C/5 min) and HPP2 (500 MPa/50 °C/5 min), respectively. The population of spores was reduced by 1.21 log10 CFU/g only after HPP2. During storage at 25 or 37 °C, the TPC in TP, HPP1, and HPP2 samples increased by 0.88/1.21, 0.41/0.62 and 0.60/0.86 log10 CFU/g, respectively, while the spores decreased below the detection limit. The retention of firmness after TP, HPP1 and HPP2 was 36.91, 91.15 and 66.48% respectively, and HPP-treated samples exhibited more retention during the storage. Color of FMP samples was not changed by TP, but slightly changed by HPP1 and HPP2. The content of capsanthin retained 78.99, 93.71 and 88.19% after TP, HPP1 and HPP2, it showed a small decrease during storage. Levels of biogenic amines (BAs) in HPP2 samples were lower than that of TP and HPP1 ones. There were better sensory quality and lower microbial level in HPP-treated samples during storage, indicating that HPP is a better choice for the preservation of FMP. Industrial relevance Consumption of fermented minced pepper (FMP), as a traditional Chinese food, is becoming increasingly popular. Considering that heat treatment may destroy some heat-sensitive quality of the products, this study evaluated the effects of high pressure processing (HPP) on quality of FMP. Findings of this study could help processors commercialize HPP to replace current thermal processing in industrial production.

High voltage electric pulse treatment of water-containing foodstuffs

This study deals with the energy efficient and enviromentally safe methods of electronic treatment of water-containing foodstuffs in order to extend their shelf life without changing their initial nutrition and biological properties. It is shown that high-voltage electric pulse treatment of fluid foodstuffs, instead of thermal pasteurization and sterilization, is less power consuming in both the processing time and the temperature of heating the medium. It is found that the following requirements must be satisfied to reach the total inactivation of microorganisms in the treated fluid medium: temperature of heating the medium in the discharge chamber must be higher than the critical one in the range of ~70°C; the high electric field intensity between the electrodes must not cause a breakdown of the medium; the pulse amplitude should be maximal; the pulse front should be minimal (up to 20 ns); and the pulse duration has to be optimally long (no less than 100 ns). It is ascertained that the high-voltage pulse treatment with these parameters leads to the improvement of the properties of the treated beverages, the acquisition of new curative properties, and the extension of their shelf life.

Effect of electrical field strength applied by PEF processing and storage temperature on the outgrowth of yeasts and moulds naturally present in a fresh fruit smoothie

Pulsed electrical field (PEF) technology offers an alternative to thermal pasteurisation of high-acid fruit juices, by extending the shelf life of food products, while retaining its fresh taste and nutritional value. Substantial research has been performed on the effect of electrical field strength on the inactivation kinetics of spoilage and pathogenic micro-organisms and on the outgrowth of spoilage micro-organisms during shelf life. However, studies on the effect of electrical field strength on the inactivation and outgrowth of surviving populations during shelf life are missing. In this study, we assessed the influence of electrical field strength applied by PEF processing and storage temperature on the outgrowth of surviving yeast and mould populations naturally present in fresh fruit smoothie in time.Therefore, an apple–strawberry–banana smoothie was treated in a continuous-flow PEF system (130L/h), using similar inlet and outlet conditions (preheating temperature 41°C, maximum temperature 58°C) to assure that the amount of energy across the different conditions was kept constant. Smoothies treated with variable electrical field strengths (13.5, 17.0, 20.0 and 24.0kV/cm) were compared to smoothies without treatment for outgrowth of yeasts and moulds. Outgrowth of yeasts and moulds stored at 4°C and 7°C was analysed by plating and visual observation and yeast growth was modelled using the modified logistic growth model (Zwietering model).Results showed that the intensity of the electrical field strength had an influence on the degree of inactivation of yeast cells, resulting in a faster outgrowth over time at lower electrical field strength. Outgrowth of moulds over time was not affected by the intensity of the electrical field strength used.Application of PEF introduces a trade-off between type of spoilage: in untreated smoothie yeasts lead to spoilage after 8days when stored at 4 or 7°C, whereas in PEF treated smoothie yeasts were (partly) inactivated and provided outgrowth opportunities for moulds, which led to spoilage by moulds after 14days (7°C) or 18days (4°C).

The Influence of High Pressure Treatment and Thermal Pasteurization on the Surface of Polymeric Packaging Films

Several common single layer films (PE-HD, PE-LD, PP-BO, PA6-BO and PET-BO) and multilayer (PS/PE, PP-BO/PEpeel and PET-BO/PE) films were treated by either high pressure (600 MPa) or temperature (80 °C/90 °C) to simulate a high pressure or thermal pasteurization process. The samples were tested by atomic force microscopy (AFM), profile method and surface energy measurements to obtain information about the influence of the treatments on the surface topography and surface energy of the samples and by differential scanning calorimetry and by tensile testing concerning material properties. As key figures arithmetic surface roughness (by AFM at Pulsed Force Mode and profile method), surface energy by surface energy measurement and adhesion between tip and surface by AFM were extracted. Results indicate an influence of both high-pressure processing and thermal-processing on the surface roughness of biaxial oriented polymer films as single layer films. Laminated biaxially oriented polymer films showed no changes regardless of which processing was performed. The surface energy was hardly affected by both of the treatments for any stretched, non-stretched, single or laminated films.

High pressure processing and thermosonication of beer: Comparing the energy requirements and Saccharomyces cerevisiae ascospores inactivation with thermal processing and modeling

In this research, pasteurization of beer by nonthermal high pressure processing (HPP) and thermosonication (TS) were compared with thermal pasteurization. The inactivation of Saccharomyces cerevisiae ascospores in beer was studied and modelled for HPP at 200, 300 and 400 MPa, and for TS at 50, 55 and 60 °C with an acoustic energy density of 16.15 W/mL. The energy requirements for equivalent ascospore inactivation by HPP, TS, and thermal processes were compared. For the same processing time, ascospore inactivation was greatest with nonthermal HPP, followed by 60 °C TS, then 60 °C thermal processing. Nonlinear survival curves which could be described by the Weibull model were observed for both HPP and TS. To achieve a 2.5 log reduction in ascospores, HPP required 77 kJ/L compared with 189 kJ/L for thermal processing and 2612 kJ/L for TS. HPP and thermosonication may be alternatives to thermal beer pasteurization, achieving greater log reductions in S. cerevisiae ascospores with shorter processing times (TS and HPP) or less energy (HPP).

UVC dosage effects on the physico-chemical properties of lime (Citrus aurantifolia) juice.

Lime juice is in high demand due to a sour taste. Commercial thermal pasteurization extends juice shelf-life; however, fruit juice subjected to thermal pasteurization tends to change color and lose vitamin content. Lime juice was irradiated with ultraviolet-C (UVC) at dosages of 22.76, 30.19, and 44.24 mJ/cm2 to investigate effects on the physicochemical properties of lime juice. pH values of lime juice did not change while total soluble solids, turbidity, titratable acidity, sweetness, and color values of lime juice did change after UV treatments. Changes in quality index indicators were prominent at the highest UV dosage of 44.24 mJ/cm2. A low UVC dosage was effective for treatment of lime juice with minimal changes in juice properties.

A Comparative Study of the Quality of Strawberry Purée Preserved by Continuous Microwave Heating and Conventional Thermal Pasteurization During Long-Term Cold Storage

This study was aimed at monitoring changes in the quality of strawberry puree preserved by continuous microwave heating (MV) at 90 and 120 °C for 10 s and conventional thermal pasteurization (CTP) at 90 °C for 15 min during cold storage (6 °C), and determining its shelf-life. The shelf-life of MV and CTP-preserved products established on the basis of microbiological changes was more than 52 weeks (<1 log cfu of yeasts, moulds, and total microbial count per gram). During this time, 43 and 34 % of polyphenols, 89 and 58 % of anthocyanins, as well as 57 and 52 % of antioxidant capacity decrease were noted, for MV and CTP-preserved samples respectively; vitamin C was completely degraded. Color changes were more visible for MV (ΔE = 10.82) compared with the CTP-preserved sample (ΔE = 5.14). The kinetic rate of degradation of nutrients was higher for MV- compared to CTP-preserved puree. The recommended cold shelf-life for the MV-preserved puree was estimated at 100 days, during which time it was of a superior quality compared with CTP-preserved puree.

Novel Radiofrequency-Assisted Thermal Processing Improves the Gelling Properties of Standard Egg White Powder.

Effect of radiofrequency (RF)-assisted thermal processing on quality and functional properties of high-foaming standard egg white powder (std. EWP, pH approximately 7.0) was investigated and compared with traditional processing (heat treatment in a hot room at 58 °C for at least 14 d). The RF-assisted thermal treatments were selected to meet the pasteurization requirements and to improve the functional properties of the std. EWP. The treatment conditions were: RF heating to 60, 70, 80, and 90 °C followed by holding in a hot air oven at those temperatures for different periods ranging from 4 h at 90 °C to 72 h at 60 °C. The quality (color and solubility) and functional properties (foaming properties: foaming capacity and foam stability; and gelling properties: water holding capacity and gel-firmness) of the std. EWP were investigated. RF-assisted thermal processing did not affect the color and solubility of std. EWP at any of the treatment conditions. In general, the foaming and gelling properties of RF-assisted thermally processed std. EWP increased with an increase in temperature and treatment duration. The optimal RF-assisted treatment conditions to produce std. EWP with similar functional properties as the traditionally processed (hot room processed) std. EWP were 90 °C for ≥8 h. These optimal conditions were similar to those for high gel egg white powder (HG-EWP, pH approximately 9.5). The RF-assisted thermal pasteurization improved the gelling properties of std. EWP to the levels of HG-EWP, leading to newer applications of this functionally improved safe product. The RF-assisted thermal processing allows the processor to produce a HG-EWP from std. EWP subsequent to processing while simultaneously pasteurizing the product, thus assuring the product safety.

Chemical and biological assessment of endocrine disrupting chemicals in a full scale dairy manure anaerobic digester with thermal pretreatment

Concentrated animal feeding operations are important sources of estrogens and their conjugates, which are introduced into the environment through manure land application. In this study, concentrations of estrogens were measured in an anaerobic co-digestion system with thermal pasteurization pretreatment. Free estrogens (estrone (E1), 17α-estradiol (E2α), 17β-estradiol (E2β), estriol (E3)) were analyzed by gas chromatography with mass spectrometry (GC/MS), and conjugated estrogens (sulfate- and glucuronide-conjugates) were analyzed by liquid chromatography with tandem mass spectrometry (LC/MS/MS). Additionally, yeast estrogen screen assay was used to determine the estrogenic potential of the manure. The total hormone concentrations (mainly E1, E2α, E2β, and sulfated estrogens) were observed at concentrations up to a total of 7100ng/L in the liquid fraction, while free estrogen levels were 630ng/kg in the solid fraction of the untreated manure. The total hormone concentration did not decrease significantly during digestion, however, the relative composition of the estrogens changed from E2α (65%) being the predominant species before digestion to mostly E1 (72%) after digestion. This conversion process has important implications because E1 is more estrogenic than E2α. Total E2 equivalents associated with E1, E2α and E2β concentrations as determined by GC/MS indicate that E1 is the most important contributor to the endocrine-disruption activity of the treated manure.

Effect of High Pressure Homogenization and Dimethyl Dicarbonate (DMDC) on Microbial and Physicochemical Qualities of Mulberry Juice.

In this study, the effect of high pressure homogenization (HPH) and dimethyl dicarbonate (DMDC) on microbial and nutrient qualities of mulberry juice was evaluated. Results showed that repeated HPH passes at 200 MPa or adding DMDC at 250 mg/L significantly inactivated the indigenous microorganisms in mulberry juice (P < 0.05), whereas some surviving microorganisms recovered to grow during storage of 4 °C. The combined treatment with 3 passes of HPH and 250 mg/L of DMDC (HPH-DMDC) decreased the population of surviving indigenous microorganisms to the level attained by heat treatment at 95 °C for 1 min (HT) with no significant increase (P > 0.05) in the population of microorganisms during subsequent storage at 4 °C. Moreover, no significant changes (P > 0.05) in the physical attributes, including pH, TSS ((o) Brix), L*, a*, and b* values were observed in the samples treated by the HPH-DMDC or by HT. Compared with HT, HPH-DMDC treatment resulted in a higher degree of retention in total phenolics, and α-glucosidase inhibitory activity, although the treatment led to higher losses in cyanidin 3-glucoside, cyanidin 3-rutinoside, and antioxidant capacity. Overall, HPH-DMDC treatment can be a useful alternative to conventional thermal pasteurization of mulberry juice, considering its ability to inactive, and inhibit indigenous microorganisms.

Processing of clear and turbid grape juice by a continuous flow UV system

Abstract The inactivation of inoculated (S. cerevisiae) and spoilage microorganisms, i.e. yeasts and lactic acid bacteria (LAB), in clear and turbid grape juice was investigated using a pilot scale UV system. The biodosimetry method was used for UV dose prediction in a continuous flow UV reactor. Weibull model was applied for fitting the inactivation data. The flow rates (774, 820 ml/min) in this system were very close to the ones used in fruit juice processing. S. cerevisiae in clear juice was reduced by 3.39 ± 0.04 at 65.50 mJ/cm2 of UV dose. 1.54 ± 0.04 and 1.64 ± 0.03 log CFU/ml reductions were obtained for spoilage yeasts and LAB in turbid juice at UV dose of 78.56 and 67.97 mJ/cm2, respectively. The soluble solids (°Brix) and pH of grape juice samples were not affected by UV-C treatment (p > 0.05). Although the color parameters slightly were changed after irradiation, the color of PCGJ and FSTGJ did not show visual difference compared to the untreated samples. Industrial relevance UV light has a potential to reduce the levels of microbial contamination in liquid foods. Although grape juice has many beneficial health effects, it has a fairly short shelf life. Therefore, pasteurization is required. But the thermal pasteurization has some undesired effects on the juice quality. Consumer demands for high quality fruit juice with fresh-like characteristics have markedly expanded in recent years. In the current study, the microbial inactivation efficiency of a pilot scale UV system for non-thermal treatment of clear and turbid grape juice was evaluated under conservative conditions. Most of the physicochemical properties of grape juice samples were not significantly affected from UV-C treatment (p > 0.05). This would be a major advantage in the processing of nutritious juice products.

Apple juice preservation through microbial adsorption by nano/micro-tubular cellulose

Abstract A novel continuous preservation process of apple juice using a nano/micro-porous cellulosic material (or “tubular cellulose”, abrrev. TC), is presented in this study. This investigation aims to the development of a non-thermal system for microbial stabilization, avoiding the degradation of food quality caused by heat. TC was used as filter in a packed-bed type bioreactor supplied with commercial apple juice contaminated with Saccharomyces cerevisiae or Lactobacillus plantarum cells at 4 °C. The effect of the filter size on the microbial load removal and chemical/sensory properties of the juice was evaluated. The system presented good operational stability during 55 and 30 days for the removal of yeast and bacteria, respectively. The increase of filter size improved the microbial removal yield and the system effectiveness. The organoleptic parameter values decreased after ΤC regeneration but then reached almost initial levels. The proposed process is a low-cost and promising alternative to existing thermal pasteurization technologies. Industrial relevance Conventional thermal pasteurization treatments are applied industrially for microbial stabilization of foods but significantly affect the organoleptic characteristics of the products. This study evaluated a novel non-thermal preservation method of contaminated apple juice that meets the consumer's demand for less processed products with high nutritional value. Commercial apple juice was contaminated with S. cerevisiae or L. plantarum cells and then was continuously pumped through tubular cellulose. The increased size of the filter leads to improved microbial removal yields. Despite the decrease of volatile compounds and colour at the start up of the process and after each filter regeneration with hot water, almost initial parameter values were achieved as the process evolved. The proposed technology can be a promising alternative of industrial pasteurization techniques for food applications.