Effect of different sterilization methods on the appearance,composition, and flavor of sugarcane juice

Cold-pressed sugarcane juice (SCJ) is a beverage rich in vitamins, carbohydrates, and antioxidants. Various sterilization methods impact fruit juice's appearance, nutrients, and flavor. Hence, this study aims to assess how different sterilization techniques affect the flavor, appearance, and nutritional value of SCJ. Freshly prepared SCJs were subjected to two sterilization methods: pasteurization (referred to as PTG) and autoclaving (referred to as HTHP). The pasteurization process was carried out at 63°C for 30 min, whereas the HTHP process was applied at 115°C for 30 min. The appearances, Brix value, colors, sugar, organic acid content, and aromatic compounds were determined. The Brix and pH values of the juice show little variation across different heat treatments. The color index of PTG was similar to that of the control group, whereas the L* value of HTHP increased about 21%, resulting in a significant color change. The glucose and fructose contents of HTHP were 7.03 and 5.41 mg/mL, which were much higher than those of PTG (3.26 and 2.33 mg/mL) and control group (3.33 and 2.48 mg/mL). A total of 77 aromatic compounds were identified in the SCJ after various heat treatments. Among them, pentanoic acid, octanal, and β-damascenone were the most abundant substances contributing to the overall flavor in the control group, PTG, and HTHP. Pasteurization preserved the original flavor of the juice, whereas autoclaving triggered the Maillard reaction, forming pyrazine and furan-like compounds that altered the SCJ's flavor. In conclusion, pasteurization retained SCJ's original characteristics, whereas HTHP induces changes in nutrition and imparts a distinct flavor.     

Comparing the impact of high pressure,pulsed electric field and thermal pasteurization on quality attributes of cloudy apple juice using targeted and untargeted analyses

The impact of low-oxygen spiral-filter press technology combined with thermal pasteurization (TP), pulsed electric field (PEF) and high pressure processing (HPP) on cloudy apple juice quality was investigated immediately after the treatments and after 3 weeks of storage at 4 °C. Based on equivalent levels of microbial safety and desired shelf-life, low and high processing intensities were selected: TP (72 °C/15 s; 85 °C/30 s), PEF (12.5 kV/cm, 76.4 kJ/L; 12.3 kV/cm, 132.5 kJ/L), and HPP (400 MPa/3 min; 600 MPa/3 min). High intensity thermal treatment resulted in a bright, yellowish color which was maintained during storage. PPO and POD activities were largely reduced by high intensity PEF and TP yet showed high resistance to HPP. The highest vitamin C content was provided by fresh juice followed by PEF-treated juices. Due to oxidative degradation reactions, vitamin C of all treated samples significantly decreased during storage. Immediately after processing, high cloud stability values were obtained in all samples; however, cloud stability decreased during storage particularly for HPP juices with high residual PME. No significant changes were observed in pH, titratable acidity, organic acid and sugar content which also corresponded to sweet and sour taste. Results from untargeted volatile profiles showed that esters increased after PEF and were better retained after HPP. Contrary to TP treatment where ester degradation reactions occurred together with the formation of off-flavors. Most of the volatiles decreased during storage which could be linked to oxidation and ester hydrolysis reactions.Industrial relevanceBeing one of the most popular fruit juices consumed worldwide, cloudy apple juice can still undergo quality changes such as color degradation, cloud loss (fast sedimentation) and flavor changes during processing and storage. This study evaluates the potential of low-oxygen spiral-filter press in combination with different preservation technologies to obtain a maximal quality of cloudy apple juice. Results showed that high intensity thermal pasteurization can effectively inactivate quality-degrading enzymes, therefore it is useful to obtain an optimal cloudy apple juice product in terms of color and cloud stability. Although HPP has minimal impact on aroma of the juice, shelf-life of the juice may be limited due to incomplete enzyme inactivation. In the case of PEF treatment, thermal effects may contribute to maintain apple juice quality.     

Inhibition of Shiga Toxin 2 (Stx2) in Apple Juices and its Resistance to Pasteurization

Abstract: In the present study, we evaluated Shiga toxin (Stx2) activity in apple juices by measuring a decrease in dehydrogenase activity of Vero cells with the microculture tetrazolium (MTT) assay. Freshly prepared juice from Red Delicious apples and Golden Delicious apples inhibited the biological activity of the bacterial toxin Stx2 produced by E. coli O157:H7 strains. Studies with immunomagnetic beads bearing specific antibodies against the toxin revealed that Stx2 activity was restored when removed from the apple juice. SDS gel electrophoresis revealed no difference (P < 0.05) in the densities or molecular weights between Stx2 in either PBS or apple juices. These results suggest that Stx2 may be reversibly bound to small molecular weight constituents in the juice. The Stx2 toxin was not inactivated on exposure to heat programs (63 °C for 30 min, 72 °C for 15 s, 89 °C for 1 s) commonly used to pasteurize apple juice, but lost all activity when exposed to 100 °C for 5 min. The results suggest that pasteurization of apple juice used to inactivate E. coli O157:H7 has no effect on Stx2, and that food-compatible and safe antitoxin compounds can be used to inhibit the biological activity of the Shiga toxin. Practical Application: This study explores the possibility of using naturally occurring antioxidative substances, in this case high phenolic apples juices, to inactivate Shiga toxin (Stx2) produced by E. coli O157:H7 in contaminated foods.     

Utilization of Endo-Polygalacturonase from Kluyveromyces fragilis in the Clarification of Apple Juice

Endo-polygalacturonase (endo-PG) from Khyveromyces fragilis produced on whey was used for the clarification of apple juice and its efficacy was compared with that of a commercial pectinase. Endo-PG was recovered from the fermentation broth with a yield of 60.7% and a purification factor of 3.85. Clarification experiments were conducted at 30°C and 50°C for different times. No significant statistical differences in the final turbidity were observed at the 1% level for samples treated with either enzyme. It was concluded that endo-PG could be successfully used in the process of clarification of apple juice.     

Evaluation of hybrid pressure-driven and osmotically-driven membrane process for non-thermal production of apple juice concentrate

This study investigates the potential of hybrid membrane processes including microfiltration (MF), ultrafiltration (UF) and forward osmosis (FO) for non-thermal concentration of apple juice. The process performance and characteristics (physicochemical properties, nutritional and aroma components and microbiological quality) of apple juice were studied. The clarity of apple juice was significantly promoted as pore size of membrane reduced. MF and UF can also ensure microbiological safety in pre-treated apple juice. According to its efficiency of filtration as well as performance of simultaneous clarification and cold-sterilization, 0.22 μm MF membrane was identified as the optimal membrane for the pre-treatment. The pre-treated apple juice can be concentrated up to 65°Brix by subsequent single stage FO. FO retained nutritional and volatile compounds of apple juice while significant reductions were found in the juice concentrated by vacuum evaporation. Hybrid MF-FO can be a promising non-thermal technology to produce apple juice concentrate with high quality.     

Reverse Osmosis and Flavor Retention in Apple Juice Concentration

Plate-and-frame (PF) and spiral-wound (SW) membrane configurations were used to study influence of reverse osmosis (RO) on flavor compounds in apple juice permeate and retentate. Low temperature (20°C) and high pressure (50 bar) were most effective operating parameters for flavor recovery. Non-volatile flavor component RO losses were due to permeation. However, loss of volatile compounds through permeation was minor compared with equipment processing losses. Flavor compounds showed more rejection by polyamide than poly-ether-urea thin-film composite membranes. The SW configuration demonstrated greater flavor losses than did PF. Chemical structure of aldehydes and esters appeared to affect flavor compound retention. Volatile losses modified the flavor profile of RO concentrated apple juice.     

APPLE JUICE QUALITY AS INFLUENCED BY ULTRAFILTRATION

Objective quality of ultrafiltered (UF) apple juice compared favorably to apple juice filtered by conventional plate and frame filtration (PF). Agtron red and green values were higher for the UF juice, indicating a lighter colored product. Agtron green values were lower after 4 months of storage and compared well to juice from conventional methods over the remaining 8 months of storage. Green color of the UF juice remained steady at storage temperatures of either 1° or 21°C and was equal to the color values of the conventional juice stored at 1°, 21° or 32°. Clarity of the UF juice was excellent and remained stable over the entire storage period at either 1 or 21° with only a slight drop in clarity at 32°. UF juice was rated significantly lower in sensory flavor than PF juice. Sensory color of the UF juice was not rated as high as the PF juice at the start of the study, but as time in storage progressed sensory color improved. Initial panel reaction to UF apple juice was that the UF juice was too light in color and watery in flavor.     

Application of biosensors in early detection of contamination with lactic acid bacteria during apple juice and concentrate production

The aim of Collective Research Project QUALI-JUICE (COLL-CT-2005, Co Nr 012461) was to introduce the biosensors in control of microbiologically pure apple juice production. Three commercial lactate biosensors were used and compared with enzyme kits assays. Parallel the microbiological analysis of the production process at one juice producing enterprise was done. The results of lactic acid assay with biosensors were in good correlation with those obtained by enzyme kits. The main benefit of biosensor use was shortening of measurement time as compared with assay by enzyme kit and possibility to measure at line. The concentration of l-lactic acid in apple pulp could be correlated with the number of lactic acid bacteria. Pasteurization process was eliminating lactic acid bacteria and the concentration of lactic acid was at this stage not exceeding 0.1 g L⁻¹. The final product (apple concentrate) contained in some cases very high amounts of lactic acid indicating secondary microbiological contamination after pasteurization step. Parallel microbiological analysis of production process and lactate assay indicated that the critical point during production was prolonged vacuum filtration after pasteurization.     

Inactivation Kinetics of Pectin Methylesterase,Polyphenol Oxidase,and Peroxidase in Cloudy Apple Juice under Microwave and Conventional Heating to Evaluate Non-Thermal Microwave Effects

Continuous-flow microwave pasteurization provides important advantages over conventional heat exchangers such as fast volumetric heating, lower tube surface temperature, and possible non-thermal effects that enhance enzymatic and bacterial inactivation. Conventional and microwave-assisted inactivation of pectin methylesterase (PME), polyphenol oxidase (PPO), and peroxidase (POD) in cloudy apple juice were investigated to evaluate non-thermal effects. Experiments were conducted to provide uniform heating with accurate temperature acquisition and similar temperature profiles for conventional and microwave treatments. A two-fraction first-order kinetic model was successfully fitted to the data in a procedure that took into account the whole time-temperature profile instead of assuming isothermal conditions. Predicted inactivation curves for pasteurization at 70 and 80 °C of the cloudy apple juice showed that PME has the highest thermal resistance (residual activity of 30% after 250 s at 80 °C) and that there was no evidence of non-thermal microwave effects on the inactivation of these enzymes.     

Effect of pulp reduction and pasteurization on the release of aroma compounds in industrial orange juice

ABSTRACT:  Release of aroma compounds in orange juice according to pulp content and pasteurization was performed by headspace-solid phase microextraction (HS-SPME), HS-SPME-GC-olfactometry, and by the determination of partition coefficients of aroma compounds between the juice and the headspace. Orange juices with 12% and 6% pulp contents were collected from a processing line before and after pasteurization. HS-SPME revealed that the 6% pulp juice was the most affected by pasteurization, with an increase in the release of several aroma compounds that are generated by heat treatment (that is, α- and β-terpinéol) and a decrease in the release of compounds sensitive to pasteurization (that is, neral and geranial). Principal component analysis of olfactometric data allowed discriminating fresh and pasteurized juices, regardless of the pulp content. The determination of the gas/liquid partition coefficients by the phase ratio variation method was possible for 7 aroma compounds. For the most hydrophobic ones, the release of aroma compounds in fresh juices was higher in the 6% pulp juice than in the 12% pulp juice. However, in pasteurized juices, the difference between their partition coefficients was less marked. Potential interactions between cloud proteins and hydrophobic aroma compounds may explain this phenomenon.     

膜技术在苹果汁加工中的应用

应用平板式超滤技术对苹果浊汁进行了过滤澄清和除菌。研究了巴式杀菌酶解或未酶解的苹果浊汁、未巴式杀菌未酶解的苹果浊汁、温度对膜通量的影响,超滤组件形式、操作参数对3种不同预处理料液的滤液质量的影响及反渗透系统的浓缩效果。结果表明:平板式超滤膜通量能满足工业需求且大于管式超滤膜,操作温度宜为50℃,当加水倍数0.09倍时,可使浓缩倍数达到20倍。苹果汁超滤液的透光率在97%以上、色值在50%以上、浊度指标小于0.3,pH值、总酸、糖度、氨基态氮等却未发生明显的变化。苹果汁超滤液质量指标和耐热细菌检查结果比较表明,平板式超滤可代替对苹果汁巴式杀菌及酶解。反渗透系统对苹果汁超滤液进行浓缩,浓缩倍数为2～2.3倍,糖截留率为100%。     

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

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 relevanceConventional 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.     

Nonthermal inactivation of polyphenol oxidase in apple juice influenced by moderate electric fields: Effects of periodic on-off and constant exposure electrical treatments

Inactivation of polyphenol oxidase (PPO) in fresh apple juice was studied in moderate electric field (MEF) treatments at field strengths in the range of 85–110 V/cm. The apple juice was subjected to periodic on-off treatments at 50 °C and constant exposure MEF treatments at 50 and 65 °C using two different electro-processing devices, specially constructed for the purpose. PPO inactivation by the electric fields was determined with respect to the corresponding control (nofield) treatments. The application of periodic on-off treatments resulted in about 100% increase (P ≤ 0.05) of the thermal inactivation rate constant of PPO at 50 °C. A similar relative increase of the thermal inactivation rate constant was observed with the constant exposure MEF treatment at 50 °C. The electric field influence was improved significantly (P ≤ 0.05) in the constant exposure MEF treatment at 65 °C. Differences in electrical energy input among the MEF treatments were observed. Results indicate both the electric field strength and the treatment temperature play critical roles in enzyme inactivation by moderate electric fields.Industrial relevanceThis study shows polyphenol oxidase enzyme in fresh apple juice can be significantly inactivated by moderate electric fields applied at below thermal pasteurization temperatures. Therefore, moderate electric field treatment applications are beneficial for the minimally processed fruit and vegetable industry.     

Shelf life and quality of skim milk processed by cold microfiltration with a 1.4-μm pore size membrane,with or without heat treatment

The objective of this study was to evaluate the effectiveness of cold microfiltration (MF), alone or in combination with heat treatment, in extending the shelf life of skim milk. Raw skim milk underwent MF at 6 ± 1°C with a ceramic membrane of 1.4-μm pore size, at a transmembrane pressure of 75.8 kPa and a crossflow velocity of 7 m/s. Samples of raw skim milk; MF skim milk; high-temperature, short-time (HTST)-pasteurized milk; and MF+HTST-pasteurized skim milk were stored at 6°C for 92 d. During the shelf-life study, the total bacterial count and degree of proteolysis were evaluated weekly. The study was replicated 3 times. Cold MF was very effective in reducing the microbial load in skim milk, and an average of 3.4 log reduction in vegetative bacteria was obtained. Although HTST pasteurization reduced the bacterial load by ～2 log, the MF+HTST process resulted in near complete elimination of vegetative microflora, with a total of ～4 log reduction. A 9-member sensory panel found no significant differences between skim milk samples processed with or without MF. The MF+HTST skim milk had only minor microbial growth after 92 d at 6°C, but its proteolytic shelf life was limited by plasmin activity. A reduction of plasmin activity and a slower rate of proteolysis were obtained by increasing the heat treatment temperature to 85°C. The results of this study can be used to make decisions regarding processing strategies that lead to increased skim milk shelf life.     

Original article: Effects of continuous dense‐phase CO2 system on antioxidant capacity and volatile compounds of apple juice

The effects of different operating conditions applied to a continuous dense‐phase carbon dioxide (DPCD) system on antioxidant capacity and volatile compounds of apple juice were compared with current heat pasteurisation method. Only the microbial tests required by Italian Regulation to assure microbiological safety to ‘fruit juices and vegetables’ were performed, and DPCD‐treated (15 MPa, 35 °C, 15 min; 25 MPa, 35 °C, 15 min), heat‐pasteurised (75 °C, 15 s) and untreated apple juice samples were considered. The DPCD processing carried out at 15 MPa resulted as effective as 25 MPa in reducing microbial cells. Trolox equivalent of DPCD treated at 25 MPa (0.41 mm ) resulted significantly (P < 0.05) lower than DPCD treated at 15 MPa (0.48 mm ). Head space analysis of volatile compounds indicated the lowest decrease in apple aroma compounds (59% esters and 59% aldehydes) in DPCD treated at 15 MPa.     

Dextransucrase Stability in Cashew Apple Juice

The use of agriculture waste as substrate for biotechnological process became an interesting alternative to reduce production costs and the negative impact of agricultural wastes disposal in the environment. In Brazil, cashew tree cultivation is done aiming the cashew nut production, and tons of cashew apples are wasted in the field after the nut removal. Thus, cashew apple juice can be used as low cost substrate for biotechnological process. In this study, the stability of dextransucrase produced in a fermentation medium using cashew apple juice as substrate was evaluated. The crude enzyme was stable at 30 °C for 30 h at pH ranging from 4.5 to 5.5. The partially purified enzyme was stable in non-fermented cashew apple juice at pH 5.0 for 96 h at 30 °C. The high stability of the enzyme in cashew apple juice at room temperature allows its industrial use without needing the enzyme purification, consequently reducing process costs.     

Evaluation of Ultrafiltration and Adsorption to Debitter Grapefruit Juice and Grapefruit Pulp Wash

Grapefruit juice and grapefruit pulp wash were ultrafiltered and debittered with a pilot system. The flow rate through the membrane increased with the transmembrane pressure up to 137.8 kPa. Limonin in grapefruit juice and grapefruit pulp wash was completely removed. The debittering process was tested at 13, 27 and 48°C. Limonin removal efficiency was independent of temperature between 13 and 48°C. However the resin column was exhausted more rapidly for na-ringin, narirutin, hesperidin, and neohesperidin particularly at 13°C. Taste panel results suggested that debittering of grapefruit pulp wash appreciably increased its flavor acceptability.     

Effects of Commercial-scale Pulsed Electric Field Processing on Flavor and Color of Tomato Juice

Effects of commercial‐scale pulsed electric field (PEF) processing on the flavor and color of tomato juice during storage at 4 deg;for 112 d were studied. Tomato juice was prepared by hot break at 88°C for 2 min and then thermally processed at 92° for 90 s or PEF processed at 40 kV/cm for 57 μs. The PEF‐processed tomato juice retained more flavor compounds of trans‐2‐hexenal, 2‐isobutylthiazole, cis‐3‐hexanol than thermally processed or unprocessed control tomato juice (P < 0.05). PEF‐processed juice had significantly lower nonenzymatic browning and higher redness than thermally processed or control juice (P < 0.05). Sensory evaluations indicated that the flavor of PEF‐processed juice was preferred to that of thermally processed juice (P < 0.01).     

Passion Fruit Juice Concentration by Ultrafiltration and Evaporation

Passion fruit juice was pretreated with pectinase, centrifugation, and pasteurization. The resulting juice was processed by Ultrafiltration (UF) to 20°Brix. The UF permeate was concentrated by evaporation to 70°Brix and combined with the UF retentate to form the final concentrated product at 40°Brix. The pretreatments caused approximately 20% flavor losses, but accomplished more than 50% flux increases. The UF recovered many important flavor constituents, and improved the rate of evaporation. The final concentrated product contained more than 30% of juice flavor. Results of sensory evaluation indicated that flavor of the reconstituted juice was inferior to fresh juice, but the two juices were not significantly different in overall acceptance.     

Comparative study on shelf life of orange juice processed by high intensity pulsed electric fields or heat treatment

The effects of high intensity pulsed electric fields (HIPEF) processing (35 kV/cm for 1,000 μs; bipolar 4-μs pulses at 200 Hz) on the microbial shelf life and quality-related parameters of orange juice were investigated during storage at 4 and 22 °C and compared to traditional heat pasteurization (90 °C for 1 min) and an unprocessed juice. HIPEF treatment ensured the microbiological stability of orange juice stored for 56 days under refrigeration but spoilage by naturally occurring microorganisms was detected within 30 days of storage at 22 °C. Pectin methyl esterase (PME) of HIPEF-treated orange juice was inactivated by 81.6% whereas heat pasteurization achieved a 100% inactivation. Peroxidase (POD) was destroyed more efficiently with HIPEF processing (100%) than with the thermal treatment (96%). HIPEF-treated orange juice retained better color than heat-pasteurized juice throughout storage but no differences (p<0.05) were found between treatments in pH, acidity and °Brix. Vitamin C retention was outstandingly higher in orange juice processed by HIPEF fitting recommended daily intake standards throughout 56 days storage at 4 °C, whereas heat-processed juice exhibited a poor vitamin C retention beyond 14 days storage (25.2–42.8%). The antioxidant capacity of both treated and untreated orange juice decreased slightly during storage. Heat treatments resulted in lower free-radical scavenging values but no differences (p<0.05) were found between HIPEF-processed and unprocessed orange juice.