Heat-treated Juice Research Articles

Benefits of isochoric freezing for carrot juice preservation.

Isochoric freezing (IF) at -5°C/77 and -10°C/100MPa was used to preserve carrot juice for 12 weeks. The juice qualities were compared to those using heat treatment (HT) at 95°C for 15s followed by cold storage at 4°C. The native population of total aerobic bacteria, yeasts, and molds in isochoric frozen juice remained below the detection limit for 12 weeks. In comparison, microbes started to grow in heat-treated juices after 3 weeks of refrigeration. The color of isochoric frozen juice appeared more deep orange than the fresh juice due to an increase in carotenoid extractability. IF was not effective in reducing the activities of peroxidase, polyphenol oxidase, and pectin methyl esterase compared with HT. However, the isochoric samples showed higher carotenoid content, polyphenol content, and antioxidant capacity compared to the fresh and heat-treated juices. PRACTICAL APPLICATION: Isochoric freezing was used to produce carrot juice with extended shelf life. Isochoric freezing could be a beneficial alternative to conventional heat treatment for carrot juice processing as the applied pressures reached total inactivation levels of spoilage microorganisms. Moreover, the low processing temperatures better retained desirable compounds and quality attributes of fresh juice throughout its shelf life.

Effect of Optimized UV-LED Technology on Modeling, Inactivation Kinetics and Microbiological Safety in Tomato Juice

This research analyzed, optimized and modeled the inactivation kinetics of pathogenic bacteria (PB1: Escherichia coli O157:H7 and PB2: Listeria monocytogenes) and determined the microbiological safety of tomato juice processed by UV-LED irradiation and heat treatment. UV-LED processing conditions were optimized using response surface methodology (RSM) and were 90% power intensity, 21 min and 273–275 nm (251 mJ/cm2) with R2 > 0.96. Using the optimal conditions, levels of PB1 and PB2 resulted a log reduction of 2.89 and 2.74 CFU/mL, respectively. The Weibull model was efficient for estimating the log inactivation of PB1 and PB2 (CFU/mL). The kinetic parameter δ showed that 465.2 mJ/cm2 is needed to achieve a 90% log (CFU/mL) reduction in PB1 and 511.3 mJ/cm2 for PB2. With respect to the scale parameter p > 1, there is a descending concave curve. UV-LED-treated tomato juice had an 11.4% lower Listeria monocytogenes count than heat-treated juice on day 28 (4.0 ± 0.82 °C). Therefore, UV-LED technology could be used to inactivate Escherichia coli O157:H7 and Listeria monocytogenes, preserving tomato juice for microbiological safety, but studies are required to further improve the inactivation of these pathogens and analyze other fruit and vegetable juices.

Isochoric freezing to extend the shelf life of pomegranate juice.

Pomegranate juice was treated by isochoric freezing (-15°C/130MPa) for 24h and then stored under three different conditions for up to 4weeks: 4°C/0.1MPa, 24°C/0.1MPa, and -10°C/100MPa. The juice microbiological stability and quality were compared to those using heat treatment at 95°C for 15s followed by cold storage at 4°C. Heat-treated and isochoric frozen (IF) pomegranate juice stored under isochoric conditions showed no spoilage microorganisms after 4weeks of storage. Also, IF juice stored at 4 or 24°C for 4weeks had lower microbial loads than those in fresh pomegranate juice. IF juice stored under isochoric conditions showed greater color stability, antioxidant capacity, and nutrient retention (anthocyanins, ascorbic acid, and total phenolic compounds) than heat-treated juices stored at 4°C. IF juice stored at 4°C also showed greater anthocyanin and ascorbic acid contents compared with heat-treated juice. PRACTICAL APPLICATION: Isochoric freezing storage at -10°C can be used to preserve the quality properties of fresh pomegranate juice. Isochoric freezing at -15°C for 24h can also be used as a pretreatment to extend the shelf life of refrigerated pomegranate juice since the applied pressures reached total inactivation levels of spoilage microorganisms.

열처리 보리수 과즙과 식초의 이화학적 특성, phytochemicals 및 생리활성

In this study, vineger was produced after heat treatment of Elaeagnus multiflora juice and its fermentative characteristics were investigated. The heat-treated juice and vinegar of E. multiflora were similar in fruit color, with b values (redness) of 39.48 (juice) and 37.56 (vinegar). After 10 days of fermentation of E. multiflora fruit, the acetic acid bacteria viable cell number, pH, acidity, reducing sugar content, and alcohol content were 4.59-4.62 log CFU/mL, 3.14-3.45, 0.2-2.12%, 0.69-35.24 mg/mL, and 0.2%, respectively. The heat-treated juice and vinegar showed significantly higher radical scavenging and digestive enzyme inhibitory activities than untreated samples, and the levels of soluble phenolics, soluble flavonoids, flavan-3-ol derivatives, and phenolic and derivatives were increased. Additioinally, the heat-treated vinegar contained major organic acids, such as acetic acid (21.82 mg/mL), and major flavan-3-ols and phenolic acids, such as catechin (72.24 μg/mL), catechin gallate (273.36 μg/mL), epigallocatechin gallate (68.35 μg/mL), protocatechuic acid (12.84 μg/mL), and salicylic acid (42.29 μg/mL). At 25 μL/mL treatment, DPPH and ABTS radical scavenging activities and α-glucosidase and pancreatic lipase inhibitory activities were 79.66%, 93.99%, 90.12%, and 64.85%, respectively. This result suggested that it is possible to produce new types of vinegar and beverages, using heat-treated E. multiflora juice.

Optimization of Shelf Stability of Sugarcane Juice with Natural Preservatives

Extracts of moringa seed and leaf (Moringa oleifera); lemon (Citrus limon) and ginger (Zingiber officinale) were added to fresh sugarcane juice in different combinations and evaluated on storage at 2, 4 and 30C. Combination of moringa seed extract with lemon and ginger showed high antimicrobial activity when compared with sodium benzoate (as chemical preservative), at the permitted level. Lemon lowered the pH of sugarcane juice to 3.01 and inhibited the growth of microorganisms during storage. Further, phytochemical analysis of methanol extract of moringa seeds and leaves revealed polyphenols, flavonoids, tannins and terpenoid compounds. It was revealed that good quality sugarcane juice (100 mL) with satisfactory storage stability at refrigeration could be prepared from heat-treated juice (72C for 15 sec) before addition of lemon (3 mL) as a combination of flavor, color enhancer and source of citric acid (antioxidant); moringa (10 mL); ginger (0.6 mL) as flavor enhancer. Practical Applications Sugarcane juice is popularly consumed in India. But large-scale production by mechanizing the manufacturing process is not carried out. Preserving raw sugarcane juice is a challenging problem because it spoils within hours of extraction. The manufacturers rely on the chemical preservatives for extending the shelf-life of sugarcane juice, which restricts its production. The research work was carried out to remove the chemical-dependent constraint with an aim to optimize the shelf-life conditions of sugarcane juice with natural preservatives. A combination of natural preservatives and low temperature storage was found as an effective way of preservation for more than a month with satisfactory sensory qualities. The findings will pave way for the marketability of sugarcane juice.

UV-C treatment using a Dean vortex technology — impact on apple juice enzymes and toxicological potential

Abstract Freshly squeezed apple juice (cultivar Gala) and commercially available naturally cloudy apple juice were treated with UV-C (254 nm, 0–53 kJ/L) using a commercial UV-C processing unit equipped with a Dean flow reactor. In this study the effect of UV-treatment on enzyme activities, as well as possible cytotoxic and genotoxic effects and furan formation in apple juice were investigated. Even at the highest dose applied (53 kJ/L) no significant effect on the activities of polyphenol oxidase, pectin esterase and polygalacturonase could be determined and residual enzyme activities above 95% were observed in all samples. By raising UV-C irradiation dose to 2.1 kJ/L, the upper limit of practical use, a slight increase in furan concentration from 2.3 to 3.7 μg/kg was observed. However, these concentrations are in the range of commercial, heat-treated juices available on the German market. UV-C treated (10.6 kJ/L) and non-treated apple juice showed no cytotoxic effect in the WST-1 assay when added in concentrations up to 20% (v/v). Furthermore, no difference on DNA strand break formations between treated and non-treated apple juice was observed. Thus, despite a slight increase in the concentration of a potentially genotoxic compound such as furan, UV-C treatment at dosages under investigation did not result in any change in the cytotoxic and genotoxic effects of apple juice on intestinal Caco-2 cells. Industrial relevance Ultraviolet treatment is a promising non-thermal technology for enhancing shelf life of liquid food. While the inactivation of food related microorganisms is well investigated little is known about the effect on compounds like enzymes and in particular the cyto- and genotoxicological potential of UV-C treated products. Our results provide useful information and assistance for regulatory authorities regarding risk and quality assessment of the emerging UV-C technology.

Changes on indigenous microbiota, colour, bioactive compounds and antioxidant activity of pasteurised pomegranate juice

Juices prepared from arils of ‘Mollar’ pomegranates were analysed for naturally occurring microorganisms, CIE Lab colour parameters, total phenols, anthocyanins and punicalagins, ellagic acid content and antioxidant capacity before and after low-, mild- and high-temperature pasteurisations (LTPs, MTPs and HTPs): 65, 80 and 90°C for 30 or 60s. Mean aerobic plate count (APC), yeast and mold count (YMC), and lactic acid bacteria (LAB) for fresh juices were 5.7, 5.36 and 4.0 log CFU/mL, respectively. MTPs and HTPs were sufficiently effective to decrease APCs to nil or negligible levels. An increase in CIE a values and decrease in CIE b values were the characteristic colour changes in heat-treated juices. The effect of pasteurisations showed that total phenols, punicalagins and ellagic acid were not much affected by thermal processing. Total anthocyanin content and antioxidant capacity were substantially and significantly influenced by the heat treatment applied. A linear relationship was observed between Trolox equivalent antioxidant capacity (TEAC) values and total anthocyanins, suggesting that they contributed strongly to the antioxidant capacity of pomegranate juice.

Effects of UV-C Light Processing on Some Quality Characteristics of Grape Juices

White and red grape juices (GJs) were subjected to ultraviolet C (UV-C) light as a non-thermal preservation technology using a coiled tube UV-C reactor with nine lamps. The effects of UV-C light on microbial (total aerobic count and yeast and mould count) and some chemical quality characteristics (total phenolics, antioxidant capacity, anthocyanin and polymeric colour, etc.) of white and red GJs were investigated. The results were compared with control (untreated) and heat-treated juice samples. Single-pass UV-C treatment (12.6 J/mL) of white and red GJs resulted in 3.51 and 3.59 log reductions in total aerobic count and, 2.71 and 2.89 log reductions in yeast and mould counts, respectively. The microbial loads of both GJs were completely eliminated after two passes through the reactor (25.2 J/mL). After UV-C and heat treatments, there were no significant changes in antioxidant capacity, total phenolics, titratable acidity, soluble solids and pH of white and red GJs (P > 0.05). The losses in monomeric anthocyanins were 6.1% and 8.7% after UV-C treatment of 12.6 and 25.2 J/mL doses, respectively. However, anthocyanin level of red GJ was significantly affected by the heat treatment with an 11.8% loss (P < 0.05). The percent polymeric colour of the red GJ with heat treatment was significantly higher compared to the colour with the UV-C treatment.

Thermal Stability of Ricin in Orange and Apple Juices

Ricin is a potent protein toxin that could be exploited for bioterrorism. Although ricin may be detoxified using heat, inactivation conditions in foods are not well characterized. Two brands of pulp-free orange juice and 2 brands of single-strength apple juice (one clarified and the other unclarified) containing 100 microg/mL added ricin were heated at 60 to 90 degrees C for up to 2 h. With increasing heating times and temperatures the heat-treated juices exhibited decreasing detectability of ricin by enzyme-linked immunosorbent assay (ELISA) and cytotoxicity to cultured cells. Z-values for ricin inactivation in orange juices were 14.4 +/- 0.8 degrees C and 17 +/- 4 degrees C using cytotoxicity assays, compared to 13.4 +/- 1.5 degrees C and 14 +/- 2 degrees C determined by ELISA. Although insignificant differences were apparent for z-values measured for the 2 orange juice brands, significant differences were found in the z-values for the 2 brands of apple juice. The z-values for ricin inactivation in the clarified and unclarified apple juices were 21 +/- 4 degrees C and 9.5 +/- 1.1 degrees C, determined by cytotoxicity assays, and 20 +/- 2 degrees C and 11.6 +/- 0.7 degrees C, respectively, using ELISA. Overall, there were no significant differences between results measured with ELISA and cytotoxicity assays. Ricin stability in orange juice and buffer was evaluated at 25 degrees C. Half-lives of 10 +/- 3 d and 4.9 +/- 0.4 d, respectively, indicated that active ricin in juice could reach consumers. These results indicate that ricin in apple and orange juices can remain toxic under some processing and product storage conditions. Ricin is a potent toxin that is abundant in castor beans and is present in the castor bean mash by-product after cold-press extraction of castor oil. U.S. Health and Human Services recognizes that ricin could be used for bioterrorism. This study reports the stability of ricin in apple and orange fruit juices at temperatures ranging from 60 to 90 degrees C (140 to 194 degrees F).

Volatile compounds and changes in flavour-related enzymes during cold storage of high-intensity pulsed electric field- and heat-processed tomato juices

The effects of high-intensity pulsed electric field (HIPEF) processing (35 kV cm(-1) for 1500 micros, using 4 micros bipolar pulses at 100 Hz) on the production of volatile compounds and flavour-related enzymes in tomato juice were investigated and compared with those of thermal processing (90 degrees C for 30 or 60 s). Tomato juice treated by HIPEF showed lower residual lipoxygenase (LOX) activity (70.2%) than juice heated at 90 degrees C for 60 s (80.1%) or 30 s (93.2%). In contrast, hydroperoxide lyase (HPL) was almost completely inactivated when the juice was subjected to 90 degrees C for 60 s, whereas roughly 50% of the control tomato juice was depleted after HIPEF treatment or thermal processing at 90 degrees C for 30 s. A slight decrease was observed in the initial LOX activity of treated and untreated samples during storage, whereas initial HPL activity was strongly affected over time. HIPEF-treated juice exhibited higher levels of compounds contributing to tomato aroma than untreated and heat-treated juices throughout storage. Thus HIPEF processing can preserve flavour quality and stability of tomato juice compared with conventional thermal treatments.

Flavour retention and related enzyme activities during storage of strawberry juices processed by high-intensity pulsed electric fields or heat

Abstract The effects of high-intensity pulsed electric fields (HIPEF) processing (35 kV/cm for 1700 μs using pulses of 4 μs at 100 Hz in bipolar mode) and thermal treatments (90 °C for 30 s or 60 s) on lipoxygenase (LOX) and β-glucosidase (β-GLUC) activities as well as on the production of volatile compounds were assessed in strawberry juice for 56 days of storage. HIPEF-treated juice kept higher residual LOX activity than heat-treated juices during the first 28 days of storage. Moreover, β-GLUC increased its initial activity just after HIPEF processing. The concentration of DMHF in HIPEF-processed strawberry juice was above those of untreated and heat-treated juices during the first 14 days of storage. On the other hand, concentrations of ethyl butanoate and 1-butanol obtained after HIPEF processing were better maintained than after thermal processing. However, thermally-treated samples showed an increase in the amount of 1-butanol beyond day 35, causing an unpleasant flavour to the product. Thus, flavour stability in HIPEF-processed strawberry juice was greater than in thermally-treated samples during storage.

Changes in quality attributes throughout storage of strawberry juice processed by high-intensity pulsed electric fields or heat treatments

Abstract The effects of high-intensity pulsed electric field (HIPEF) processing (35 kV/cm for 1700 μs applying 4-μs pulses at 100 Hz in bipolar mode) on color, viscosity and PME and PG activities in strawberry juice were studied and compared to those of heat treatments (90 °C for 60 s or 30 s) through 63 days of storage. L∗ and viscosity values of the HIPEF-processed juices were higher than those found in the thermally treated. In addition, HIPEF-treated juice exhibited lower 5-(hydroxymethyl)-2-furfural (HMF) concentration and browning index than heat-treated juices throughout storage. On the other hand, HIPEF-treated juice maintained low residual pectin methylesterase (PME) activity (13.1%) for 63 days, whereas in the case of the thermally treated, 22.2 and 48.8% was retained after 60 s and 30 s, respectively. Strawberry juice treated by HIPEF achieved lower residual polygalacturonase (PG) activity (73.3%) than those of heat-processed at 90 °C for 60 s (76.2%) or 30 s (96.8%). Thus, HIPEF could be a feasible alternative to thermal processing to minimize browning and viscosity loss in strawberry juice during storage.

Inhibitory Effects of Na-Hypochlorite and Heating on the Mycobiota Associated with Fruits or Juice of Passion (Passiflora edulis Sims) in Uganda

A total of 34 species belonging to 21 genera of fungi were recorded on passion fruits of both pure and hybrid origin in Uganda, however, the pure type exhibited wider spectrum (28 species and 16 genera) than the hybrid type (21 & 15). Also, yeasts (unidentified and Rhodotorula mucilaginosa) were also encountered in high numbers. Moreover, the mean count of all mycobiota obtained from the pure type was higher than that of hybrid, despite the bigger size of the later. Members of yeasts and Cladosporium followed by Phoma, Penicillium, Fusarium and Alternaria species dominated on passion fruits of pure origin, while only C. cladosporioides, F. solani and yeasts dominated on the hybrid type. Treatment with Na-hypoehlo- rite exhibited inhibitory effects on the total myeobiotie propagules as well as the dominant species from fruits of both types. The current results, therefore, suggest the use of Na-hypoehlorite to control the post-harvest mycobiota associated with passion fruits. Regarding the mycobiota contaminating passion juice, yeasts were found to be the major contaminants with Candida parapsilosis being the most common. Moulds constituted only a minor proportion with Acremonium strictum followed by Fusarium chlamydosporum, R moniliforme, R acuminatum and F. solani as the most dominant species. In the heat-treated juice samples, the counts of the most commonly encountered mycobiota (both yeasts and molds) were significantly inhibited or completely eliminated. Some unidentified Bacillus species were also recovered from the juice, however, their counts in the heated samples were increased but insignificantly.

Ascorbic acid stability during refrigerated storage of orange–carrot juice treated by high pulsed electric field and comparison with pasteurized juice

The degradation kinetics of ascorbic acid was determined in orange–carrot juice treated by PEF in order to establish its shelf life. Different electric field intensities (25, 30, 35, and 40 kV/cm) and different treatment times (from 30 to 340 μs) were studied. The ascorbic acid degradation rate ( k) obtained was −0.009 ± 0.0008 μs −1, −0.0140 ± 0.0009 μs −1, −0.0220 ± 0.0023 μs −1 and −0.0187 ± 0.0049 μs −1 for fields of 25, 30, 35, and 40 kV/cm, respectively. The treatment selected was 25 kV/cm. The shelf life of the orange–carrot juice treated by pulses at 25 kV/cm for two times (280 μs and 330 μs) was compared with a heat-treated juice (98 °C, 21 s) kept in refrigerated storage at 2 and 10 °C. The remaining concentration of ascorbic acid in the pasteurized orange–carrot juice was 83%, whereas in the PEF-treated juice it was 90%. The ascorbic acid degradation rate in the juice stored at 2 °C was less than in the juice stored at 10 °C, and in the pasteurized juice it was greater. PEF treatment at 25 kV/cm for 280–330 μs extended the half-life of the juice stored at 2 °C to 50 days.