Comparing the effects of high hydrostatic pressure and high temperature short time on papaya beverage

Effect of the High Hydrostatic Pressure Process on the Microbial and Physicochemical Quality of Shalgam

The processing of shalgam requires the use of an appropriate processing technique due to yeast overgrowth. With advancements in processing technology, high hydrostatic pressure (HHP) as nonthermal and nonchemical preservation has gained attention for its potential. Response surface methodology with the Box-Behnken experimental design was used to make sense of the effects of HHP parameters, namely, pressure (100-500 MPa), temperature (20-40 °C), and time (5-15 min), on microbial and physicochemical factors (pH, total soluble solids, titratable acidity, bioactive compounds, color values). The reduction in the counts of total mesophilic aerobic bacteria, lactic acid bacteria, and yeast-mold increased proportionally with the increase of all pressure levels, application temperatures, and pressurization times (p < 0.05). Stability was maintained in pH, total solubility, and some color parameters such as L*, a*, ΔE, yellow color tone, and red color tone. All findings of the bioactive components (phenolic content, flavonoid content, antioxidant activity, and monomeric anthocyanin content) in the RSM design showed a significant change only in proportion to the square of time (p < 0.05). The optimum pressurization parameter combination of shalgam was determined as a pressure of 367 MPa, temperature of 31.9 °C, and process time of 10.5 min. Under these conditions, values of yeast and mold (Y&M) reduction, total flavonoid content (TFC), total monomeric anthocyanin contents (TMACs), titratable acidity (TA), and reducing sugar content (RSC) were obtained as 4.30 log cfu/mL, 192.89 mg QE/100 mL, 11.88 mg/100 mL, 2.41 glactic acid/L, and 6.78 mg/100 mL, respectively. In particular, the findings in the basic color parameters proved that there was no significant change in the saturated red color of the shalgam. Gallic acid, caffeic acid, chlorogenic acid, catechin, cyanidin-3-O-glucoside, malvidin-3-O-glucoside, and peonidin-3-O-glucoside derivatives are dominant phenolic and anthocyanin compounds, which are frequently found in turnip plants. No important losses in bioactive components were observed, despite changes in pressure and temperature parameters. The HHP method can be suggested to have great potential in the processing of shalgam (fermented turnip beverage) in terms of its ability to maintain the flavors, colors, and nutrients, in addition to ensuring microbiological safety when compared to other preservation methods.

Benefits of isochoric freezing for carrot juice preservation

Isochoric freezing (IF) at -5°C/77 and -10°C/100 MPa was used to preserve carrot juice for 12 weeks. The juice qualities were compared to those using heat treatment (HT) at 95°C for 15 s 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.

The antioxidant capacity and nutrient composition characteristics of lotus (Nelumbo nucifera Gaertn.) seed juice and their relationship with color at different storage temperatures

The effects of different storage temperatures on the nutritional quality, color, and antioxidant capacity of lotus seed juice and the correlations between various physicochemical indices and antioxidant capacity during storage were investigated in this study. The results showed that the overall retention rate of various nutrients and antioxidant activity in lotus seed juice under low-temperature storage was better than that under 37 °C storage. Meanwhile, temperature had a significant effect on increasing the browning of lotus seed juice and the change in L*. The results of Pearson correlation and redundancy analysis (RDA) showed that the reduction in antioxidant activity in lotus seed juice aggravated the browning index of the system at high temperatures. The color changes in the system were closely related to the clarity of lotus seed juice and aging of starch at low temperatures.

Effect of Storage Conditions on the Stability of Polyphenols of Apple and Strawberry Purees Produced at Industrial Scale by Different Processing Techniques

During a food product's life, storage conditions affect its composition of nutrients, bioactive compounds, and sensory attributes. In this research, strawberry and apple purees were selected as a model to examine how the storage of various purees industrially produced with different technologies affect the bioactive phenolic compounds, color, and sensory attributes. Specifically, fruit products processed on an industrial scale by different technologies including freezing, thermal treatment (mild and standard), and high-pressure processing were studied, as well as storage for up to 12 months at -20, 4, and 24 °C. In strawberry puree, storage conditions had a stronger impact on phenolic compound levels, particularly on anthocyanins, whereas in apple puree, the initial processing techniques exerted a greater influence than storage conditions, mainly caused by the hot or cold crushing processes. In general, proanthocyanidins were the major phenolic group and the most stable during storage, while anthocyanins were the group most affected by both processing and storage. Apple flavonols and dihydrochalcones were quite stable, while strawberry ellagitannins suffered higher degradations during storage. Through our analysis, it is found that during storage, the stability of polyphenols in each fruit is different, and processing and storage can be either detrimental or even beneficial. The selection of the ideal storage conditions (time and temperature) is a key factor to maintaining the polyphenol content in sensitive fruits such as strawberries. However, storage conditions are in some cases more important to minimizing the polyphenol losses than how the product is processed.

Microbial inactivation and quality impact assessment of red pepper paste treated by high pressure processing

The study aimed to investigate inactivation of naturally occurring microorganisms and quality of red pepper paste treated by high pressure processing (HPP). Central composite rotatable design was employed to determine the impacts of pressure (100-600 MPa) and holding time (30-600 s). HPP at 527 MPa for 517 s reduced aerobic mesophilic bacteria count by 4.5 log CFU/g. Yeasts and molds counts were reduced to 1 log CFU/g at 600 MPa for 315 s. Total phenols, carotenoids and antioxidants activity ranged from 0.28 to 0.33 g GAE/100 g, 96.0-98.4 mg βc/100 g and 8.70-8.95 μmol TE/g, respectively. Increase (2.5-6.7%) in these variables was observed with increasing pressure and holding time. Total color difference (ΔE∗) values (0.2-2.8) were within the ranges of 'imperceptible' to 'noticeable'. Experimental results were fitted satisfactorily into quadratic model with higher R² values (0.8619-0.9863). Optimization process suggested treatment of red pepper paste at 536 MPa for 125 s for maximum desirability (0.622). Validation experiments confirmed comparable percentage of relative errors. Overall, this technique could be considered as an efficient treatment for the inactivation of microorganisms that naturally occur in red pepper paste with minimal changes in its characteristics.

Inactivating Food Microbes by High-Pressure Processing and Combined Nonthermal and Thermal Treatment: A Review

High-pressure processing (HPP) is a mild technology alternative to thermal pasteurization and sterilization of different food products. HPP has emerged to provide enormous benefits to consumers, i.e., mildly processed food and additive-free food. It effectively retains bioactive compounds and extends the shelf life of food commodities by inactivating bacteria, yeast, mold, and virus. The limitation of HPP in inactivating spores can be overcome by using other thermal and nonthermal processing sequentially or simultaneously with HPP. This review summarizes the applications of HPP in the fruits and vegetables, dairy, meat, fish, and poultry sector. It also emphasizes microbial food safety and the effectiveness of HPP in the load reduction of microorganisms. Comprehensive information about the synergistic effect of HPP with different techniques and their effectiveness in ensuring food safety is reported. The summarized data would be handy to interested researchers and industry personnel.

Effect of high hydrostatic pressures on microorganisms, total phenolic content and enzyme activity of mamey (Pouteria sapota) nectar

Mamey (Pouteria sapota) is a Mexican native fruit of sweet flavor and high content of antioxidants. Some of these antioxidants are  sensitive to high temperatures. Nonthermal technologies such as high hydrostatic pressures (HHP) could be an adequate alternative to traditional thermal pasteurization. Mamey nectars were treated under different HHP conditions and the effects on native microorganisms (mesophilic bacteria, molds and yeast), pectinmethylesterase (PME) and polyphenoloxidase (PPO) activities as well as on total phenolic content (TPC), were evaluated. Most HHP treatments conditions were equally effective to inactive native microorganisms. The application of HHP improved the extraction of TPC showing increments of 24% (400 MPa/2 min) to 64% (500 MPa/2 min) compared with the control samples. At 500 MPa/5 and 10 min maximum inactivation levels of PPO of about 40% were obtained, while PME activity showed decrements up to 70% at 400 MPa/5 min. HHP showed to be a potential technology to preserve mamey nectar, but more conditions should be tested to reach higher enzyme inactivation.

Ifs and buts of non-thermal processing technologies for plant-based drinks' bioactive compounds

Vegetables and fruits contain a variety of bioactive nutrients and non-nutrients that are associated with health promotion. Consumers currently demand foods with high contents of healthy compounds, as well as preserved natural taste and flavour, minimally processed without using artificial additives. Processing alternatives to be applied on plant-based foodstuffs to obtain beverages are mainly referred to as classical thermal treatments that although are effective treatments to ensure safety and extended shelf-life, also cause undesirable changes in the sensory profiles and phytochemical properties of beverages, thus affecting the overall quality and acceptance by consumers. As a result of these limitations, new non-thermal technologies have been developed for plant-based foods/beverages to enhance the overall quality of these products regarding microbiological safety, sensory traits, and content of bioactive nutrients and non-nutrients during the shelf-life of the product, thus allowing to obtain enhanced health-promoting beverages. Accordingly, the present article attempts to review critically the principal benefits and downsides of the main non-thermal processing alternatives (High hydrostatic pressure, pulsed electric fields, ultraviolet light, and ultrasound) to set up sound comparisons with conventional thermal treatments, providing a vision about their practical application that allows identifying the best choice for the sectoral industry in non-alcoholic fruit and vegetable-based beverages.

Non-conventional Stabilization for Fruit and Vegetable Juices: Overview, Technological Constraints, and Energy Cost Comparison

This study will provide an overview and a description of the most promising alternatives to conventional thermal treatments for juice stabilization, as well as a review of the literature data on fruit and vegetable juice processing in terms of three key parameters in juice production, which are microbial reduction, enzyme inactivation, and nutrient-compound retention. The alternatives taken into consideration in this work can be divided, according to the action mechanism upon which these are based, in non-conventional thermal treatments, among which microwave heating (MWH) and ohmic heating (OH), and non-thermal treatments, among which electrical treatments, i.e., pulsed electric fields (PEF), high-pressure processing (HPP), radiation treatments such as ultraviolet light (UVL) and high-intensity pulsed light (PL), and sonication (HIUS) treatment, and inert-gas treatments, i.e., the pressure change technology (PCT) and supercritical carbon dioxide (SC-CO2) treatments. For each technology, a list of the main critical process parameters (CPP), advantages (PROS), and disadvantages (CONS) will be provided. In addition, for the non-thermal technologies, a summary of the most relevant published result of their application on fruit and vegetable juices will be presented. On top of that, a comparison of typical specific working energy costs for the main effective and considered technologies will be reported in terms of KJ per kilograms of processed product.

Effect of High Hydrostatic Pressure on the Extractability and Bioaccessibility of Carotenoids and Their Esters from Papaya (Carica papaya L.) and Its Impact on Tissue Microstructure

High hydrostatic pressure (HHP) is a non-thermal technology widely used in the industry to extend food shelf-life and it has been proven to enhance the extractability of secondary metabolites, such as carotenoids, in plant foods. In this study, fresh-cut papaya pulp of varieties (Sweet Mary, Alicia and Eksotika) from the Canary Islands (Spain) were submitted to the HHP process (pressure: 100, 350 and 600 MPa; time: come-up time (CUT) and 5 min) to evaluate, for the first time, individual carotenoid and carotenoid ester extractability and to assess their bioaccessibility using an in vitro simulated gastrointestinal digestion assay, following the standardized INFOGEST® methodology. In addition, changes in papaya pulp microstructure after HHP treatments and during the different phases of the in vitro digestion were evaluated with optical light microscopy. HPLC-DAD (LC-MS/MS (APCI+)) analyses revealed that HHP treatments increased the carotenoid content, obtaining the highest extractability in pulp of the Sweet Mary papaya variety treated at 350 MPa during 5 min (4469 ± 124 μg/100 g fresh weight) which was an increase of 269% in respect to the HHP-untreated control sample. The highest carotenoid extraction value within each papaya variety among all HHP treatments was observed for (all-E)-lycopene, in a range of 98-1302 μg/100 g fresh weight (23-344%). Light micrographs of HHP-treated pulps showed many microstructural changes associated to carotenoid release related to the observed increase in their content. Carotenoids and carotenoid esters of papaya pulp submitted to in vitro digestion showed great stability; however, their bioaccessibility was very low due to the low content of fatty acids in papaya pulp necessary for the micellarization process. Further studies will be required to improve papaya carotenoid and carotenoid ester bioaccessibility.

Impact of High-Pressure Processing on Antioxidant Activity during Storage of Fruits and Fruit Products: A Review

Fruits and fruit products are an essential part of the human diet. Their health benefits are directly related to their content of valuable bioactive compounds, such as polyphenols, anthocyanins, or vitamins. Heat treatments allow the production of stable and safe products; however, their sensory quality and chemical composition are subject to significant negative changes. The use of emerging non-thermal technologies, such as HPP (High Pressure Processing), has the potential to inactivate the microbial load while exerting minimal effects on the nutritional and organoleptic properties of food products. HPP is an adequate alternative to heat treatments and simultaneously achieves the purposes of preservation and maintenance of freshness characteristics and health benefits of the final products. However, compounds responsible for antioxidant activity can be significantly affected during treatment and storage of HPP-processed products. Therefore, this article reviews the effect of HPP treatment and subsequent storage on the antioxidant activity (oxygen radical absorbance capacity (ORAC) assay), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity assay, ferric reducing antioxidant power (FRAP) assay, 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging capacity assay or Trolox equivalent antioxidant capacity (TEAC) assay), and on the total phenolic, flavonoid, carotenoid, anthocyanin and vitamin contents of fruits and different processed fruit-based products.

Effect of nonthermal treatments on selected natural food pigments and color changes in plant material

In recent years, traditional high-temperature food processing is continuously being replaced by nonthermal processes. Nonthermal processes have a positive effect on food quality, including color and maintaining natural food pigments. Thus, this article describes the influence of nonthermal, new, and traditional treatments on natural food pigments and color changes in plant materials. Characteristics of natural pigments, such as anthocyanins, betalains, carotenoids, chlorophylls, and so forth available in the plant tissue, are shortly presented. Also, the characteristics and mechanism of nonthermal processes such as pulsed electric field, ultrasound, high hydrostatic pressure, pulsed light, cold plasma, supercritical fluid extraction, and lactic acid fermentation are described. Furthermore, the disadvantages of these processes are mentioned. Each treatment is evaluated in terms of its effects on all types of natural food pigments, and the possible applications are discussed. Analysis of the latest literature showed that the use of nonthermal technologies resulted in better preservation of pigments contained in the plant tissue and improved yield of extraction. However, it is important to select the appropriate processing parameters and to optimize this process in relation to a specific type of raw material.

Retention of polyphenols and vitamin C in cranberrybush purée (Viburnum opulus) by means of non-thermal treatments

The effects of high pressure processing (HPP; 200-600 MPa for 5 or 15 min) and pulsed electric field (PEF; 3 kV/cm, 5-15 kJ/kg) treatment on physicochemical properties (conductivity, pH and total soluble solids content), bioactive compounds (vitamin C, total phenolic (TPC), total flavonoid (TFC), total anthocyanin (TAC) and chlorogenic acid contents), antioxidant capacities (DPPH and CUPRAC assays) and polyphenol oxidase (PPO) activity of cranberrybush purée were evaluated immediately after processing. The results were compared to an untreated purée. According to the results, conductivity increased significantly after PEF (15 kJ/kg) treatment. PEF and HPP treatments resulted in a better retention of bioactive compounds (increase in TPC in the range of ~4-11% and ~10-14% and TFC in the range of ~1-5% and ~6-8% after HPP and PEF, respectively) and antioxidant activity (as measured with CUPRAC method) compared to untreated sample. HPP reduced residual enzyme activity of PPO comparatively better than PEF.

Phenolic Compounds in Mesoamerican Fruits-Characterization, Health Potential and Processing with Innovative Technologies

Diets rich in phenolic compounds have been associated to reducing the risk of metabolic syndrome and its derived disorders. Fruits are healthy components of the human diet because of their vitamin, mineral, fiber and phenolic profile. However, they have a short shelf-life which is limited by microbiological growth and enzymatic activity. Innovative preservation methods such as high hydrostatic pressure, pulsed electric fields, ultrasound, microwave, cold plasma and ultraviolet light have become popular for the processing of fruits because they can preserve nutritional quality. In this review, the phenolic profile and health potential of 38 Mesoamerican fruits were assessed. Phenolic compounds were classified based on their contribution to the diet as flavonoids, phenolic acids, tannin, lignins and stilbenoids. Due to this composition, fruits showed a wide range of bioactivities which included anti-inflammatory, anti-diabetic, anti-hypertensive and anti-obesity activities, among others. Phenolic content in fruits submitted to innovative food processing technologies depended on parameters such as enzymatic activity, antioxidant capacity, microstructure integrity and cell viability. Innovative technologies could increase phenolic content while assuring microbiological safety by (i) promoting the release of bound phenolic compounds during processing and (ii) inducing the synthesis of phenolic compounds by activation of phenylpropanoid pathway during storage.

Effects of high pressure processing (HPP) on microorganisms and the quality of mango smoothies during storage

The objective of this study is to investigate the effects of high pressure processing (HPP) on the quality of mango smoothies and the inactivation of microorganisms therein, with heat treatments used as the control. Comparative analysis was conducted on the microbiological changes in the mango smoothies subjected to HPP at 400-600 MPa for 0-15 min. The total plate count (TPC) and the yeast and mold (YM) counts were found to be significantly inactivated through increases in the pressure and treatment time (p < 0.05). Conditions of 90 °C/20 min (HT), 500 MPa/8 min (HPP-500) and 600 MPa/5 min (HPP-600) were, thus, selected as the subsequent treatment for a storage study at 4 °C for 15 days, since these conditions had similar inactivation effects on TPC and YM. After 15 days of storage, the TPC was found to have increased by 3.87, 3.54 and 3.36 log10 cycles in the mango smoothies treated by HT, HPP-500 and HPP-600, respectively, while the YM counts remained at less than 1 log10 cycle in all samples. During storage, compared to the HT and HPP-600 samples, both the color and viscosity at 100 s-1 of samples treated by HPP-500 were found to be better maintained. Carotene content was better retained in storage after the HPP process than after the HT process. However, the different treatments had no effect on the pH nor on the total soluble solids (TSS) in the samples. The study ascertained that HPP-500 is able to ensure both the microbial safety and the quality of mango smoothies more effectively than HT and HPP-600.

Changes in Physicochemical Properties and Volatiles of Kiwifruit Pulp Beverage Treated with High Hydrostatic Pressure

Physicochemical properties and volatiles of kiwifruit pulp beverage treated with high hydrostatic pressure (HHP, 400–600 MPa/5–15 min) were investigated during 40-day refrigerated storage. Compared with heat treatment (HT), HHP ranged from 400–500 MPa was superior in retaining vitamin C, fresh-like color and volatiles, while soluble solids content and pH were not affected significantly. Furthermore, HHP improved brightness and inhibited browning of kiwifruit pulp beverage. Samples treated at 400 MPa for 15 min showed significantly higher vitamin C content and lower ∆E values over 40 days than heat-treated kiwifruit pulp beverage. The total content of alcohols, esters, acids, and ketones gradually increased, whereas the total aldehydes content decreased during storage. Interestingly, HHP treatment at 500 MPa for 15 min mostly retained important characteristic volatiles including hexanal and (E)-2-hexenal, indicating this treatment was more conducive to preserve the original fruity, fresh, grassy and green notes of kiwifruit pulp beverage than HT.

Application of non-thermal pretreatment techniques on agricultural products prior to drying: a review

BACKGROUND

Most agricultural crops contain high moisture content (80-95% wet basis (wb)) which makes them very susceptible to microbial damage leading to shorter shelf-life and high postharvest losses. The high perishability of these agricultural products requires preservation techniques to prolong their shelf-lives. Drying remains an important component of processing in this regard. Therefore, any pretreatment methods for drying agricultural product that decreases the moisture content and minimizes drying time by conserving the quality of the crop product is of prime significance. This article is a comprehensive review of recent developments of non-thermal pretreatment (NTP) methods. A summary of their significance, emerging and innovative methods of this technology together with its applications and limitations are discussed. This article further examines the environmental impact of NTP techniques.

RESULTS

NTP techniques, such as high pressure, ultrasound, pulsed electric field and osmotic dehydration methods are essential operations for pre-dehydration of agricultural products prior to drying. These techniques can avoid the deleterious effects of heat on nutritive value, colour and flavour of agricultural products compared to thermal pretreatments. They also enhance the inactivation of the enzymes, improve energy efficiency and mass transfer, reduce processing time, preserve bioactive compounds, improve drying kinetics and drying rate, minimize enzymatic browning, and enhance product quality.

CONCLUSION

These findings will provide a better understanding of different NTP methods and also make available more information for selecting pretreatment techniques for drying of agricultural products. © 2020 Society of Chemical Industry.

Effects of high hydrostatic pressure on the microbial inactivation and extraction of bioactive compounds from açaí (Euterpe oleracea Martius) pulp

The aim of this study was to investigate the effects of high hydrostatic pressure (HHP) on the inactivation of Lactobacillus fructivorans, on the inactivation of Alicyclobacillus acidoterrestris spores and on the extraction of anthocyanins and total phenolics from açaí pulp. The tested conditions comprised pressures of 400-600 MPa, treatment times of 5-15 min, and temperatures of 25 °C and 65 °C. Results were compared to those of conventional thermal treatments (85 °C/1 min). Regarding A. acidoterrestris spores, applying HHP for 13.5 min, resulted in a value of four-decimal reduction. L. fructivorans presented considerable sensitivity to HHP treatment, achieving inactivation rates above 6.7 log cycles at process conditions at 600 MPa and 65 °C for 5 min. All samples of açaí pulp processed showed absence of thermotolerant coliforms during the 28 days of refrigerated storage (shelf life study). The açaí pulps processed by HHP (600 MPa/5 min/25 °C) had anthocyanin extraction increased by 37% on average. In contrast, conventional thermal treatment reduced anthocyanin content by 16.3%. For phenolic compounds, the process at 600 MPa/5 min/65 °C increases extraction by 10.25%. A combination of HHP treatment and moderate heat (65 °C) was shown to be an alternative to thermal pasteurization, leading to microbiologically safe products while preserving functional compounds.

Effects of high hydrostatic pressure on the overall quality of Pêra-Rio orange juice during shelf life

The effect of high hydrostatic pressure on antioxidant activity, total phenolic compounds, physicochemical characteristics, color, pectin methylesterase activity, and microbiological count were evaluated during the shelf life of Pêra-Rio orange juice. Pressurized (520 MPa, 60 ℃, for 360 s), non-processed and pasteurized (95 ℃/30 s) orange juice were compared at zero time of storage. Pressurized and pasteurized juices were studied during a refrigerated 90-day shelf life. Pressurization did not cause expressive change in physicochemical characteristics of Pêra-Rio orange juice along shelf life, but significantly reduced pectin methylesterase residual activity to 13% and microbiological counts below detection levels up to 68 days of storage, with small counts (30.0 × 10 CFU/mL mesophilic aerobic bacteria and 20.7 × 10 CFU/mL yeast and mold) at 90 days, capable of ensuring the juice's stability along shelf life. Lightness ( L*) and b* values were significantly reduced by high hydrostatic pressure during shelf life, while a* values were significantly higher. Ascorbic acid decreased around 80% during shelf life. Antioxidant activity remained stable after processing and during storage.

Comparative Evaluation of the Antioxidant Capacities, Organic Acids, and Volatiles of Papaya Juices Fermented by Lactobacillus acidophilus and Lactobacillus plantarum

Fermentation of foods by lactic acid bacteria is a useful way to improve the nutritional value of foods. In this study, the health-promoting effects of fermented papaya juices by two species, Lactobacillus acidophilus and Lactobacillus plantarum, were determined. Changes in pH, reducing sugar, organic acids, and volatile compounds were determined, and the vitamin C, total phenolic content, and flavonoid and antioxidant capacities during the fermentation process were investigated. Juices fermented by Lactobacillus acidophilus and Lactobacillus plantarum had similar changes in pH and reducing sugar content during the 48 h fermentation period. Large amounts of aroma-associated compounds and organic acids were produced, especially lactic acid, which increased significantly (p<0.05) (543.18 mg/100 mL and 571.29 mg/100 mL, resp.), improving the quality of the beverage. In contrast, the production of four antioxidant capacities in the fermented papaya juices showed different trends after 48 hours’ fermentation by two bacteria. Lactobacillus plantarum generated better antioxidant activities compared to Lactobacillus acidophilus after 48 h of fermentation. These results indicate that fermentation of papaya juice can improve its utilization and nutritional effect.

Polyphenol content and antioxidant capacity of fruit and vegetable beverages processed by different technology methods

The purpose of the natural drinks production is the preservation of biologically active compounds in maximal amount in prepared drinks. The issue is the loss of these substances due to conventional conservation methods, such as pasteurization. Pascalization, a conservation method using high pressure, performs a new trend in conservation. According to available research, it causes only a minimal loss of bioactive compounds. Influence of conservation technology of fruit and vegetable beverages on the content of bioactive substances - polyphenols, flavonoids and on their antioxidative activity has been investigated. Their content has been compared in fresh juice samples, in samples conserved by pasteurization and after the appliance of high pressure treatment - pascalization (HPP). HPP has a positive effect on total antioxidative capacity of juices - broccoli with apple (increase of the amount from 189.12 mg.100 mL-1 to 217.12 mg.100 mL-1) and beetroot and on total polyphenol content within all samples of beverages except from carrot juice. Decrease of the amounts of flavonoids has been observed within all beverages. For drinks after pasteurization treatment there is evident the decrease of total polyphenols content and total antioxidant activity, besides carrot juice, where the antioxidant capacity value had increased from 37.24 to 43.14 mg.100 mL-1. The flavonoid content of fruit and vegetable juices after heat treatment had increased only in the juice prepared from broccoli with apple (from 40.71 mg.100 mL-1 to 45.14 mg.100 mL-1), the content in other juices had decreased. However, the decrease of the flavonoid content is lower after heat treatment in comparison to HPP, except the samples of cabbage juice with apple. With the exception of flavonoids, HPP has been proved as a gentle conservation technology enabling preserving higher amounts of bioactive substances with antioxidative properties if compared with the heat treatment. For the samples treated by HPP there was observed statistically significant difference in comparison with fresh juice in all factors mentioned above (p <0.05).