Effects of high pressure treatment on the quality and storage of kimchi

The effects of high pressure treatment on the microflora and storage of kimchi were investigated. In a bacterial suspension, numbers of Lactobacillus plantarum were reduced by 6 logs by 500 MPa, at 25 °C for 10 min. Kimchi juice did not alter the rate of inactivation of lactic acid bacteria by high pressure treatment. There was no change in the texture of kimchi subjected to a pressure of 400 MPa, but an increase in cutting force was observed at 600 MPa. When kimchi was pressurized at 400 MPa for 10 min at 25 °C and subsequently stored at 20 °C for 4 weeks, the total number of viable cells stayed at 10³ CFU mL⁻¹. High pressure treatment above 400 MPa prevented excessive acidification that typically occurs during the extended storage of kimchi. The inflation of pouches as a result of accumulated carbon dioxide was also prevented by high pressure treatment. Although colour changes were accelerated by high pressure treatment, this study demonstrates that high pressure treatment can be used to control overripening during the distribution and storage of kimchi products.     

Guava puree with reduced stone cell content: preparation and characteristics of concentrates and nectars

A decanter centrifuge was used to decrease the content of stone cells in guava puree before evaporation. Concentration factors between 3.3- and 4.3-fold were achieved. Thirty-seven per cent of the stone cells could be removed in a small decanter, whereas virtually all sclereids are removed on an industrial scale. Small significant increases in moisture contents, total soluble solids and titratable acidity and decreases in pectin fractions and ascorbic acid contents (average 38%) occurred during processing; guava colour became darker, redder and less yellow. The apparent viscosity of the puree decreased after centrifugation and increased again during evaporation. Nectars prepared from puree with reduced stone cell content were the most stable. Concentration of puree reduced cloud stability of nectars by up to 34% after 35 days storage, but homogenization improved the stability. Panel members only found significant differences in the colour of nectars prepared from the three concentrates.     

Effects of Dense Phase Carbon Dioxide Pasteurization on the Physical and Quality Attributes of a Red Grapefruit Juice

ABSTRACT:  Red grapefruit juice was treated with continuous dense phase carbon dioxide (DPCD) equipment to inactivate yeasts and molds and total aerobic microorganisms. A central composite design was used with pressure (13.8, 24.1, and 34.5 MPa) and residence time (5, 7, and 9 min) as variables at constant temperature (40 °C), and CO₂ level (5.7%) after experimentally measuring CO₂ solubility in the juice. Five log reduction for yeasts and molds and total aerobic microorganisms occurred at 34.5 MPa and 7 min of treatment. A storage study was performed on the fresh juice DPCD treated at these conditions. °Brix, pH, titratable acidity (TA), pectinesterase (PE) inactivation, cloud, color, hue tint and color density, total phenolics, antioxidant capacity, and ascorbic acid were measured after the treatment and during 6 wk storage at 4 °C. During storage, the DPCD-treated juice showed no growth of total aerobic microorganisms and yeasts and molds. Cloud increased (91%) while percent PE inactivation was partial (69.17%). No significant (α= 0.05) differences were detected between treated and untreated samples for °Brix, pH, and TA. Treated juice had higher lightness and redness and lower yellowness. No significant differences (α= 0.05) were detected for the hue tint values while the color density value was higher for the treated samples compared to the untreated. The treatment and the storage did not affect the total phenolic content of the juice. Slight differences were detected for the ascorbic acid content and the antioxidant capacity. The experimental results showed evidence that the treatment can maintain the physical and quality attributes of the juice, extending its shelf life and safety.     

Effect of combined treatments of high-pressure,citric acid and sodium chloride on quality parameters of tomato puree

Tomato puree was subjected to combined treatments of high hydrostatic pressure and natural additives [citric acid and sodium chloride (NaCl)]. Their effects on the most important quality parameters of tomato puree as colour and viscosity, and biochemical parameters as enzymatic activities (polyphenoloxidase, peroxidase, and pectin methylesterase) and total protein content, and microorganisms (total microbial counts and yeasts and moulds) were studied. Response surface methodology was employed where the experiment was carried out according to a central composite face-centred design. The variables ranges used were: 50–400 MPa (pressure), 0–0.8% w/w (concentration of NaCl) and 0–2% w/w (concentration of citric acid) while temperature and holding time of high pressure treatments were constants at 25 °C and 15 min respectively. The results showed that enzymatic inactivation was significantly improved with these combined treatments at high values of pressure and concentration of additives. A very significant reduction of 4 logarithmic units was observed when pressure was increased to 400 MPa for total microbial counts. Thus, combined "hurdles" may be effective to produce minimally processed tomato products with optimal sensorial and microbiological characteristics.     

Effects of High Pressure and Heat Treatment on Pectic Substances and Related Characteristics in Guava Juice

Effects of high pressure treatment on guava juice pectic substances and related juice characteristics were investigated and compared with heat treatment. The viscosity and turbidity of guava juice pressurized at 600 MPa and 25°C for 10 min increased slightly; whereas the viscosity of juice heated at 95°C for 5 min decreased while turbidity increased. There were no apparent changes in water soluble, oxalate soluble and alkali soluble pectin in pressurized juice. However, heat treatment of juice decreased water and alkali soluble pectins and slightly increased oxalate soluble pectin. High pressure treatment resulted in no marked changes in pectic and cloud substances of guava juice, and maintained the natural viscous of the juice.     

Chlorophyll, colour and pH changes in H.T.S.T. processed green pea puree

Summary. Pea puree of pH 6.95 and pH 8.45 was heat processed in thermal death-time tubes at temperatures between 115.6°C and 148.9°C to a process value of F₀= 6.0. Chlorophyll pigments, Hunterlab colour indices and pH were determined before and after high temperature-short time (H.T.S.T.) processing and during storage for 18 months at 20°C, 2.8°C, and −23.3°C.
Highly significant correlations were found between per cent conversion of chlorophylls to pheophytins and objective colour indices derived from tristimulus measurements on stored pea puree. the degree of chlorophyll conversion, and hence puree colour, were both markedly affected by process temperature, product pH, storage time and storage temperature, but long-term storage stability was achieved only by combinations of two or more variables.
Changes in pH of processed and stored puree were directly related to changes in pigments and colour, and it appears that pH control during processing and storage offers the most likely means of colour and pigment retention in heat processed chlorophyll-containing foods.     

Efficacy of Pressure-Assisted Thermal Processing, in Combination with Organic Acids, against Bacillus amyloliquefaciens Spores Suspended in Deionized Water and Carrot Puree

ABSTRACT:  Effect of organic acids (acetic, citric, and lactic; 100 mM, pH 5) on spore inactivation by pressure-assisted thermal processing (PATP; 700 MPa and 105 °C), high pressure processing (HPP; 700 MPa, 35 °C), and thermal processing (TP; 105 °C, 0.1 MPa) was investigated.  Bacillus amyloliquefaciens  spores were inoculated into sterile organic acid solutions to obtain a final concentration of approximately 1.3 × 10⁸ CFU/mL.  B. amyloliquefaciens  spores were inactivated to undetectable levels with or without organic acids after 3 min PATP holding time. At a shorter PATP treatment time (approximately 2 min), the inactivation was greater when spores were suspended in citric and acetic acids than in lactic acid or deionized water. Presence of organic acids during PATP resulted in 33% to 80% germination in the population of spores that survived the treatment. In contrast to PATP, neither HPP nor TP, for up to 5 min holding time with or without addition of organic acids, was sporicidal. In a separate set of experiments, carrot puree was tested, as a low-acid food matrix, to study spore recovery during extended storage following PATP. Results showed that organic acids were effective in inhibiting spore recovery in treated carrot puree during extended storage (up to 28 d) at 32 °C. In conclusion, addition of some organic acids provided significant lethality enhancement ( P  < 0.05) during PATP treatments and suppressed spore recovery in the treated carrot puree.     

Combined high-pressure and thermal treatments for processing of tomato puree: evaluation of microbial inactivation and quality parameters

The effects of combined high-pressure thermal treatments on consistency, viscosity, colour, lycopene content, enzyme activity and micro-organisms were determined, and compared to conventional pasteurisation and sterilisation processes of tomato puree. High-pressure processing at ambient temperature (HPP) improved the colour and viscosity compared to heat pasteurisation, while the water binding capacity and lycopene content were unaffected by HPP. Products treated at 700 MPa, 20 °C resulted in inactivation of the natural flora to a level below the detection limit. After pressure treatment and during chilled storage a increase in viscosity was observed. HPP caused partial inactivation of polygalacturonase (70%), but activation of pectin methylesterase. After high-pressure sterilisation treatments combined with elevated starting temperatures (≥80 °C, HPS, one or two pulses) an ambient stable product was obtained. HPS (one pulse, 700 MPa, 30 s, 90 °C) reduced B. stearothermophilus spore contamination level in inoculated meatballs in tomato puree with at least 4.5 log units. HPS resulted in more than 99% inactivation of polygalacturonase and pectin methylesterase. HPS resulted in a lower viscosity compared to conventional sterilised samples, whereas the water binding capacity was improved. Colour appreciation was improved and lycopene content was retained compared to a 40% loss after conventional sterilisation.     

Inactivation of Aspergillus niger in Mango Nectar by High-Pressure Homogenization Combined with Heat Shock

ABSTRACT:  This research evaluated the inactivation of a heat-resistant  Aspergillus niger  conidia in mango nectar by high-pressure homogenization (HPH) combined with heat shock.  A.niger  were inoculated in mango nectar (10⁶ conidia mL⁻¹) and subjected to HPH (300 to 100 MPa) and heat shock (80 °C for 5 to 20 min) before or after HPH. Processes were evaluated according to number of decimal reductions reached by each isolated or combined process. Scanning electron microscopy was performed to observe conidia wall after pressure treatment. Pressures below 150 MPa did not inactivate  A. niger  while pressures of 200 and 300 MPa resulted in 2 and more than 6 log reductions, respectively. D_{80 °C} of  A. niger  was determined as 5.03 min. A heat shock of 80 °C/15 min, reaching 3 decimal conidia reductions, was applied before or after a 200 MPa pressure treatment to improve the decimal reduction to 5 log cycles. Results indicated that HPH inactivated  A. niger  in mango nectar at 300 MPa (>6.24 log cycles) and that, with pressure (200 MPa) combined with post heat shock, it was possible to obtain the same decimal reduction, showing a synergistic effect. On the other hand, pre heat shock associated with HPH resulted in an additive effect. The observation of  A. niger  conidia treated by HPH at 100 and 200 MPa by scanning electron microscopy indicated that HPH promoted intense cell wall damage, which can sensitize the conidia to post heat shock and possibly explain the synergistic effect observed.
Practical Application : The results obtained in this paper are relevant to elucidate the mechanism of conidia inactivation in order to develop the application of HPH as an alternative pasteurization process for the fruit nectar industry.     

Microbial, Enzymatic, and Chemical Changes During Storage of Fresh and Processed Orange Juice

Microbial, enzymatic, and chemical comparisons were made on orange juice stored at 4°C without pasteurization, with light pasteurization (66°C, 10 sec) directed at vegetative microorganisms, and with full pasteurization (90°C, 60 sec) directed at the heat stable isozyme of pectinesterase. Effects of oxygen-barrier and nonbarrier packaging were also examined. Oxygen-barrier packaging did not benefit unpasteurized juice. However, lightly and fully pasteurized juices in barrier cartons exhibited lower microbial counts, greater ascorbic acid retention, and apparent slowing of cloud loss by the third week of storage. During the first 22 days storage, microbial, cloud, sugar, and ascorbic acid values for lightly pasteurized juice were similar to those of juice receiving full pasteurization.     

Storage stability of a stimulant coconut water–acerola fruit juice beverage

The objective of this work was to study the stability of a beverage formulated with acerola fruit juice and green coconut water with added caffeine. The beverage was prepared with 25% acerola pulp, 75% green coconut water and sugar up to 12°Brix, and caffeine (125 mg L⁻¹), heat processed at 90 °C for 30 s and packed in 250-mL glass bottles. Chemical, physicochemical, microbiological and sensory analyses of the beverage were performed just after processing and during 6 months of storage at room temperature (27 °C). The vitamin C content decreased significantly throughout storage, from 399.5 to 189.6 mg 100 mL⁻¹, although it has remained relatively high. The anthocyanins initially present (0.025 mg 100 mL⁻¹) were completely lost during the storage at a mean rate of 4 μg 100 mL⁻¹ month⁻¹. The product was microbiologically stable during storage. Colour changes were also observed with absorbance at 420 nm, with average values ranging from 0.19 to 0.24. However, according to the sensory analyses the product was acceptable during the 6 months of storage, presenting sensory scores (colour, taste and global acceptance) from 6.5 to 5.5, which suggests its potential for market.     

Effect of sonication on orange juice quality parameters during storage

Freshly squeezed orange juice was sonicated at various amplitude levels (40%, 70%, 100%), treatment times (2, 6 and 10 min) at a constant frequency of 20 kHz. Samples were stored for periods of up to 30 days at 10 °C. The combined effect of amplitude level, treatment time and storage period on pH, ^oBrix, titratable acidity, colour values ( L* , a* , b* ), non-enzymatic browning (NEB), cloud value and ascorbic acid content were investigated. Second order polynomial models were employed to investigate the effect of independent variables. No significant differences ( P <  0.05) in ^oBrix and titratable acidity were observed. Significant changes were observed in juice pH and colour values. During storage NEB increased while both cloud value and ascorbic acid content decreased. Predictive models developed for colour values, cloud value, NEB and ascorbic acid content were highly significant and were closely correlated to experimental data. Degradation mechanisms are proposed for the key quality parameters.     

High pressure and pasteurization effect on duck foie gras

The effects of combined high pressure (300 and 400 MPa) and low temperature (50°C) treatments on the microbial contamination of duck foie gras samples were compared with those of classical thermal pasteurization (85°C at the coldest point). A multilayer packaging film (PE/PA/PE) was selected from two films commonly used for these types of food, by preliminary tests showing its ability to limit microbiological development in such samples. In each experiment, microbiological contamination was analysed on treated and untreated samples, and results were systematically compared with those obtained from a classically pasteurized sample of the same liver. A pasteurization type effect (drastic reduction of vegetative mesophilic and psychrophilic contaminations, destruction of coliforms and of Staphylococcus aureus ) was obtained at this temperature with samples pressurized at 400 MPa for at least 10 min.     

Colour degradation and rheology of green chilli puree during thermal processing

The kinetics of degradation of both green- and total-colour of green chilli puree was studied at selected temperatures (50–90 °C). A fractional conversion concept was applied to determine the kinetic parameters. The degradation of green- and total-colour followed first order reaction kinetics. In the case of green colour the data was based on changes in Hunter – a value while L  ×  a  ×  b was found to adequately represent total colour change. Dependence of the rate constant during heat treatment obeyed the Arrhenius relationship. The activation energy values for green- and total-colour degradation were 23.04 and 25.02 kJ mol^–1, respectively. These results indicated that total colour should be used as the quality indicator during thermal processing of green chilli puree. The pungency of green chilli puree decreased during thermal processing as the capsaicin content was reduced from 559 to 441 μg g^–1 while the Scoville heat unit decreased from 8500 to 7480. The puree behaved as a shear-thinning fluid and the flow activation energy at 100 r.p.m. equalled 19.22 kJ mol^–1.     

Colour changes in thermally processed cupuaçu (Theobroma grandiflorum) puree: critical times and kinetics modelling

Summary Colour changes in thermally treated cupuaçu ( Theobroma grandiflorum ) fruit puree were modelled mathematically. Isothermal experiments in the temperature range of 80–115 °C were performed and colour was measured by a tristimulus colorimeter. At each temperature total colour difference (TCD*) increased and normalized L* decreased with processing time, both following a power law model. The power of the model was temperature-dependent and described by the Arrhenius law. To estimate the model constants, a one-step non-linear regression was performed on all data. Activation energies of 31 and 36 kJ/mol were determined for TCD* and normalized L*, respectively. These results should prove useful in the design of pasteurization processes which minimize colour changes in cupuaçu puree.     

Quality degradation kinetics of pasteurised and high pressure processed fresh Navel orange juice: Nutritional parameters and shelf life

A kinetic study of post processing quality loss was conducted after high pressure processing (600 MPa, 40 °C, 4 min) or thermal pasteurisation (80 °C, 60 s) of fresh Navel orange juice. Selection of processing conditions was mainly based on pectin methylesterase inactivation. Ascorbic acid loss, colour, viscosity and sensory characteristics were measured during storage at different isothermal conditions (0–30 °C). Increased shelf life (based on ascorbic acid retention) was achieved for high pressurised compared to thermally pasteurised juice, ranging from 49% (storage at 15 °C) to 112% (storage at 0 °C). Activation energy values for ascorbic acid loss were 68.5 and 53.1 kJ/mol, respectively, for high pressurised and thermally treated juice. High pressure processing resulted in better retention of flavour of untreated juice and superior sensory characteristics compared to thermal pasteurisation. Colour change was linearly correlated to ascorbic acid loss for both types of processing. Slightly higher apparent viscosity values were determined for high pressurised juice.Industrial relevanceApplication of high hydrostatic pressure on orange juice industry. Fresh orange juice is a product of high commercial and nutritional value due to its rich vitamin C content and its desired sensory characteristics. High Hydrostatic Pressure (HHP) is an alternative non-thermal technology that has been proposed for application on orange juice. Such a treatment denaturates enzymes and eliminates microorganisms responsible for spoilage of orange juice without detrimental effects on the sensory and nutritional quality of juice. The effect of HHP on the stability of fresh orange juice has been studied by different research groups, while orange juices processed with the new technology have already been commercially available in Japan, U.S.A., Mexico and Europe. However, a systematic kinetic approach of the effect of HHP on different quality indexes (not only microbial spoilage) immediately after processing, as well as during a long term storage of the processed orange juice is needed, in order to achieve an optimal process design and a successful application of the new technology in orange juice industry. Such kinetic data for parameters related to the quality and nutritional value of fresh orange juice were gathered in the present work providing therefore industry with useful information for the HHP stabilization of orange juice and the production of a high quality product. Due to the great benefits of HHP compared to the conventional pasteurization that emerged from this work regarding the quality, shelf life and nutritional characteristics of fresh orange juice, HHP technology is an advantageous alternative process for high valued products like orange juice.     

KINETICS OF HEAT/ENZYMIC DEGRADATION OF ASCORBIC ACID IN FLUTED PUMPKIN (Telfairia occidentalis) LEAVES

Thermal/enzymic degradations of ascorbic acid in whole, chopped and pureed fluted pumpkin leaves were studied from 60 to 100C (5–60 min). Degradation of ascorbic acid followed first order kinetics with the rate constants having maximum values at 80–90C. Ascorbic acid degradation exhibited strong deviation from linearity in thermal resistance, Arrhenius and absolute reaction rate plots at 100C indicating inactivation of the oxidative enzymes around 90C. At lower temperatures (60–90C) ascorbic acid was more stable in the whole and chopped leaves than in the pureed system. Activation energies ranged from 49 to 50.8 KJ mol⁻¹. At 100C, the puree matrix offered more protection to ascorbic acid.     

Selection of Process Conditions for High Pressure Pasteurization of Sea Buckthorn Juice Retaining High Antioxidant Activity

Sea buckthorn berries juice is a nutritious beverage, rich in vitamin C and carotenoids with high antioxidant activity. The main requirements for a freshly squeezed sea buckthorn juice production are the cloud stability and antioxidant activity retention after processing. Appropriate process technologies and conditions have to be applied in order to inactivate pectin methyl esterase (PME), responsible for cloud loss, while maintaining the nutritional characteristics and antioxidant activity of the juice. The objectives of the present work were to study and model the effect of thermal treatment and high pressure (HP) processing on the inactivation kinetics of endogenous PME and on total antioxidant activity alteration. Thermal treatment significantly affected PME inactivation and residual antioxidant activity. Processing even at mild process conditions (60 °C for 1 min) resulted in 2.5-fold antioxidant activity reduction and 50 % PME inactivation compared to untreated sample. Pressure and temperature acted synergistically for PME inactivation that followed first-order kinetics with a residual PME activity at all pressure–temperature combinations used (200–600 MPa and 25–35 °C). The effect of temperature and pressure on the inactivation rate constants was expressed through the activation energy and activation volume, respectively. Values of 163 kJ/mol and ?17 mL/mol at reference pressure of 600 MPa and reference temperature of 35 °C were estimated, respectively. Antioxidant activity of the samples was expressed through the determination of the effective concentration (EC₅₀). A slight increase in sea buckthorn antioxidant activity when applying pressures (200–600 MPa) at ambient temperature (25 °C) was observed compared to the corresponding value of untreated juice. Processing at higher temperatures did not significantly alter the total antioxidant activity of sea buckthorn juice. For sample treated at 600 MPa–35 °C for 5 min, a 5 % reduction of total antioxidant activity was observed. These conditions are proposed as effective process conditions for sea buckthorn juice cold pasteurization, based on the higher antioxidant activity retention and simultaneous PME inactivation.     

Pasteurization of carrot juice by combining UV-C and mild heat: Impact on shelf-life and quality compared to conventional thermal treatment

The combination of UV-C radiation and mild heat (UV-H) treatment is a promising strategy for synergistically increasing microbial inactivation in low UV-transmitting juices. In this research, we explored the suitability of UV-H treatment in carrot juice pasteurization and its impact on juice quality during shelf-life compared to that of thermal pasteurization. UV-H treatment at 60 °C (3.92 J/mL, 3.6 min) enabled reductions of over 5 log₁₀ cycles in the reference pathogens and a significant reduction in spoilage yeasts, bacteria, and bacterial spores. The activity of pectin methylesterase and polyphenol oxidase was reduced by UV-H treatment to levels close to those of low-temperature pasteurization (60 °C/18.1 min). The native population of total aerobic bacteria, lactic acid bacteria, and yeasts and molds of UV-H-treated juice remained undetectable during 29 days of cold storage. Furthermore, viscosity, cloud stability, and the color of fresh juice were better preserved by UV-H treatment than by thermal pasteurization throughout storage.Industrial relevanceThis study demonstrates that UV-H treatment is a beneficial alternative to conventional thermal processing in carrot juice pasteurization, since appropriate inactivation levels of pathogenic and spoilage microorganisms can be reached while better preserving the quality attributes of fresh juice throughout its shelf-life.     

Composition, sensory quality and respiration during ripening and storage of edible wild mango (Irvingia gabonensis)

The effects of tree and room ripening and of storage at chill temperatures and at 26–29°C on the sensory quality, composition and respiration of edible wild mango fruits were investigated.
Fruits harvested at the mature green stage and ripened at 26–29°C were slightly preferred to tree-ripened fruits in colour and texture. Apart from a lower moisture content, room-ripened fruits were comparable in composition with tree-ripened fruits. During storage at 26–29°C, CO₂ production increased sharply from 22 ml kg^-1 h^-1 at the end of the first day, reaching a maximum of 91 ml kg^-1 on day 5 and declining thereafter; O₂ consumption followed a similar trend. The respiratory climacteric coincided with the onset of ripening. Fruits held at 12–15°C developed symptoms of chilling injury including pitting and black spots in mature green fruits, and brownish discoloration, pitting, surface scald, excessive softening and decay in ripe fruits.