Thermal Pasteurization Research Articles

Effect of Voltage and Frequency in Pasteurization Pulsed Electric Field (PEF) Continous System of Pineapple (Ananas comosus [L.] Merr) Juice

Pineapple which is one of the perishable commodities with high water content about 90.73% in 100 gr of fresh material. Thermal pasteurization has a weakness that can degrade the quality of fruit juice products. In contrast, non thermal processes have expectations which is don’t make decreasing quality of the product. One of the non-thermal pasteurization type called Pulsed Electric Field (PEF). Nowadays, PEF system have two type batch and continous, which respectively used in this research is PEF continous system. This study uses research methods group random design (GRD) with two factorial that voltage (20, 30 and 40 kV) and frequency (10, 20, 30 and 40 kHz). Based on these studies it is known that the voltage and frequency is significantly different to the value of Total Plate Count (TPC), and absorbance. However there aren’t significantly different with the pH, vitamin C, viscosity, total dissolved solid (TDS), total sugar and color. The treatment based on the microbial test are at a voltage of 40 kV and a frequency of 40 kHz which can reduce bacteria significantly 1.01x103 cfu/mL or 0.94 by log cycle with the effectiveness of microbial death by 88.5%. The treatment based on the microbial test are at a voltage of 40 kV and a frequency of 30 kHz which The result indicates that physical and chemical characteristic of pineapple juice become 3.98 of pH, total dissolved solid (TDS) of 6.25 °brix, total sugar of 14.75 % viscosity of 3 cp, vitamin C of 7.6 mg/100ml, absorbance of 0.67, color on the brightness (L*) value of 24.05, redness (a*) of 6.35, and yellowish (b*) of 7.5. This result shows that PEF continuous respectively work system to pasteurize the pineapple juice.

Innovative Techniques of Processing Human Milk to Preserve Key Components.

Human milk not only contains all nutritional elements that an infant requires, but is also the source of components whose regulatory role was confirmed by demonstrating health-related deficiencies in formula-fed children. A human milk diet is especially important for premature babies in the neonatal intensive care unit (NICU). In cases where breastfeeding is not possible and the mother’s own milk is insufficient in volume, the most preferred food is pasteurized donor milk. The number of human milk banks has increased recently but their technical infrastructure is continuously developing. Heat treatment at a low temperature and long time, also known as holder pasteurization (62.5 °C, 30 min), is the most widespread method of human milk processing, whose effects on the quality of donor milk is well documented. Holder pasteurization destroys vegetative forms of bacteria and most viruses including human immunodeficiency virus (HIV) herpes and cytomegalovirus (CMV). The macronutrients remain relatively intact but various beneficial components are destroyed completely or compromised. Enzymes and immune cells are the most heat sensitive elements. The bactericidal capacity of heat-pasteurized milk is lower than that of untreated milk. The aim of the study was for a comprehensive comparison of currently tested methods of improving the preservation stage. Innovative techniques of milk processing should minimize the risk of milk-borne infections and preserve the bioactivity of this complex biological fluid better than the holder method. In the present paper, the most promising thermal pasteurization condition (72 °C–75 °C,) and a few non-thermal processes were discussed (high pressure processing, microwave irradiation). This narrative review presents an overview of methods of human milk preservation that have been explored to improve the safety and quality of donor milk.

Anthocyanins, non-anthocyanin phenolics, tocopherols and antioxidant capacity of açaí juice (Euterpe oleracea) as affected by high pressure processing and thermal pasteurization

Abstract We studied the effect of high pressure processing (HPP) (400, 450, 500, and 600 MPa/5 min/20 °C) and thermal pasteurization (85 °C/1 min) on anthocyanins, non-anthocyanin phenolic compounds, tocopherols and antioxidant capacity toward oxygen and nitrogen reactive species of acai juice. HPP was more effective for the preservation of anthocyanins than thermal pasteurization (up to 40%), probably due to its thermal-sensitivity. A significant increase was observed for the non-anthocyanin compounds' content at 500 MPa, possibly related to cell wall rupture due to the applied pressure. As a result, this sample showed greater antioxidant capacity (ORAC and total phenolic compounds). On the other hand, H2O2 scavenging capacity, tocopherols and vitamin E activity were not affected, whereas scavenging capacity against HOCl and NOC formation was not well correlated with bioactive compounds concentration. Nevertheless, these properties were effectively preserved in HPP treatments. These results indicate that HPP may provide acai juice with high functional quality. Industrial relevance Acai juice (AJ) has been increasingly valued worldwide due to its bioactive compounds and health-promoting effects, however, thermal pasteurization (TP), usually applied to AJ preservation, may cause degradation of these compounds and damage AJ bioactivities. Our results contribute to understanding how the main bioactive compounds and functional properties of AJ are affected by high pressure processing (HPP) and TP. In addition, they represent an important advance in the field of emerging preservation technologies as it indicates optimal high pressure conditions for AJ processing. Ultimately, given that HPP adds values to food products, our results may be used by the food industry to produce new acai-based formulations with high market value.

The spatial-temporal working pattern of cold ultrasound treatment in improving the sensory, nutritional and safe quality of unpasteurized raw tomato juice

In considering the adverse nutritional and flavor consequences of thermal pasteurization on fruit juices, freshly squeezed and unpasteurized fruit juices, commonly called raw juices, are of increasing demand as they are served in bars, restaurants and at home. Apparently, due to lack of controlled processing regime as did in a juice factory, the raw juice often undergoes a rapid phase separation and is at the risk of microbial unsafety. To this end, an attempt of cold ultrasound treatment (CUT, 87.52 W/cm2, 10 °C) was implemented to a raw tomato juice up to 30 min. Appreciatively, the physical stability, nutritional value and microbial safety substantially improved. On a CUT time scale, cloud stability and total phenolic content continuously increased; the total plate count was adversely altered; the rheological parameters (viscosity, thixotropy and shear-thinning tendency) and total carotenoids obtained shared a parabolic changing pattern but peaked at 15 min and 10 min, respectively. Finally, the ascorbic acid sharply increased at an earlier stage (5 min), and then remained stable throughout the whole process. Notably, the occurrences of these improvements are of spatial-temporal nature and resulted from different cavitation induced stress fields. At the initial stage, CUT chiefly worked via the mechanical field with the particles in pulp phase, making them smaller and releasing the soluble materials into serum phase. When the particles larger than approximately of 160 μm were completely disintegrated, the CUT entered its second stage and mainly functioned in the serum phase via both mechanical and chemical fields. As a result, the serum pectin and carotenoids were depolymerized and degraded, respectively. The present results are valuable in uncovering the mechanism and kinetics underlying the ultrasound treatment of fruit juices and the present CUT is highly recommended due to its high maneuverability and excellent performance.

High hydrostatic pressure pasteurization of a draft sake brewed using a Niigata-sake yeast

ABSTRACTDraft (non-pasteurized) sake typically has a fresh flavor, but usually has to be consumed as soon as possible because of its short shelf life due to the potential for over-fermentation by residual yeast. In contrast, thermally pasteurized sake has a long shelf life, but the fresh flavor is lost during heat sterilization. High hydrostatic pressure (HHP) treatment can be used as a non-thermal pasteurization process while maintaining the characteristics of a draft sake. We evaluated the HHP inactivation behavior of sake yeast for the application of HHP pasteurization as an alternative to thermal pasteurization. The results showed complete pasteurization of sake yeast in the draft sake by HHP treatment at 400 MPa for 10 min. The viable cell count in HHP-pasteurized sake was below the detection limit during storage at 10°C for 3 months. Thus, we have established a HHP pasteurization technology to prevent over-fermentation and succeeded in producing a prototype of HHP-sparkling-cloudy sake, which we have designated AWANAMA.

Inactivation of Bacillus subtilis and quality assurance in Chinese bayberry (Myrica rubra) juice with ultrasound and mild heat

Combined ultrasound and mild heat (UH) and traditional thermal pasteurization (TP) were employed to inactivate thermoacidophilic B. subtilis suspended in Chinese bayberry juice. Flow cytometry was used to evaluate different action mechanisms of these two treatments. The changes of physicochemical properties, anthocyanin content, and volatile components were also studied to assess the effects on juice quality. Results showed a 5-log reduction was achieved in 36.91 min by TP, 23.06 min by UH55°C 400W, 14.18 min by UH63°C 200W, 9.59 min by UH63°C 400W, and the inactivation date had a high goodness of fit with Weibull model, exhibiting a fast drop in first and a slow decline at last. Compared to the TP, UH treatment was not only able to cause lethal effect by compromising membrane integrity, inactivating esterase activity, but also destroying nucleic acids through the flow cytometry analysis. The pH and soluble solids content of bayberry juice had no significant changes with different treatments, while the light transmittance of UH groups during storage was higher, the color and anthocyanin retention were better than TP treatment. The GC-MS analysis indicated UH treatment can significantly inhibit the decline of key aromatic substances of bayberry juice, including 1-hexanol, (Z)-3-hexenol, (Z)-3-nonenol and dihydro-5-pentyl-2(3H)-furanone.

Moderate intensity Pulsed Electric Fields (PEF) as alternative mild preservation technology for fruit juice

Moderate intensity Pulsed Electric Fields (PEF) was studied for microbial inactivation as an alternative to high intensity PEF or to classical thermal pasteurization. The process is characterized by the application of electric pulses, allowing an increase of the product temperature by the ohmic heat generated by the pulses. A systematic evaluation of the effect of parameters electric field strength (E) and pulse width (τ) on the inactivation of Escherichia coli, Listeria monocytogenes, Lactobacillus plantarum, Salmonella Senftenberg and Saccharomyces cerevisiae in orange juice was carried out in a continuous flow system. A wide range of conditions was evaluated, and both E and τ were shown to be important in the efficacy to inactivate micro-organisms. Remarkably, PEF conditions at E = 2.7 kV/cm and τ = 15–1000 μs showed to be more effective in microbial inactivation than at E = 10 kV/cm and τ = 2 μs.Inactivation kinetics of the tested PEF conditions were compared to an equivalent thermal process to disentangle non-thermal effects (electroporation) from thermal effects responsible for the microbial inactivation. At standard high intensity PEF treatment a non-thermal inactivation at E = 20 kV/cm and τ = 2 μs pulses was observed and attributed to electroporation. Non-thermal effects could also be resolved with moderate intensity PEF at E = 2.7 kV/cm and pulse width between τ = 15–1000 μs. Microbial inactivation at these moderate intensity PEF conditions was studied in more detail at different pH and medium conductivity for E. coli and L. monocytogenes in watermelon juice and coconut water. Under moderate intensity PEF conditions the effectiveness of treatment was independent of pH for all evaluated matrices in the pH range of 3.8–6.0, whereas under high intensity PEF conditions the pH of the product is a critical factor for microbial inactivation. This suggests that the inactivation proceeds through a different mechanism at moderate intensity PEF, and speculations for this mechanism are presented. In conclusion, moderate intensity PEF conditions at E = 2.7 kV/cm and pulse width of 15–1000 μs has potential for industrial processing for the preservation of fruit juices and pH neutral liquid food products.

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

Abstract 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 relevance Being 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.

High Hydrostatic Pressure Processing Better Preserves the Nutrient and Bioactive Compound Composition of Human Donor Milk

When mother's milk is insufficient, pasteurized human donor milk (DM) is the recommended supplement for hospitalized very-low-birth-weight infants. The current method of pasteurization (Holder, 62.5°C, 30 min) negatively affects heat-sensitive nutrients and bioactive proteins. Objectives of this study were to compare changes in DM composition after thermal pasteurization (Holder and flash-heating) and nonthermal methods [UV-C irradiation and high hydrostatic pressure (HHP)]. We hypothesized that nonthermal techniques would result in fewer changes to composition. Holder, flash-heating (brought to boil), UV-C irradiation (250 nm, 25 min), and HHP (500 MPa, 8 min) were studied. Pools of milk from 17 women known to contain bacteria at >5×107 colony forming units (CFU)/L were collected from the Rogers Hixon Ontario Human Milk Bank and underwent each pasteurization technique. Macronutrients, heat-sensitive micronutrients (vitamin C, folate), and bioactive components [bile-salt-stimulated lipase (BSSL), lysozyme, lactoferrin] were measured in raw and pools of pasteurized milk. Milk was cultured to determine how well each technique produced a culture negative result (detection limit <1×103 CFU/L). Folate was reduced by 24-27% after Holder, flash-heating, and UV-C (P<0.05); no reduction was observed after HHP. All pasteurization methods reduced vitamin C (60-75%, P<0.001). BSSL was abolished after Holder and flash-heating (P<0.001), reduced after UV-C (48%, P<0.001), but unaffected by HHP. Lysozyme activity was reduced after flash-heating (44%) and UV-C (74%, P<0.004) but unaffected by Holder or HHP. Lactoferrin was reduced by all methods (P<0.02) but most severely by flash-heating (74%) and least severely by HHP (25%). Holder and UV-C reduced lactoferrin by ∼48%. All pasteurization methods reduced the number of culture positive DM samples (P<0.001). HHP better preserves human milk composition than Holder pasteurization. Future research on the feasibility of HHP for pasteurizing human milk is warranted because its implementation may improve the nutritional status and health of DM-fed infants.

Influence of unit operations on immunoglobulins and thermal stability of colostrum fractions

Colostrum-based ingredients are gaining significance in the global nutraceutical market as dietary supplements, but compositional variation, bioactive heat sensitivity and lack of appropriate preservation technologies hamper commercial colostrum processing. The effect of commonly employed unit operations on the physicochemical and nutraceutical components of skim colostrum was determined, and effects of membrane processing on its thermal gelation temperature, key to further liquid processing, were monitored. Homogenisation and high-shear mixing did not alter immunoglobulin content. However, commercial thermal pasteurisation (72 °C, 15 s) and batch pasteurisation (63 °C, 30 min) led to 56.4% and 24.6% denaturation of IgG, respectively. Microfiltration eliminated microbial load of diluted skim colostrum to render it practically sterile, while ultrafiltration concentrated the proteins of colostrum fractions. Concentration of protein, particularly immunoglobulins, resulted in lowering of thermal gelation temperature. Skim colostrum and colostrum whey can, therefore, be preserved by employing microfiltration and concentrated with simultaneous purification by ultrafiltration.

Hygienization of mixed animal by-product using Pulsed Electric Field: Inactivation kinetics modeling and recovery of indicator bacteria

The hygienization of animal by-products (ABP) assisted by Pulsed Electric Field (PEF) was studied as a transfer of the innovative athermal pasteurization technology developed in food engineering to replace the conventional thermal hygienization process. The strains Enterococcus faecalis ATCC 19433 and Escherichia coli ATCC 25922 were selected as indicator bacteria. A systematical investigation was carried out concerning the inactivation kinetics of the indicator bacteria at different electric field strength (10, 15, 20 and 25 kV·cm−1), the kinetic modeling using coupled Weibull model, the effect of PEF energy input and the recovery of PEF-injured bacteria at 3 °C for 7 days. Results show that a PEF treatment at 25 kV·cm−1 for an effective time over 30 ms would be sufficient to achieve a 5-log10 reduction of Ent. faecalis. It complies with the EU regulation No. 142/2011 to validate an alternative hygienization technology other than thermal pasteurization. The Weibull model coupled with a secondary model proved efficient to estimate the survival kinetic curves of two indicator bacteria treated by PEF. The injured E. coli could not regenerate after PEF exposure while Ent. faecalis could get self-recovery. This preliminary work confirms that PEF was able to give the hygienization of ABP in terms of the bacterial reduction requirement of EU.

Reduction of Zygosaccharomyces rouxii Population in Concentrated Grape Juices by Thermal Pasteurization and Hydrostatic High Pressure Processing

Zygosaccharomyces rouxii is the most frequent spoilage yeast species detected in concentrated grape juice. In order to reduce Z. rouxii populations and consequently extend the microbiological shelf life of this product, different programs of thermal pasteurization and high hydrostatic pressures processing were evaluated. Results showed that pasteurization temperatures higher than 75 °C are necessary to reduce Z. rouxii population in concentrated grape juice. Reduction of 7 logarithms can be reached after 90 s at 75 and 80 °C, and 5 s at 85 °C of pasteurization treatment. High hydrostatic pressure treatment above 500 MPa for 2 min are necessary to reduce 7 logarithms of Z. rouxii population and to significantly extend the shelf life of concentrate grape juice. Extension of holding times from 3 to 5 min, at the different high hydrostatic pressures evaluated, did not improve the Z. rouxii population reduction, nor the shelf life extension of concentrate grape juice. In conclusion, thermal pasteurization and high hydrostatic pressure could be suitable treatments to achieve the reduction of Z. rouxii population below the recommendation limit (102 CFU/g) and extension of the microbiological shelf life of concentrate grape juice.

Survival and Behavior of Encapsulated Probiotics (Lactobacillus plantarum) in Calcium-Alginate-Soy Protein Isolate-Based Hydrogel Beads in Different Processing Conditions (pH and Temperature) and in Pasteurized Mango Juice.

Hybrid alginate-soy protein isolate-based hydrogel beads were prepared and evaluated to enhance the survival of the encapsulated probiotics (Lactobacillus plantarum) during heat processing to incorporate in mango juice. The solutions of sodium alginate-soy protein isolate (SA-SPI) with probiotic cells were dropped into the gelation bath containing calcium chloride (3% w/v) solution to develop various types of hydrogel beads. The level of survival of probiotics in encapsulated beads under acidic conditions (pH 2, 3, and 6.5) and bile salt (0.5 and 1.0% w/v) was evaluated. The survival of the encapsulated probiotics to thermal processing was evaluated by treating the beads in saline solution (0.9% w/v) at 30, 50, 63, and 72°C. The encapsulated probiotic bacteria were found alive even after treatment at 72°C for 90 s. Most of the free cells did not survive at the temperature higher than 50°C and very low pH (pH 2 and 3). The survival of probiotic cells was found higher with the hybrid hydrogel beads containing alginate and soy protein isolate (1:8 w/w). Furthermore, mango juice fortified with encapsulated L. plantarum in hydrogel beads was subjected to thermal pasteurization at 72°C for 90 s.

Comparison of UV-C and thermal pasteurisation for the quality preservation of pineapple-mango juice blend

Comparison of UV-C and thermal pasteurisation for the quality preservation of pineapple-mango juice blend

UV irradiation as a comparable method to thermal treatment for producing high quality stabilized milk whey

Whey is a valuable by-product of the dairy industry, due to the high nutritional, biochemical and functional properties of the contained proteins. As for other dairy products, to guarantee the microbiological safety of whey, thermal treatments are generally used. However, these processes can have a significant impact on the quality of the product. Thus, in recent years, interest in the use of non-thermal treatments in the dairy industry is significantly grown. In the present work, the use of UV irradiation as stabilizing treatment has been investigated on whey obtained from the Parmigiano-Reggiano cheese production. Two treatments were tested: UV treatment “1” which is characterized by three passages and UV treatment “2” by six ones.On skimmed whey samples, microbiological tests showed UV treatment 2 and the thermal treatment have the same effectiveness on Enterobacteriaceae, but UV treatment 2 is more effective than thermal treatment on total viable counts.Molecular characterization of the protein and total amino acid content was used as markers for the quality of the product.The results highlight that UV treatment can be equivalent to thermal pasteurization in terms of microbiological stabilization, and better preserving the whey quality.

Influence of different pasteurization techniques on antidiabetic, antioxidant and sensory quality of debittered bitter gourd juice during storage

Debittered bitter gourd juice was subjected to gamma irradiation doses of 0, 0.25, 0.5, 0.75, 1, 1.5 and 2.5 kGy and thermal pasteurization at temperatures of 65, 75, 85 and 95 °C. Shigella boydii was the most heat resistant pathogen tested (D10 of 42.8 s at 65 °C) while Bacillus cereus was the most resistant pathogen to irradiation with a D10 of 0.46 kGy. No significant (p < 0.05) effect of thermal pasteurization was observed on antidiabetic (α-amylase and α-glucosidase inhibition) activity, however, a 10% increase in α-glucosidase inhibition was observed in irradiated (2.5 kGy) samples. A significant (p < 0.05) but marginal reduction (up to 10%) was observed in antidiabetic activity during storage for a period of 90 days. Thermal pasteurization at 65 °C demonstrated significantly (p < 0.05) higher sensory quality as compared to irradiated (2.5 kGy) samples. This is first report on effect of pasteurization on antidiabetic activity of bitter gourd juice.

UV-C light processing of Cantaloupe melon juice: Evaluation of the impact on microbiological, and some quality characteristics, during refrigerated storage

UV-C light is a non-thermal technology with potential application in food industries. The objective was to assess UV-C radiation effect (13.44 W/m2) on microbiological decontamination and some quality characteristics of Cantaloupe melon juice, during refrigerated storage.Juice was inoculated with Listeria innocua (non-pathogenic surrogate of L. monocytogenes) and Alicyclobacillus acidoterrestris spores (spoilage indicators) used as indicators of the UV-C treatment efficacy. Total mesophylls and yeasts and molds were also enumerated. Results demonstrated that 5 min of exposure allowed 3.7 ± 0.3 log10 cycles reduction of L. innocua, while for A. acidoterrestris, 20 min were required to decrease 4.7 ± 0.1 log10 cycles.At the end of refrigerated storage for 13 days, UV-C treated juices retained color, total phenolics content and antioxidant activity, and yeast and molds did not grow.Since UV-C process was effective on microbial inactivation and allowed juice quality maintenance, it can be considered as a promising alternative to thermal pasteurization.

Influence of ultra‐high pressure homogenisation on physicochemical and sensorial properties of orange juice in comparison with conventional thermal processing

SummaryThe effect of different ultra‐high pressure homogenisation (UHPH) treatments on physicochemical and sensorial properties of orange juice was studied in comparison with thermal pasteurisation (90 °C, 1 min). UHPH treatments consisted on combinations of two inlet temperatures (10 or 20 °C) and three pressures (100, 200 and 300 MPa). Effect of treatments was assessed on general quality parameters (colour, pH, °Brix, titratable acidity, reducing sugars and non‐enzymatic browning index), particle size distribution and cloud stability. None of the UHPH treatments caused significant differences in the °Brix, reducing sugars, pH and non‐enzymatic browning index with respect of fresh or pasteurised juice. Only titratable acidity was significantly lower when inlet temperature of UHPH treatments was 20 °C. UHPH treatments significantly reduced the particle size and in consequence the cloudiness and the total colour value (∆E*) increased. The overall consumer acceptability of UHPH and pasteurised juices was similar.

The effect of convective heating and microwave heating on antioxidant enzymes in pooled mature human milk

The effects of convective and microwave heating at constant temperature (62.5, 66 and 70 °C) on the activity of antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPx) in pooled mature human milk were compared. Activities of the enzymes were determined using spectrophotometric kits. Activity of GPx decreased significantly in the first stage of heating when milk samples were warmed to pasteurisation temperature. CAT was the most thermolabile enzyme but microwave heating induced a smaller decrease in CAT activity than convective heating. SOD was most resistant to thermal pasteurisation, regardless of the heating method. SOD and GPx activity temporary increased during microwaves heating. Considering shorter pasteurisation period and lower demand for energy, it can be concluded that microwaves pasteurisation enjoys special merits. However, still there is no clear answer as to whether the microwave field itself can affect the antioxidant enzymes of human milk.

Effect of thermal pasteurization and ultraviolet treatment on the quality parameters of not-from-concentrate apple juice from different varieties

ABSTRACTConsumers are increasingly seeking not-from-concentrate (NFC) juice as a convenient, less expensive alternative to fresh juice. This study evaluated the effect of thermal pasteurization (TP) and ultraviolet (UV) treatment of NFC apple juice on microbial growth and changes in the quality parameters. Both TP and UV decreased the total number of bacteria, mould and yeast and achieved the requirement of commercial sterilization in the NFC juice. The soluble solids, total sugars and phenolics in the juice were not significantly affected by both UV and TP. The shelf life of NFC samples treated with UV and TP was extended for 3 and 5 weeks longer than freshly squeezed juices, respectively. However, the samples treated with UV could effectively avoid the increasing of turbidity and improve quality characteristics. UV is a suitable alternative to TP during processing, because UV effectively retains fresh-like properties.