Inactivation of spoilage yeasts in apple juice by UV–C light and in combination with mild heat

The UV–C resistance of yeasts (Saccharomyces cerevisiae, Saccharomyces bayanus, Zygosaccharomyces bailii, Dekkera anomala and Dekkera bruxellensis) commonly involved in juice spoilage was investigated. Saccharomyces spp. showed the greatest UV resistance and yeast inactivation decreased with absorptivity of the medium. To improve the UV lethal effect on yeasts in juice, UV treatment was combined with heat (UV–H) (45–60 °C). The inactivation of S. cerevisiae by UV–H treatments between 52.5 and 57.5 °C was greater than use of both technologies individually, suggesting a synergistic effect. Modeling of inactivation data found that a combination of UV–C light with mild temperatures (50–60 °C) produced a 5-log₁₀ reduction of S. cerevisiae in clarified apple juice with lower UV doses (up to a 89.3% of reduction at 57.5 °C) and treatment times (up to 63% of reduction at 52.5 °C) than those needed for UV treatments or heat alone.Industrial relevanceThis investigation demonstrated the lethal efficacy of the combination of UV–C radiation and heat to improve the inactivation of spoilage yeasts in juice. Combined UV–H treatments synergistically increased yeast inactivation, with this approach being less effective than for bacteria. In any case, UV–H at mild temperatures would be an alternative to heat pasteurization treatments, enabling the inactivation of pathogenic bacteria and reducing the concentration of spoilage microorganisms like yeasts, obtaining a safe and stable product at lower temperatures.     

Effects of pulsed thermosonication treatment on fungal growth and bioactive compounds of Berberis vulgaris juice

In this study, the single and combined effects of pulsed‐ultrasound amplitude (100 W, 30 kHz with 25 and 50% amplitude levels for up to 30 min) and temperature (65 °C and 75 °C) on fungal growth, total phenolics, flavonoids and antioxidant activity of Berberis vulgaris juice were investigated. The combination of pulsed ultrasound at 50% amplitude for 30 min at temperature of 75 °C as the most effective treatment was resulted in a reduction of about?3.083 ± 0.02, ?3.04 ± 0.03, ?3.10 ± 0.01 and ?2.88 ± 0.02 log (N/N₀) on S. cerevisiae, A. flavus, A. versicolor and B. fulva, respectively. Additionally, the highest total phenolics, flavonoids and antioxidant activity were noted for the barberry juice after 30 min of sonication with 50% pulsed‐ultrasound amplitude at either 65 °C or 75 °C. Pulsed thermosonication is a promising technology to extend the shelf life of B. vulgaris fruit juice because of the improvement of antioxidant activity as well as microbial quality.     

Shelf Life Determination of Sliced Portuguese Traditional Blood Sausage—Morcela de Arroz de Monchique through Microbiological Challenge and Consumer Test

Morcela de Arroz (MA) is a ready‐to‐eat blood and rice cooked sausage produced with pork, blood, rice, and seasonings, stuffed in natural casing and cooked above 90 °C/30 min. It is commercialized whole, not packed, with a restricted shelf life (1 wk/0 to 5 °C). The objective of this work was to establish sliced MA shelf life considering both the behavior of L. monocytogenes through a microbiological challenge test (MCT) and the consumer acceptability of MA stored: vacuum packed (VP), modified atmosphere packed (MAP: 80% CO₂/20% N₂), and aerobic packed (AP). The MCT was conducted inoculating ±3 log CFU/g of L. monocytogenes cell suspension on the MA slices. Packaged samples were stored at 3 ± 1 °C and 7 ± 1 °C until 20 d. At 3 ± 1 °C, L. monocytogenes behavior was not affected by packaging or storage time. At 7 ± 1 °C, the pathogen increased nearly 1 log CFU/g in the first 4 d. L. monocytogenes populations in AP were higher (P < 0.05) than in MAP. The pathogen may grow to hazardous levels in the 1st days if a temperature abuse occurs. Considering the acceptability by the consumers, the shelf life of MA stored at 3 ± 1 °C was 4.4 d for AP, 8.1 d for VP, and 10.4 d for MAP. The sensory shelf life established based on sensory spoilage is shorter than the shelf life to maintain the population of L. monocytogenes in safe levels.     

Characterisation of malolactic conversion by Oenococcus oeni to reduce the acidity of apple juice

The high concentration of malic acid is responsible for the acidity and sourness in apple juice. Bio‐conversion of malic acid to lactic acid through malolactic conversion (MC) in apple juice using Oenococcus oeni was investigated. When apple juice was inoculated with O. oeni (1 × 10⁶ CFU mL^?1), over 90% of malic acid was converted into lactic acid within 96 h at room temperature. When pH of apple juice was adjusted to 4.1 prior to inoculation, MC was completed within 60 h. MC was enhanced at a higher temperature (30°C) when compared with room temperature. The rate of MC was directly proportional to the number of bacteria added and MC was completed within 24 h at 1 × 10⁹ CFU mL^?1 initial cell density. MC occurred equally under aerobic and anaerobic conditions. The sensory analysis of partial MC‐applied juice when compared against control revealed potential for use of MC for manufacture of low‐acid apple juice.     

Killer strains of Saccharomyces: application for apple wine production

The aim of this study was to evaluate possible application of killer strains Saccharomyces paradoxus CBS 3702 (K1), S. cerevisiae CBS 6505 (K2) and S. capensis CBS 7903 (K3) for apple wine production. Apple musts were obtained from Jonagold apples. The optimal pH value of killer toxins activity, the temperature of their formation and the spectrum of activity against selected wine spoilage fungal strains were analysed. The influence of yeast strains on the chemical composition, volatile profile and sensory properties of apple wines was determined using high‐performance liquid chromatography and gas chromatography methods. The pH values of 4.2 (K1, K3) and 4.6 (K2), and a temperature of 28 °C, were optimal for the action of toxins. The analysed killer strains inhibited growth of seven of the 11 tested wine spoilage fungal strains. The samples obtained using the S. cerevisiae killer strain were characterized by the highest fermentation rate, highest ethanol concentration and a balanced level of volatiles, but their taste was described as bitter. S. capensis gained the highest scores in the sensory evaluation. It could be used for semi‐sweet or semi‐dry cider production, because of the lower amounts of ethanol formation but higher synthesis of glycerol, volatile esters and higher alcohols. Copyright © 2016 The Institute of Brewing & Distilling     

Thermal degradation kinetics of anthocyanins from Chinese red radish (Raphanus sativus L.) in various juice beverages

Thermal and storage stabilities of red radish anthocyanins (RRAs) in various juice beverages (apple, grape, peach, pear, pomegranate and lemon) were studied over temperature range 70–90 °C and 4–25 °C. RRAs degradation in all juice beverages followed first-order reaction kinetics. RRAs showed a much faster degradation rate during storage at room temperature (t _1/2 value ≤84.0 days) than did in refrigerated temperature (t _1/2 ≥value 130.9 days). The rate constant (k), E _a and Q ₁₀ values for RRAs in juice beverages varied from 1.33 to 0.33, 47.94 to 14.77 kJ mol^?1 and 1.16 to 1.89 at 70–90 °C. During heating, RRAs in peach and pomegranate showed higher stability than others at these temperatures. There was a positive correlation (R ² > 0.9128) between ascorbic acid content of juice beverages (8–36 mg/100 mg) and stability of RRAs at 70–90 °C. It was found that RRAs in apple and pear juice beverage were more stable than in other juice beverages.     

Use of High-Intensity Ultrasound and UV-C Light to Inactivate Some Microorganisms in Fruit Juices

Novel technologies that involve non-thermal processes have been investigated in the last two decades as full or partial alternatives to conventional heat treatment. The main objective of this study was to evaluate the survival of single or strain cocktail of Escherichia coli, Saccharomyces cerevisiae, and a yeast cocktail in orange (pH 3.5; 9° Brix) and/or apple (pH 3.1; 12° Brix) juices and in 0.1% w/w peptone water processed by two non-thermal techniques: high-intensity ultrasound (USc) and/or short-wave ultraviolet radiation (UV-C). USc treatments (20 kHz, 95 μm-wave amplitude) were performed using a stainless steel continuous flow cell with a 13-mm probe (0.2 L/min; 40°C). The UV-C device consisted of a 90-cm long UV-C-lamp (100 W) placed inside a glass tube leaving an annular flow space (0.2 L/min; 40°C). Inoculated systems were recirculated through simultaneous or consecutive USc and UV-C devices and samples were taken at preset time intervals. Microbial populations were monitored by plate count technique. In peptone water and apple juice, UV-C radiation provoked higher E. coli ATCC 35218 inactivation than USc treatment. E. coli ATCC 35218 and its cocktail were more sensitive than S. cerevisiae KE162 and the cocktail of yeasts. UV-C efficiency was highly dependent on media nature. The poor single effect of UV-C light in orange juice was enhanced by the combination with USc. Combined treatment was more effective in simultaneous rather than in a series of USc − UV-C arrangement.     

Synthesis of octadecyl acrylate-co-ethylene glycol dimethacrylate resin for removal of dark-colored compound from apple juice and comparison with polyvinylpolypirrolidone (PVPP)

Adsorption process has an importance for improving the color of juice and also stabilizing the final product during the shelf life. In this study, polyvinylpolypirrolidone (PVPP) and octadecyl acrylate-co-ethylene glycol dimethacrylate (ODA-EGDMA) polymeric resins were used as adsorbents for improving the color properties of apple juice. The ODA-EGDMA resin was prepared by classical suspension polymerization technique and characterized by electron microscopy. The obtained spherical particles diameters were between 20 and 140 μm. PVPP was selected as reference polymeric material for its importance in the juice industry. The adsorption kinetics of dark-colored compounds on adsorbent polymeric resins were studied at different adsorbent resins concentrations (1, 2, 4, and 8 g adsorbent resin per liter of apple juice) at the constant temperature (20 °C) in batch reactor. Langmuir adsorption model was applied for both PVPP and ODA-EGDMA polymeric adsorbents. The Langmuir isotherms were plotted for both polymeric adsorbents by evaluation of the absorbance data of apple juice at 420 nm. Langmuir isotherm's empirical constants known as K _ad and Q ₀ were calculated from the equilibrium data. Numerical value of K _ad and Q ₀ were determined as 5.0578 and 0.3089 for the ODA-EGDMA polymeric resin, 2.4824 and 0.5268 for the PVPP adsorbent, respectively. The scope of this study included comparison of reusability and regeneration properties of the each polymeric adsorbent. For this purpose, series of experiment were done in pack bed column application. Pressure drop measured throughout the PVPP pack bed column was 4.8 times higher than ODA-EGDMA pack bed column at same flow rate (2.5 mL/min) during the this group experiment. ODA-EGDMA resin and PVPP were regenerated with NaOH (4% w/v, 50 °C) after each run. After regeneration, average removal of dark color (relative absorbance change at 420 nm) of apple juice was determined as 76.47±0.90% for ODA-EGDMA and 91.51±0.86% for PVPP adsorbent resin.     

Effect of Food Composition on the Heat Resistance of Yeast Ascospores

The ascospores of Saccharomyces cerevisiae were over 100-fold more resistant than vegetative cells of the same strain. The D₆₀ of spores in apple juice was 6.1 min and the z value was 3.8°C; in a Chenin blanc wine the D₅₅ was 0.57 min and the z value was 6.7°C. The presence of sugar in the heating medium increased spore resistance while alcohol reduced it; varying pH over the range 3.0 to 7.0 had little effect.     

Changes in quality attributes of pulsed light and thermally treated mixed fruit beverages during refrigerated storage (4 °C) condition

The effect of batch pulsed light (PL) irradiation (3000 J cm⁻²) on the shelf-life of the beverage blend comprising apple ber (Indian jujube), carambola (star fruit), and black table grapes was investigated. The equivalent thermally treated beverage (90 °C|5 min) exhibited greater stability from microbial and enzymatic spoilage but retained 27% less antioxidants and 14% less vitamin C than PL-treated juice. Thermally and PL-treated blends possessed sensory scores of 5.8 and 7.2, respectively. The beverage's microbial shelf-life (population ≤ 6-log₁₀ cfu/mL) was extended to 45 days at 4 °C after the PL treatment. The PL exposure did not alter the pH and soluble solids during storage. The PL-treated juice, after 45 days, was placed on par with the freshly prepared juice by the sensory panel. The PL-treated juice preserved 61% more antioxidants, 38.8% more phenolics, and 68.2% more vitamin C than the thermally pasteurized beverage after 45 days of refrigerated storage.Industrial relevanceWhile the fruit processing industry demands microbial safety and enzymatic stability, today's consumer demands juices of high nutritional quality. This study utilizes under-explored fruits like apple ber (Indian jujube) and carambola (star fruit) to make a shelf-stable mixed fruit beverage. This study will help the industry understand the potential of PL treatment in accomplishing microbial safety, enzymatic stability, and nutritional quality, along with the utilization of under-explored fruits.     

Monitoring the sensorial and microbiological quality of pasteurized white asparagus at different storage temperatures

Changes in sensory quality and proliferation of pathogenic and spoilage microorganisms in pasteurized white asparagus were measured as a function of storage temperature. The main sensorial attributes studied with regard to storage time were the general appearance of the product, turgidity and package swelling. There was a significant correlation between the deterioration in sensorial quality and microbial evolution, which was even more marked at higher temperatures. After 13 days at 4°C, 6 days at 10°C, 5 days at 20°C and 84 h at 30°C organoleptic deterioration and, consequently, the end of shelf life were detected. A significant growth of spoilage flora was observed, which might be responsible for the drop in pH levels during the final period of analysis (from 6.3 to 3.5–4 until 148 h). There was greater lactic acid bacteria (LAB) growth as the temperature and CO₂ concentration increased, reaching a final concentration of approximately 10⁸ CFU g^?1 at all temperatures. We found no positive samples of Clostridium spp at 10 and 4°C. Among the species isolated at 20–30°C Clostridium septicum and in lower proportions Clostridium perfringens were encountered. The possible presence of Listeria monocytogenes was analyzed, but there were no positive samples in the final product. Pasteurized white asparagus maintains good organoleptic characteristics with a relatively long shelf‐life at low temperatures, which leads to an adequate acceptance among consumers. Copyright © 2006 Society of Chemical Industry     

Kinetic study of high pressure microbial and enzyme inactivation and selection of pasteurisation conditions for Valencia Orange Juice

Keeping quality of fresh orange juice is highly dependent on pectinolytic enzyme activity and the growth of spoilage microorganisms. The inactivation kinetics of indigenous pectin methylesterase (PME) and of the two more pressure resistant species of spoilage lactic acid bacteria (LAB) Lactobacillus plantarum and L. brevis in freshly squeezed Valencia orange juice under high hydrostatic pressure (100–500 MPa) combined with moderate temperature (20–40 °C) was investigated. PME inactivation followed first order kinetics with a residual PME activity (15%) at all pressure–temperature combinations used. The values of activation energy and activation volume were estimated at each pressure and at each temperature, respectively. Values of 90 kJ/mol and ?30 mL/mol at reference pressure of 300 MPa and reference temperature of 35 °C were estimated respectively. The corresponding z_T and z_P values of LAB inactivation were also estimated at all conditions tested. Values of 19.5 °C and 95 MPa at reference pressure of 300 MPa and reference temperature of 30 °C were estimated respectively for L. plantarum, while the corresponding values for L. brevis were 40 °C and 82 MPa, respectively, at the same reference conditions. Pressure and temperature were found to act synergistically both for PME and LAB inactivation. The PME and LAB inactivation rate constants were expressed as functions of the temperature and pressure process conditions. These functions allow the determination of the pressure/temperature conditions that achieve the target enzyme and microbial inactivation at a selected processing time. The process conditions of 350 MPa at 35 °C for 2 min are proposed as effective for Valencia orange juice cold pasteurisation.     

Radiant energy under vacuum (REV) technology: A novel approach for producing probiotic enriched apple snacks

The feasibility of vacuum impregnation in combination with air drying + radiant energy vacuum (REV) drying to produce shelf stable probiotic enriched apple slices was evaluated. The shelf life of the products was monitored at 25 and 4 °C. The results demonstrated that bacterial stability at 25 °C depended on the dehydration techniques; with the longest shelf life in air drying +REV drying followed by freeze drying and air drying. Storage at 4 °C showed no significant changes in bacterial population up to 180 days in all samples. Sensory properties of the air drying +REV and freeze dried apple slices remained above the acceptable level for 30 days at 25 °C and 180 days at 4 °C. The results also revealed that dried apple slices were able to provide prominent protection to the cells in acidic gastric juice.     

Changes in the odors of reconstituted apple juice during thermal processing

Influences of the thermal treatment on the odors of apple juice were investigated by sensory methodology. Reconstituted juice was treated at 80, 90, 100, 110 and 120 °C for 2.0∼320 s by a continuous-flow thermal treatment. Treated juices were subjected to a series of sensory evaluations. The odors of apple juice changed markedly with the treatment temperature and residence time. The quality optimum points were observed around 65 s for 80 °C, 25 s for 90 °C and 15 s for 100 °C. Points of subjective equality on the thermal degradation of apple juice odor were also estimated. Present data enabled the thermal treatment of reconstituted apple juice to be optimized.     

Influence of cold chain interruptions on the shelf life of fresh pork and poultry

In this study, the influence of fluctuations of the cold chain on the growth of Pseudomonas spp. on fresh pork and poultry and, therefore, their shelf life was evaluated. Thus, four storage trials were examined. In each trial, shelf life at the control scenario (4 °C, constant) was compared with shelf life at two dynamic scenarios including temperature shifts from 4 to 7 and to 15 °C, respectively. Overall, fresh pork and fresh poultry showed similar spoilage patterns at dynamic temperature conditions with remarkable reductions in the shelf life when short temperature upshifts occurred at the beginning of the storage. Reductions were up to 2 days (up to over 30%), although the storage time with an abusive temperature was <5% of the total storage time. As expected, scenarios with shifts to 15 °C led to higher shelf life reductions than scenarios with shifts to 7 °C for both meat types.     

Development of predictive models evaluating the spoilage-delaying effect of a bioprotective culture on different yeast species in yogurt

Yeast spoilage of fermented dairy products causes challenges for the dairy industry, including economic losses due to wasted product. Food cultures with bioprotective effects are becoming more widely used to help ensure product quality throughout product shelf life. To assist the dairy industry when evaluating product quality throughout shelf life and the effect of bioprotective cultures, we aimed to build stochastic models that provide reliable predictions of yeast spoilage in yogurt with and without bioprotective culture. Growth characterizations of Debaryomyces hansenii, Yarrowia lipolytica, Saccharomyces cerevisiae, and Kluyveromyces marxianus at storage temperatures of 7, 12, and 16°C during a 30-d storage period were conducted in yogurt with and without a bioprotective culture containing Lacticaseibacillus rhamnosus strains. The kinetic growth parameters were calculated using the Buchanan growth model, and these parameters were used as baseline values in Monte Carlo models to translate the yeast growth into spoilage levels. The models were developed using 100,000 simulations and they predicted yeast spoilage levels in yogurt by the 4 yeast types. Each modeled yogurt batch was set to be contaminated with yeast at a concentration drawn from a normal distribution with a mean of 1 log₁₀ cfu/mL and standard deviation of 1 log₁₀ cfu/mL and stored for 30 d at a temperature drawn from a normal distribution with a mean of 6.1°C and a standard deviation of 2.8°C. Considering a spoilage level of 5 log₁₀ cfu/mL, the predicted number of spoiled samples was reduced 3-fold during the first 10 d and by 2-fold at the end of shelf life when a bioprotective culture was added to the yogurt. The models were evaluated by sensitivity analyses, where the main effect factors were maximum yeast population, storage temperature, and yeast strain. The models were validated by comparing the model output to actual observed spoilage data from a European dairy using the bioprotective culture. When the model prediction, based on a mixture of the 4 specific yeast strains, was compared with spoilage data from the European dairy, the observed effect of bioprotective cultures was considerably higher than predicted, potentially influenced by the presence of contaminating strains more sensitive to a bioprotective culture than those characterized here. The developed Monte Carlo models can predict yeast spoilage levels in yogurt at specific production settings and how this may be affected by various parameters and addition of bioprotective cultures.     

Inactivation of Saccharomyces cerevisiae and Lactobacillus plantarum in orange juice using ultra high-pressure homogenisation

Yeasts and lactic acid bacteria are the usual contaminants in orange juice and responsible for decreasing the shelf life of the product. Ultra high-pressure homogenisation has been shown to be an alternative to the traditional thermal pasteurisation of pumpable foods. The product was pumped through a homogeniser valve at 100 MPa, 150 MPa, 200 MPa, 250 MPa and 300 MPa using two synchronized overlapped intensifiers at a flow rate of approximately 270 mL/min. The inlet temperature was kept at 10 °C, pH at 4.1 and soluble solids at 10.0 °Bx. After processing, the product was immediately cooled to 4 °C and the microbiological count was determined. The study showed that Lactobacillus plantarum and Saccharomyces cerevisiae are sensible to ultra high-pressure homogenisation treatment. The results indicated that pressures higher than 250 MPa were able to completely destroy initial loads of 1.2 × 107 UFC/mL of L. plantarum and 2.9 × 105 UFC/mL of S. cerevisiae in orange juice, making this technology a promising way to nonthermally process orange juices.Industrial relevanceThis paper deals with inactivation of microorganism contaminants of orange juice using dynamic ultra high process technology. It is of industrial interest and relevance to evaluate the use of this non-thermal emerging technology to process fluid foods that may result into better taste, optimum product functionality, safety and quality characteristics.     

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

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

Biomass and Patulin Production by Byssochlamys nivea in Apple Juice as Affected by Sorbate, Benzoate, SO2 and Temperature

The effects of potassium sorbate, sodium benzoate, SO₂ and incubation temperature on biomass and patulin production by Byssochlamys nivea in apple juice were determined. Growth at 21, 30 and 37°C over a 25-day incubation period was significantly retarded by 75 ppm SO₂, 150 ppm potassium sorbate and 500 ppm sodium benzoate. Biomass accumulated to approximately 500 mg/100 ml in control samples of apple juice. Patulin was produced in the highest concentrations at 21°C after 20 days incubation. After reaching a maximum concentration at 30 and 37°C, a rapid decline in patulin content was observed. Patulin production was also observed at 12°C. On the basis of concentration, SO₂ had the most significant effect on the rate of biomass and patulin production by B. nivea followed by potassium sorbate and sodium benzoate, respectively.