Symposium on 'nutritional effects of new processing technologies'. New processing technologies: an overview

Clinical Potential of Hyperbaric Pressure-Treated Whey Protein

Whey protein (WP) from cow's milk is a rich source of essential and branched chain amino acids. Whey protein isolates (WPI) has been demonstrated to support muscle accretion, antioxidant activity, and immune modulation. However, whey is not readily digestible due to its tight conformational structure. Treatment of WPI with hyperbaric pressure results in protein unfolding. This enhances protein digestion, and results in an altered spectrum of released peptides, and greater release of essential and branched chain amino acids. Pressurized whey protein isolates (pWPI), through a series of cell culture, animal models and clinical studies, have been demonstrated to enhance muscle accretion, reduce inflammation, improve immunity, and decrease fatigue. It is also conceivable that pWPI would be more accessible to digestive enzymes, which would allow for a more rapid proteolysis of the proteins and an increased or altered release of small bioactive peptides. The altered profile of peptides released from WP digestion could thus play a role in the modulation of the immune response and tissue glutathione (GSH) concentrations. The research to date presents potentially interesting applications for the development of new functional foods based on hyperbaric treatment of WPI to produce products with more potent nutritional and nutraceutical properties.

Characterization of in vitro antifungal activities of small and American cranberry (Vaccinium oxycoccos L. and V. macrocarpon Aiton) and lingonberry (Vaccinium vitis-idaea L.) concentrates in sugar reduced fruit spreads

In this study, cranberry and lingonberry concentrates were added to commercial sugar-reduced fruit spreads (raspberry-Aloe vera, strawberry-guava, and strawberry-lime), and tested for their antifungal activities. Selected strains of the species Absidia glauca, Penicillium brevicompactum, Saccharomyces cerevisiae and Zygosaccharomyces bailii, as well as xerophilic environmental isolates of the genera Penicillium and Eurotium were used for challenge testing. Initially, varying concentrations of synthetic antifungal agents, such as sodium benzoate, potassium sorbate and butyl 4-hydroxybenzoate were tested against these fungi on wort agar containing 31% fructose at different pH values. Subsequently, the experiments were conducted in fruit spreads containing different concentrations of cranberry and lingonberry concentrates. The results of this study demonstrate that these concentrates were able to inhibit growth of visible colonies of xerophilic and non-xerophilic fungi. Cranberry and lingonberry concentrates are interesting candidates for natural preservation against fungal growth in sugar reduced fruit spreads.

Promoting Bacillus cereus spore germination for subsequent inactivation by mild heat treatment

Sublethal heat treatment may activate dormant spores and thereby potentiate the conversion of spores to vegetative cells. As the germinated spore is known to possess lower heat resistance than its dormant counterpart, it has been postulated that double heat treatment, i.e., spore heat activation followed by germination and then by heat inactivation, can be used to control spores in foods. Production of refrigerated processed foods of extended durability often includes more than one heat treatment of the food components. This work simulates conventional heat treatment procedures and evaluates double heat treatment as a method to improve spore control in model food matrixes of meat broth and cream sauce. Bacillus cereus NVH 1230-88 spores were supplemented in food model matrixes and heat activated at 70°C and then heat inactivated at 80 or 90°C. The samples were held at 29 to 30°C for 1 h between primary and secondary heat treatments, to allow spore germination. Nutrients naturally present in the food matrixes, e.g., amino acids and inosine, could act as germinants that induce germination. The levels of germinants could be too low to produce effective germination within 1 h. Following primary heat treatment, some samples were therefore supplemented with a combination of L-alanine and inosine, a germinant mixture known to be effective for B. cereus spores. In both matrixes, a combination of double heat treatment (heat activation, germination, and inactivation) and addition of germinants gave a reduction in spore counts equivalent to or greater than that obtained with a single heat treatment for 12 min at 90°C. Addition of germinants was essential to induce effective germination in cream sauce during 1 h at 29 to 30°C, and germinants were therefore a crucial supplement to obtain an effect of double heat treatment in this matrix. These data will be valuable when setting up temperature-time-germinant combinations for an optimized spore reduction in mild-heat-treated foods.

Effect of α-Cyclodextrin–Cinnamic Acid Inclusion Complexes on Populations of Escherichia coli O157:H7 and Salmonella enterica in Fruit Juices

Cinnamic acid (CA), a naturally occurring organic acid found in fruits and spices, has antimicrobial activity against spoilage and pathogenic bacteria, but low aqueous solubility limits its use. The purpose of this study was to determine the effectiveness of solubility-enhancing α-cyclodextrin–CA inclusion complexes against Escherichia coli O157:H7 and Salmonella enterica serovars suspended in apple cider or orange juice at two different incubation temperatures (4 and 26°C). Two concentrations (400 and 1,000 mg/liter) of α-cyclodextrin-CA inclusion complex were aseptically added to apple cider inoculated with E. coli O157:H7 (7 log CFU/ml) and orange juice inoculated with a cocktail of six Salmonella enterica serovars (7 log CFU/ml). Samples were extracted at 0 min, at 2 min, and at 24-h intervals for 7 days, serially diluted in 0.1% peptone, spread plated in duplicate onto tryptic soy agar, and incubated at 35°C for 24 h. Populations of E. coli O157:H7 in apple cider were significantly reduced (P ≤ 0.05) during the 7-day sampling period in all solutions regardless of temperature. Compared with the controls, populations were significantly reduced by the addition of 400 and 1,000 mg/liter inclusion complex, but reductions were not significantly different (P ≥ 0.05) between the two treatment groups (400 and 1,000 mg/liter). Salmonella was significantly reduced in all solutions regardless of temperature. There were significant differences between the control and each inclusion complex concentration at 4 and 26°C. Coupled with additional processing steps, α-cyclodextrin–CA inclusion complexes may provide an alternative to traditional heat processes.

Filamentous fungi for production of food additives and processing aids

Filamentous fungi are metabolically versatile organisms with a very wide distribution in nature. They exist in association with other species, e.g. as lichens or mycorrhiza, as pathogens of animals and plants or as free-living species. Many are regarded as nature's primary degraders because they secrete a wide variety of hydrolytic enzymes that degrade waste organic materials. Many species produce secondary metabolites such as polyketides or peptides and an increasing range of fungal species is exploited commercially as sources of enzymes and metabolites for food or pharmaceutical applications. The recent availability of fungal genome sequences has provided a major opportunity to explore and further exploit fungi as sources of enzymes and metabolites. In this review chapter we focus on the use of fungi in the production of food additives but take a largely pre-genomic, albeit a mainly molecular, view of the topic.

Inactivation kinetics of three Listeria monocytogenes strains under high hydrostatic pressure

High hydrostatic pressure (HHP) inactivation of three Listeria monocytogenes strains (EGDe, LO28, and Scott A) subjected to 350 MPa at 20 degrees C in ACES buffer resulted in survival curves with significant tailing for all three strains. A biphasic linear model could be fitted to the inactivation data, indicating the presence of an HHP-sensitive and an HHP-resistant fraction, which both showed inactivation according to first-order kinetics. Inactivation parameters of these subpopulations of the three strains were quantified in detail. EGDe showed the highest D-values for the sensitive and resistant fraction, whereas LO28 and Scott A showed lower HHP resistance for both fractions. Survivors isolated from the tail of LO28 and EGDe were analyzed, and it was revealed that the higher resistance of LO28 was a stable feature for 24% (24 of 102) of the resistant fraction. These HHP-resistant variants were 10 to 600,000 times more resistant than wild type when exposed to 350 MPa at 20 degrees C for 20 min. Contrary to these results, no stable HHP-resistant isolates were found for EGDe (0 of 102). The possible effect of HHP survival capacity of stress-resistant genotypic and phenotypic variants of L. monocytogenes on the safety of HHP-processed foods is discussed.

Effects of sonication on the kinetics of orange juice quality parameters

The effects of sonication on pH, degrees Brix, titratable acidity (TA), cloud, browning index, and color parameters ( L*, a*, and b*) of freshly squeezed orange juice samples were studied. Ultrasonic intensity (UI) levels of 8.61, 9.24, 10.16, 17.17, and 22.79 W/cm2 and treatment times of 0 (control), 2, 4, 6, 8, and 10 min were investigated. No significant changes in pH, degrees Brix, and TA ( p < 0.05) were found. Cloud value, browning index, and color parameters were significantly affected by ultrasonic intensity and treatment time. Changes in cloud value followed first-order kinetics, whereas browning index, L*, a*, and b* values followed zero-order kinetics. Reaction rate constants were linearly correlated ( R2 > 0.90) to ultrasonic intensity.

Effects of CO2 on the resuscitation of Listeria monocytogenes injured by various bactericidal treatments

To assure the microbiological safety and quality of a food product, a combination of preservation hurdles is often used. Therefore, the effects of carbon dioxide at concentrations of 0, 20, 40 and 60% in modified atmospheres on the resuscitation of Listeria monocytogenes cells injured by mild bactericidal treatments during storage at 7 degrees C were examined. The bactericidal treatments were intense light pulses (ILP), chlorine dioxide (ClO(2)), lactic acid (LA) and heat. The results indicated additional bactericidal effects of CO(2) on cultures treated with LA, ClO(2) and ILP, with additional reductions in viable L. monocytogenes of 0.5-1.0 log cfu/ml. Lag phase duration was significantly different between the different treatments, with non-treated cells having the shortest lag phase, followed by that of heat, intense light pulses, lactic acid and finally ClO(2) treated cells. Maximum growth rate was also estimated and results showed a negative correlation with increasing CO(2) concentrations. A relationship was found between the amount of sub-lethally damaged cells after a mild inactivation treatment and the lag phase duration in the CO(2) environment. Current findings demonstrate the possibility that combining mild decontamination treatments and packaging in a CO(2) enriched environment could reduce the risk of L. monocytogenes infections in food due to an extension of the lag phase.

Pulsed electric fields-processed orange juice consumption increases plasma vitamin C and decreases F2-isoprostanes in healthy humans

Orange juice, a rich source of vitamin C, accounts for 60% of all fruit juices and juice-based drinks consumed in western Europe. Orange juice preservation is currently accomplished by traditional pasteurization. Pulsed electric fields (PEF) have been studied as a nonthermal food preservation method. Food technology needs in the area of processing are driven by nutrition. Therefore, the objectives of this study were to assess the bioavailability of vitamin C from pulsed electric fields-treated orange juice in comparison with freshly squeezed orange juice and its impact on 8-epiPGF(2alpha) concentrations (biomarker of lipid peroxidation) in a healthy human population. Six subjects consumed 500 mL/day of pulsed electric fields-treated orange juice and six subjects consumed 500 mL/day of freshly squeezed orange juice for 14 days, corresponding to an intake of about 185 mg/day of ascorbic acid. On the first day of the study, subjects drank the juice in one dose, and on days 2-14 they consumed 250 mL in the morning and 250 mL in the afternoon. Blood was collected every hour for 6 hours on the first day and again on days 7 and 14. In the dose-response study, the maximum increase in plasma vitamin C occurred 4 hours postdose. Vitamin C remained significantly higher on days 7 and 14 in both orange juice groups. Plasma 8-epiPGF(2alpha) concentrations was lower at the end of the study (P < 0.001) in both groups. Plasma levels of vitamin C and 8-epiPGF(2alpha) were inversely correlated. Pulsed electric fields-preservation of orange juice retains the vitamin C bioavailability and antioxidant properties of fresh juice with a longer shelf-life.

Effect of acid adaptation on inactivation of Salmonella during drying and storage of beef jerky treated with marinades

This study evaluated the influence of pre-drying marinade treatments on inactivation of acid-adapted or nonadapted Salmonella on beef jerky during preparation, drying and storage. The inoculated (five-strain composite, 6.0 log CFU/cm2) slices were subjected to the following marinades (24 h, 4 degrees C) prior to drying at 60 degrees C for 10 h and aerobic storage at 25 degrees C for 60 days: (1) no marinade, control (C), (2) traditional marinade (TM), (3) double amount of TM modified with added 1.2% sodium lactate, 9% acetic acid, and 68% soy sauce with 5% ethanol (MM), (4) dipping into 5% acetic acid and then TM (AATM), and (5) dipping into 1% Tween 20 and then into 5% acetic acid, followed by TM (TWTM). Bacterial survivors were determined on tryptic soy agar with 0.1% pyruvate and xylose-lysine-tergitol 4 (XLT4) agar. Results indicated that drying reduced bacterial populations in the order of pre-drying treatments TWTM (4.8-6.0 log CFU/cm2)> or =AATM> or =MM>TM> or =C (2.6-5.0 log CFU/cm2). Nonadapted Salmonella were significantly (P<0.05) more resistant to inactivation during drying than acid-adapted Salmonella in all treatments. Bacterial populations decreased below the detection limit (-0.4 log CFU/cm2) as early as 7 h during drying or remained detectable even after 60 days of storage, depending on acid adaptation, pre-drying treatment, and agar media. The results indicated that acid adaptation may not cause increased resistance of Salmonella to the microbial hurdles involved in jerky processing and that use of modified marinades in manufacturing jerky may improve the effectiveness of drying in inactivating Salmonella.