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The study aimed to investigate inactivation of naturally occurring microorganisms and quality of red pepper paste treated by high pressure processing (HPP). Central composite rotatable design was employed to determine the impacts of pressure (100–600 MPa) and holding time (30–600 s). HPP at 527 MPa for 517 s reduced aerobic mesophilic bacteria count by 4.5 log CFU/g. Yeasts and molds counts were reduced to 1 log CFU/g at 600 MPa for 315 s. Total phenols, carotenoids and antioxidants activity ranged from 0.28 to 0.33 g GAE/100 g, 96.0–98.4 mg βc/100 g and 8.70–8.95 μmol TE/g, respectively. Increase (2.5–6.7%) in these variables was observed with increasing pressure and holding time. Total color difference (ΔE∗) values (0.2–2.8) were within the ranges of ‘imperceptible’ to ‘noticeable’. Experimental results were fitted satisfactorily into quadratic model with higher R2 values (0.8619–0.9863). Optimization process suggested treatment of red pepper paste at 536 MPa for 125 s for maximum desirability (0.622). Validation experiments confirmed comparable percentage of relative errors. Overall, this technique could be considered as an efficient treatment for the inactivation of microorganisms that naturally occur in red pepper paste with minimal changes in its characteristics.
The impact of Pulsed Electric Fields (PEF) on the peeling ability of different fruits and vegetables in particular tomatoes, peaches, peppers, and oranges were investigated. Samples were exposed to a fixed electric field strength of 2.15 kV/cm. The specific energy ranged from 0.6 kJ/kg to 50.3 kJ/kg. The treated raw materials were analysed regarding to the peeling ability, skin size and weight and firmness. The best result for tomatoes at a specific energy of 1.2 kJ/kg induced a high score of peeling ability that led to less product loss and could therefore increase the yield by 33.84%–41.53% compared to untreated samples. Moreover, an increased skin size by a factor of 3.7 was observed. However, PEF had no significant impact on peeling ability of oranges, peppers, and peaches. Although oranges showed an improvement in peeling ability by up to 32%, this cannot be traced back to the PEF treatment. The different properties and structures of the raw materials were discussed and provided indications about the limitation of PEF.
The present study investigates properties of heat-induced, self-standing gels of globular proteins. Native egg white protein (EWP) with 9,8 wt% protein and 0,395 wt% NaCl content was adjusted to pH = 7,0 and heated from 25 to 85 °C via Ohmic heating (OH) and conventional heating (COV) with respective come-up times (CUT, 240 and 1200 s) and holding times (HOLD, 30 and 900 s). Gels heated under OH showed lower denaturation levels and less water holding capacity. When HOLD was short, the firmness of OH gels exceeded COV gel firmness but deceeded at long HOLD. Similarly, at short HOLD OH samples presented higher hydrophobic interactions whereas at long HOLD COV gels showed more hydrophobic interactions. This correlated with changes of intermolecular beta-sheet structures which increased with HOLD at COV but decreased or remained unchanged during OH. Furthermore, as an SDS-PAGE revealed the main EWP, ovalbumin, did not fully denature when heated via OH, this lead to the assumption that the oscillatory electric field partially interferes the complete denaturation and development of intermolecular beta-sheet structures and hydrophobic interactions during thermal gelation of this protein. Scanning electron microscopy also showed deviances in network structures between OH and COV as COV gels exhibited a denser and OH gels a more open and porous network structure.
Повышение эффективности снятия покровной ткани с плодов томата импульсным электрическим полем
(2022)
Electrophysical technologies are a global trend of sustainable agriculture and food industry. Peeling is an energy-intensive procedure of fruit and vegetable processing. The research featured the effect of pulsed electric field (PEF) treatment on tomato peeling effectiveness. The assessment included such factors as specific effort, energy costs, and product losses in comparison with thermal and electrophysical methods. Tomatoes of Aurora variety underwent a PEF treatment at 1 kV/cm. The expended specific energy was 1, 5, and 10 kJ/kg. The tomatoes were visually evaluated with optical microscopy before and after processing. The peeling effectiveness and mass loss were measured with a texture analyzer and digital scales. The PEF treatment decreased the specific force of mechanical peel removal by 10% (P < 0.05). The mass loss decreased by 4% (P < 0.05) at 1 kJ/kg. The PEF method resulted in cell electroporation, which activated the internal mass transfer of moisture from the endocarp region between the mesocarp and the integumentary tissue. The hydrostatic pressure produced a layer of liquid, which facilitated the peeling. In comparison with thermal treatment (blanching), ohmic heating, and ultrasonic processing, the PEF technology had the lowest production losses and energy costs. The research proves the prospects of the PEF treatment in commercial tomato processing.
Applications of pulsed electric fields for processing potatoes: Examples and equipment design
(2022)
In the last two decades, pulsed electric fields (PEF) have successfully been introduced into the food industry, as one of the most promising and "game changing" technologies. This review is devoted to the recent applications of pulsed electric fields used in processing potatoes. The potato processing market size was estimated to be ca. USD 24.83 billion (2018) and with an annual growth rate of 5.2%. The physicochemical characteristics of potatoes and the specificity of potato processing lines makes a pulsed electric field very versatile and flexible allowing one to achieve different technological aims by its implementation into technological lines. In this paper, a short analysis of the potato structure and its nutritional properties, applications of moderate electric fields, ohmic heating, and pulsed electric fields are presented. Moreover, the basic electroporation effects, metabolic responses, texture modification and different PEF assisted processes applied to the potato are discussed. Finally, some examples of commercial applications and a brief description of the available equipment for the PEF processing of potatoes are presented.
Der Bereich Ernährung wird in den kommenden Jahrzehnten vor zahlreichen Herausforderungen stehen, die sich aus den veränderten Lebensgewohnheiten und globalen Konsummustern bei gleichzeitig hohem Ressourcenverbrauch ergeben. Vor diesem Hintergrund wird in diesem Papier ein neu entwickeltes Instrument zur Verringerung der Auswirkungen auf die Ernährung vorgestellt, der sogenannte Ernährungsfußabdruck. Das Instrument basiert auf der Umsetzung des Konzepts einer nachhaltigen Ernährung in Entscheidungsprozessen und der Unterstützung einer ressourcenschonenden Gesellschaft. Das Konzept integriert jeweils vier Indikatoren aus den beiden ernährungsrelevanten Bereichen Gesundheit und Umwelt und verdichtet sie zu einem leicht kommunizierbaren Ergebnis, das sich in seinen Ergebnissen auf eine Wirkungsebene beschränkt. Anhand von acht Mittagsmahlzeiten werden die Methodik und ihre Berechnungsverfahren detailliert vorgestellt. Die Ergebnisse unterstreichen die allgemeine wissenschaftliche Sichtweise auf Lebensmittel; Mahlzeiten auf der Basis von tierischem Eiweiß sind im Hinblick auf ihre Gesundheits- und Umweltauswirkungen relevanter. Das Konzept scheint für Verbraucher nützlich zu sein, um ihre eigene Wahl zu bewerten, und für Unternehmen, um ihre internen Daten, ihre Benchmarking-Prozesse oder ihre externe Kommunikationsleistung zu erweitern. Methodische Unzulänglichkeiten und die Interpretation der Ergebnisse werden erörtert, und die Schlussfolgerung zeigt das Potenzial der Instrumente für die Gestaltung von Übergangsprozessen und für die Verringerung des Verbrauchs natürlicher Ressourcen durch die Unterstützung von Entscheidungen und Wahlmöglichkeiten von Lebensmittelanbietern und Verbrauchern.
The impact of Pulsed Electric Field (PEF) processing pre-treatment on the texture and kinetics of in vitro starch digestibility of French fries made from two potato cultivars (Solanum tuberosum L.) containing dry matter content ranging from 19 to 22% was investigated. Whole and steam-peeled potato tubers were treated with a pilot scale PEF unit (electric field strength of 1.1 and 1.9 kV/cm with energy input <10 kJ/kg or ∼50 kJ/kg). This trial was carried out in a commercial French-fry plant using an industrial scale cutter, blancher, fryer and blast-freezer to prepare the frozen par-fried French fry samples. After subsequent final batch frying of the frozen fries, at 180 °C for 3 min to mimic the typical preparation practice at restaurant, retail and household, the outer crust of the fries produced from PEF-treated potatoes was significantly harder (9.4–16.3 N) than crust produced from untreated potatoes (6.9–8.5 N). High intensity (1.9 kV/cm with energy input ∼50 kJ/kg) PEF processing was found to cause defects (i.e. hollowness in the internal core) in the fries. A fractional conversion model was a good fit for the starch digestion kinetics of all French fry samples during the small intestinal phase (based on standardised INFOGEST static in vitro digestion assay). A lower % of total starch hydrolysis was predicted for French fries produced from high dry matter (>21%) tubers pretreated with PEF at electric field strength of 1.9 kV/cm. The findings generated in this study demonstrate PEF pretreatment may influence the texture of French fries and the extent of starch digestion that occurs.
The impact of pulsed light (PL) treatment on naturally occurring microorganisms, mycotoxins, and on physicochemical properties in red pepper powder was investigated. Powder samples were exposed to different PL treatments up to 61 pulses, with fluence ranging from 1.0 to 9.1 J/cm2. The highest fluence applied (9.1 J/cm2, 61 pulses, 20 s) resulted in 2.7, 3.1, and 4.1 log CFU/g reduction of yeasts, molds, and total plate counts (TPC), where initial microbial loads were 4.6, 5.5, and 6.5 log CFU/g, respectively. At the same fluence intensity, a maximum reduction of 67.2, 50.9, and 36.9% of aflatoxin B1 (AFB1), total aflatoxins (AF), and ochratoxin A (OTA) were detected, respectively. Proportional increase in temperature of the samples was observed from the absorbed PL energy, reaching maximum of 59.8°C. The inactivation of investigated microorganisms and mycotoxins followed first-order kinetics (R2 > 0.95). The fluence intensity at 6.9 and 9.1 J/cm2 did not cause degradation, but rather a significant (p < .05) and apparent increase of total phenols. Total color difference (ΔE*) revealed only “slight differences,” compared to the untreated sample. In conclusion, higher reduction of microbial load and mycotoxins in red pepper powder could be achieved, when higher treatment intensity was applied. This suggests the PL as a potential technology for decontamination of red pepper powder and other spice powders.
Bilder, die hängen bleiben. Wie lassen sich transdisziplinäre Transformationsprozesse gestalten?
(2020)
The influence of moderate electric fields (MEF) on thermally induced gelation and network structures of patatin enriched potato protein (PPI) was investigated. PPI solutions with 9 wt% protein (pH 7) and 25 mM NaCl were heated from 25 to 65 °C via OH (3–24 V/cm) or conventional heating (COV) at various come-up (240 s and 1200 s) and holding times (30 s and 600 s). Self-standing gels were produced but less proteins denatured when heated via OH. Further, SDS-PAGE and GPC measurements revealed more native patatin remaining after OH treatment. Scanning electron microscopy showed OH gels to have more gap-like structures and frayed areas than COV treated gels which resulted in lower water holding capacity. On molecular scale, less hydrophobic interactions were measured within the protein network and FTIR trials showed the MEF to affect beta-sheet structures. OH gels further showed lower rigidity and higher flexibility, thus, gelling functionality was affected via OH.
The kiwifruit processing industry is focused on product yield maximization and keeping energy costs and waste effluents to a minimum while maintaining high product quality. In our study, pulsed electric field (PEF) pretreatment enhanced kiwifruit processing to facilitate peelability and specific peeling process and enhanced valorization of kiwifruit waste. PEF optimization was applied to obtain the best treatment parameters. A 32 factorial design of response surface methodology was applied to find the effect of time elapsed after PEF treatment and the PEF-specific energy input on specific peeling force and kiwifruit firmness as response criteria. Under the optimized condition, the specific peeling force decreased by 100, and peelability increased by 2 times. The phenolic content and antioxidant capacity of PEF-treated kiwifruit bagasse were 5.1% and 260% richer than the control sample. Overall, the optimized PEF pretreatments incorporated into kiwifruit processing led to decreased energy demand and increased productivity.
Novel foods by process are a special case in the catalogue of the ten novel food categories according to Article 3 (2) point (a) of the Novel Food Regulation (EU) 2015/2283, since the other nine categories derive their assessment as possible novel foods from their purely substantial properties. In the case of novel foods by process, the problem of dealing with the reference date of 15 May 1997, which is in the end a random reference date, is particularly significant. It would make more sense to have a dynamic reference date that ‘moves along the timeline’ or at least is reset from time to time and is more up-to-date. The characteristic that a process causes ‘significant changes in the composition or structure of the food, affecting its nutritional value, metabolism or level of undesirable substances’ must be understood in such a way that it is only a question of the generation of undesirable substances through the application of the process, but not their reduction, e.g. the reduction of undesirable microorganisms. Finally, the question also arises as to how the assessment of the process technology relates to the assessment of a food in the context of a novel food by composition category. This concerns the exemption for foods that have a history of use as safe foods, which, according to the view taken here, must also be interpreted into the category of novel foods by process.
Plant-based proteins are rapidly emerging, while novel technologies are explored to offer more efficient extraction processes. The current study aimed to evaluate the effects of pulsed electric fields (PEFs) and temperature on the extraction of soluble proteins from nettle leaves (Urtica dioica L.) and identify an optimal operational range for the highest yield of soluble proteins. Extractions and kinetic modeling were conducted with whole and ground dried leaves at different temperatures (30–70 °C) and specific energy of PEF (0–30 kJ kg−1) with extraction times of up to 60 min. The influence of temperature and specific energy on the soluble protein extraction yields was investigated and modeled using composite central design and response surface methodology. The experimental results were fitted to Peleg's kinetic model, which satisfactorily described the extraction process (R2 > 0.902), and PEF treated samples resulted in a higher soluble protein yield and shortened processing time. Response surface methodology showed that the linear effect of temperature and quadratic effect of PEF (p < 0.01) were highly significant for protein yield. In the optimized PEF-extraction region (specific energy between 10 and 24 kJ kg−1, and 70–78 °C), soluble protein yield was higher than 60% after 5 minutes of extraction. The achieved results are relevant for developing processes for PEF assisted extraction of soluble proteins from leaves. Understanding the effects of PEFs and process parameters is crucial to obtain high protein yields, while requiring low energy and short processing time.