Pasteurization of human milk by a benchtop High-Temperature Short-Time device

A new small-scale continuous-flow High-Temperature Short-Time (HTST) pasteurizer has been designed for treating human milk. The efficacy of the new HTST device was assessed on inoculated Listeria monocytogenes, Staphylococcus aureus and Chronobacter sakazakii, as well as on raw human milk bacteria. The milk biochemical quality after HTST pasteurization was assessed in comparison to a standard Holder pasteurization, by determining the secretory IgAs (sIgAs) content, the protein profile, lysozyme and the Bile Salt Stimulated Lipase (BSSL) activities. No pathogen or bacterial growth was detected after HTST pasteurization with the new instrument. Changes in the protein profile were observed in the milk pasteurized according to both processes. The sIgAs content and BSSL activity were significantly higher in the milk pasteurized with the new device than in the same milk treated by the standard Holder pasteurization. In conclusion, the new HTST apparatus: (i) can effectively pasteurize human milk with a better retention of sIgAs content and BSSL activity; (ii) comply to human milk banking safety requirements.Industrial relevanceCurrently, 210 active human milk banks are located in Europe (and 17 more are planned). The majority of the European banks still use Holder-based pasteurizers, which, despite efficacy in ensuring microbiological safety, are known to reduce/disrupt important nutritional and non-nutritional biological factors. Although already widely established in food industry, the advantages of HTST technology were tested only at small laboratory scale for human milk. The device tested in the present research was specifically designed to provide human milk banks with the technology they need to ensure a safe and lower-impact pasteurization process, that is suitable for processing different volumes of donations. The device can pasteurize up to 10 L of milk per hour, with a minimum volume of 100 mL. The system is designed to be cleaned-in-place (CIP) after each pasteurization run and sanitized immediately prior to the next use, being thus more suitable for treating pools of milk from different donors than milk from single donations. Italian and EU patents have been filed for the device, within a partnership between public research institutions, stakeholders (Italian association of donor milk banks), and a private company in the sector of dairy processing equipment. The device has achieved a Technology Readiness Level (TRL) 6 (Prototype demonstration in a relevant environment). The cost of the new device will be comparable to that of a typical human milk Holder pasteurizer.     

Short communication: Investigation into Mycobacterium avium ssp. paratuberculosis in pasteurized milk in Italy

This study investigated the presence of viable Mycobacterium avium ssp. paratuberculosis (MAP) in pasteurized milk produced by Italian industrial dairy plants to verify the prediction of a previously performed risk assessment. The study analyzed 160 one-liter bottles of pasteurized milk from 2 dairy plants located in 2 different regions. Traditional cultural protocols were applied to 500 mL of pasteurized milk for each sample. The investigation focused also on the pasteurization parameters and data on the microbiological characteristics of raw milk (total bacterial count) and pasteurized milk (Enterobacteriaceae and Listeria monocytogenes). No sample was positive for MAP, the pasteurization parameters complied with European Union legislation, and the microbiological analysis of raw and pasteurized milk showed good microbiological quality. The results show that a 7-log (or >7) reduction could be a plausible value for commercial pasteurization. The combination of hygiene practices at farm level and commercial pasteurization yield very low or absent levels of MAP contamination in pasteurized milk, suggesting that pasteurized milk is not a significant source of human exposure to MAP in the dairies investigated.     

In vitro digestion of foods using pH-stat and the INFOGEST protocol: Impact of matrix structure on digestion kinetics of macronutrients,proteins and lipids

It is currently admitted that food structure can facilitate or delay the release of nutrients during digestion and their absorption by the human body. The aim of this study is to propose an in vitro method able to assess the behavior of lipo-proteinic matrices with different structures during digestion. Two model matrices of exactly the same compositions (10% oil, 15% whey proteins, w/w) were designed: i) A liquid emulsion (LE) made of small fat droplets (1 μm) dispersed in a liquid continuous phase containing native whey proteins, ii) a solid emulsion (SE) made of a continuous whey protein gel entrapping large oil droplets (20 μm). The two matrices were digested through an in vitro gastro-intestinal protocol based on the INFOGEST guidelines using pH-stat to monitor the enzymatic hydrolyses of both proteins and lipids. By further digesting lipid-free matrices in the same conditions, the contributions of the proteolytic and lipolytic reactions were evaluated. Significant differences were observed between matrices at both short and long digestion times. The initial rates of both proteolysis and lipolysis were slower for SE than LE because of the gel state of the continuous phase. At the end of the experiments, SE led to a smaller extent of lipolysis (DH_{lip_SE} = 51% < DH_{lip_LE} = 81%) but a greater extent of proteolysis (DH_{prot_SE} = 80% > DH_{prot_LE} = 52%) because of the higher sensitivity to digestion of denatured whey proteins. These results highlight the impact of matrix structure on enzyme accessibility, and show that the proposed method is suitable to monitor the digestion of complex food matrices.     

HPLC of proteose peptones for evaluating ageing of packaged pasteurized milk

The proteolysis of casein (CN) occurring in packaged pasteurized milk (PM) during refrigerated storage was studied with relation to hygienic and microbiological characteristics of starting raw milk. Six batches of raw milk having standard plate count (SPC) from 1.5×10⁴ to 2.5×10⁵ cfu mL⁻¹ and somatic cell count (SCC) from 1.6×10⁵ to 4.4×10⁵ units mL⁻¹ were pasteurized (73 °C for 15 s), packaged and stored at 4 °C for 12 days. Capillary zone electrophoresis of CN showed breakdown of β-CN in all PM samples during storage. An HPLC method for monitoring proteose peptones (PP) formation was developed. Level of PP in PM samples increased, with keeping time from 667–789 to 947–1383 mg L⁻¹ and PP formation was significantly (P<0.05) related to SCC of starting raw milk. Electrospray ionization–mass spectrometry showed that PP were mainly represented by PP-5 from either A¹ or A² variants of β-CN. Five commercial samples of PM were analysed for PP formation during 14-day storage at 4 °C. Commercial samples prepared by microfiltration process or bactofugation combined with pasteurization showed the slowest formation of PP. The effect of storage temperature on PP formation was evaluated by keeping a conventional PM sample at either 8 or 12 °C for 12 days. Proteolysis of all major CNs upon action of plasmin and bacterial proteinases was observed under these conditions. PP level thus proves to be a reliable analytical index for evaluating the ageing of packaged PM during refrigerated storage.     

Effects of somatic cell counts in milk on physical and chemical characteristics of yoghurt

The quality of plain stirred yoghurt produced from whole milk with somatic cell counts (SCC) at low (147,000 cells mL⁻¹), intermediate (434,000 cells mL⁻¹) and high (1,943,000 cells mL⁻¹) levels was examined. Each milk treatment was obtained from selected cows, according to its SCC status and milk composition. Yoghurt samples were analysed on days 1, 10, 20 and 30 after production. Analyses included pH, acidity, fat, lipolysis (expressed as free fatty acids, FFA), proteolysis and apparent viscosity. Viscosity of high SCC yoghurt was higher (P<0.05) than the low SCC yoghurt on days 10, 20 and 30 of storage. High SCC yoghurt also had higher FFA content (P<0.05). SCC did not affect pH, acidity, fat content and proteolysis of the yoghurt (P>0.05). Results indicate that SCC in milk increases the lipolysis in the resulting yoghurt during storage for 30 d.     

Cheese made from instant infusion pasteurized milk: Rennet coagulation,cheese composition,texture and ripening

Milk subjected to instant infusion pasteurization (IIP) at 72 °C, 100 °C and 120 °C (holding time 0.2 s) exhibited increased rennet coagulation time and decreased curd firming rate for increasing heat treatment temperature, when compared with raw or high temperature short time pasteurized (HTST) milk. However, addition of 4.5 mm or 9.0 mm of calcium restored the impaired rennet coagulation ability. Open texture cheeses produced from IIP milk (100 °C and 120 °C) contained significantly more moisture, had lower pH and shorter texture than similar cheese from IIP at 72 °C and HTST pasteurized milk. Cheese ripening was also affected by heat treatment, and different patterns of casein breakdown and peptide formation resulted from cheeses made from milk treated to IIP at 100 °C and 120 °C compared with cheeses made using IIP at 72 °C or HTST.     

Influence of lupin-based milk alternative heat treatment and exopolysaccharide-producing lactic acid bacteria on the physical characteristics of lupin-based yogurt alternatives

In the present study we investigated the influence of heat treatment of lupin-based (LB) milk alternatives and different exopolysaccharide (EPS)-producing lactic acid bacteria on the physical characteristics of set-type LB yogurt alternatives. LB milk alternatives, obtained from protein isolate of Lupinus angustifolius cv. Boregine, were either pasteurized at 80 °C for 60 s or ultra-high temperature (UHT) heated at 140 °C for 10 s and was fermented with Lactobacillus plantarum TMW 1.460 and 1.1468, Pediococcus pentosaceus BGT B34 and Lactobacillus brevis BGT L150. Fermentation duration was strongly affected by heat treatment: different strains needed between 25 to 35 h in UHT LB milk alternative to reach a pH of 4.5 compared to 14 to 24 h in pasteurized LB milk alternative. EPS extraction revealed slightly higher amounts of EPS for UHT LB yogurt alternatives (~ 0.5–0.9 g/l; pasteurized: ~ 0.4–0.7 g/l). The more intensive heat treatment (UHT) resulted also in better rheological (apparent viscosity, hysteresis loop area, flow point, elastic, viscous and complex modulus) and textural properties (firmness, consistency, cohesiveness and index of viscosity) of the investigated LB yogurt alternatives. Furthermore, LB yogurt alternatives out of UHT milk alternative revealed a lower tendency to syneresis, measured with siphon and centrifugation method. This work contributes to the fundamental knowledge of the textural properties of LB yogurt alternatives.     

Use of high-pressure-treated milk for the production of reduced-fat cheese

Pasteurized (65°C, 30 min), pressurized (400 MPa, 22°C, 15 min) and pasteurized–pressurized milks were used for reduced-fat (approximately 32% of total solids) cheese production. Pressurization of milk increased the yield of reduced-fat cheese through an enhanced β-lactoglobulin and moisture retention. In addition, pressurisation of pasteurized skim milk improved its coagulation properties. The cheeses made from pasteurized–pressurized and pressurized milks showed a faster rate of protein breakdown than the cheese made from pasteurized milk, that might be mainly attributed to a higher level of residual rennet. Hardness of the experimental cheeses, as determined by both the sensory panel and instrumental analyses, decreased as the moisture content and proteolytic degradation of the cheese increased (pasteurized>pressurized>pasteurized–pressurized). In general terms, pressurization of reduced-fat milk prior to cheese-making improved cheese texture and thus accounted for a higher overall acceptability, except for the cheeses made from pasteurized–pressurized milk at 60 d of ripening, whose acceptability score was adversely affected by bitterness.     

Influence of high intensity ultrasound on microbial reduction,physico-chemical characteristics and fermentation of sweet whey

The aim of this study was to investigate the influence of high intensity ultrasound on quality of reconstituted sweet whey in order to substitute thermal treatments i.e. pasteurization. Also, it was intended to study the influence of ultrasound on fermentation process of pasteurized or thermo-sonicated whey with respect to culture activation and sensory properties of the fermented whey. In the first stage, whey was subjected to treatments with different power inputs (480 W, 600 W) over 6.5, 8 and 10 min at constant temperature (45 °C, 55 °C). Treated whey samples were analyzed for microbiological quality, particle size distribution, protein content, acidity, electrical conductivity, viscosity and sensory properties. All of the analyzed parameters were compared with the control sample (pasteurized) and fresh whey. Subsequently, influence of high intensity ultrasound on pasteurized or thermo-sonicated whey fermentation with yoghurt culture and with monoculture Lactobacillus acidophilus La-5 was investigated. Ultrasound treatments were applied for culture activation prior to or after the inoculation. Whey thermo-sonication by nominal power of 480 W for 10 min at 55 °C resulted in better microbiological quality and sensory properties in comparison to whey pasteurization. Ultrasound treatments with nominal input power of 84 W over 150 s resulted in the highest increase of the viable count during the activation process. Whey fermentation by ultrasonicated culture La-5 lasted 30 min shorter and resulted in higher viable cells count.Industrial relevanceAttached paper (“Influence of high intensity ultrasound on microbial reduction, physico-chemical characteristics and fermentation of sweet whey”) reports the influence of high intensity ultrasound on quality and fermentation process of sweet whey. Also, the influence of high intensity ultrasound on pasteurized or thermo-sonicated whey fermentation with yoghurt culture and with monoculture Lactobacillus acidophilus La-5 was investigated.Whey proteins are thermo-labile proteins and degradable at higher temperatures (above 60 °C), and at conventional processing (pasteurization), denaturation and precipitation of proteins occur. Ultrasound gives a great replacement for pasteurization where precipitation does not occur. Also, ultrasonic treatment of the whey results in homogenization and thus, stability is increased. When microbiological cultures for fermentation, prior to the inoculation in the samples, are treated by ultrasound their activity is higher (explained in the paper) and thus fermentation is faster.From an economical point of view, processing by ultrasound can reduce costs a lot, since fermentation time is shorter, and the same effect as pasteurization is achieved. Ultrasonic treatment is a future in the dairy industry.     

Considerations for post-lethality treatments to reduce Listeria monocytogenes from fully cooked bologna using ambient and pressurized steam

During processing of ready-to-eat (RTE) deli meats, any secondary processing procedures such as peeling and cutting introduce the distinct possibility of cross-contamination between equipment, personnel, and food. To eliminate or reduce pathogens such as Listeria monocytogenes and ensure food safety, RTE deli meats can be pasteurized prior to or after packaging. In this study, ambient steam in-package pasteurization was compared with pressurized steam prepackaging pasteurization to reduce L. monocytogenes from fully cooked RTE bologna. The bologna (14 cm diameter×1.5 cm thickness) samples were surface-inoculated to contain about 8 log₁₀ of L. monocytogenes. To achieve 2 log reductions for L. monocytogenes, the bologna samples needed to be treated for about 10 s in pressurized steam at 131 °C or for about 2.5 min in ambient steam at 100 °C. The pasteurization time using pressurized steam treatment was about 75–90% shorter than using ambient steam treatment. Pressurized steam treatment may be integrated into a vacuum packaging unit to effectively eradicate L. monocytogenes from RTE meats just prior to sealing the retail packages to further reduce the treatment time, avoid post-treatment recontaminations by pathogens, and improve food safety without detrimentally affecting meat quality.     

Milk enhances intestinal absorption of green tea catechins in in vitro digestion/Caco-2 cells model

The effect of milk on the absorption of polyphenols is still controversial so far. In order to determine the impact of milk addition on green tea catechins bioaccessibility and intestinal absorption an in vitro digestion/Caco-2 cell model was applied. Green tea extract (GTE) was solubilized in distilled water at 23 °C and 100 °C, combined with skimmed milk (GTE + 10% milk and GTE + 25% milk) and subjected to simulated gastric and intestinal digestion, followed by transepithelial absorption in Caco-2 cells monolayers. In the mixture with milk, gallated catechins: ECG and EGCG showed binding to milk proteins while EC and EGC seemed to have weaker affinity. Catechins were stable during gastric incubation and very sensitive to intestinal digestion. Bioaccessibility of green tea catechins brewed at 100 °C was higher than brewed at 23 °C. Catechins from digested GTE with 10% and 25% milk exhibited enhanced intestinal permeability in Caco-2 model in comparison to non-digested GTE and digested GTE without milk. Apparent permeability coefficients (P_app) of EGCG and ECG in digested GTE with 25% milk were significantly higher compared to those in GTE with 10% milk, and amounted to 2.41 × 10^− 6 cm/s and 1.39 × 10^− 6 cm/s. The recoveries of all catechins in GTE with milk in Caco-2 cells after 2 h incubation were significantly higher than that without milk. To summarize, these data suggest that milk addition may increase catechin bioavailability by enhancing their transepithelial absorption and uptake from green tea extract.     

Proteolysis in Milk Associated with Increasing Somatic Cell Counts

Individual cow samples were collected and preserved with potassium dichromate. Somatic cells counts were determined. Tyrosine value was used as an index of proteolysis. Sixty-six samples ranged in somatic cell count from < 50,000 to > 2,000,000/ml. Initial milk tyrosine values and tyrosine values for milks incubated for 24 h at 37°C showed proteolytic activity increased with increasing somatic cell count. The increase in proteolysis in preserved milk refrigerated for 72 h at 6.7°C was over 1.5 times greater in milks with > 1,000,000 cells/ml than in milks with < 60,000 cells/ml. When preserved milks were laboratory pasteurized, cooled, and stored at 6.7°C for 14 d, some proteolytic activity was detected in milks at all concentrations of somatic cells, and proteolysis increased as somatic cell counts increased. Laboratory-pasteurized samples of milk with various somatic cell counts were also incubated at 30°C for 3 and 6 h to duplicate the proteolysis that could occur during the ripening, coagulation, cutting, and cooking steps of cheese making. Again, the greatest increases in tyrosine were in milks with high somatic cell count. Protease(s) associated with elevated somatic cell counts will damage raw milk quality upon storage, pasteurized fluid milk over shelf-life, and milk during cheese making.     

Proteolysis and storage stability of UHT milk produced in Turkey

The effect of raw milk quality (total and psychrotrophic bacterial and somatic cell counts, proteinase and plasmin activity) and UHT temperature (145 or 150 °C for 4 s) on proteolysis in UHT milk processed by a direct (steam-injection) system was investigated during storage at 25 °C for 180 d. High proteinase activity was measured in low-quality raw milk, which had high somatic cell count, bacterial count and plasmin activity. The levels of 12% trichloroacetic acid–soluble and pH 4.6-soluble nitrogen in all milk samples increased during storage, and samples produced from low-quality milk at the lower UHT temperature (145 °C) showed the highest values. Bitterness in UHT milk processed from low-quality milk at 145 °C increased during storage; gelation occurred in that milk after 150 d. The RP-HPLC profiles of pH 4.6-soluble fraction of the UHT milk samples produced at 150 °C showed quite small number of peaks after 180 d of storage. Sterilization at 150 °C extended the shelf-life of the UHT milk by reducing proteolysis, gelation and bitterness.     

Plasmin activity in direct-steam-injection UHT-processed reconstituted milk: Effects of preheat treatment

Ultra-high-temperature (UHT)-processed reconstituted milk that is subjected to a minimal preheat treatment during the direct-steam-injection heating process may have a shortened shelf-life as a result of plasmin-mediated proteolysis. Some manufacturers apply a preheat treatment before UHT treatment (140 °C for 4 s) with the aim of prolonging the shelf-life. Preheat treatments are, however, often arbitrary in terms of temperature and holding time. The aim of the current work was to determine guidelines for the minimum preheat treatment that will effectively inhibit or prevent plasmin-type enzyme activity in UHT milk. A selected range of preheat treatments was applied to milk preparations reconstituted from several batches of low-heat skim milk powder. Increased plasmin-type proteolysis was observed after intermediate preheat treatments at ⩾80 and <90 °C. Effective inhibition of plasmin-type proteolysis was obtained by preheating at 90 °C for 30 or 60 s.     

Screening for and characterization of Lactococcus lactis bacteriophages with high thermal resistance

Fifty-six Lactococcus lactis phage isolates collected from different German dairies and obtained from a starter culture manufacturer were tested for their heat resistance. About 40% of these isolates resisted treatment at 80 °C for 5 min when they were heated in milk. The most resistant phage isolate, P1532, was collected from sour cream. Plaque-formation was still detectable even after heating at 97 °C for 5 min. The second heat-resistant one, P680, showed some plaque-forming ability after heating at 95 °C for 5 min. Kinetic parameters for the thermal inactivation of these two resistant phages were determined for temperatures ranging from 70 to 97 °C. The inactivation of phage P1532 in skim milk and in buffer medium were found to follow first-order kinetics and did not exhibit tailing, whereas in the inactivation curves of phage P680 tailing was observed. The D-value of P1532 at pasteurization temperature of 72 °C was calculated as 112 min.     

Biochemical changes throughout the ripening of a traditional Spanish goat cheese variety (Babia-Laciana)

The physico-chemical characteristics, proteolysis (classical nitrogen fractions, caseins and their degradation products and free amino acids), and lipolysis (fat acidity and free fatty acids) were studied throughout the ripening of three batches of Babia-Laciana cheese, a Spanish traditional variety made from raw goats’ milk. The main compositional characteristics of this cheese at the end of the ripening are its high content of total solids (TS) (78.0±2.4 g 100 g⁻¹ of cheese) and fat (61.1±1.2 g 100 g⁻¹ of TS), the presence of residual lactose (1.6±0.8 g 100 g⁻¹ of TS) and its low content of sodium chloride (1.1±0.7 g 100 g⁻¹ of TS) and ash (2.8±0.5 g 100 g⁻¹ of TS). Its pH values (4.44±0.72) are extraordinarily low. The evolution and final values of the different nitrogen fractions show that this cheese undergoes a very slight proteolysis, a fact which was corroborated when the caseins and their degradation products were quantified: β-casein did not undergo any modification throughout ripening, while only 21% of the α_s-caseins were degraded. Free amino acids content increased by a factor of about 7 throughout ripening, resulting in a high content of γ-amino butyric acid and a low content of glutamic acid at the end of the process. Fat acidity increased very slightly, approximately 4.5 times, during ripening, reaching final values of 3.5±2.2 mg KOH g⁻¹ of fat. The total free fatty acids content showed a similar evolution to fat acidity. At the end of the ripening process, the main free fatty acid was C_18:1, followed by C₁₆ and C₁₀.     

Inactivation of Escherichia coli O157:H7 and Listeria monocytogenes in milk by caprylic acid and monocaprylin

Listeria monocytogenes and Escherichia coli O157:H7 are major foodborne pathogens implicated in various outbreaks involving pasteurized or unpasteurized milk, and various dairy products. The objective of this study was to determine the antibacterial effect of caprylic acid (CA, C_8:0) and its monoglyceride, monocaprylin (MC) on L. monocytogenes and E. coli O157:H7 in whole milk. A five-strain mixture of E. coli O157:H7 or L. monocytogenes was inoculated in autoclaved milk (10⁶ CFU/ml) containing 0, 25, or 50 mM of CA or MC. At 37°C, all the treatments, excepting 25 mm CA, reduced the population of both pathogens by approximately 5.0 log CFU/ml in 6 h. At 24 h of storage at 8°C, MC at both levels and CA at 50 mM decreased L. monocytogenes and E. coli O157:H7, respectively by >5.0 log CFU/ml. At 48 h of 4°C storage, populations of L. monocytogenes and E. coli O157:H7 were decreased to below detection level (enrichment negative) by 50 mm of MC and CA, respectively. Results indicate that MC could potentially be used to inhibit L. monocytogenes and E. coli O157:H7 in milk and dairy products, but sensory studies need to be conducted before recommending their use.     

Polymorphonuclear neutrophils and Escherichia coli proteases involved in proteolysis of casein during experimental E. coli mastitis

An Escherichia coli mastitis model was used to characterize enzymes involved in bovine mammary tissue damage and proteolysis in milk. One-quarter each of four cows were inoculated with a suspension (10⁴ cfu mL⁻¹) of E. coli P4:O32. Blood and milk were collected before inoculation and for 216 h afterwards. Intracellular elastase, collagenase and cathepsin activities were measured by flow cytometry of peripheral blood leukocytes and milk polymorphonuclear neutrophils (PMNs). Leukopenia occurred in peripheral blood 9 h after infection, concomitant with an increase in somatic cell count in milk. Milk PMNs had lower activity of cathepsins and collagenase than peripheral blood PMNs. In parallel, milk samples were studied by zymography, and several proteases were detected in mastitic milk. These activities increased after infection, to reach a peak in 6 h. However, total protease profiles and plasmin activities differed. It was concluded that proteases released by PMNs and E. coli contribute to proteolysis of casein during mastitis, as well as plasmin.     

Pasteurization of fermented red pepper paste by ohmic heating

Ohmic heating was applied to a Korean traditional fermented food containing red pepper paste, called Gochujang with low thermal conductivity (0.458 W/m ∙ K), by varying frequencies (40–20,000 Hz) and applied voltages (20–60 V). Contrary to conduction heating, the entire sample was heated uniformly, and the specific heating rate was found to be highly dependent on the frequency, peaking at 5 kHz and 60 V. The results showed that complex differential equation and the Runge–Kutta fourth-order method are suitable for simulating the temperature profile during ohmic heating. The deactivation of vegetable cells of Bacillus strains on fermented red pepper paste by ohmic heating was indicated by a 99.7% reduction, compared with conduction heating for 8 min at 100 °C producing a 81.9% reduction. The organoleptic and physicochemical qualities of the samples pasteurized by ohmic heating were nearly the same as those of raw samples, and higher than those of conventionally heated samples.Industrial relevanceThe present study designed and implemented a novel sterilization process based on a static ohmic heating system with low-frequency AC at the laboratory scale for fermented red pepper paste with a low thermal conductivity (0.458 W/m ∙ K).The developed system was used to investigate the mechanisms and characteristics underlying the induction of ohmic heating and then, tested the pasteurization effect against microorganisms in fermented red pepper paste.Comparing with conventional heating processes, ohmic heating could provide rapid and uniform heating, thereby is more suitable for pasteurization and sterilization of viscous foods as fermented red pepper paste on industrial thermal processing.     

An investigation of the plasmin–plasminogen system in caprine milk and cheese

The variability in activities of plasmin (PL) and plasminogen (PG) in bulk milk samples from different breeds of goats was investigated. The mean PL activity was higher (19.56±4.72 U g⁻¹) than in milk from other ruminant species, while PG-derived activity was, surprisingly, lower (12.84±5.31 U g⁻¹). No significant differences in PL and PG levels were observed among goat breeds, but PL activity and PL/PG ratio increased in late lactation compared with early lactation. PL activities in pilot-scale curds (acid or rennet) and in some Italian cheeses made from caprine milk were also measured. Generally, acid curds and cheeses had lower residual PL and PG-derived activities than rennet curds and semi-hard cheeses. In addition, the PL/PG ratio was greatly reduced in rennet curds, due to a higher extent of PG-derived activity. Measurement of proteolysis of β-casein in curds confirmed that more extensive proteolysis occurred in rennet curds, which had higher residual PL activities.