Martin Buffa

Application of high pressure treatment for cheese production

Abstract High hydrostatic-pressure treatment offers the food industry a new technology for food preservation. Interest in high pressure application on milk has recently increased. Pressures between 300 and 600 MPa can inactivate microorganisms including most infectious food-borne pathogens. In addition to microbial destruction, it has been reported that high pressure improves rennet or acid coagulation of milk and increases cheese yield. A lot of work has been published on microorganism inactivation, denaturation of whey proteins, changes in the mineral distribution and coagulating properties on model or real milk systems. However, practical applications of high pressure treatment in the dairy industry have received little attention. This paper examines recent work in this area and summarizes parts of our ongoing work toward the development of high pressure applications for the cheese industry.

Proteolysis in goat cheese made from raw, pasteurized or pressure-treated milk☆

Primary and secondary proteolysis of goat cheese made from raw (RA), pasteurized (PA; 72 °C, 15 s) and pressure-treated milk (PR; 500 MPa, 15 min, 20 °C) were examined by capillary electrophoresis, nitrogen fractionation and HPLC peptide profiles. PA milk cheese showed a more important hydrolysis (P<0.05) of αs1-casein than RA milk cheese at the first stages of ripening (15 days), while PR milk cheese had a level between those seen in PA and RA milk cheeses. Degradation of β-casein was more important (P<0.05) in PA and PR than in RA milk cheeses at 15 days of ripening. However, from thereon β-casein in PR and RA milk cheeses was hydrolyzed at essentially similar rates, but at lower rates (P<0.05) than in PA milk cheeses. Pressure treatment could induce proteolysis of β-casein in a way, which is different from that produced by heat treatment. There was an increase in 4.6-soluble nitrogen (WSN) and in trichloroacetic acid (TCASN) throughout ripening in cheeses, but higher contents (P<0.05) in PA and PR milk cheeses at the end of ripening were observed. PR milk cheeses contained considerably higher content (P<0.05) of free amino acids than RA or PA milk cheeses. In general, heat and pressure treatments had no significant effect on the levels of hydrophobic and hydrophilic peptides.

Factors Affecting Bacterial Inactivation during High Hydrostatic Pressure Processing of Foods: A Review

Although, the High Hydrostatic Pressure (HHP) technology has been gaining gradual popularity in food industry since last two decades, intensive research is needed to explore the missing information. Bacterial inactivation in food by using HHP applications can be enhanced by getting deeper insights of the process. Some of these aspects have been already studied in detail (like pressure, time, and temperature, etc.), while some others still need to be investigated in more details (like pH, rates of compression, and decompression, etc.). Selection of process parameters is mainly dependent on type of matrix and target bacteria. This intensive review provides comprehensive information about the variety of aspects that can determine the bacterial inactivation potential of HHP process indicating the fields of future research on this subject including pH shifts of the pressure treated samples and critical limits of compression and decompression rates to accelerate the process efficacy.

Changes in chemical and microbiological characteristics of goat cheese made from raw, pasteurized or high-pressure-treated milk

Abstract High-pressure treatment offers to the dairy industry a new technique for food preservation. Very little research is available on the use of high pressure and its potential for cheesemaking. The use of high-pressure treated milk to produce goat cheese has been studied. The effect of high pressure on the ripening process of goat cheese, including the microbiological quality of goat milk and cheese has been included.

Lethality and injuring the effect of compression and decompression rates of high hydrostatic pressure on Escherichia coli O157:H7 in different matrices

The effect of compression and decompression rates of high hydrostatic pressure (HHP) on Escherichia coli O157:H7 was investigated. Samples of orange juice, skimmed milk and Tris buffer were inoculated with E. coli O157:H7 and subjected to 600 MPa for 3 min at 4°C with fast, medium and slow compression and decompression. Analyses immediately after HHP treatment revealed that E. coli in milk and juice treated with fast compression suffered more than slow compression rates. Slow decompression resulted in higher inactivation of E. coli in all matrices. After overnight storage, highest stress-recovery (1.19 log cfu/mL) was observed in Tris buffer. Healthy cells were<1 log cfu/mL in milk and buffer samples, but no growth was detected in orange juice for any of the treatments immediately after HHP. After 15 days at 4°C, E. coli cells in skimmed milk and Tris buffer recovered significantly, whereas the recovery of sublethally injured cells was inhibited in orange juice.

High pressure applications in milk treatment for cheese-making and accelerated ripening

Abstract Several studies have been carried out in order to evaluate the effect of high hydrostatic pressure on food components, its impact on microorganisms and enzymes, and the modifications it produces at the nutritional and sensory level. However, practical applications of high pressure treatment have received little attention. This paper examines our recent ongoing work toward the development of high pressure applications, such as the production of raw milk cheeses from high pressure-treated milk and the possibility of cheese ripening acceleration.

Thermal Deterioration of the Trans-/Cis-Ratio of Bittering Agents of Commercial Beers

The use of reduced isomerised hop extracts to achieve both bitterness and light stability became very popular during the last decade. Changes during storage in four hop extracts and seven commercial lager beers are studied using HPLC and spectrophotometric techniques. The degradation of the iso-α-acids and tetrahydro iso-α-acids as a function of time is represented by the ratio, in percentage, of the sum of trans-isomer concentration to the sum of the cis-isomer concentration (T/C). The results provided conclusive evidence that the gradual decreased of bitterness intensity in beer was due to the degradation of iso-α-acids, notably to the instability of the trans-iso-α-acids. When the beers were stored for 14 days at 45°C the decrease of the T/C average varied from 8.6 to 14.0%, except in lemon beer, in which case, T/C decreased 36.9%. The results allowed us to infer that in open storage and/or warm conditions the deterioration of beer was critical above 35°C. On the other hand, the results showed that tetrahydro iso-α-acids remained unaltered.