UHT Milk Processing and Effect of Plasmin Activity on Shelf Life: A Review

Abstract

Abstract:The demand for ultra-high-temperature (UHT) processed and aseptically packaged milk is increasing worldwide. A rise of 47% from 187 billion in 2008 to 265 billon in 2013 in pack numbers is expected. Selection of UHT and aseptic packaging systems reflect customer preferences and the processes are designed to ensure commercial sterility and acceptable sensory attributes throughout shelf life. Advantages of UHT processing include extended shelf life, lower energy costs, and the elimination of required refrigeration during storage and distribution. Desirable changes taking place during UHT processing of milk such as destruction of microorganisms and inactivation of enzymes occur, while undesirable effects such as browning, loss of nutrients, sedimentation, fat separation, cooked flavor also take place. Gelation of UHT milk during storage (age gelation) is a major factor limiting its shelf life. Significant factors that influence the onset of gelation include the nature of the heat treatment, proteolysis during storage, milk composition and quality, seasonal milk production factors, and storage temperature. This review is focused on the types of age gelation and the effect of plasmin activity on enzymatic gelation in UHT milk during a prolonged storage period. Measuring enzyme activity is a major concern to commercial producers, and many techniques, such as enzyme-linked immunosorbent assay, spectrophotometery, high-performance liquid chromatography, and so on, are available. Extension of shelf life of UHT milk can be achieved by deactivation of enzymes, by deploying low-temperature inactivation at 55• C for 60 min, innovative steam injection heating, membrane processing, and high-pressure treatments.

Daya Simpan Susu Pasteurisasi Ditinjau Dari Kualitas Mikroba Termodurik Dan Kualitas Kimia

“…Proses pemanasan bisa jadi dapat memodifikasi struktur molekul protein, tetapi perubahan tersebut tidak merubah nilai fungsional dari protein seperti kelarutan dan emulisi protein, serta tidak berpengaruh secara signifikan terhadap nilai nutrisi. Chavan et al (2011) menambahkan bahwa pada proses pemanasan dapat terjadi penurunan jumlah mikroba dan inaktivasi enzim. Tetapi proses pemanasan juga menyebabkan dampak yang tidak diinginkan seperti brawning, kehilangan nutrisi, sedimentasi, pemisahan lemak dan rasa gosong.…”

Modelling the effect of pH, sodium chloride and sodium pyrophosphate on the thermal resistance of Escherichia coli 0157:H7 in ground beef

“…We have been actively involved in modelling a wide range of pathogen growth and survival in foods for N25 years (our work has been widely reviewed and cited, e.g., Pujol, Albert, Magras, Johnson & Membre, 2015;Pujol, Albert, Johnson & Membre, 2013;Daneshmand, Beton, Hill, Gehr & Frigon, 2012;Munoz-Cuevas, Metris & Baranyi, 2012;Black, Ye, Harte & Davidson, 2010;Kang, Kim & Yoon, 2010;Huang, Hwang & Phillips, 2011;Chavan, Chavan, Khedkar & Jana, 2011;Deeth, 2010;Ross & Dalgaard, 2004;McMeekin, Olley, Ross & Ratkowsky, 1993).…”

Proteolysis of milk heated at high temperatures by native enzymes analysed by trinitrobenzene sulphonic acid (TNBS) method

“…Generally, heat labile enzymes are inactivated by unfolding followed by molecular scrambling, whereas heat resistant enzymes are inactivated by covalent modification such as cystine cross-links and deamination of asparagines and glutamine residues. Proteinases, lipases and phospholipase (from psychrophic bacteria, mostly Pseudomonas) are stable at room temperature but survive pasteurisation and UHT treatment (Chavan et al, 2011).…”

“…Fax: +255 232 604402. cooked flavor also take place. Gelation of UHT milk during storage (age gelation) is a major factor limiting its shelf life (Chavan et al, 2011).…”