Microstructure of pasteurized process cheese manufactured from vacuum condensed and ultrafiltered milk

Abstract

-Milk standardized to 45 g·kg -1 protein (UF1 and CM1) and 60 g·kg -1 protein (UF2 and CM2) using ultrafiltered milk (150 g·kg -1 protein) or vacuum condensed milk (120 g·kg -1 protein) was used for manufacturing Cheddar cheese. Pasteurized Process cheeses were manufactured using a 1:1 blend of 18-week and 30-week Cheddar cheese. The moisture content of the Process cheeses ranged from 393 to 402 g·kg -1 . Fat content was the highest in the control cheese (350 g·kg -1 ) and the lowest in UF2 (316 g·kg -1 ). Microstructure of cheeses was observed using cryo-scanning electron microscopy. Fat globules of different sizes embedded in the continuous protein network were observed. Whereas, a porous structure with relatively large pores was noted in the control cheese, more compact protein masses were observed in cheeses made from concentrated milk. Fat globules in all cheeses were surrounded by cavities. Firmness of cheese was associated with less porous (compact) protein network. Large areas of dense highly fused protein were observed in UF2 cheeses, which showed the highest resistance to compression (highest firmness). Fractures in the protein network were observed as the firmness of cheese increased. Such fractures reduced the ability of protein network to entrap fat and increased the level of free oil. Appendages connecting fat globules to protein network were seen in cheese containing low amounts of free oil which indicated good emulsifying properties. The continuous less rigid protein structure with good emulsifying properties (the presence of appendages connecting protein network to fat globules) produced cheese with increased meltability. This study shows that the application of concentrated milks for Cheddar cheese-making influences Process cheese functionality and structure. La teneur en matière grasse la plus élevée a été obtenue dans le fromage témoin (350 g·kg -1 ) et la plus faible dans le fromage UF2 (316 g·kg -1 ). La microstructure des fromages a été observée par cryo-microscopie électronique à balayage (cryo-SEM). Des globules gras de différentes tailles, imbriqués dans le réseau protéique continu, ont été observés. Alors qu'une structure poreuse, avec des pores relativement larges, a été observée dans les fromages témoins, des masses protéiques plus compactes sont apparues dans les fromages obtenus avec le lait concentré. Dans tous les fromages, les globules gras étaient entourés de cavités. La fermeté du fromage était associée à un réseau protéique moins poreux (compact). De larges zones de protéines denses très fusionnées ont été observées dans les fromages UF2 présentant la plus grande résistance à la compression (fermeté maximale). Avec l'augmentation de la fermeté des fromages, des fractures sont apparues dans le réseau protéique, réduisant sa capacité à inclure la matière grasse et augmentant le taux de matière grasse libre. Des joints de connexion reliant les globules gras au réseau protéique ont été observés dans le fromage ayant le moins de matière grasse libre, et donc de bonnes pro...

Impact of Innovative Formson the Chemical Composition and Rheological Properties of Jameed

“…The hardest jameed (sample A) had less porous and more compact structure. Similar observations were reported by Mistryet al [21] that showed that in the firmest cheese, a very compact protein network was observed. Soodamet al [22] found that small gaps appear at the interface between the fat and protein phases by week 13 of ripening period of Cheddar cheese, which could arise from proteolysis of the protein network leading to a weaker structure that behaves differently during microscopy sample preparations.…”

Effect of Jameed Form on the Chemical Composition, Rheological and Microbial Properties

“…Similar observations were reported by Mistry et al (2006) who showed that in the firmest cheese, a very compact protein network was observed. Soodam et al (2014) found that small gaps appear at the interface between the fat and protein phases by week 13 of ripening period of Cheddar cheese, which could arise from proteolysis of the protein network leading to a weaker structure that behaves differently during microscopy sample preparations.…”

Microstructure of milk gel and cheese curd observed using cryo scanning electron microscopy and confocal microscopy

“…A number of studies describe the use of transmission electron microscopy (TEM) (Kheadr, Vachon, Paquin, & Fliss, 2002), scanning electron microscopy (SEM) (Fallico et al, 2006;Kimber, Brooker, Hobbs, & Prentice, 1974;McMahon, Fife, & Oberg, 1999) and cryo scanning electron microscopy (cryo SEM) (Hassan, Frank, & Elsoda, 2003;Mistry, Hassan, & Acharya, 2006) to examine the microstructure of the final cheese product. A limited number of studies have also looked at the microstructure of intermediate samples collected during cheese manufacture such as the gel and/or cooked curd using light microscopy (Bowland & Foegeding, 2001;Lagaude, Fernandez, Cuq, & Marchesseau, 2004), fluorescence microscopy (Yiu, 1985), confocal laser scanning microscopy (CLSM) (Auty, Twomey, Guinee, & Mulvihill, 2001;Heilig, Göggerle, & Hinrichs, 2009;Oiseth & McKinnon, 2006), SEM (Kalab & Harwalkar, 1973;Merrill, Oberg, McManus, Kalab, & McMahon, 1996) and cryo SEM (Mellema, Walstra, can Opheusden, & van Vliet, 2002).…”

“…This technique has been shown to preserve the fine microstructure of hydrated samples such as yoghurt (Amatayakul, Sherkat, & Shah, 2006), rennetinduced gels (Mellema et al, 2002), Cheddar cheese (Mistry et al, 2006) or Karish and Feta cheeses (Hassan et al, 2003). In addition, the sample can be freeze fractured under cryogenic conditions exposing the internal microstructure.…”