Preservation of the Microbiological and Biochemical Quality of Raw Milk by Carbon Dioxide Addition: A Pilot-Scale Study

Abstract

Carbon dioxide treatment of refrigerated raw milk was evaluated as a method for extending storage life by inhibiting growth of psychrotrophic bacteria and other bacterial groups in raw milk. The effect of CO2 acidification followed by degasification and pasteurization on biochemical and microbiological properties of cold stored milk was studied on a pilot scale, Two CO2 treatments (acidification to pH 6.2 and to pH 6.0) were compared with a control (untreated) milk during 4 days of storage at 4°C. Total bacterial counts in the categories of milk established in this study were mainly determined by the proteolytic psychrotroph levels. The inhibitory capability of CO2 was greater in the low-quality than in the high-quality milk category. Acidification at pH 6.0 was more inhibitory than that at pH 6.2, especially against proteolytic psychrotrophs. Neither caseins nor whey proteins were affected by CO2 treatment and pasteurization. Organic acid (orotic, citric, uric, formic, acetic, propionic, and hippuric) concentrations did not change after CO2 treatment, cold storage, or the pasteurization process; the lactic acid content of CO2-treated milks remained constant during the refrigeration time but increased slightly in the control. In general, lower amounts of volatile compounds were produced in CO2-treated milks during refrigeration than in control milk. Ethanol and 2-propanol levels were most affected by degasification and pasteurization. Sensory evaluation revealed no significant differences between CO2-treated milk after degasification and pasteurization and the untreated milk used as control. It was concluded that degasification and pasteurization on a pilot scale eliminated CO2 from milk with minimum detrimental effects on its biochemical and sensory properties, making this process acceptable for milk preservation.

Culture-independent bacterial community profiling of carbon dioxide treated raw milk

“…The effectiveness of CO 2 in extending the storage life of raw milk and cottage cheese has been well established (Amigo et al, 1995;Hotchkiss, 1991, 1993;Espie and Madden, 1997;King and Mabbitt, 1982;Kosikowski and Brown, 1973;Maniar et al, 1994;Moir et al, 1993;Roberts and Torrey, 1988;Ruas-Madiedo et al, 1996;Ruas-Madiedo et al, 1998b). CO 2 treatment is already routinely used in commercial cottage cheese production in the US (Loss and Hotchkiss, 2003), and an unpublished scaled-up field trial of CO 2 treatment of raw milk showed a 4 day increase in storage life of the treated sample (Hotchkiss et al, 2006).…”

“…Carbon dioxide has emerged as an attractive preservative of raw milk as it is inhibitory against the growth of psychrotrophic bacteria including P. fluorescens (Hotchkiss et al, 2006;Loss and Hotchkiss, 2003;Martin et al, 2003), it is generally regarded as safe (GRAS), its treatment method is non-thermal, simple and economical, and it does not have adverse effects on the nutritional content of milk (Loss and Hotchkiss, 2003;Ruas-Madiedo et al, 1996;Sierra et al, 1996). The effectiveness of CO 2 in extending the storage life of raw milk and cottage cheese has been well established (Amigo et al, 1995;Hotchkiss, 1991, 1993;Espie and Madden, 1997;King and Mabbitt, 1982;Kosikowski and Brown, 1973;Maniar et al, 1994;Moir et al, 1993;Roberts and Torrey, 1988;Ruas-Madiedo et al, 1996;Ruas-Madiedo et al, 1998b).…”

Inhibition of bacterial growth in sweet cheese whey by carbon dioxide as determined by culture-independent community profiling

“…The effectiveness of CO 2 in shelf-life extension has been well established in raw milk and cottage cheese (Amigo et al, 1995;Chen andHotchkiss, 1991, 1993;Espie and Madden, 1997;King and Mabbitt, 1982;Kosikowski and Brown, 1973;Maniar et al, 1994;Moir et al, 1993;Roberts and Torrey, 1988;Ruas-Madiedo et al, 1996;Ruas-Madiedo, Bascarán, et al, 1998) and has already been adopted in commercial cottage cheese production in the US (Loss and Hotchkiss, 2003). However, there have been no studies on carbonation of whey, so it would be of interest to test the potential of CO 2 to act as a whey preservative.…”

Effect of acidification of raw milk on psychrotrophic microrganims.

“…Resultados parecidos foram obtidos por Ruas-Madiedo et al (1996), onde o leite tratado com CO 2 reduziu em 1 a 1,5 logaritmos o crescimento de mesófilos. Ma, Barbano e Santos (2003) constataram que ao adicionar 1500 ppm de CO 2 ao leite cru, houve uma diminuição de 1 a 2 ciclos logarítmicos na contagem de mesófilos e de 2 ciclos logarítmicos na de psicrotróficos após 21 dias de armazenamento a 4 °C.…”

“…A redução do pH do leite de 6,8 para 6,0 com CO 2 causou uma inibição de 1,41 log 10 UFC/mL em psicrotróficos após 4 dias de armazenamento a 7 ºC (SIERRA et al, 1996). A mesma redução de pH diminuiu a contagem de psicrotróficos lipolíticos em 1 log 10 UFC/mL após 4 dias a 4 ºC (RUAS -MADIEDO et al, 1996 (Tecnal,modelo TE 184,Brasil). Ao final da linha de gás conectou-se um dispersor de gás (Figura 1, F) feito de vidro Pyrex provido de placa porosa na extremidade inferior.…”