How viable are probiotic bacteria in yoghurts?
Foodinfo Online FSTA Reports -->8 October 2004
Probiotic bacteria such as Lactobacillus acidophilus and Bifidobacterium spp. have numerous health benefits, which have lead to their incorporation into dairy foods such as yoghurts. However, for probiotic bacteria to be therapeutically effective, a minimum viable count of 106 to 107 cfu/g of these bacteria is necessary.
Standards introduced by food authorities worldwide have encouraged manufacturers to guarantee adequate viability of these bacteria throughout product shelf life. However, several recent market surveys have indicated a steady decline in counts of L. acidophilus and Bifidobacterium spp. throughout the shelf life of probiotic yoghurts. Oxygen toxicity is considered a significant factor in influencing the viability of these probiotic bacteria in yoghurts.
The agitation and mixing steps during manufacture can incorporate high amounts of oxygen into the product. In addition, during storage, oxygen can diffuse into yoghurt through the high-impact polystyrene (HIPS) packaging. As a result, polystyrene-based gas barrier packaging and active packaging films have been developed. A study by Talwalkar et al.1 investigated the effects of packaging materials on the dissolved oxygen content and survival of the probiotic bacteria, L. acidophilus and Bifidobacterium spp., in yoghurt stored at 4--6°C for 42 days. The yoghurts were packaged in oxygen-permeable HIPS, oxygen-barrier material (Nupak) and Nupak with an oxygen-scavenging film (Zero2).
No significant decreases were observed in bacterial viability of any of the yoghurts tested, suggesting that oxygen alone is not a significant factor in causing poor viability of these bacteria in yoghurt.
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1 Talwalkar, A; Miller, CW; Kailasapathy, K; Nguyen, MH (2004).
Effect of packaging materials and dissolved oxygen on the survival of probiotic bacteria in yoghurt. International Journal of Food Science and Technology 39 (6) 605-611.
AN: 2004-09-Pl1566
TI:
Effect of packaging materials and dissolved oxygen on the survival of probiotic bacteria in yoghurt.
DA:
7-May-2004
DT:
Journal Article
AU:
Talwalkar, A.; Miller, C. W.; Kailasapathy, K.; Nguyen, M. H.
PY:
2004
AD:
Correspondence (Reprint) address, K. Kailasapathy, Cent. for Advanced Food Res., UWS, Locked Bag 1797, NSW 1797, Australia.
SO:
International Journal of Food Science & Technology 39 (6) 605–611
RF:
22 ref.
LA:
English
SN:
0950-5423
AB:
Oxygen toxicity has been suggested to be a significant factor influencing the viability of probiotic bacteria, such as Lactobacillus acidophilus and Bifidobacterium spp., in yoghurts. Along with manufacturing steps (particularly agitation and mixing), which incorporate high amounts of oxygen into the yoghurt, the packaging materials used may also affect the level of oxygen diffusing into the product. This study investigated the effects of packaging materials having different oxygen permeabilities on the levels of dissolved oxygen and survival of the probiotic bacteria in yoghurt. Oxygen adapted and non-oxygen adapted strains of L. acidophilus and Bifidobacterium spp. were incorporated in yoghurts, which were packaged in oxygen permeable high-impact polystyrene (HIPS), oxygen-barrier material (NupakTM) and NupakTM with an oxygen scavenging film (Zero2TM). Results showed that, during storage, the level of dissolved oxygen increased steadily in HIPS packaged yoghurt, but remained low in yoghurts packaged in NupakTM and Zero2TM. In all yoghurts, no significant decreases were observed in the viability of either oxygen adapted or non-oxygen adapted cells of L. acidophilus and Bifidobacterium spp. It is suggested that, although the level of dissolved oxygen in yoghurt can be influenced by the type of packaging material, it may not affect the survival of probiotic bacteria in yoghurts.
SC:
Milk and dairy products
KW:
BIFIDOBACTERIUM; INHIBITION; LACTOBACILLUS; LACTOBACILLUS ACIDOPHILUS; MICROORGANISMS; OXYGEN; PACKAGING MATERIALS; PERMEABILITY; PROBIOTIC BACTERIA; YOGHURT
