Effect of heat treatment and spray drying on lactobacilli viability and resistance to simulated gastrointestinal digestion
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R. Paéz et al. / Food Research International 48 (2012) 748–754
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Effect of heat treatment and spray drying on lactobacilli viability and resistance to simulated gastrointestinal digestion
R. Paéz a, L. Lavari a, G. Vinderola b,⁎, G. Audero a, A. Cuatrin a, N. Zaritzky c, J. Reinheimer b
Article history: Received 13 April 2012 Accepted 16 June 2012 Available online 28 June 2012 Keywords: Heat treatment Spray drying Viability Gastrointestinal digestion Lactobacilli | Commercial probiotic bacteria are delivered mainly as frozen or freeze-dried cultures. However, spray drying is a lower cost technology that could be used for the production of probiotic cultures. In this work we aimed at screening among lactobacilli strains for candidates able to survive to spray drying and to study the effects of a preliminary mild heat treatment and different food matrices on post-drying survival and simulated gastric acid resistance. Heat resistance (survival to exposure at 60 °C for 5 min) in MRS broth or in 10% (wt/vol) skim milk was assessed in 22 strains of Lactobacillus casei, Lactobacillus paracasei, Lactobacillus acidophilus and Lactobacillus plantarum. Five strains (L. casei Nad, L. plantarum com, L. paracasei A13, L. plantarum 8329 and L. acidophilus A9) were selected for spray drying in 20% (wt/vol) skim milk and storage at 5, 25 or 37 °C for 75 days. For L.p. A13, L.p. com and L.a. A9 no differences in cell viability were observed due to spray drying. However, for L.c. Nad and L.p. 8329 cell death due to spray drying was 0.16 and 0.49 log orders CFU ml−1 when a mild heat treatment (52 °C for 15 min) was applied and 0.85 and 0.95 log cycles, respectively, without preliminary mild heat treatment, showing that heat treatment enhanced survival to spray drying. The application of a heat treatment was effective for enhancing survival during storage of L.p. 8329, irrespective of the storage temperature and period. No significant cell loss at 5 and 25 °C was observed for L.c. Nad. For this strain, at 37 °C no cell counts of lactobacilli were observed after 30 days of storage. For L.a. A9, L.p. com and L.p. A13 a reduction in cell viability was observed along storage as temperature increased. Resistance to simulated gastrointestinal digestion was enhanced by spray drying. The application of a mild heat treatment before spray drying may enhance cell survival during storage and the resistance to gastrointestinal digestion. Spray drying might be used for enhancing cell functionality in a strain-dependant way. © 2012 Elsevier Ltd. All rights reserved. |
a INTA EEA Rafaela, Ruta 34 km 227, Rafaela, Santa Fe, Argentina b Instituto de Lactología Industrial (INLAIN, UNL-CONICET), Facultad de Ingeniería Química, Universidad Nacional del Litoral, 1° de Mayo 3250, Santa Fe, Argentina c Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CIDCA, UNLP‐CONICET) La Plata, Argentina[pic 2]
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a r t i c l e | i n f o | a b s t r a c t |
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1. Introduction | industrial manufacture of dried lactobacilli cultures is achieved mainly by freeze-drying, that applies gentle, low-temperature drying conditions. |
The diversification of the market of probiotic foods relies on the availability of new strains or new formats of probiotic cultures. Until now, fermented dairy products, mainly fermented milks, have been used as the most successful commercial food products for the delivery of probiotic bacteria (Figueroa-González, Quijano, Ramírez, & Cruz-Guerrero, 2011; Saxelin, 2008), being frozen and freeze-dried cultures the commercially available formats of starter and probiotic bacteria. In particular, the production of dried cell cultures is particularly interesting because, unlike frozen cultures, dehydrated cultures demand less storage capacity and lower cost of transport and refrigeration. However, the maintenance of cell viability during drying and storage is a major challenge. Insufficient or too extensive dehydration (moisture >5.0% (wt/wt) or b2.8% (wt/wt), respectively) causes bacterial inactivation (Zayed & Roos, 2004). Presently,
[pic 6] ⁎ Corresponding author at: Instituto de Lactología Industrial (INLAIN, UNL-CONICET), Facultad de Ingeniería Química, Universidad Nacional del Litoral, 1° de Mayo 3250, Santa Fe, Argentina. Tel. + 54 342 4530302x4. E-mail address: gvinde@fiq.unl.edu.ar (G. Vinderola). 0963-9969/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodres.2012.06.018 |
However, freeze-drying is a discontinuous and expensive process with low yields and time and energy demanding (Knorr, 1998; Meng, Stanton, Fitzgerald, Daly, & Ross, 2008). Spray drying is an interesting and promising low-cost alternative because it is relatively inexpensive and allows the continuous production of large amounts of dried cells within short time periods (Gardiner et al., 2000). However, it should be mentioned that cell dehydration may inevitably cause membrane damage and inactivation depending on the technological conditions applied. In spray drying bacterial cultures are exposed to different stresses (osmotic, heat, oxidative) due to the quite harsh conditions of temperature required for product dehydration, which can cause a partial thermal inactivation of cells.
The incorporation of probiotic cultures into fermented dairy products relies almost exclusively on the use of frozen or freeze-dried cultures provided by foreign companies. In particular in Argentina, many medium to big-size dairy industries possess the technological infrastructure for the production of spray dried probiotics. Spray drying can offer a 6 times less expensive alternative every kg of water removed compared to freeze-drying (Knorr, 1998). However it was observed that the success of its application is highly strain specific (Ananta, Volkert, & Knorr, 2005; Corcoran, Ross, Fitzgerald, & Stanton, 2004; Desmond, Stanton, Fitzgerald, Collins, & Ross, 2002a; Gardiner et al., 2000; Lian, Hsiao, & Chou, 2002; O'Riordan, Andrews, Buckle, & Conway, 2001).
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