Water activity‐temperature state diagrams of freeze‐dried Lactobacillus acidophilus (La‐5): Influence of physical state on bacterial survival during storage

Abstract

in Wiley InterScience (www.interscience.wiley.com).Water activity-temperature state diagrams for Lactobacillus acidophilus freeze-dried in a sucrose or a lactose matrix were established based on determination of stabilized glass transition temperatures by differential scanning calorimetry during equilibration with respect to water activity at fixed temperatures. The bacteria in the lactose matrix had higher stabilized glass transition temperatures for all a w investigated. The survival of Lactobacillus acidophilus determined as colony forming units for up to 10 weeks of storage at 20 C for (i) a w ¼ 0.11 with both freeze-dried matrices in the glassy state, (ii) a w ¼ 0.23 with the bacteria in the lactose matrix in a glassy state but with the bacteria in sucrose matrix in the nonglassy state, and (iii) a w ¼ 0.43 with both freeze-dried matrices in a nonglassy state showed that the nature of the sugar was more important for storage stability than the physical state of the matrix with the nonreducing sucrose providing better stability than the reducing lactose.

Viability ofLactobacillus plantarumTISTR 2075 in Different Protectants during Spray Drying and Storage

“…Another possible reason is nonenzymatic browning and lipid oxidation, which are strongly temperature dependent. [49][50][51] Although these predicted models deviated from the Arrhenius theory, few studies have been successful in predicting the viability of microorganisms during storage. [32][33][34] This indicates that the predicted model may vary according to the strain of the microorganisms as well as the capacity of the protectants used.…”

Evaluación de la Estabilidad y Viabilidad de Dos Cepas Probióticas Microencapsuladas por Lecho Fluidizado

“…Lian et al (2002), mencionan que estructuras porosas facilitan el escape de calor desde el interior de la partícula, causando menos lesiones a los microorganismos encapsulados, por lo tanto esto puede ser una de las razones que contribuyeron a la mayor supervivencia después del secado de F1, pero al no estar bien protegidos a los efectos perjudiciales del oxígeno atmosférico y la humedad, aumenta las probabilidades de muerte o destrucción de las células en un posterior almacenamiento (Fatemeh et al 2011;Semyonov et al, 2012 Ademas, Pastuña-Pullutasig et al (2016), mencionan que la obtención una superficie lisa compacta y libre de poros evita el contacto directo con el oxígeno, previniendo así su degradación y alargando su tiempo de vida útil. Sin embargo, algunos autores señalan que la supervivencia durante el secado, no necesariamente se relaciona con la supervivencia durante el almacenamiento (Chávez y Ledeboer, 2007;Kurtmann et al, 2009). A pesar de las diferencia significativas en el almacenamiento de las dos cepas probióticas con los distintos encapsulantes, se obtuvo un alto recuento de células viables en todas las formulaciones, las cuales se mantuvieron por encima de los niveles recomendados por la FAO (2001) que es entre 10 6 -10 7 UFC/g de microorganismos viables para un alimento probiótico, durante los 90 días almacenamiento, Kailaspathy y Chin (2000), señalan que esto es lo más importante para evaluar la aplicabilidad de un producto pulverizado.…”

Effect of drying methods of microencapsulated Lactobacillus acidophilus and Lactococcus lactis ssp. cremoris on secondary protein structure and glass transition temperature as studied by Fourier transform infrared and differential scanning calorimetry

“…In addition to T g , storage at low a w , particularly at its monolayer state, was effective in extending the shelf life of products (Rahman, 2010). Water activity and T g of freeze-dried matrix containing lactobacilli has been proven to influence the survival of lactobacilli (Kurtmann et al, 2009). An increase in a w and moisture content results in decrease in T g (Kurtmann et al, 2009, Pehkonen et al, 2008, Roos, 1995, and vice versa.…”

“…Water activity and T g of freeze-dried matrix containing lactobacilli has been proven to influence the survival of lactobacilli (Kurtmann et al, 2009). An increase in a w and moisture content results in decrease in T g (Kurtmann et al, 2009, Pehkonen et al, 2008, Roos, 1995, and vice versa. The second order transition, from a glassy to a rubbery state, likely occurs due to moisture adsorption during storage at higher a w .…”

“…Storage at room temperature above T g might increase the chance of glass transition (Santivarangkna et al, 2011), in which molecular mobility would increase along with the formation of crystalline state. Glass transition temperature is also influenced by a w of storage: an increase in a w results in a decrease in T g (Higl et al, 2007;Kurtmann et al, 2009). The mechanism of bacterial protection by sugars during dehydration has been established, but the effect of long-term storage at room temperature on the changes in phospholipid bilayers and secondary protein structures of bacterial cells has not.…”