Role of Glassy State on Stabilities of Freeze‐Dried Probiotics

Abstract

High viability of dried probiotics is of great importance for immediate recovery of activity in fermented foods and for health-promoting effects of nutraceuticals. The conventional process for the production of dried probiotics is freeze-drying. However, loss of viability occurs during the drying and storage of the dried powder. It is believed that achieving the "glassy state" is necessary for survival, and the glassy state should be retained during freezing, drying, and storage of cells. Insight into the role of glassy state has been largely adopted from studies conducted with proteins and foods. However, studies on the role of glassy state particularly with probiotic cells are on the increase, and both common and explicit findings have been reported. Current understanding of the role of the glassy state on viability of probiotics is not only valuable for the production of fermented foods and nutraceuticals but also for the development of nonfermented functional foods that use the dried powder as an adjunct. Therefore, the aim of this review is to bring together recent findings on the role of glassy state on survival of probiotics during each step of production and storage. The prevailing state of knowledge and recent finding are discussed. The major gaps of knowledge have been identified and the perspective of ongoing and future research is addressed.

Microencapsulation of Lactobacillus plantarum MTCC 5422 in fructooligosaccharide and whey protein wall systems and its impact on noodle quality

“…The similar findings were reported by Capela et al (2006) where the addition of FOS to fresh yoghurt retained the probiotic cells viability during freeze drying, but had a negative effect on freeze dried yoghurt after 4 weeks of storage at 4°C. Loss of viability during storage of encapsulated probiotic cells in the dried state was also reported (Capela et al 2006;Santivarangkna et al 2011). Dehydration suppress the metabolic activity of cells by removal of moisture, but insufficient removal of moisture may allow the resumption of metabolism at low rate, thus leads to cell death (Fu and Chen 2011).…”

“…Sugars are usually incorporated as cryoprotectants to minimise the damage to the cell wall and cell membrane during freeze drying. Ability of sugars to form glassy matrices enhances the cell survival during dehydration (Santivarangkna et al 2011). However these matrices permeate water vapour, gases and small organic molecules during storage that affects the cell viability.…”

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

“…This state is unstable and is temperature-dependent. At a certain temperature (known as T g ), the transformation from a solid-like to a liquid-like state initiates along with an increase in molecular mobility; this phenomenon is recognized as a glass transition (Santivarangkna et al, 2011). Therefore, storage at temperature below T g is considered to be useful in maintaining products in their amorphous Means followed by the same letters indicate no statistical difference (P ≥ 0.05).…”

“…Mechanisms of dehydrated bacterial protection by sugars can be explained by water replacement theory (Crowe et al, 1988) or the formation of amorphous state (Santivarangkna et al, 2011). The Fourier transform infrared (FTIR) technique has been used to investigate the role of sugars in retarding conformational changes of bacterial cell envelopes and proteins (Leslie et al, 1995;Oldenhof et al, 2005;Santivarangkna et al, 2010).…”

“…The extremely high viscosity of dehydrated products in the amorphous state is capable of decreasing molecular mobility reducing adverse chemical reactions; however, this solid state is metastable and strongly depends on the glass transition temperature (T g ). 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).…”