Elsevier

Journal of Functional Foods

Volume 25, August 2016, Pages 447-458
Journal of Functional Foods

Effect of encapsulant matrix on stability of microencapsulated probiotics

https://doi.org/10.1016/j.jff.2016.06.020Get rights and content

Highlights

  • Dried glucose syrup is better than glucose in combination with protein as encapsulant for probiotics.

  • Hydrolysed whey protein and intact whey protein in combination with sugars protect probiotics equally.

  • Microencapsulation maintained physical powder flow characteristics and colour during non-refrigerated storage.

  • Microencapsulation benefits long term stability under non-refrigerated storage.

  • A combination of matrix formulation, packaging and storage is essential for long-term stability.

Abstract

Spray dried microencapsulated formulations [25% protein:25% sugar:25% resistant starch (RS):20% oil:5% Lactobacillus rhamnosus GG (LGG)] were compared with commercial freeze dried LGG during non-refrigerated storage with or without packaging. Microencapsulated spray dried LGG was more stable on storage at 25 °C (32, 57 or 70% relative humidity) than freeze dried LGG. The viability of microencapsulated formulations was greater in formulations containing dried glucose syrup compared with glucose, but the type of protein (whey protein isolate or hydrolysed whey protein) has less of an effect. Viability was correlated to the properties of water in the formulations. After long term storage (12 months, 25 °C) in moisture barrier bags, viability was >107 CFU/g for FD LGG and microencapsulated formulations without glucose. Only the microencapsulated formulations were free-flowing and maintained an acceptable colour. There are benefits of microencapsulation for long term packaged non-refrigerated storage and short term storage in open environments.

Introduction

The increasing evidence of potential health benefits of probiotics over a wide range of clinical conditions is driving the market for probiotics (Parvez, Malik, Ah Kang, & Kim, 2006). Consumer demand for a much wider range of functional foods containing probiotics continues to increase. The development of shelf stable probiotic ingredients presents a significant challenge to the food and supplement industries wanting to meet the market for probiotic-containing functional foods and supplements that are stable under non-refrigerated storage conditions.

Probiotics are live microorganisms sensitive to heat, moisture, oxygen and acidic environments. Their sensitivities tosurrounding environments vary depending on the strain (Lankaputhra & Shah, 1995). Probiotic microorganisms must be alive until they reach the site of action in the body to exert their beneficial effect on the host (Favaro-Trindade & Grosso, 2002). Probiotic products need to contain more than 10 million colony forming units (CFU) per gram to effectively provide a claimed health benefit (Jorgen, 2001). Therefore, maintaining cell viability and probiotic function in the final product is important (Kailasapathy, 2002).

Different strategies have been examined for keeping probiotics viable under various environmental stresses. Much effort has been given to protect the microorganisms by microencapsulation and addition of different protectants (Tripathi & Giri, 2014). Microencapsulation may be used to overcome the problems of poor stability of probiotics, both inthe product as well as in the gastrointestinal environment (Sarkar, 2010).

Microencapsulation protects live cells from their surrounding environment during processing and storage and offers potential to keep probiotics alive for longer (Mortazavian et al, 2007, Ross et al, 2005). The challenge in developing robust encapsulation technology is the selection of suitable food grade materials together with the appropriate process that provide acceptable viability over long term storage especially if the cells are stored at ambient temperature and humidity (Harel & Tang, 2014). Different microencapsulation strategies involve various processing and drying operations that are widely practiced in the food industry, such as freeze drying, spray drying, spray chilling, coextrusion, gel-matrix entrapment, and fluid bed coating (Doleyres, Lacroix, 2005, Gismondo et al, 1999). Various proteins (Chávez, Ledeboer, 2007, Heidebach et al, 2010, Picot, Lacroix, 2004), granular starch (Crittenden et al., 2001), polysaccharides (Sultana et al., 2000) and cryoprotectants (Li et al., 2011) have been used alone or in combination as the protective matrix to improve probiotics stability. Heated protein–carbohydrate–oil emulsions used as encapsulant matrix enhanced the protection of spray dried probiotics during non-refrigerated storage and gastrointestinal transit (Crittenden, Weerakkody, Sanguansri, & Augustin, 2006). Addition of lipophilic antioxidants (e.g. tocopherols) to the encapsulant matrix improved the survival of probiotics during storage, but addition of hydrophilic antioxidants (e.g. sodium ascorbate) was detrimental to the survival of spray dried Lactobacillus rhamnosus GG (LGG) during storage (Ying et al., 2011). The inclusion of glucose to the protein–carbohydrate (1:2 ratio) encapsulant matrix to replace part of maltodextrin or inulin (Ying, Sun, Sanguansri, Weerakkody, & Augustin, 2012), or addition of thermoprotectants, such as trehalose (Conrad, Miller, Cielenski, & de Pablo, 2000), has been shown to enhance the viability of microencapsulated probiotics during storage.

The enhanced survival of spray dried probiotics during storage (Ying et al., 2012) with the inclusion of glucose in protein–carbohydrate encapsulant matrix was attributed to the interaction of glucose with the cell membrane and suppression of water mobility (Hoobin et al., 2013). However, the addition of glucose caused a large decrease in glass transition temperature (Ying et al., 2012), which had detrimental effects on powder physical characteristics, such as flowability, during long term storage at ambient conditions with high temperature and humidity. Substituting dried glucose syrup (DGS) for glucose in an encapsulant matrix will increase glass transition temperature and potentially translate to better probiotic storage stability at high humidity. Hydrolysed whey protein (HWP) has been shown to be effective as an encapsulant, enhancing the survival of probiotics during processing and storage (Doherty et al., 2010). The protective effect was considered to be due to the small peptides in HWP and the hydrophilic nature of the HWP that enhanced interaction with cell membranes. However, some HWP may have a bitter taste because of some small peptides. Whey protein isolate (WPI) has a blander taste than HWP and provides an alternative protein ingredient for the microencapsulation matrix.

In this study we compared the stability of spray dried microencapsulated LGG formulations (25% protein:25% sugar:25% resistant starch (RS):20% oil:5% LGG) with that of a commercial sample of FD LGG. We examined the effect of substitution of DGS for glucose, and WPI for HWP, on the storage stability of spray dried LGG microcapsules. The survival of powdered probiotics that were exposed to different relative humidity (RH) at 25 °C was examined over 35 days. The moisture sorption properties of the microencapsulated formulations and their relationship with the viability of probiotics were examined. The long term viability and physical properties of LGG formulations packed in triple laminated foil barrier bags during 12 month storage was also assessed. It was envisaged that these experiments would provide insights into the viability and usability of LGG preparations in both open and closed environments.

Section snippets

Materials

Commercial freeze dried L. rhamnosus GG stabilised with sugar (FD LGG) was obtained from Valio Ltd. (Helsinki, Finland). The specifications for the commercial LGG state the formulation contains 45% sucrose. Materials used for encapsulation were WPI (Alacen 895, Fonterra Co-operative Group Ltd., Hamilton, New Zealand), HWP (Muscle Brand Pty. Ltd., Petersham, NSW, Australia), DGS (maltodextrin DE30, Fieldose 30, Grain Products, Tamworth, NSW, Australia), glucose (dextrose monohydrate, Penford

Results and discussion

The FD LGG had an initial viability of (3.13 ± 0.22) × 1010 CFU/g (Powder 1). When FD LGG was added at 5% (w/w, dry basis, ~1.57 x 109 CFU/g) in the formulation and analysed after spray drying, the SD powder microcapsules had initial viability of (6.12 ± 3.61) × 108 CFU/g (Powder 2), (5.54 ± 0.94) × 108 CFU/g (Powder 3) and (2.83 ± 0.22) × 109 CFU/g (Powder 4) before storage, which show that there is minimal loss during processing and spray drying. The low initial CFU in the SD formulations is

Conclusion

The encapsulant matrix formulation containing DGS [HWP (or WPI)–DGS–RS–oil matrix] provided better probiotic protection during storage compared to the formulation containing glucose [HWP–Glucose–RS–oil matrix]. SD LGG formulations with HWP (or WPI)–DGS–RS–oil matrix had the highest % survival (~2 log10 loss, equivalent to commercial FD LGG), while also maintaining the physical characteristics (e.g. colour, powder flow properties) of the microencapsulated probiotic powder, after 12 months'

Acknowledgement

The authors gratefully acknowledge Li Jiang Cheng and Sukhdeep Bhail for technical support, and Wayne Beattie for assisting in spray drying the samples.

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