Application of Porous Starch

Food Application

Flavor Delivery

Raw materials can easily lose their original flavor during production processes. To improve the sensory attributes of food products, flavors are widely added. However, flavors, which are generally liquid blends of molecules in solvents, are often liable to damage when exposed to heat, air, humidity, and other factors. To achieve longer stability, flavors are generally converted into a powder form. Usually, a liquid flavor is dispersed into a bulk powder carrier, such as salt or maltodextrin. After spray drying, microencapsulation is performed to protect the liquid flavor from the outside environment, thus prolonging its shelf life, whereas a simple blended flavor is not protected from oxygen, air, moisture, or heat. However, recently, the application of PS for flavor delivery has received considerable attention in the food industry, due to its advantages such as lower production costs (simple plating rather than spray drying) and the high liquid-to-powder ratio achieved (even higher than with spray drying); Glenn GM, Klamczynski AP compared the tomato flavor carrying performance between plating flavor onto PS, encapsulating flavor by spray drying and blending flavor onto a nonporous conventional carrier (maltodextrin). Although, these three flavor systems showed similar flavor content after sterilization and similar behavior during their shelf life, flavor delivery with PS was preferred due to easy processing and low cost. Moreover, the flavor delivery capacity of PS was confirmed to be related to the polarity of the solvent used for plating; thus, a better flavor delivery system with PS may be expected following appropriate solvent selection.

Probiotic Encapsulation

Nowadays, the incorporation of probiotics into functional foods is encouraged as they play an important role in health promotion. For example, Lactobacillus plantarum 299v has health properties including the improvement of irritable bowel syndrome and vascular endothelial function. Thus, it is widely added to many food products, especially fermented milks. However, its applications are limited by the viability of probiotic cells, which is affected by processing and storage conditions and the environment in the gastrointestinal tract. Li H, Thuyho VT proposed the encapsulation of L. plantarum 299v with PS to facilitate its functional effect in the body. With encapsulation, the effects of probiotic bacteria and enzyme-resistant starch could be combined in one product. Compared to free bacteria (L. plantarum 299v), PS-encapsulated bacteria showed greater acid and bile salt tolerance, with a significantly lower reduction in viability over the entire test period. Moreover, encapsulation with maize starch granules combined with a gelatinized starch coating significantly improved the heat tolerance of L. plantarum 299v.

Food Preservation

Allicin is the main compound derived from garlic and possesses various biological functions such as antiparasitic, antihypertensive, cardioprotective, anti-inflammatory, and anticancer properties. Allicin, due to its broad-spectrum of antibacterial activity against Gram-negative and Gram-positive bacteria, is regarded as a potential food preservative, which may be used in the food industry. However, it has low stability and water solubility. Wang et al., investigated encapsulation of allicin using β-cyclodextrin with PS via spray drying to increase its solubility which limits its use as food preservatives. The solubility of microencapsulated allicin was significantly improved, leading to direct dissolution in water. By retaining the desired antimicrobial activity of allicin, encapsulation also improved the stability of allicin microcapsules against heat, pH, light, and oxygen during allicin loading from approximately 20% to 40%.

Drug Delivery

As the most acceptable route for the treatment of chronic diseases, oral delivery has limitations in that the therapeutic efficacy of active ingredients significantly depends on their systemic exposure after oral administration. The application of many commercial drugs or potential drug candidates is restricted due to the fact that they are poorly soluble in water and exhibit low bioavailability following oral delivery. Several approaches have been developed to improve the oral absorption of lipophilic drugs. Of these approaches, PS is considered a promising candidate due to its stable pore structure, high pore volume, and good biocompatibility. With its high specific surface area, PS can be applied in the adsorption of liquid flavors and plant oils, tissue engineering scaffolds, and controlled drug delivery.

Wu C, Wang Z prepared a biodegradable porous starch foam (BPSF) as a carrier to improve the dissolution and enhance the oral bioavailability of lovastatin, a statin drug, naturally found in foods such as oyster mushrooms and red yeast rice, which is used to lower cholesterol (hypolipidemic agent) in those with hypercholesterolemia to reduce the risk of cardiovascular disease. The Brumauer–Emmet–Teller specific surface area (BET-SSA) and total pore volume of BPSF were estimated to be 127.75 m2 /g and 0.38 mL/g. The rod-shaped lovastatin was observed to disperse in the pores and surface of BPSF. The in vitro drug release studies revealed that the use of hydrophilic BPSF as a carrier for poor water-soluble drugs resulted in the fast release of lovastatin. The release of 80% lovastatin required 15 min using the BPSF system, while 45 min was required for the current commercial product. In addition, enhanced oral bioavailability of lovastatin loaded in BPSF, in comparison with crude lovastatin and commercial capsules, was also observed.

Zhang Z, Huang J prepared a PS-based self-assembled nano-delivery (PSN) for loading lipophilic probucol. The probucol-loaded nanocarrier (PLN) was used to investigate the biodistribution of PSN in rat intestine, cellular uptake of PSN in Caco-2 cell monolayers, and the pharmacokinetic behavior of PSN in rats. The results showed that PLN, formed by self-assembly when PSN was dispersed in gastrointestinal (GI) fluids, were nanometer-sized particles with a narrow size distribution and exhibited good stability in GI fluids. Using the PSN delivery system, the aqueous solubility of probucol was increased over 50,000-fold, and the cumulative release of probucol was increased by more than 80% in GI fluids. The distribution of probucol in the duodenum, jejunum, and ileum was also improved 7.17-, 15.99-, and 33.61-fold by PSN. With PSN, the oral bioavailability of probucol was greatly improved by approximately 9.96-fold, compared to that of the free drug suspension, confirming that the PS-based system enhanced the oral absorption of lipophilic drugs.

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