Hae-Soo Kwak

Physicochemical, microbial, and sensory properties of yogurt supplemented with nanopowdered chitosan during storage.

This study was carried out to determine the possibility of adding nanopowdered chitosan (NPC) into cholesterol-reduced yogurt to improve the functionality of yogurt and the effects of adding NPC on the physicochemical, microbial, and sensory properties of the products during storage. The pH values and mean lactic acid bacteria counts of NPC-added (0.3 to approximately 0.7%, wt/vol) and cholesterol-reduced yogurt ranged from 4.19 to 4.41 and from 4.75 x 10(8) to 9.70 x 10(8) cfu/mL, respectively, when stored at 4 degrees C for 20 d, thereby indicating a possibility of prolonging the shelf life of yogurt. In color, the a* and b* values for cholesterol-reduced yogurt were not significantly influenced by the addition of NPC (0.1 to approximately 0.7%, wt/vol); however, the L* values significantly decreased with the addition of the greatest concentration (0.7%, wt/vol) of NPC at 0-d storage. The sensory test revealed that the astringency scores significantly increased at 0-d storage when the greatest concentration (0.7%, wt/vol) of NPC was added into cholesterol-reduced yogurt. Based on the data obtained from the current study, it is concluded that concentrations (0.3 to ~0.5%, vol/vol) of NPC could be used to produce an NPC-added and cholesterol-reduced yogurt without significantly adverse effects on the physicochemical, microbial, and sensory properties.

The accelerated ripening of cholesterol-reduced Cheddar cheese by crosslinked β-cyclodextrin

This study was carried out to investigate the influence of salt content on cholesterol-reduced Cheddar cheese obtained by a treatment with crosslinked beta-cyclodextrin (beta-CD) and to find if the ripening process was accelerated in cholesterol-reduced cheese. The crosslinked beta-CD used was made by adipic acid. A primary study indicated that the chemical and rheological properties were not changed by the salt addition and the composition of Cheddar cheese treated with crosslinked beta-CD was similar to untreated Cheddar cheese. Approximately 91 to 92% cholesterol reduction was observed in the cheeses that were treated using beta-CD. In a subsequent study, we found accelerated ripening by the crosslinked beta-CD based on the productions of short-chain free fatty acids and free amino acids. In rheological properties, elasticity, cohesiveness, and gumminess scores in the cholesterol-reduced Cheddar cheese were significantly greater at 5 wk ripening than those in the control at 4 mo ripening. At the early stage of ripening, most flavor properties such as rancidity, bitterness, and off-flavor in the cholesterol-reduced cheese were greater. With ripening, however, those scores changed to similar or lower scores than those in the control. The present study indicated that the crosslinked beta-CD treatment for cholesterol removal showed accelerated ripening effect on the properties of Cheddar cheese.

Effect of Nano-Calcium-Enriched Milk on Calcium Metabolism in Ovariectomized Rats

This study was designed to examine the effect of different kinds of calcium enrichment on serum and urine indices of mineral status in ovariectomized rats. Twenty-four 7-week-old Sprague-Dawley female rats were divided into four groups, ovariectomized, and fed diets containing the following: (1) Control, non-Ca-enriched milk; (2) OVX1, calcium carbonate-enriched milk; (3) OVX2, ionized Ca-enriched milk; and (4) OVX3, nano-Ca-enriched milk. After 18 weeks of feeding, the food efficiency ratio in the nano-Ca-fed group was significantly lower compared with those in the Control and OVX2 groups. There was no difference in serum and fecal Ca among the groups. The bone/total alkaline phosphatase ratio was significantly higher in rats fed milk enriched with nano-Ca (59%) and calcium carbonate (62%) than in control (44%) animals. Urinary Ca was the highest in the nano-Ca-enriched group; however, urinary excretions of deoxypyridinoline and hydroxyproline were significantly decreased in the nano-Ca-enriched group. The present results indicate that consumption of nano-Ca-enriched milk resulted in an increase of urinary excretion of calcium and a decrease in deoxypyridinoline and hydroxyproline in ovariectomized rats.

The effect of high pressure-low temperature treatment on physicochemical properties in milk.

This study was carried out to investigate the effect of high pressure-low temperature (HPLT) treatment on physicochemical properties and nutrients in milk. The milk was treated at 200 MPa and -4 degrees C for 10, 20, and 30 min. Protease and lipase activities of HPLT-treated milk were highly inactivated compared with that of raw milk. Among time treatments, the 30-min treatment showed the lowest activities compared with others. Absorbance of thiobarbituric acid increased with time in HLPT-treated milks; however, no difference was observed between the raw milk and milk treated for 10 min. The concentrations of short-chain fatty acids except C(4) in HPLT-treated milks increased with time. The total free amino acids in HPLT-treated milks were greater than that of the raw milk for the 30-min treatment. L-Ascorbic acid, niacin, and riboflavin in HPLT-treated milks were significantly lower compared with concentrations in raw milk. For color, the L-value of HPLT-treated milks was significantly lower than that of the raw milk; however, there was no difference in the a-value for 10 min and in the b-value at 20 min between the raw milk and the HPLT-treated milks.

Effect of isoflavone-enriched milk on bone mass in ovariectomized rats.

This study examined the effect of isoflavone-enriched milk on bone loss in ovariectomized (OVX) rats. Thirty 6-week-old Sprague-Dawley female rats were divided into two groups: sham-operated and OVX. The OVX group was subdivided into three dietary groups (OVX, non-isoflavone-enriched milk; OVX+Iso, isoflavone-enriched milk; and OVX+Iso+Vit+Ca, isoflavone-, vitamins D and K-, and Ca-enriched mik). After 19 weeks of feeding, the food efficiency ratio and body weight gain in the sham-operated group were significantly lower compared with those in the other groups. The bone alkaline phosphatase and total alkaline phosphatase activities were significantly higher in isoflavone-enriched groups (OVX+Iso and OVX+Iso+Vit+Ca) when compared with the sham-operated group. Urinary excretions of deoxypyridinoline and hydroxyproline were significantly higher with ovariectomy, but mostly normalized in the OVX+Iso and OVX+Iso+Vit+Ca groups. The rats in the OVX+Iso and OVX+Iso+Vit+Ca groups showed higher femur and tibia weights. A significant increase was found in bone density of femur and trabecular bone area in the OVX+Iso+Vit+Ca group, which almost reached that of the sham-operated group, whereas no difference was found among the OVX and OVX+Iso groups. The histological areas of the proximal tibia sections showed highly filled trabecular bone in both isoflavone-enriched groups (OVX+Iso and OVX+Iso+Vit+Ca). The present study indicated that isoflavone-enriched milk may have a partial preventive effect on ovariectomy-induced bone loss; however, vitamins D and K and Ca enrichment with isoflavone may enhance effectiveness for increasing bone mass in OVX rats.