*3.1. Morphology*

The appearance of both types of ginseng according to puffing pressure is shown in Figure 1. Originally, Canadian ginseng was bigger than American ginseng before puffing, and regardless of the puffing pressure, the volume of Canadian ginseng was larger than that of American ginseng. It was reported previously that browning was further enhanced at high pressure in puffed red ginseng [18]. In particular, the surface was frayed starting at 784 kPa and separated from the interior at 882 kPa, resulting in the formation of blisters or air pockets inside the ginseng.

**Figure 1.** Morphology of puffed American and Canadian ginsengs.

Puffing also changed the color of both ginsengs (Table 1). Regardless of the ginseng type, the L value decreased as the puffing pressure increased, suggesting increased pigmentation with puffing. The a and b values were higher than those of the control groups but decreased as the puffing pressure increased. This indicated that puffing increased the redness and yellowness of both ginsengs. On the other hand, the highest redness and yellowness values were observed at the lowest puffing pressure tested. The L value was consistent with the trend of MRPs content, which increased with increasing puffing pressure (Table 2). The higher were the temperature and pressure, the more active was the Maillard reaction between amino acids and sugars in ginseng [23,33].


**Table 1.** Color, extraction yield, and crude saponin content of puffed American and Canadian ginsengs.

A, American ginseng; C, Canadian ginseng. \* Values with the same letter in the column are not significantly different *(p* < 0.05).

**Table 2.** Antioxidant activity (2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2--azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical scavenging activities), TPC, TFC, acidic polysaccharides, and Maillard reaction products (MRPs) of puffed American and Canadian ginsengs.


A, American ginseng; C, Canadian ginseng; DPPH, DPPH radical scavenging activity; ABTS, ABTS radical scavenging activity; TPC, total phenolic content; TFC, total flavonoid content; AP, acidic polysaccharides; VCE: vitamin C equivalent; GAE: gallic acid equivalent; CE: catechin equivalent; GA, galacturonic acid; MRPs, Maillard reaction products. \* Values with the same letter in the column are not significantly different (*p* < 0.05).

#### *3.2. Extraction Yield and Crude Saponin Content*

The extraction yields and crude saponin content of puffed American and Canadian ginsengs are shown in Table 1. Before puffing, in the control group, both extraction yield and crude saponin content of Canadian ginseng were higher than those of American ginseng. Puffed American and Canadian ginsengs revealed higher extraction yields and crude saponin contents than those of the control groups. Puffing caused cell wall breakdown and porous structure formation, resulting in easy elution of active components from ginseng [18]. Although puffing increased both extraction yield and crude saponin content in American and Canadian ginsengs, no increasing trends in yield and content with increasing puffing pressure were found. The puffed American and Canadian ginsengs showed the highest extraction yield at 784 kPa and 880 kPa, respectively. In contrast, both ginsengs showed the

highest crude saponin content at 686 kPa. Consequently, puffing increased both extraction yield and crude saponin content of each ginseng type at different puffing pressures.

#### *3.3. Changes in Ginsenosides*

The HPLC chromatograms of puffed American and Canadian ginsengs are shown in Figure 2. In control groups of American and Canadian ginsengs, Rb1, Rb2, Rc, Rd, and Re were the major ginsenosides, all known to be characteristic of ginseng. In contrast, after puffing, the major ginsenoside content gradually decreased as puffing pressure increased in both American and Canadian ginsengs, resulting in the production and increase of minor ginsenosides such as Rg2, Rg3, Rh2, and compound K. Puffing of ginseng has been reported to decrease the content of major ginsenosides and increase that of minor ginsenosides, especially Rg3 in *P. ginseng* [18,25].

The changes in the ginsenoside profiles of puffed American and Canadian ginsengs are shown in Figure 3. The content of all major ginsenosides except Rg1 (Rb1, Rb2, Rc, Rd, Re) increased up to 686 kPa and then decreased as the puffing pressure increased in both ginsengs. Decomposition or thermal conversion of ginsenosides occur when heat is applied [34]. The increase in major ginsenoside content at 686 kPa may be attributed to non-soluble polymer components converting into soluble ones due to puffing and to the increased penetration of the extraction solvent due to the porous structure of the tissue [23]. Another possible explanation is the weakening of the binding force due to the destruction of cell walls and to changes in the molecular structure induced by puffing [18,35]. In this study, ginsenosides Rg2, Rg3, Compound K, and Rh2 were newly produced by deglycosylation and pyrolysis of major ginsenosides. Their concentrations increased with increasing puffing pressure. Especially, Compound K concentration greatly increased at 980 kPa compared to the control group in both puffed ginsengs. The contents of ginsenosides Rg2 and Rg3 also significantly increased in both puffed ginsengs. This result is slightly different from previous results on puffed ginseng [25] and puffed red ginseng [18], possibly because different ginseng varieties were used. *P. quinquefolius* has a different ginsenoside profile compared to *P. ginseng*, resulting in different ginsenoside products after puffing. Unlike *P. ginseng,* the levels of ginsenoside F1 and F2 of *P. quinquefolius* were relatively high and did not change with puffing, indicating that those ginsenosides are heat-resistant and not easily transformed by puffing.

#### *3.4. Antioxidant Activity, TPC, and TFC*

Antioxidant activities (DPPH and ABTS), TPC, and TFC of puffed American and Canadian ginsengs are shown in Table 2. In the control group, no significant differences (*p* < 0.05) in antioxidant activities were observed between American and Canadian ginsengs. Puffed American and Canadian ginsengs showed much higher antioxidant activities, TPC, and TFC compared to the control group. In DPPH, puffing increased the activity approximately 5–6 times compared to the control group, regardless of the puffing pressure, in both American and Canadian ginsengs. ABTS, TPC, and TFC but not DPPH increased with increasing puffing pressure. ABTS radical scavenging activity increased more than 10 times compared with the control group. Especially, at 980 kPa, ABTS of both ginsengs increased approximately 40 times over that of the control group. TPC and TFC in both American and Canadian ginsengs also showed the highest levels at 980 kPa, approximately 20 and 10 times higher than those of the control group, respectively. Water-soluble substances that affect the antioxidant activity exist in an insoluble state in combination with other substances. The increases of antioxidant activities, TPC, and TFC may be explained by the weakening of the molecular binding caused by heat treatment and elution of those materials into a water-soluble state [36] and the increase of certain substances such as maltol, a Maillard reaction product [15]. TPC [23] and TFC [37,38] have been reported to increase with increasing temperature and heat treatment time. Likewise, in this study, antioxidant activities, TPC, and TFC of American and Canadian ginsengs increased during puffing with increasing temperature and holding time.

**Figure 3.** Changes in ginsenoside content of puffed American and Canadian ginsengs.

#### *3.5. Acidic Polysaccharides and MRPs*

The changes in acidic polysaccharides content of puffed American and Canadian ginsengs are shown in Table 2. Before puffing, American and Canadian ginsengs showed similar acidic polysaccharides contents. However, after puffing, the content of acidic polysaccharides of both ginsengs increased significantly (*p* < 0.05) compared to those of the non-puffed counterparts; the highest levels of acidic polysaccharides resulted from puffing at 980 kPa. No significant differences (*p* < 0.05) were observed by puffing at 686, 784, or 882 kPa in both American and Canadian ginseng. Ginseng contains 60–70% (dry basis) of carbohydrates, the major components of which are pectin and starch [39]. The acidic polysaccharides of ginseng consist of a pectin-like substance with a molecular weight of 34,600 Da, whose main component is galacturonic acid [22]. The majority of the polysaccharides from *P. quinquefolius* are in the neutral form, and their acidic form increases with thermal processing. The content of acidic polysaccharides of ginseng tends to increase with heat treatment [22,32]. Moreover, acidic polysaccharides are affected by temperature rather than heat treatment time [22]. Depending on the specific characteristics of puffing, the greatest concentration of acidic polysaccharides in this study was produced by pu ffing at 980 kPa in both American and Canadian ginsengs.

The MRPs of pu ffed American and Canadian ginsengs are shown in Table 2. The MRPs of both American and Canadian ginsengs before pu ffing were not significantly di fferent (*p* < 0.05) and gradually increased with increasing pu ffing pressure. The increase in MRPs with thermal processing of American ginseng has been reported [15], and those changes were correlated with changes in antioxidant activity, TPC, and TFC [23,37,38].

#### *3.6. Relationships between Antioxidant Activities, TPC, TFC, MRPs, and Acidic Polysaccharides*

The results of the Pearson correlations among antioxidant activities, TPC, TFC, amount of MRPs, and acidic polysaccharides content of pu ffed American and Canadian ginsengs are shown in Table 3. In American ginseng, ABTS correlated well with acidic polysaccharides content, TPC, and amount of MRPs. TFC was in good correlation with TPC and amount of MRPs. TPC and amount of MRPs had good correlation with all other parameters except for DPPH. Moreover, acidic polysaccharides content had a good correlation with amount of MRPs, ABTS, and TPC. In contrast, the correlations for Canadian ginseng were slightly di fferent from those of American ginseng; ABTS correlated well with acidic polysaccharides content, TPC, and TFC. The amount of MRPS had a good correlation with TPC and TFC. TPC and TFC h ad good correlation with all other parameters except for DPPH. Likewise, acidic polysaccharides content had a good correlation with ABTS and TFC.


**Table 3.** Pearson correlations between amount of MRPs, DPPH, ABTS, TPC, TFC, and acidic polysaccharides content of pu ffed American and Canadian ginsengs.

MRPs, Maillard reaction products; DPPH, DPPH radical scavenging activity; ABTS, ABTS radical scavenging activity; TPC, total phenolic content; TFC, total flavonoid content; AP, acidic polysaccharides. \* indicates *p* < 0.05; \*\* indicates *p* < 0.01; \*\*\* indicates *p* < 0.001.

Although the correlation patterns of American and Canadian ginsengs were not the same, two common correlations were observed. First, acidic polysaccharides content showed the strongest correlation with ABTS in both American and Canadian ginsengs. Second, DPPH did not correlate well with any other antioxidant parameter in either American or Canadian ginseng. These results sugges<sup>t</sup> that compounds and mechanisms related to ABTS are very closely related to acidic polysaccharides content, and that DPPH has distinctive characteristics, di fferent from the other antioxidant parameters evaluated in this study. It is interesting to note that this result is not casual, and this di fference may come from the di fferent sources of the samples, their di fferent reactivity when subjected to pu ffing, and so on. Further analysis is needed for clarifying this result.
