Figure 1. Schematic diagram of four different experiments for evaluating the indirect effect of proteolytic enzymes on in vitro starch digestion of cooked samples of control isolated navy bean cotyledon cells (INC-Control). Abbreviations: AMG—amyloglucosidase, IVT—invertase, PPA—porcine pancreatic α-amylase.

Figure 1. Schematic diagram of four different experiments for evaluating the indirect effect of proteolytic enzymes on in vitro starch digestion of cooked samples of control isolated navy bean cotyledon cells (INC-Control). Abbreviations: AMG—amyloglucosidase, IVT—invertase, PPA—porcine pancreatic α-amylase.

Figure 2. Representative brightfield light micrographs (A–F) and scanning electron micrographs (G–L) of isolated navy bean starch (INS), native INCs, control INCs, and INCs preincubated with pepsin for 1, 4, or 24 h at 37 °C and pH 2.0. Scale bar = 100 µm.

Figure 2. Representative brightfield light micrographs (A–F) and scanning electron micrographs (G–L) of isolated navy bean starch (INS), native INCs, control INCs, and INCs preincubated with pepsin for 1, 4, or 24 h at 37 °C and pH 2.0. Scale bar = 100 µm.

Figure 3. In vitro starch hydrolysis curves of cooked samples of control INCs (○) and INCs pretreated with pepsin for 1 h (▼), 4 h (■), and 24 h (△). INS (●) was included as a reference. Errors bars represent the standard deviations.

Figure 3. In vitro starch hydrolysis curves of cooked samples of control INCs (○) and INCs pretreated with pepsin for 1 h (▼), 4 h (■), and 24 h (△). INS (●) was included as a reference. Errors bars represent the standard deviations.

Figure 4. Representative brightfield light micrographs taken at 0 and 120 min of small intestinal digestion of control INCs and INCs pretreated with pepsin for 1, 4, and 24 h. The cells were stained with Lugol’s iodine reagent for detecting the presence of starch. Red arrows indicate empty “gap spaces”. Scale bar = 100 µm.

Figure 4. Representative brightfield light micrographs taken at 0 and 120 min of small intestinal digestion of control INCs and INCs pretreated with pepsin for 1, 4, and 24 h. The cells were stained with Lugol’s iodine reagent for detecting the presence of starch. Red arrows indicate empty “gap spaces”. Scale bar = 100 µm.

Figure 5. In vitro starch hydrolysis curves of cooked samples of control INCs from four experiments differing in protease combinations. Symbols (●, △, ○, ▼) represent the four experiments (see Experimental Section 2.5.2). Errors bars represent the standard deviations. Abbreviations: GP—gastric pepsin, PP—pancreatin proteases. Figure 5. In vitro starch hydrolysis curves of cooked samples of control INCs from four experiments differing in protease combinations. Symbols (●, △, ○, ▼) represent the four experiments (see Experimental Section 2.5.2). Errors bars represent the standard deviations. Abbreviations: GP—gastric pepsin, PP—pancreatin proteases.

Table 1. Physicochemical properties of INS, control INCs, and INCs pretreated with pepsin for 1, 4, or 24 h.

Table 1. Physicochemical properties of INS, control INCs, and INCs pretreated with pepsin for 1, 4, or 24 h.

Navy Bean MaterialAM (%)TS (% dwb)P (% dwb)SP (g/g)SS (%)INC-Control28.8 ± 0.0 a64.3 ± 0.5 e17.6 ± 0.7 a5.2 ± 0.1 d5.5 ± 0.0 cINC-1h28.6 ± 0.2 a70.5 ± 0.4 d11.4 ± 0.3 b5.4 ± 0.1 cd5.5 ± 0.0 cINC-4h27.8 ± 0.3 a73.4 ± 0.2 c9.2 ± 0.3 c5.6 ± 0.0 c6.1 ± 0.1 cINC-24h29.0 ± 0.0 a80.2 ± 0.5 b2.7 ± 0.2 d7.4 ± 0.2 b8.3 ± 0.3 bINS28.0 ± 0.7 a91.9 ± 0.9 a0.3 ± 0.2 e12.6 ± 0.1 a16.9 ± 0.2 a

Table 2. Kinetic parameters of in vitro starch digestion of cooked samples of INS, control INCs, and pepsin-treated INCs.

Table 2. Kinetic parameters of in vitro starch digestion of cooked samples of INS, control INCs, and pepsin-treated INCs.

Navy Bean MaterialsR10 (mg/mL/min) fH120 (%) gINC-Control1.40 ± 0.11 c70.6 ± 0.6 eINC-1h1.50 ± 0.03 c73.2 ± 0.3 dINC-4h2.07 ± 0.13 b77.6 ± 0.6 cINC-24h2.11 ± 0.13 b80.6 ± 1.6 bINS2.76 ± 0.13 a85.1 ± 0.4 a

Table 3. Kinetic parameters of in vitro starch digestion of cooked samples of control INCs from four experiments differing in protease combinations.

Table 3. Kinetic parameters of in vitro starch digestion of cooked samples of control INCs from four experiments differing in protease combinations.

ExperimentsR10 (mg/mL/min) cH120 (%) dExp.1 (GP + PP)1.40 ± 0.11 a70.6 ± 0.6 aExp.2 (PP only)1.41 ± 0.07 a69.9 ± 0.7 aExp.3 (GP only)0.97 ± 0.04 b70.8 ± 0.9 aExp.4 (without GP + PP)1.04 ± 0.04 b65.8 ± 1.6 b