Stability of polyphenols in chokeberry (Aronia melanocarpa) subjected to in vitro gastric and pancreatic digestion

Berries and red fruits are dietary sources of polyphenols with reported health benefits. As part of the diet, polyphenols are ingested as complex mixtures immersed in a food matrix which is digested in the gut. Epithelial cells lining the gut are regularly exposed to these digested mixtures. To understand the effects of dietary polyphenols on human gut health it is essential to determine their stability and fate in the lumen. In this work, we investigated the effects of an in vitro gastric and pancreatic digestion on the stability and composition of the major polyphenols in chokeberry juice. Digestion was carried out with a mixture of pepsin-HCl for 2 h, followed by a 2 h incubation with pancreatin and bile salts at 37 °C with shaking, in the absence of light and under N₂. After digestion, the chokeberry samples were acidified, filtered and HPLC-DAD/HPLC–MS–MS analysed to determine the content of total soluble recovered phenolics. Gastric digestion had no substantial effect on any of the major phenolic compounds in chokeberry, namely anthocyanins, flavan-3-ols, flavonols and caffeic acid derivatives. However, these compounds were significantly altered during the pancreatic digestion and this effect was more marked for anthocyanins (approximately 43% was lost during the 2 h treatment with pancreatin). Flavonols and flavan-3-ols decreased by 26% and 19%, respectively. Neochlorogenic acid decreased by 28% whereas chlorogenic acid was increased by 24%. In vitro digestion of standard phenolic compounds, representing each of the groups of phenolics in chokeberry, confirmed some of the observed changes. Interactions with the digestive enzymes were not responsible for the observed losses which were mostly due to the chemical conditions during pancreatic digestion. Our results, in accordance with previously published results, show that dietary polyphenols are highly sensitive to the mild alkaline conditions in the small intestine and that a good proportion of these compounds can be transformed into other unknown and/or undetected structural forms with different chemical properties and, consequently, different bioaccessibility, bioavailability and biological activity.     

Changes in the antioxidant activity of loach (Misgurnus anguillicaudatus) protein hydrolysates during a simulated gastrointestinal digestion

A two-stage in vitro digestion model system (a pepsin treatment for 2 h followed by a pancreatin treatment for 2 h, both at 37 °C) was used to simulate the process of human gastrointestinal (GI) digestion to determine the changes in antioxidant activities of loach peptide previously prepared by papain digestion. Results showed that the final GI digests contained 38.1% free amino acids, with short chain peptides (<500 Da) making up the rest of the biomass. Enzymatic breakdown of the GI digests increased their hydroxyl (12% increase), 2,2′-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) (5% increase) radical scavenging activity, the reducing power (77% increase) and the chelating ability of Cu²⁺ (12% increase), compared to the blank. The results showed that the digestion by gastrointestinal proteases can be used to produce antioxidant peptides, with the advantage that the peptides formed will resist physiological digestion in GI tract.     

In vitro human digestion models for food applications

In vitro digestion models are widely used to study the structural changes, digestibility, and release of food components under simulated gastrointestinal conditions. However, the results of in vitro digestion models are often different to those found using in vivo models because of the difficulties in accurately simulating the highly complex physicochemical and physiological events occurring in animal and human digestive tracts. This paper provides an overview of current trends in the development and utilisation of in vitro digestion models for foods, as well as information that can be used to develop improved digestion models. Our survey of in vitro digestion models found that the most predominant food samples tested were plants, meats, fish, dairy, and emulsion-based foods. The most frequently used biological molecules included in the digestion models were digestive enzymes (pancreatin, pepsin, trypsin, chymotrypsin, peptidase, α-amylase, and lipase), bile salts, and mucin. In all the in vitro digestion models surveyed, the digestion temperature was 37 °C although varying types and concentrations of enzymes were utilised. With regard to digestion times, 2 h (the stomach, small intestine, and large intestine each) was predominantly employed. This survey enhances the understanding of in vitro digestion models and provides indications for the development of improved in vitro digestion models for foods or pharmaceuticals.     

Dietary and host-related factors influencing carotenoid bioaccessibility from spinach (Spinacia oleracea)

Several dietary and host related factors potentially influencing carotenoid (beta-carotene, lutein and zeaxanthin) bioaccessibility from spinach, including different concentrations of sodium, calcium and magnesium, were systematically investigated by means of an in vitro digestion model. Bioaccessibility was highest when milk (4% fat) and lowest when skimmed milk or more complex food matrices such as sausage were added to the meal. Micellarisation significantly depended on the presence and concentration of bile salts and pancreatin (p < 0.001, Bonferroni) but was unaffected by pepsin. Micellarisation significantly decreased to 61.4 ± 3.0% of control (p < 0.001, Dunnett’s) at high cholesterol (114 mg/test meal) but not at similar stigmasterol concentrations. Calcium and magnesium ?13.8 mM individually inhibited micelle formation ( >40% on average), presumably due to the generation of insoluble soaps with fatty acids and bile salts. Increased sodium concentrations (280 and 460 mM) altered carotenoid micellarisation patterns, favoring beta-carotene isomers (p < 0.001, Bonferroni) but decreasing lutein and zeaxanthin (p < 0.001 and p < 0.05, respectively, Bonferroni). This study suggests that minerals may impact carotenoid bioavailability.     

Factors affecting lipase digestibility of emulsified lipids using an in vitro digestion model: Proposal for a standardised pH-stat method

The control of lipid digestibility within the human gastrointestinal tract is important for the development of many functional food and pharmaceutical products. The influence of product composition and microstructure on lipid digestibility is typically studied using in vitro digestion methods. This article focuses on the impact of various experimental factors on lipid digestion in oil-in-water emulsions, using a pH-stat method that simulates the small intestine. The rate and extent of lipid digestion were found to increase with: increasing lipase (from 0 to 4.8 mg/ml), decreasing bile extract (from 20 to 0 mg/ml), increasing CaCl₂ (from 0 to 20 mM), decreasing lipid (from 2.5 to 0.1 wt.%); decreasing droplet diameter (from d = 800 to 200 nm), and decreasing fatty acid molecular weight (medium chain triglycerides versus corn oil). These affects are interpreted in terms of the surface area of lipid exposed to the aqueous phase, and factors affecting the accumulation of reaction products (fatty acids) at the oil–water interface. Based on our own and others’ work, we propose a standardised in vitro digestion model to test emulsified lipids, based on pH-stat titration. This study has important implications for designing and testing delivery systems that control lipid digestion using the pH-stat method.     

Development and validation of a UPLC–ELSD method for fast simultaneous determination of five bile acid derivatives in Calculus Bovis and its medicinal preparations

A reverse phase ultra-performance liquid chromatography coupled with evaporative light scattering detection (UPLC–ELSD) method was successfully established for simultaneous determination of five bile acid derivatives in Calculus Bovis and its medicinal preparations using a Waters Acquity UPLC T3 C₁₈ column (2.1 × 50 mm, 1.8 μm) with gradient elution of 0.2% aqueous formic acid and acetonitrile. The influence of liquid flow-rate and column temperature, gas flow-rate and drift tube temperature on resolution was investigated to get the optimized parameters and conditions. This method was validated according to the regulatory guidelines with respect to precision, accuracy and linearity. Under optimum conditions, the five analytes were baseline separated in 11 min with detection and quantification limits ranged in 3.0–6.0 ng and 6.0–18.0 ng, respectively, which provided about a twofold reduction in analysis time and good efficiency and sensitivity by comparing a conventional high performance liquid chromatography (HPLC) method.     

Habituation to organic acid anions induces resistance to acid and bile in Listeria monocytogenes

We evaluated the intrinsic and inducible resistance of four human pathogenic strains of Listeria monocytogenes to acid and bile, factors associated with virulence. Cells were grown in media at pH 7.4, or in media at pH 6.0 containing 0 (HCl control) or 4.75 mM of different organic acids, harvested at stationary or mid log phase, and challenged for 1 h in acid or bile. Stationary phase cells were intrinsically more resistant to either challenge than log phase cells, and large differences between strains were evident among the latter. Compared to the HCl control, habituation to log phase with organic acids induced significant (p < 0.05) and meaningful (≥ 1 log) increases in acid resistance of three of four strains tested, and in bile resistance of two strains suggesting that exposure to organic acid anions may enhance virulence in L. monocytogenes.     

Particle size-starch–protein digestibility relationships in cowpea (Vigna unguiculata)

The kinetics of starch and protein digestion in hammer- and cryo-milled cowpea (70–370 μm) were investigated. The pH during the protein digestion reduced with time, and both the starch and protein digestion exhibited monophasic digestograms, which were suitably (r² > 0.97, p < 0.001) described by a modified first-order kinetic model. The in vitro protein digestibility of the cowpea (>80%) was independent of the milling conditions. The hammer-milled cowpea digested more, but the reciprocal of its rate of protein digestion was independent of the square of the particle size. The rate of protein digestion in the cryo-milled cowpea inversely depended (p < 0.05) on the square of the particle size, with 67 × 10⁻⁷ cm² s⁻¹ as the diffusion coefficient. For the starch digestion, diffusion coefficients (cm² s⁻¹) were 0.6 × 10⁻⁷ (hammer-milled) and 0.3 × 10⁻⁷ (cryo-milled). The protein digestion proceeded at a much faster (100×) rate than the starch digestion.     

Impact of phytochemical-rich foods on bioaccessibility of mercury from fish

The effects of phytochemical-rich foods on bioaccessibility of mercury in fish tissue (the amount of mercury that is released from fish into gastrointestinal tract fluid following a simulated digestion) were investigated using an in vitro digestion. Total mercury in the aqueous phase following a simulated digestion of fish with added food treatments was used to measure mercury bioaccessibility. Green tea extract (31–2000 mg), black tea extract (31–2000 mg), and soy protein (50–100 mg) significantly reduced mercury bioaccessibility by 82–92%, 88–91%, and 44–87%, respectively. Grapefruit juice (0.5–10 ml) did not reduce mercury in the aqueous phase. Wheat bran (50–1000 mg) decreased mercury bioaccessibility (84%); oat bran and psyllium reduced bioaccessibility (by 59–75%, 15–31%, respectively) at amounts greater than 500 mg. We therefore suggest that co-consumption of foods containing phytochemicals at the same time as fish that contains mercury may potentially reduce mercury absorption compared to eating fish alone.     

Digestibility and β-carotene release from lipid nanodispersions depend on dispersed phase crystallinity and interfacial properties

The influence of interfacial structure and lipid physical state on colloidal stability and digestibility of solid lipid nanoparticle dispersions (SLN) and canola oil-in-water emulsions (COE) stabilized with the non-ionic surfactants Poloxamer 188 (P188) and Tween 20 (T20) were examined and the release of encapsulated β-carotene (BC) under simulated gastrointestinal conditions determined. While the SLN and COE were all stable during exposure to gastric conditions (mean diameter ～115 nm), more destabilization was observed for the COE than SLN during the duodenal phase. ζ-Potential measurements indicated rapid adsorption of bile salts (BS) and phospholipids (PL) to both solid and liquid interfaces, with greater surfactant displacement observed for the COE. Compared to the SLN, significantly more lipolysis and BC transfer to the aqueous phase was observed for both the COE-P188 and COE-T20 (p < 0.05). The properties of the colloidal structures present in the aqueous phase, which are important in terms of the uptake of lipolytic products and lipophilic bioactives, depended on non-ionic surfactant type, the extent of lipid digestion, as well as the presence of BS and PL.     

In vitro binding of bile acids by blueberries (Vaccinium spp.), plums (Prunus spp.), prunes (Prunus spp.), strawberries (Fragaria X ananassa), cherries (Malpighia punicifolia), cranberries (Vaccinium macrocarpon) and apples (Malus sylvestris)

The in vitro binding of bile acids by blueberries (Vaccinium spp.), plums (Prunus spp.), prunes (Prunus spp.), strawberries (Fragaria X ananassa), cherries (Malpighia punicifolia) cranberries (Vaccinium macrocarpon) and apples (Malus sylvestris) was determined using a mixture of bile acids secreted in human bile at a duodenal physiological pH of 6.3. Six treatments and two blank incubations were conducted to testing various fresh raw fruits on an equal dry matter basis. Considering cholestyramine (bile acid binding, cholesterol lowering drug) as 100% bound, the relative in vitro bile acid binding on dry matter (DM), total dietary fiber (TDF) and total polysaccharides (PCH) basis was for blueberries 7%, 47% and 25%; plums 6%, 53% and 50%; prunes 5%, 50% and 14%; strawberries 5%, 23% and 15%; cherries 5%, 37% and 5%; cranberries 4%, 12% and 7%; and apple 1%, 7% and 5%, respectively. Bile acid binding on DM basis for blueberries was significantly (P ? 0.05) higher than all the fruits tested. The bile acid binding for plums was similar to that for prunes and strawberries and significantly higher than cherries, cranberries and apples. Binding values for cherries and cranberries were significantly higher than those for apples. These results point to the relative health promoting potential of blueberries > plums = prunes = strawberries = cherries = cranberries > apples as indicated by their bile acid binding on DM basis. The variability in bile acid binding between the fruits tested maybe related to their phytonutrients (antioxidants, polyphenols, hydroxycinnamic acids, flavonoids, anthocyanins, flavonols, proanthocyanidins, catechins), structure, hydrophobicity of undigested fractions, anionic or cationic nature of the metabolites produced during digestion or their interaction with active binding sites. Inclusion of blueberries, plums, prunes, strawberries, cherries and cranberries in our daily diet as health promoting fruits should be encouraged. Animal studies are planned to validate in vitro bile acid binding of fruits observed herein to their potential of atherosclerosis amelioration (lipid and lipoprotein lowering) and cancer prevention (excretion of toxic metabolites).     

In vitro binding of bile acids by bananas,peaches, pineapple,grapes, pears,apricots and nectarines

The in vitro binding of bile acids by bananas (Musa × paradisiaca), peaches (Prunus persica), pineapple (Ananus comosus), grapes (Vitis spp.), pears (Pyrus communis), apricots (Prunus armeniaca) and nectarines (Prunus persica, nectarina) was determined using a mixture of bile acids secreted in human bile at a duodenal physiological pH of 6.3. Six treatments and two blank incubations were conducted, testing various fresh fruits on an equal dry matter basis. Considering cholestyramine (bile acid binding, cholesterol lowering drug) as 100% bound, the relative in vitro bile acid binding percentages on dry matter (DM), total dietary fibre and total polysaccharides basis were 2–9%, 15–101% and 10–101%, respectively. Bile acid binding, on a DM basis, for bananas was significantly (P ? 0.05) higher and that for nectarines significantly lower than those for peaches, pineapple, grapes, pears and apricots. The bile acid bindings for peaches and pineapple were similar and significantly higher than those for grapes, pears and apricots. Binding values for grapes and pears were significantly higher than apricots. These results point to the relative health promoting potential of bananas > peaches = pineapple > grapes = pears > apricots > nectarines, as indicated by their bile acid binding on a DM basis. The variability in bile acid binding between the fruits tested maybe related to their phytonutrients, antioxidants, polyphenols, flavonoids (anthocyanins, flavonols, and proanthocyanidins), structure, hydrophobicity of undigested fractions, anionic or cationic nature of the metabolites produced during digestion or their interaction with active binding sites. Animal studies are planned to validate in vitro bile acid binding of fruits, observed herein, to their healthful potential, atherosclerosis amelioration and cancer prevention.     

Angiotensin I-converting enzyme (ACE) inhibitory peptides derived from arachin by simulated gastric digestion

In silico analysis of the sequences of arachin, the major storage protein of peanut suggests that it is laden with antihypertensive peptides. Physiological proteases pepsin, trypsin, chymotrypsin and pancreatin were used to release these peptides. The degree of proteolysis and in vitro angiotensin I-converting enzyme (ACE) inhibition was maximum with pepsin. The ACE inhibitor index of human gastric juice catalysed digestion was similar to pepsin demonstrating that such peptides can be produced in vivo following ingestion of arachin. Three peptides purified from the simulated gastric fluid digests were synthesized. Among them, the pentapeptide, NAQRP was the most potent with an IC₅₀ of 32 ± 2 μM. Molecular docking simulation with human tACE indicate that in addition to a favourable C-terminal Pro residue, the length of the peptides advocate ACE inhibitor potency. These results further potentiate the use of arachin/peanut proteins as functional ingredients in auxiliary therapeutic foods toward blood pressure management.     

Protection of Lactobacillus acidophilus from bile salts in a model intestinal juice by incorporation into the inner-water phase of a W/O/W emulsion

Lactic acid bacteria have been paid increasing attention as a probiotics, but their viability is affected by the various digestive processes of their host such as the acidic stomach solution and bile acids. The protection of Lactobacillus acidophilus JCM 1132 against the cytotoxic bile acids was examined by incorporating the bacteria in the inner-water phase of a W/O/W emulsion. Sodium glycodeoxycholate and sodium glycochenodeoxycholate (6 mmol/l each) significantly decreased the cell viability from 5.2×10⁶ cfu/ml to 4.0×10³ and 1.3×10² cfu/ml, respectively, when the bacteria were directly dispersed in the solutions at pH 7 for 2 h. However, their incorporation in the inner-water phase of the W/O/W emulsion improved the viabilities to 1.6×10⁶ and 2.3×10⁴ cfu/ml, respectively. This improvement was ascribed to the inclusion of the bacteria in the emulsion because the viability of the bacteria, which were dispersed with the emulsion containing no bacteria in the solution, was very low. Although sodium deoxycholate decreased the viability of the cells included in the W/O/W emulsion, the inclusion significantly improved the cell viability against primary and secondary bile acids.     

Interaction of curcumin with phosphocasein micelles processed or not by dynamic high-pressure

The binding of curcumin to native-like phosphocaseins (PC) dispersed in simulated milk ultrafiltrate at pH 6.6 was assessed by fluorescence spectrophotometry. Curcumin binds to native-like PC micelles with ∼1 binding site per casein molecule, and a binding constant of 0.6–5.6 × 10⁴ M⁻¹. Dynamic high pressure (or ultra-high pressure homogenisation, UHPH) at 200 MPa did not affect the binding parameters of curcumin to processed PC. UHPH-processing of PC dispersions at 300 MPa was followed by a slight but significant (p = 0.05) increase in the binding constant of curcumin to processed PC, which may result from the significant UHPH-induced dissociation of initial PC micelles into neo-micelles of smaller sizes, and from the corresponding 1.5–2-fold increase in micelle surface area. PC–curcumin complexes were resistant to pepsin but were degraded by pancreatin, providing the possibility of a spatiotemporally controlled release and protection of bound biomolecules. UHPH-processed PC did not induce TC7-cell damage or major inflammation as assessed by LDH release or IL-8 secretion, respectively, compared with native-like PC. PC micelles could provide a valuable submicron system to vectorise drugs and nutrients.     

Rapid,simple and sensitive determination of the apparent formation constants of trans-resveratrol complexes with natural cyclodextrins in aqueous medium using HPLC

The study of the complexation of trans-resveratrol with natural cyclodextrins (CDs) in aqueous medium under different physico-chemical conditions of pH or temperature is essential if this antioxidant compound is to be used successfully in the food industry as ingredient of functional foods, due its poor stability, bioavailability and solubility. In this paper, a rapid, simple and sensitive determination of the apparent formation constant of trans-resveratrol/CD complexes by HPLC in aqueous medium has been investigated for first time. It can be observed that trans-resveratrol forms a 1:1 complex with α-, β- and γ-CD. The highest value of the apparent formation constant (K_F = 1922 ± 89 M⁻¹) was found for β-CD and a strong dependence of K_F on pH can be seen in the region where the trans-resveratrol begins the deprotonation of their hydroxyl groups. Moreover, an increase in the system’s temperature produced a decrease in the values of K_F. Finally, to gain information on the mechanism of the trans-resveratrol affinity for CD, the thermodynamic parameters of the complexation were obtained.     

Nitrosamine formation from different Catha edulis leaves extracts under simulated gastric condition

Nitrosamines are well-known carcinogenic and toxic compounds for humans and animals. The aim of this study was to investigate the possible formation of nitrosamine compounds from aqueous extracts of five different types of Catha edulis leaves using nitrite as a nitrosation agent, either in aqueous solution or under simulated normal fasting stomach conditions (at 37 °C and pH 2) for 1 h. Nitrosoephedrine was used as a reference compound in this study. Nitrosation of aqueous extracts of the different types of Catha edulis leaves with constant concentration of nitrite (14.4 mM) in aqueous solution showed total apparent nitrosamine compounds to be in the range 94–319 mg/100 g DM (dry matter) of CE (Catha edulis) leaves. In contrast, nitrosamines formed in simulated gastric fluid were much lower, in the range 23–79 mg/100 g DM of CE leaves. Based on the moderate formation of nitrosamines with the Sabri Catha edulis leaves, the latter was selected for investigating the effect of varying levels of nitrite in aqueous solution and simulated gastric juice. The nitrosation of aqueous extracts of Sabri Catha edulis with different levels of nitrite in aqueous solution yielded a dose-dependent amount of total apparent nitrosamine compounds, these being undetected at ?0.5 mM sodium nitrite in aqueous solution and ?1 mM in simulated gastric juice. This raises the question of whether the observed high incidence of esophageal and forestomach carcinomas in Yemen could be attributed to the formation of nitrosamines in vivo from the secondary amines present in Catha edulis leaves.     

Desiccation of adhering and biofilm Listeria monocytogenes on stainless steel: Survival and transfer to salmon products

The foodborne bacterial pathogen, Listeria monocytogenes, commonly contaminates foods during processing, where the microorganisms are potentially subjected to low relative humidity (RH) conditions for extended periods of time. The objective of this study was to examine survival during desiccation (43% RH and 15 °C) of biofilm L. monocytogenes N53-1 cells on stainless steel coupons and to assess subsequent transfer to salmon products. Formation of static biofilm (2 days at 100% RH and 15 °C) prior to desiccation for 23 days significantly (P < 0.05) improved survival of cells desiccated in initial low salt concentrations (0.5%) compared to the survival for non-biofilm cells also desiccated in low salt, indicating the protective effect of the biofilm matrix. Osmoadaptation of cells in 5% NaCl before formation of the static biofilm significantly (P < 0.05) increased long-term desiccation survival (49 days) irrespectively of the initial salt levels (0.5% and 5% NaCl). The efficiency of transfer (EOT) of desiccated biofilm cells was significantly (P < 0.05) lower than EOTs for desiccated non-biofilm bacteria, however, as biofilm formation enhanced desiccation survival more bacteria were still transferred to smoked and fresh salmon. In conclusion, the current work shows the protective effect of biofilm formation, salt and osmoadaptation on the desiccation survival of L. monocytogenes, which in turn increases the potential for cross-contamination during food processing.     

Bifidobacterium Bb-12 microencapsulated by spray drying with whey: Survival under simulated gastrointestinal conditions,tolerance to NaCl,and viability during storage

Bifidobacterium Bb-12 was microencapsulated by spray drying with whey. This present work investigated the survival of these microcapsules under simulated gastrointestinal conditions, as well as their tolerance to NaCl and their viability during storage. The results showed a small decrease in the viability of microencapsulated Bifidobacterium at low pH. In relation to the exposure of Bifidobacterium to bile, microencapsulation with whey did not protect the probiotic cells; however, the viability of the microcapsules remained >6 log cfu/g, even after 24 h of incubation at the highest bile concentration analyzed. No growth was noted with either the free cells or the microencapsulated cells on MRS-LP with NaCl. The viability of the microcapsules stored at 4 °C remained high and constant for 12 weeks. When the microcapsules were added to a dairy dessert, the probiotic count remained above 7 log cfu/g for 6 weeks. Therefore, whey is a promising encapsulating agent for Bifidobacterium Bb-12.     

Modelling starch digestion in sweetpotato with biphasic digestograms

The kinetics of starch digestion in 20 sweetpotato samples obtained from Papua New Guinea were investigated using an in vitro procedure based on glucometry. Irrespective of the cultivars (3-mun, Carot kaukau, Wahgi besta, Nillgai, Baiyer kaukau, and 1-mun), provinces, farmers and locations, the samples exhibited biphasic digestograms, possibly due to initial impediments to amylolysis and/or transport of digestion products by non-starch components (e.g. plant cell walls). The biphasic digestograms were segmented into two monophasic digestograms using a second-order polynomial (average r² = 0.723; p < 0.001), and a modified first-order kinetic model adequately described the digestograms (average r² = 0.984, p < 0.001; mean relative deviation modulus, MRDM, =8). Generally, the digestion rate constants (initial, K_i = 3.2-5.2 × 10⁻³ min⁻¹; final, K_f = 3.8-18.4 × 10⁻³ min⁻¹) indicated faster digestion during the final segment after the initial impediments to digestion had possibly been overcome. K_i was significantly (p < 0.05) different among the samples, which did not significantly (p < 0.05) differ in K_f. A logistic model, which treated each digestogram as a single process, also adequately described the biphasic behaviours (average r² = 0.994, p < 0.001; mean relative deviation modulus, MRDM, =15). The digestion parameters from the segment and logistic approaches significantly (p < 0.05) differed among the sweetpotato samples. The rate of digestion from the logistic model was significantly (p < 0.05) related to the initial and final rates of digestion from the segment approach (K = 3.99 K_i + 0.65 K_f; r² = 0.456; p < 0.001). Irrespective of the approach, maximum starch digestion was less than 100% in some samples to indicate the presence of resistant starch type 1, 2 or both. The present study is the first to model biphasic starch digestograms.