Cross-linked-substituted (esterified/etherified) starch derivatives as aqueous heavy metal ion adsorbent: a review.

Starch is a biopolymer with outstanding economic and environmentally friendly attributes which has driven technological innovations to enhance its applications in food and non-food industries. Starch is constituted by O-H groups with valency and electronic characteristics that can initiate adsorption of aqueous heavy metal ions (AHMIs). However, this can be enhanced using various modification sequences. A common procedure is the cross-linking and substitution of the O-H groups via esterification and/or etherification reactions to produce starch derivative adsorbents (SDAs) with improved structural and functional properties for adsorption of AHMIs. The efficiency of SDAs developed using these procedures depends on the botanical source of the native starch base, porosity and structural stability of the derivative (i.e. degree of cross-linking), substituted functional group(s), degree of substitution and the steric/conformation effects of the substituted groups. Many works have been done to optimize these factors, and this review highlighted some of the tailored procedures and the results obtained.

Nutritional implications of olives and sugar: attenuation of post-prandial glucose spikes in healthy volunteers by inhibition of sucrose hydrolysis and glucose transport by oleuropein.

PURPOSE: The secoiridoid oleuropein, as found in olives and olive leaves, modulates some biomarkers of diabetes risk in vivo. A possible mechanism may be to attenuate sugar digestion and absorption. METHODS: We explored the potential of oleuropein, prepared from olive leaves in a water soluble form (OLE), to inhibit digestive enzymes (α-amylase, maltase, sucrase), and lower [14C(U)]-glucose uptake in Xenopus oocytes expressing human GLUT2 and [14C(U)]-glucose transport across differentiated Caco-2 cell monolayers. We conducted 7 separate crossover, controlled, randomised intervention studies on healthy volunteers (double-blinded and placebo-controlled for the OLE supplement) to assess the effect of OLE on post-prandial blood glucose after consumption of bread, glucose or sucrose. RESULTS: OLE inhibited intestinal maltase, human sucrase, glucose transport across Caco-2 monolayers, and uptake of glucose by GLUT2 in Xenopus oocytes, but was a weak inhibitor of human α-amylase. OLE, in capsules, in solution or as naturally present in olives, did not affect post-prandial glucose derived from bread, while OLE in solution attenuated post-prandial blood glucose after consumption of 25 g sucrose, but had no effect when consumed with 50 g of sucrose or glucose. CONCLUSION: The combined inhibition of sucrase activity and of glucose transport observed in vitro was sufficient to modify digestion of low doses of sucrose in healthy volunteers. In comparison, the weak inhibition of α-amylase by OLE was not enough to modify blood sugar when consumed with a starch-rich food, suggesting that a threshold potency is required for inhibition of digestive enzymes in order to translate into in vivo effects.

Impact of resistant starch in three plantain (Musa AAB) products on glycaemic response of healthy volunteers.

BACKGROUND AND AIM OF THE STUDY: Plantains can be eaten in various forms providing a good opportunity to study the effect of starch type on glycaemic response, and so three products differing in their types of available carbohydrate and contents of resistant starch were tested. METHODS: Boiled unripe plantain (BUP), boiled unripe plantain crisps (BUPC), ripe raw plantain (RRP) and white bread as reference (all 25 g available carbohydrate portion) were given to ten pre-screened healthy individuals. Postprandial glycaemic responses and glycaemic indices (GI) were measured. RESULTS: Peak blood glucose for BUP, BUPC and RRP was at 45, 45 and 30 min post-meal time, respectively. The peak blood glucose concentrations for BUP, BUPC and RRP (1.8 ± 0.8, 2.3 ± 0.8, 1.9 ± 0.7 mmol/L, n = 10, respectively) reflected the in vitro quantities/types of rapidly available glucose (RAG) in the samples. On the other hand, mean GI ± SEM values obtained for the test products (BUP = 44.9 ± 3.6, BUPC = 55.0 ± 4.2, RRP = 38 ± 4.4, n = 10) were neither significantly different nor directly correlated with RAG. CONCLUSIONS: The results show a potential link between RAG and GI, but the correlation is confounded by the presence of other constituents in the plantains.