starch gelatinisation
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Genetic engineering of maize plants for improved yield, drought and pest resistance has received considerable attention in agricultural research. The aim of this work is to determine the effect of genetic modification of maize plant on some pharmaceutically relevant fundamental properties of its isolated starches. Properties of starches isolated from PVA 39 and IWD 15 maize genotypes were compared with starch from unmodified maize grains. Morphology studied by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) were evaluated. Swelling capacity, amylose content, pasting behaviour of the starches were also determined. SEM revealed that all the starches are largely irregular and polygonal with few round shaped granules. FTIR showed identical peaks in all the starch samples and DSC revealed higher enthalpies of starch gelatinisation from the modified grains. Modification also increased amylose content, swelling capacity and viscosity of the starches. Genetic modification increased amylose content which positively affected pharmaceutically important properties like moisture sorption and viscosity, thus, increasing their value in formulations especially as binders.

Ensuring aquafeeds meet the expected nutritional and physical specifications for a species is paramount in research and for the industry. This study aimed to examine the feasibility of predicting the proximate composition and starch gelatinisation (or cook) of aquaculture feeds (aquafeeds) regardless of their intended target species by near infrared (NIR) spectroscopy. Aquafeed samples used for nutrition experiments on various aquatic species with different nutritional requirements, as well as aquafeeds manufactured under varying extrusion conditions and steaming time to generate variable starch cook were used in this study. The various size pellets were ground before scanning by NIR spectroscopy, then models were developed to estimate dry matter, ash, total lipid, crude protein, and gross energy as well as starch cook. Proximate prediction models were successfully produced for diets with R2 values between 0.88 and 0.97 (standard error of cross-validation (SECV) 0.43 to 1.46, residual predictive deviation (RPD) 4.6 to 15.6), while starch cook models were produced with R2 values between 0.91 and 0.97 (SECV 3.60 to 5.76, RPD 1.2 to 1.9). The developed NIR models allow rapid monitoring of the nutritional composition, as well as starch cook, one of the major physical properties of aquafeeds. Models that provide rapid quality control assessment of diet characteristics is highly desirable in aquaculture research and the aquafeed industry.

Sugar has multiple roles in baked products; competing for water and as such reducing starch gelatinisation and gluten development, behaving as a fluid during cooking, recrystallising on cooling; roles which influence properties such as aeration, texture and mouthfeel. Partial replacement with inulin, can provide beneficial nutritional and functional properties. This paper investigated the degree of polymerisation (DP) of two commercial inulins and their influence on baked product properties as a 30% sugar replacer. The two inulins varied substantially in their proportion of longer fructans (32.7% compared to 17.5% of DP > 11). The lower DP inulin led to a cake batter with very similar viscoelastic properties to the standard sugar batter, and subsequently to a very similar baked cake crumb structure, cake texture and mouthfeel. The higher DP inulin led to a more viscous batter, and cake with a less homogenous crumb structure that was perceived to be dryer and more mouthcoating. The subsequent use of the lower DP inulin in a biscuit formulation resulted in a slightly less elastic dough and consequently a softer and less crunchy biscuit. In summary, the success of inulin in providing functional properties that can enable sugar reduction in baked products is dependent on the degree of polymerisation of the inulin and rheological parameters needed in the specific bakery matrix.

Disulphide bonds and sulphhydryl concentrations were evaluated to determine the effects on rheological, thermodynamic, pasting, and dynamic rheological characteristics of mixed flours. Gluten samples, first treated with sodium sulphite of different concentrations, were added into flour at a 4% level, which had a significant impact on free sulphhydryl, disulphide bonds, and the ratio of the two indices. There was no relevance between the ratio and other parameters except for free sulphhydryl. The mixed flour doughs had reduced water absorption, dough development time, dough stability time as well as degree of weakening (P < 0.05). Disulphide bonds were associated negatively with the rate of starch gelatinisation (C3–C2), peak, and setback and these characteristics were correlated strongly with dough development time, dough stability time, and progressive protein weakening (C2–C1). The stability of starch gelatinisation and cooking stability of mixed flours did not remain significantly different. The larger the concentration of sodium sulphite, the higher the peak, breakdown, final viscosity, and setback values, but there were no significant differences between samples. For all samples, storage modulus and loss modulus increased with increasing scanning frequency. For mixed doughs, the trend lines of moduli decreased with increasing levels of reduction in added gluten. There was no substantial effect on thermal properties of flours.

NaCl promotes starch gelatinisation via selective interactions with –OH groups and assists auto-catalysed hydrolysis, reducing energy use by 70% in microwave compared to conventional heating.

AbstractThe glycaemic index (GI) concept has highlighted the detrimental metabolic impact of consuming foods high in rapidly released carbohydrates. However, diverse food properties such as slow release carbohydrates, viscous fibre, fructose, fat and protein can all result in foods with low GI values, with not all of them considered to be health beneficial.The study aim was to identify the mechanisms responsible for the GI values for various food groups. Data was collated and evaluated for GI, presented here as mean (range), macronutrient composition and starch digestibility measures with a focus on slowly digestible starch expressed as percent available starch (%SDS).Wheat breads had high GI values for both white, 73 (59–88) and wholemeal, 70 (52–85). While wheat flour contains > 50% SDS, the moist heat conditions during baking gelatinises starch and most breads had low %SDS 5 (3–10). Rye breads containing kernels had lower GI, 59 (41–78) and higher %SDS, 16 (12–24). Cooked grains had diverse GI 57 (29–75), with a key determinant being kernel integrity, influenced both by grain type and cooking conditions. Typical GI and %SDS values respectively for cooked grains were: white rice 65, 28; bulgur wheat 48, 40; pearl barley 29, 53. Pasta was similar in that matrix integrity determines starch digestibility and hence GI, 49 (40–57). Pasta thickness, ingredients and cooking time all influence %SDS 37 (30–47). The fat and sugar in bakery products sometimes contributed to lower GI, 66 (55–92), while the %SDS was low 5 (1–9). For biscuits, varied moisture content during baking impacts on the extent of starch gelatinisation explaining the range in %SDS 24 (12–42) and GI 51 (47–56). Crackers are baked with high moisture and consequently had low %SDS, 6 (5–7) and high GI, 67 (60–78). Breakfast cereals, produced by extrusion had low %SDS, 3 (2–4), but sugar contents contributed to a wide GI range, 69 (46–87).This study highlights the prevalence of rapidly digestible starch in many types of cereal based foods, due to processing techniques that result in easily dispersed food matrices and gelatinised starch. High fat and sugar products can have low or medium GI values despite having high contents of rapidly released carbohydrates, and as such GI could be considered an inconsistent measure of carbohydrate quality. Having information on starch digestibility profiles can identify the low GI foods that are rich in slow release carbohydrates, the consumption of which should be promoted.

Mixolab has been used for rapid assessment of common wheat quality, but data about hulled wheats quality are rare. The aim of this work was to test the potential of Mixolab II in the baking quality evaluation of emmer wheat varieties. The varieties were characterised by low both – gluten content (1.7–11.0%) and Zeleny sedimentation (11.3–12.8 ml), as well as rheological properties showed lower baking quality. Significant differences in protein and starch-amylase part of Mixolab curve indicate the genotype and climatic effect. In average, emmer varieties were characterised by high protein weakening (C2 – 0.29 Nm), speed of protein weakening at the level of α = –0.05 Nm/min, starch gelatinisation (C3 – 1.61 Nm), amylolytic activity (C4 – 1.35 Nm) and starch retrogradation (C5 – 1.98 Nm). Zeleny test positively correlated with difference C1-C2 and slope α. Falling number positively correlated with C3, C4, C5 and slope γ. Farinograph dough stability, gluten content together with Mixolab parameter C2 are the most promising characteristics to predict baking quality of emmer.

AbstractThe source of starch may interfere with glycaemic control in dogs, but few studies have evaluated these aspects in diabetic dogs. This study compared the effects of two isonutrient diets with different starch sources, peas and barley (PB) v. maize (Mi), on diabetic dogs. The Mi diet was processed in order to generate a lower starch gelatinisation index. In all, fifteen adult diabetic dogs without other conditions were included. The animals were fed two dry extruded rations with moderate levels of fat and starch and high levels of protein and fibre using a random, double-blind cross-over design. Glycaemic curves over 48 h were developed via continuous glucose monitoring after 60 d on each diet and with the same neutral protamine Hagedorn (NPH) insulin dosage. The following were compared: fasting, mean, maximum and minimum blood glucose, maximum and minimum glycaemia difference, glycaemic increment, area under the glycaemic curve, area under the glycaemic increment curve and serum fructosamine concentration. Paired t tests or Wilcoxon signed-rank tests were used to compare the amount of food and nutrients ingested and the dietary effects on glycaemic variables between the diets. Dogs fed the PB diet presented a lower average mean interstitial glucose (P=0·01), longer mean hypoglycaemic time (P<0·01), shorter mean hyperglycaemic time (P<0·01) and smaller difference between maximum and minimum blood glucose levels (P=0·03). Thus, the processing applied to the Mi diet was not sufficient to achieve the same effects of PB on glycaemic control in diabetic dogs.

AbstractWhole-grain oats have been identified as a type of food that blunts blood glucose increase after a meal. However, processing of oats changes the physical characteristics of the grain, which may influence human glycaemic response. Therefore, the effect of different processes on acute postprandial glycaemic response, quantified using glycaemic index (GI) measurements, was investigated in a systematic review. A review of the literature identified twenty publications containing fifty-six individual tests. An additional seventeen unpublished tests were found in an online database. Of the seventy-two measurements included in the review, two were for steel-cut oats, eleven for large-flake oats, seven for quick-cooking (small flake) oats, nine for instant oatmeal and twenty-eight for muesli or granola. One granola measurement was identified as an outlier and was removed from the statistical analysis. In all, fifteen clinical tests were reported for rolled oat porridge that did not specify the type of oats used, and thus the effect of processing could not be assessed. Steel-cut oats (GI=55 (se 2·5)), large-flake oats (GI=53 (se 2·0)) and muesli and granola (GI=56 (se 1·7)) elicited low to medium glycaemic response. Quick-cooking oats and instant oatmeal produced significantly higher glycaemic response (GI=71 (se 2·7) and 75 (se 2·8), respectively) than did muesli and granola or large-flake oatmeal porridge. The analysis establishes that differences in processing protocols and cooking practices modify the glycaemic response to foods made with whole-grain oats. Smaller particle size and increased starch gelatinisation appear to increase the glycaemic response.