Use of pullulanase as a biocatalyst for starch hydrolysis: Part 1. Study of the effect of pullulanase on maize amylopectin starch

The use of debranching enzymes in starch hydrolysis is a topical direction for obtaining new types of starch products with controlled properties and a potential for the further use. The aim of the work was to study an effect of pullulanase (EC3.2.1.41) on maize amylopectin starch in the native and gelatinized state. The objects of the research were maize amylopectin starch and enzyme preparation Promozyme D6 (Novozymes, Denmark). High-performance liquid chromatography (HPLC) was used to determine the carbohydrate composition of hydrolysates. The mass fraction of reducing substances (RS) was determined by the Lane and Eynon method. A rotational viscometer was used to measure dynamic viscosity of the starch hydrolysis products. It was found that analyzed starch in the native state showed low enzymatic sensitivity to the action of pullulanase with insignificant changes in viscosity, solubility and iodine binding capacity of the samples. Pullulanase showed the highest effect on gelatinized starch during the first eight hours of incubation. After eight hours, the maximum degree of starch hydrolysis by pullulanase at a dose of 10 units/g dry matter (DM) was 4.7% on DM basis, iodine binding capacity of the hydrolysate was D600 = 0.343 (in the control experiment D600 = 0.154), and the viscosity of the hydrolysate decreased from 7887 mPa · s to 4.3 mPa · s. Hydrolysates cooled to 8 °C and held for 20 hours along with hydrolysates that were not cooled showed high susceptibility to attack by glucoamilase (97–98%) at 60 °C and 24 hours of saccharification, which suggested the absence of their resistance to the action of glucoamilase in the conditions of the experiment. The use of pullulanase in dextrinization of the analyzed starch, which was gelatinized and partly hydrolyzed by α-amylase (RS6.1%), enabled obtaining hydrolysates with the mass fraction of reducing substances in a range of 10–24% on DM basis with the process duration of 2 to 24 hours and the enzyme dose of 2–10 units, which contained mainly maltotriose, maltohexose and maltoheptose with their total amount of 45–60% on DM basis. The results indicate a need for further research of the biocatalytic action of pullulanase to develop new methods for enzymatic modification of starch.

The Physical and Chemical Characteristics of Potato Doughnuts Using Semi-Liquid Local Yeast Derived from Myrrh of Red Fermented Palm Sap

Natural or local yeasts are microorganisms from natural ingredients obtained from fermentation without the need for artificial additives. The objectives of the present study were 1.) to evaluate the physical quality of potato doughnuts produced from the local yeast derived from residue of red fermented palm sap, 2) to obtain the best treatment from the use of local yeast in making doughnuts. In the fermentation process, yeast converts sugar and carbohydrates in the dough into carbon dioxide gas (CO2) and alcohol. Doughnuts are made from wheat flour, but the addition of potato paste can improve the texture so that it is softer and tender due to the interaction between gelatinized starch and gluten but can reduce its swelling power. The experiment was designed using a completely randomized design (CRD) with three treatments and five replications to produce 15 experimental units. The treatments were a) Control (commercial yeast); b) Wheat flour: potato paste: local yeast; 2:1:1; c) Wheat flour: potato paste: local yeast; 2:1:2 and d) Wheat flour: potato paste: local yeast; 2:1:3. The results showed that the best treatment formula was obtained in the treatment B (wheat flour: potato paste: local yeast; 2:1:1) with 20,6% moisture content, 2,09% protein content and 3,644 color value (very like), 3,800 taste value (very like) and texture/tenderness with a value of 1032,500.

An Assessment of Starch Composition and Gelatinization in Traditional and Non-traditional Dog Food Formulations

Gelatinization of starch content in pet foods can be impacted by several factors including moisture, retention time, and ingredients used. Starch gelatinization has been associated with digestibility but isn’t well studied using ingredients common in non-traditional canine diets. The objective of this research was to examine the impacts of dietary ingredient profile (traditional vs non-traditional) and assess impacts to total starch content and starch gelatinization. Traditional diets (n = 10) utilizing meat-based ingredients including chicken, chicken by-product meal, meat and bone meal and plant-based ingredients including rice, barley, oats, and corn were examined in comparison with non-traditional diets (n = 10) utilizing meat-based ingredients including alligator, buffalo, venison, kangaroo, squid, quail, rabbit, rabbit and salmon along with plant-based ingredients including tapioca, peas, chickpeas, lentils, potato, and pumpkin. Representative samples were collected via grab sample technique (5 samples/diet) and were assessed for total starch content as well as percent starch gelatinization. Difference between ingredient type was assessed using a Students t-test in SAS 9.4. Significance was set at P < 0.05. Distribution of total starch content based on ingredient type (traditional vs non-traditional) revealed that mean total starch content was higher in traditional diets as compared to non-traditional diets (P <0.0001). Conversely, starch gelatinization was found to be higher in non-traditional diets (P < 0.0001). Total starch content and total gelatinized starch had a strong negative correlation (P < 0.01) in traditional diets, though no correlation was observed in non-traditional diets. This negative correlation indicates a decrease in total gelatinized starch associated with increased total starch content. These novel data reveal important differences between starch content and gelatinization and could impact manufacturing processes for ingredient types as well as feeding recommendations. Unpredicted variation between ingredient formulations could potentially lead to decreased digestibility and absorption and may result in nutrient deficiencies.

Valorization of Rice Straw into Cellulose Microfibers for the Reinforcement of Thermoplastic Corn Starch Films

In the present study, agro-food waste derived rice straw (RS) was valorized into cellulose microfibers (CMFs) using a green process of combined ultrasound and heating treatments and were thereafter used to improve the physical properties of thermoplastic starch films (TPS). Mechanical defibrillation of the fibers gave rise to CMFs with cumulative frequencies of length and diameters below 200 and 5–15 µm, respectively. The resultant CMFs were successfully incorporated at, 1, 3, and 5 wt% into TPS by melt mixing and also starch was subjected to dry heating (DH) modification to yield TPS modified by dry heating (TPSDH). The resultant materials were finally shaped into films by thermo-compression and characterized. It was observed that both DH modification and fiber incorporation at 3 and 5 wt% loadings interfered with the starch gelatinization, leading to non-gelatinized starch granules in the biopolymer matrix. Thermo-compressed films prepared with both types of starches and reinforced with 3 wt% CMFs were more rigid (percentage increases of ~215% for TPS and ~207% for the TPSDH), more resistant to break (~100% for TPS and ~60% for TPSDH), but also less extensible (~53% for TPS and ~78% for TPSDH). The incorporation of CMFs into the TPS matrix at the highest contents also promoted a decrease in water vapor (~15%) and oxygen permeabilities (~30%). Finally, all the TPS composite films showed low changes in terms of optical properties and equilibrium moisture, being less soluble in water than the TPSDH films.

A Starch-Milk Paste Enables the Incorporation of Ripened Cheese in Novel Fresh Cheese

Research background: Fresh cheese varieties represent an important share of the whole cheese market. Although with great variability in terms of composition and method of preparation, fresh cheese varieties are bland in flavor and their production originates whey drainage. On the other hand, the cheese market is also responsible for a significant amount of food waste. These motivated the development of a novel fresh cheese incorporating ripened cheese, which can then represent a valorization of ripened cheese surpluses. Experimental approach. A variable amount of ripened cheese was dispersed in a paste of gelatinized starch (normal corn or waxy rice) in milk, producing melted cheese bases. These cheese bases were diluted with milk, sometimes enriched with skim milk powder, and then renneted. The resultant fresh cheese was characterized for macronutrients content, and physical properties. Sensory analyses of samples incorporating mature Cheddar, goats’, or ewes’ cheese were carried out. Results and conclusions. Gel formation of the initial mixture was hindered above 8 % (m/m) incorporation of ripened cheese, which could be overcome by the addition of skim milk powder. These observations are corroborated by the hardness values from texture analysis tests. Evaluation of syneresis of different samples enabled to conclude that addition of 2 % (m/m) starch and of 2.8 % (m/m) skim milk powder contribute to reduce its magnitude by half. Sensory analysis with a consumer panel indicated a preference for a more consistent texture of the fresh cheese, and for the Cheddar flavor. Novelty and scientific contribution. A novel fresh cheese variety incorporating dispersed ripened cheese was prepared. The proposed method is versatile and quite straightforward and does not use polyphosphate salts or originate whey wastage. The fresh cheese physical and sensorial properties can be manipulated by the amounts and types of starch, ripened cheese, and skim milk powder added; such tailoring of fresh cheese properties widens product portfolio capacity for a larger number of consumer groups. The ripened cheese added can come from non-sellable pieces and unsold stocks from the retail sector, contributing to a reduction of food waste.