Effect of various types of fermentation on in vitro protein and starch digestibility of differently processed pearl millet

Millet starch: A review

The demand for millets and their products is becoming popular globally due to their various health-promoting properties. The major constituent of the millet is its starch which contributes about 70% of total millet grain and decides the quality of millet-based food products. The application of starch for various purposes is dependent upon its physicochemical, structural, and functional properties. A native starch does not possess all the required properties for a specific use. However, product-specific properties can be achieved by modifying the structure of starches. Information deficit on millet starch has undermined its potential use in new food product design. The objective of this review is to examine the chemical composition, characterization, structural chemistry, digestibility, hydrolysis, and modification techniques of the millet starches. The review paper also discusses the various applications of native and modified starches in the food industry.

Effect of decortication methods on the chemical composition, antinutrients, Ca, P and Fe contents of two pearl millet cultivars during storage

Purpose

The purpose of this paper is to evaluate the impact of modern and traditional decortication methods on the chemical composition, antinutrients, Ca, P and Fe contents during storage of two pearl millet cultivars (white and green) grown in Sudan.

Design/methodology/approach

The grains of each cultivar were either decorticated traditionally using traditional stone dehuller or by using modern dehuller. The chemical composition, antinutrients and Ca, P and Fe contents of the cultivars were evaluated during storage for six months.

Findings

The results showed that both methods of decortication (modern and traditional) employed significantly decreased ash, protein, oil and crude fiber contents but increased moisture and nitrogen free extract contents of the grains for both cultivars. Storage resulted in a slight and gradual decrease in the chemical composition of the treated and untreated grains of the cultivars. Modern decortication of the grains significantly (P=0.05) reduced tannin content in both cultivars compared to untreated and traditionally decorticated grains. Phytic acid content of the white cultivar was not affected by the method of decortication used but modern decortication reduced that of green cultivar. Decrease in tannin and phytic acid was observed as the storage continued in both treated and untreated cultivars. Decortication significantly (P=0.05) reduced the Ca, P and Fe contents in both cultivars grains. Lower P and Fe contents were found in modern decorticated grains compared to traditional decorticated ones. Storage of the cultivars resulted in gradual decrease in Ca, P and Fe contents.

Research limitations/implications

Processing methods such as decortication affect the quality attributes of pearl millet cultivars. The application of modern decortication method on pearl millet cultivars has better quality attributes than those treated with traditional decortication.

Originality/value

The study uses decortication methods (traditional and modern) to improve the quality attributes of pearl millet cultivars. Antinutrients such as tannin and phytic acid were observed to reduce the bioavailability of minerals like Fe. Decortication of the grains significantly reduced the level of such antinutrients and improved bioavailability of minerals.

In vitro dynamic model simulating the digestive tract of 6-month-old infants

Background

In vivo assays cannot always be conducted because of ethical reasons, technical constraints or costs, but a better understanding of the digestive process, especially in infants, could be of great help in preventing food-related pathologies and in developing new formulas with health benefits. In this context, in vitro dynamic systems to simulate human digestion and, in particular, infant digestion could become increasingly valuable.

Objective

To simulate the digestive process through the use of a dynamic model of the infant gastroenteric apparatus to study the digestibility of starch-based infant foods.

Design

Using M.I.D.A (Model of an Infant Digestive Apparatus), the oral, gastric and intestinal digestibility of two starch-based products were measured: 1) rice starch mixed with distilled water and treated using two different sterilization methods (the classical method with a holding temperature of 121°C for 37 min and the HTST method with a holding temperature of 137°C for 70 sec) and 2) a rice cream with (premium product) or without (basic product) an aliquot of rice flour fermented by Lactobacillus paracasei CBA L74. After the digestion the foods were analyzed for the starch concentration, the amount of D-glucose released and the percentage of hydrolyzed starch.

Results

An in vitro dynamic system, which was referred to as M.I.D.A., was obtained. Using this system, the starch digestion occurred only during the oral and intestinal phase, as expected. The D-glucose released during the intestinal phase was different between the classical and HTST methods (0.795 grams for the HTST versus 0.512 for the classical product). The same analysis was performed for the basic and premium products. In this case, the premium product had a significant difference in terms of the starch hydrolysis percentage during the entire process.

Conclusions

The M.I.D.A. system was able to digest simple starches and a more complex food in the correct compartments. In this study, better digestibility of the premium product was revealed.

Effects of lactic acid fermentation and gamma irradiation of barley on antinutrient contents and nutrient digestibility in mink (Mustela vison) with and without dietary enzyme supplement

The experiment was conducted to study the effects of fermentation of barley, using two different strains of lactic acid bacteria, a Lactobacillus plantarum/pentosus strain isolated from spontaneously fermented rye sourdough (AD2) and a starch-degrading Lactobacillus plantarum (AM4), on contents of mixed-linked (1 --> 3) (1 --> 4)-beta-glucans, alpha-amylase inhibitor activity, inositol phosphates, and apparent digestibility of macronutrients in mink. Effects of fermentation were compared with effects of gamma irradiation (gamma-irradiation: 60Co gamma-rays at 25 kGy). The diets were fed to mink with and without a supplementary enzyme preparation. Both lactic acid fermentation and gamma-irradiation followed by soaking and incubation, reduced concentrations of soluble beta-glucans, phytate and alpha-amylase inhibitor activity. Dietary enzyme supplementation increased significantly digestibility of crude protein, fat, starch and crude carbohydrate (CHO). Fermentation of the barley increased digestibility of starch and CHO. Fermentation with lactic acid bacteria AD2 resulted in higher starch and CHO digestibility than strain AM4, and had greater effect than gamma-irradiation, soaking and incubation. The highest digestibility of starch and CHO was obtained after AD2 fermentation followed by enzyme supplementation. It is concluded that both lactic acid fermentation of barley and enzyme supplementation have positive nutritional implications in the mink by limiting the effects of antinutrients and improving digestibility and energy utilization.

Effect of probiotic fermentation on antinutrients and in vitro protein and starch digestibilities of indigenously developed RWGT food mixture

Indigenously developed RWGT food mixture which contained rice flour, whey, sprouted green gram paste and tomato pulp (2:1:1:1 w/w) was autoclaved 1.5 kg/cm2, 15 min, 121 degrees C), cooled and fermented with 2% liquid culture (containing 10(6) cells/ml broth). Two types of fermentations were carried out i.e. single culture fermentation [L. casei, L. plantarum (37 degrees C, 24 hr.)] and sequential culture fermentation [S. boulardii (25 degrees C, 24 hr.) + L. casei (37 degrees C, 24 hr.)]; S. boulardii [(25 degrees C, 24 hr.) + L. plantarum (37 degrees C, 24 hr.)]. All the fermentations drastically reduced the contents of phytic acid, polyphenols and trypsin inhibitor activity while significantly improving the in vitro digestibilities of starch and protein. Sequential culture fermentations brought about higher changes as compared to single culture fermentations.