Reduction in Phytic Acid Levels in Soybeans During Tempeh Production, Storage and Frying

Soybean fermentation: Microbial ecology and starter culture technology

Fermented soybean products, including Soya sauce, Tempeh, Miso, and Natto have been consumed for decades, mainly in Asian countries. Beans are processed using either solid-state fermentation, submerged fermentation, or a sequential of both methods. Traditional ways are still used to conduct the fermentation processes, which, depending on the fermented products, might take a few days or even years to complete. Diverse microorganisms were detected during fermentation in various processes with Bacillus species or filamentous fungi being the two main dominant functional groups. Microbial activities were essential to increase the bean's digestibility, nutritional value, and sensory quality, as well as lower its antinutritive factors. The scientific understanding of fermentation microbial communities, their enzymes, and their metabolic activities, however, still requires further development. The use of a starter culture is crucial, to control the fermentation process and ensure product consistency. A broad understanding of the spontaneous fermentation ecology, biochemistry, and the current starter culture technology is essential to facilitate further improvement and meet the needs of the current extending and sustainable economy. This review covers what is currently known about these aspects and reveals the limited available information, along with the possible directions for future starter culture design in soybean fermentation.

Nutritional Composition and Estimated Iron and Zinc Bioavailability of Meat Substitutes Available on the Swedish Market

Transition towards plant-based diets is advocated to reduce the climate footprint. Health implications of a diet composed of meat substitutes are currently unknown, and there are knowledge gaps in their nutritional composition and quality. Samples of available meat substitutes were bought in two convenience stores in the city of Gothenburg, Sweden, and were included in the study. Meat substitutes (n = 44) were analyzed for their contents of dietary fiber, fat, iron, zinc, phytate, salt, total phenolics and protein, as well as for their amino acid and fatty acid composition. Bioavailability of iron and zinc was estimated based on the phytate:mineral molar ratio. We found large variations in the nutritional composition of the analyzed meat substitutes. Amino acid profiles seemed to be affected by processing methods. Mycoprotein products were rich in zinc, with a median content of 6.7 mg/100 g, and had very low content of phytate, which suggests mycoprotein as a good source of zinc. Degradability of fungal cell walls might, however, pose as a potential aggravating factor. None of the products could be regarded as a good source of iron due to very high content of phytate (9 to 1151 mg/100 g) and/or low content of iron (0.4 to 4.7 mg/100 g). Phytate:iron molar ratios in products with iron contents >2.1 mg/100 g ranged from 2.5 to 45. Tempeh stood out as a protein source with large potential due to low phytate content (24 mg/100 g) and an iron content (2 mg/100 g) close to the level of a nutrition claim. Producers of the products analyzed in this study appear to use nutritional claims regarding iron that appear not in line with European regulations, since the iron is in a form not available by the body. Meat substitutes analyzed in this study do not contribute to absorbed iron in a relevant manner. Individuals following mainly plant-based diets have to meet their iron needs through other sources. Salt and saturated fat were high in certain products, while other products were more in line with nutritional recommendations. Further investigation of the nutritional and health effects of protein extraction and extrusion is needed. We conclude that nutritional knowledge needs to be implemented in product development of meat substitutes.

Analysis of Improved Nutritional Composition of Potential Functional Food (Okara) after Probiotic Solid-State Fermentation

Okara is a major agro-waste, generated as a byproduct from the soymilk and tofu industry. Since okara has a high nutritive value, reusing it as a substrate for solid state biofermentation is an economical and environmental friendly option. Rhizopus oligosporus and Lactobacillus plantarum were the probiotic FDA-approved food-grade cultures used in this study. The study revealed that biofermenting okara improves its nutritional composition. It was found that the metabolomic composition (by GC-MS analysis) and antioxidant activity (by DPPH test) improved after the microbial fermentations. Of the two, okara fermented with R. oligosporus showed better results. Further, the metabolites were traced back to their respective biosynthesis pathways, in order to understand the biochemical reactions being triggered during the fermentation processes. The findings of this entire work open up the possibility of employing fermented okara as a potential functional food for animal feed.

Composición química y calidad nutritiva de garbanzo (Cicer arietinum L.) fresco y endurecido después de la fermentación en estado sólido (FES)/Chemical composition and nutritional quality of fresh and hardened chickpea (Cicer arietinum L) after the solid state fermentation (SSF)

Solid state fermentation (SSF) represents a technological alternative for a great variety of legumes and cereals, or combinations of them, to improve their nutritional quality and to obtain edible products with palatable sensorial characteristics. Chickpeas (Cicer arietinum L.) are prone to develop the hardening phenomenon, also known as hard-to-cook (HTC) defect, when stored under adverse conditions of high temperature (≥ 25 °C) and high relative humidity (≥ 65%). This hard-to-cook phenomenon causes increases in cooking time, decreases in nutritional quality and deterioration of sensorial attributes of chickpea. The objective of this work was to study the effect of SSF on chemical composition and nutritional quality of fresh and hardened chickpeas. The hardening of chickpea ( Cicer arietinum L. Blanco Sinaloa 92 variety) for human consumption, was produced by accelerated storage (33-35 °C, RH = 75%, 180 days). A Rhizopus stolonifer spore suspension (1 x 106 spores/mL) was used as starter for the fermentation. The temperature and time of the SSF process were 35.8 °C and 42.7 h, respectively. The tempeh was obtained from fresh and hardened chickpea. The SSF process caused a significant increase ( p ≤ 0.05) in crude protein, true protein (19.6-19.9 to 23.2-23.4%), protein solubility, in vitro digestibility (68.6-73.1% to 79.9-80.5%), available lysine (2.19-3.04 to 3.19-4.07 g lysine/ 16 N), palmitic acid, and stearic acid, and a significant decrease ( p ≤ 0.05) in lipids, minerals, linoleic acid, phytic acid (8.82-10.73 to 2.11 g phytic acid/g dry matter), and tannins (16.1-22.4 to 3 mg catechin/g dry matter). The SSF process improved significantly the quality of fresh and hardened chickpea.

The influence of traditional stir-frying with oil on acceptability, antioxidant activities, nutrients, and the phytic acid content of fermented soybean (tempeh)

Purpose

– The purpose of this paper was to investigate the acceptability of processed tempeh and the effect of stir-frying on uncooked tempeh composition, total phenolic content (TPC), antioxidant (AO) activities and the phytic acid (PA) concentration.

Design/methodology/approach

– Fermentation was performed in the solid-state using soybean (Glycine max) inoculated with Rhizopus oligosporus. The acceptability of tempeh was evaluated by administering a questionnaire. The TPC of uncooked and stir-fried tempeh was examined using Folin-Ciocalteu’s method, and PA was analyzed by high-performance liquid chromatography. AO activities were measured by the thiobarbituric acid reactive substance (TBARS) and ferric ion reducing/antioxidant power methods. The stir-fried tempeh was more acceptable than other preparations to the panelists.

Findings

– In comparison with the uncooked tempeh, stir-fried tempeh showed higher fat composition, in addition to decreased levels of minerals, PA and TBARS.

Originality/value

– Soy foods are an important source of protein. However, conventional cooking methods could change the chemical properties in soy foods. To avoid additional oil that adds calories, consumers might opt for other cooking methods, such as steaming.

Fermented soyabean and vitamin C-rich fruit: a possibility to circumvent the further decrease of iron status among iron-deficient pregnant women in Indonesia

Objective

Increasing the consumption of Fe-rich foods and thus improving Fe bioavailability without significantly increasing diet cost is the most sustainable intervention for improving Fe intake. We assessed the effect of supplementary food consisting of fermented soyabean (tempeh) and vitamin C-rich fruit consumed during pregnancy on maternal iron deficiency (ID).

Design

Pregnant women were randomly allocated by village into optimized diet and control groups. Supplementary food was given 6 d/week at home. The average weekly food provided comprised 600 g of tempeh, 30 g of meat, 350 g of guava, 300 g of papaya and 100 g of orange. Hb, ferritin and transferrin receptor (TfR) concentrations were measured at 12–20 and at 32–36 weeks of gestation.

Setting

Thirty-nine villages in Indonesia.

Subjects

Pregnant women (12–20 weeks of gestation, n 252).

Results

At baseline, mean Hb, ferritin and TfR concentrations and body Fe concentration were within the normal range and did not differ between groups. At near term, mean Hb, ferritin and body Fe decreased, whereas mean TfR increased significantly in both groups. The mean changes in Fe status were similar in both groups. In Fe-deficient women, consumption of an optimized diet was associated with smaller decreases in Hb (1·02 (95 % CI 0·98, 1·07) g/l; P = 0·058), ferritin (1·42 (95 % CI 1·16, 1·75) μg/l; P = 0·046) and body Fe (2·57 (95 % CI 1·71, 3·43) mg/kg; P = 0·073) concentrations, compared with a state of no intervention. Fe-deficient women at baseline benefited more from supplementary food compared with Fe-replete women.

Conclusions

Daily supplementary food containing tempeh and vitamin C-rich fruits during pregnancy might have positive effects on maternal ID.

Implications of antinutritional components in soybean foods

There are a number of components present in soybeans that exert a negative impact on the nutritional quality of the protein. Among those factors that are destroyed by heat treatment are the protease inhibitors and lectins. Protease inhibitors exert their antinutritional effect by causing pancreatic hypertrophy/hyperplasia, which ultimately results in an inhibition of growth. The lectin, by virtue of its ability to bind to glycoprotein receptors on the epithelial cells lining the intestinal mucosa, inhibits growth by interfering with the absorption of nutrients. Of lesser significance are the antinutritional effects produced by relatively heat stable factors, such as goitrogens, tannins, phytoestrogens, flatus-producing oligosaccharides, phytate, and saponins. Other diverse but ill-defined factors appear to increase the requirements for vitamins A, B12, D, and E. The processing of soybeans under severe alkaline conditions leads to the formation of lysinoalanine, which has been shown to damage the kidneys of rats. This is not generally true, however, for edible soy protein that has been produced under milder alkaline conditions. Also meriting consideration is the allergenic response that may sometimes occur in humans, as well as calves and piglets, on dietary exposure to soybeans.

Tempeh: a mold-modified indigenous fermented food made from soybeans and/or cereal grains

A variety of indigenous fermented foods exist today; however, tempeh has been one of the most widely accepted and researched mold-modified fermented products. Tempeh is a traditional fermented food made from soaked and cooked soybeans inoculated with a mold, usually of the genus Rhizopus. After fermentation has occurred, the soybeans are bound together into a compact cake by dense cottony mycelium. An important function of the mold in the fermentation process is the synthesis of enzymes, which hydrolyze soybean constituents and contribute to the development of a desirable texture, flavor, and aroma of the product. Enzymatic hydrolysis also may decrease or eliminate antinutritional constituents; consequently, the nutritional quality of the fermented product may be improved. Current technology and new scientific advancements have enabled researchers to examine specific strains of Rhizopus and new substrates such as cereal grains. Because Kansas produces numerous cereal grains, production of a fermented tempeh-like product using wheat, sorghum (milo), oats, rye, barley, corn, and triticale is a definite possibility for generating a Kansas Value-Added Product. In this study, several different tempeh-like products were produced using various cereal grains inoculated with Rhizopus oligosporus NRRL 2549 or R. oligosporus NRRL 2710. Grains used included hard red winter wheat, triticale, yellow sorghum (milo), and red sorghum (milo). The grain source as well as the strain of R. oligosporus used influenced the product's appearance, flavor, and patty integrity. Results showed that R. oligosporus NRRL 2549 produced more mycelium at a more rapid rate than did the R. oligosporus NRRL 2710 strain. The combination of red sorghum and R. oligosporus NRRL 2549 yielded a product with good patty texture, aroma, and appearance. Furthermore, the red sorghum fermented product was well suited for slicing. On the other hand, yellow sorghum inoculated with either R. oligosporus NRRL 2549 or R. oligosporus NRRL 2710 failed to produce an organoleptically suitable product. Triticale also was found to be an unacceptable substrate for the production of a tempeh-like product. Although the fermented wheat product had a desirable aroma and flavor, it lacked patty integrity and crumbled when sliced. Further research is needed to evaluate the economic significance and industrial applications of these tempeh-like products.

Effect of rabadi fermentation on phytic acid and in vitro digestibility of barley

Rabadi, an indigenous fermented food, was prepared by mixing cereal flour with buttermilk, allowing it to ferment at 30, 35 and 40 degrees C for 6, 12, 18, 24 and 48 h and cooking the fermented mixture for 0.5 h with continuous stirring. Two types of rabadi were prepared i.e. autoclaved and unautoclaved. In autoclaved type of rabadi cereal flour was mixed with water, autoclaved (0.103 MPa = 15 psi for 15 min), cooled, mixed with buttermilk and fermented. As this type of rabadi was precooked prior to fermentation, hence, the fermented product did not require cooking afterwards, while in unautoclaved rabadi, barley flour and buttermilk were mixed, fermented and then cooked prior to consumption. Phytic acid was reduced drastically at all the temperatures and periods of fermentation in both autoclaved and unautoclaved type of rabadi; greater reduction occurred at higher temperature and duration of fermentation. A significant improvement in the in vitro digestibility of starch and protein was observed; maximum improvement was noticed when fermentation was carried out at 40 degrees C for 48 h in both the types of rabadi. Phytic acid had a significant (P < 0.05) negative correlation with digestibility (in vitro) of proteins and starch of barley flour rabadi.

Food biotechnology review: traditional solid-state fermentations of plant raw materials--application, nutritional significance, and future prospects

This review on the use of indigenous solid-state fermentations (SSF) describes the microbiological transformation of plant raw materials into highly nutritious foods and flavor-enhancing ingredients. Traditional fermented foods from most countries of the world may be classified into the following categories: fungal fermentation followed by brining, SSF principally using bacteria, lactic acid fermentation followed by fungal fermentation, production of fermented doughs, alcoholic fermentation, and fermented food ingredients. Scientific studies of the principles behind SSF, identification of the essential microorganisms, development of suitable and versatile equipment, control of the process, and quality control of the substrate and final product can very well lead to a substantial increase at a world level in the availability and consumption of these fermented foods. The application of modern biotechnology in some countries is already changing the ancient methods of making fermented foods.