In vitro determination of volatile compound development during starter culture-controlled fermentation of Cucurbitaceae cotyledons

Effects of Lentilactobacillus buchneri and Kazachstania bulderi on the Quality and Flavor of Guizhou Fermented Red Sour Soup

In this study, the effects of Lentilactobacillus buchneri (L. buchneri: CCTCC M 2023228) and Kazachstania bulderi (K. bulderi: CCTCC M 2023227) on the quality characteristics and volatile flavor substances in fermented red sour soup were explored based on natural fermentation. Compared to natural fermentation (nitrite: 5.5 mg/kg; amino acid nitrogen: 0.17 g/100 g; lycopene: 63.73 µg/mL), three fortified fermentation methods using L. buchneri, K. bulderi, and both strains together significantly reduced the concentrations of nitrite (2.62, 2.49, and 2.37 mg/kg), amino acid nitrogen (0.03 g/100 g, 0.02 g/100 g, and 0.05 g/100 g), and lycopene (26.64, 32.45, and 51.89 µg/mL). Total acid content (11.53 g/kg) and lactic acid bacteria count (285.9 ± 1.65 × 106 CFU/mL) were the elements most significantly increased by fortified fermentation with L. buchneri relative to other fermentation methods. A total of 99 volatile compounds were determined in red sour soup and could be roughly classified into alcohols, aldehydes, ketones, and esters. Fortified fermentation with two strains and fortified fermentation with K. bulderi increased the content of methyl butanoate and 3-hydroxybutan-2-one-acetoin (D). This study confirmed the effects of L. buchneri and K. bulderi on the quality and flavor of fermented red sour soup and provided a theoretical basis for the fortified fermentation of red sour soup.

Evaluation and comparison of physicochemical properties, volatile substances, and microbial communities of leaf mustard (Brassica juncea var. multiceps) under natural and inoculated fermentation

Due to the uncontrolled fermentation process and unstable quality of naturally fermented leaf mustard, inoculated fermentation is receiving more attention. Here, the physicochemical properties, volatile compounds, and microbial community in leaf mustard under natural fermentation (NF) and inoculated fermentation (IF) were analyzed and compared. The contents of total acid, crude fiber, and nitrite of leaf mustard were measured. Headspace-solid phase microextraction-gas chromatography-mass spectrometry and orthogonal projection on latent structure-discriminant analysis were used to analyze the differences of volatile compounds in NF and IF leaf mustard. Moreover, Illumina MiSeq high-throughput sequencing technology was employed to reveal the composition of microbiota. The results showed that the nitrite content in leaf mustard after IF (3.69 mg/kg) was significantly lower than that after NF (4.43 mg/kg). A total of 31 and 25 kinds of volatile components were identified in IF and NF, respectively. Among the detected compounds, 11 compounds caused the differences between IF and NF leaf mustard. The results of inter-group difference analysis showed that there were significant differences in fungal flora between IF and NF samples. Saccharomycetes, Kazachstania, and Ascomycota were the landmark microorganisms in IF leaf mustard and the landmark microorganisms in NF were Mortierellomycota, Sordariomycetes, and Eurotiomycetes. The abundance of probiotics (such as Lactobacillus) in IF leaf mustard (51.22%) was higher than that in NF (35.20%) and the abundance of harmful molds (such as Mortierella and Aspergillus) was opposite. Therefore, IF leaf mustard showed the potential to reduce the content of nitrite and harmful molds and increase the beneficial volatile compounds and probiotics. PRACTICAL APPLICATION: Leaf mustard of inoculated fermentation (IF) showed better fermented characteristics than natural fermentation in terms of lower nitrite content, greater beneficial volatile substances, and better potential for increasing probiotics and reducing harmful molds. These results provided a theoretical basis for IF leaf mustard and contributed to the industrial production of fermented leaf mustard.

Microorganisms present in artisanal fermented food from South America

Artisanal fermented products (foods and beverages) are produced in an artisanal way in many countries around the world. The main purpose of fermentation is to preserve the food, improve its safety, increase the nutritional and health-promoting value and add specific flavours. In South America, there is a great variety of fermented food produced in an artisanal way. Different raw materials are used such as potatoes, sweet potato, cassava, maize, rice, milk (cow, ewe, goat) and meat (beef, goat, lamb, llama and guanaco). Some of these fermented foods are typical of the region and are part of the culture of native communities, e.g. tocosh, masa agria, puba flour, charqui, chicha, champu and cauim among others (indigenous foods). However, other fermented foods produced in South America introduced by mainly European immigration, such as cheeses and dry sausages, and they are also produced in many different parts of the world. In this work, the microbial composition of the different artisanal fermented products produced in South America is reviewed, taking into consideration the associated raw materials, fermentation conditions and methodologies used for their production.

Physicochemical, Mineral and Sensory Characteristics of Instant Citrullus lanatus mucosospermus (Egusi) Soup

Defatted egusi flour offers a food option high in protein and essential micronutrients. An instant processing method was adopted in a ready-to-eat instant soup using egusi grit, hydrocolloid, and defatted flour. A D-optimal quadratic mixture model was used to study the effect of the independent variables (grit, flour, and hydrocolloid) qualities. The quadratic model was adequate to navigate the design space for taste and appearance. The numerical optimization for appearance and taste of instant soup (IES) was used to obtain the optimal soup mix of 10 g of hydrocolloid, 57.2 of defatted flour and 17 g of grits. Sixteen trace and five major mineral elements were found in the egusi soup, with a high concentration of phosphorus (1220.4, 1326.2 and 1277.9 mg/100 g), potassium (1220.4, 1326.2 and 1277.9 mg/100 g), magnesium (822.2, 905.3 and 863.70 mg/100 g), calcium (172.3, 190.9 and 183.4 mg/100 g) and iron (53.7, 57.5 and 29.5 mg/100 g), and for instant egusi soups from boiled egusi grit (IESBG), instant egusi grit from spherified grit (IESSG) and instant egusi grit from extruded grit (IESEG), respectively. The amino acid profile of instant egusi soup offers all essential amino acids necessary to nourish the body. Phosphorus content was significantly (p ≤ 0.05) high across the three soups: 1742, 1836 and 1838 mg/100 g for IESBG, IESSG, and IESEG, respectively; IESSG and IESEG were significantly (p ≤ 0.05) higher in minerals when compared with IESBG. Instant egusi soup differed significantly (p ≤ 0.05) in lightness (L*), while the redness (a*) and yellowness (b*) did not vary significantly.

Selection and use of indigenous mixed starter cultures for mustard leaves fermentation and the improvement of cuocai characteristics

BACKGROUND

To improve the characteristics and safety of traditional cuocai, the selection and use of mixed starter cultures is important. This study aimed to isolate the main indigenous lactic acid bacteria (LABs) and yeast species from spontaneous fermented mustard leaves, and they were used as starter cultures to ferment mustard leaves.

RESULTS

Five predominant LABs, namely Q-1 (Enterococcus faecalis), G-1 (Lactobacillus plantarum), G-3 (Lactobacillus pentosus), and G-2 and G-4 (Lactobacillus buchneri) strains, and the two yeast strains J-1 (Issatchenkia orientalis) and J-2 (Issatchenkia occidentalis) were isolated from cuocai. From the results, Lb. plantarum and I. orientalis strains exhibited strong growth ability, fast acidification, and potent low-pH tolerance. Therefore, they were chosen as the mixed starter cultures to ferment mustard leaves. During the process of culture-dependent fermented mustard leaves, the changes of acidity, total crude protein, and total sugar were similar to those of culture-independent fermented mustard leaves, while the nitrite content of culture-dependent fermented mustard leaves was significantly lower than that of culture-independent fermented cuocai. According to gas chromatography-mass spectrometry analysis, the main volatile flavor compounds of fermented mustard leaves were alcohols, aldehydes, esters, and sulfides. There was no significant difference of volatile flavor compounds between the processes of culture-dependent and culture-independent fermentations.

CONCLUSION

Therefore, it was suggested that Lb. plantarum and I. orientalis strains could be used to ferment cuocai instead of the traditional ferment method to control the quality and shelf safety of cuocai. © 2017 Society of Chemical Industry.

Produce from Africa's Gardens: Potential for Leafy Vegetable and Fruit Fermentations

A rich variety of indigenous fruits and vegetables grow in Africa, which contribute to the nutrition and health of Africa's populations. Fruits and vegetables have high moisture and are thus inherently prone to accelerated spoilage. Food fermentation still plays a major role in combating food spoilage and foodborne diseases that are prevalent in many of Africa's resource disadvantaged regions. Lactic acid fermentation is probably the oldest and best-accepted food processing method among the African people, and is largely a home-based process. Fermentation of leafy vegetables and fruits is, however, underutilized in Africa, although such fermented products could contribute toward improving nutrition and food security in this continent, where many are still malnourished and suffer from hidden hunger. Fermentation of leafy vegetables and fruits may not only improve safety and prolong shelf life, but may also enhance the availability of some trace minerals, vitamins and anti-oxidants. Cassava, cow-peas, amaranth, African nightshade, and spider plant leaves have a potential for fermentation, as do various fruits for the production of vinegars or fruit beers and wines. What is needed to accelerate efforts for production of fermented leaves and vegetables is the development of fermentation protocols, training of personnel and scale-up of production methods. Furthermore, suitable starter cultures need to be developed and produced to guarantee the success of the fermentations.