The effects of the methods (drying and grinding in the liquidiser) on the crude protein solubility of Mimosa pigra and Water spinach

Nguyen Thi Thu Hong^1,2 and Nguyen Thi Ngoc Trang³

¹ An Giang University, An Giang, Vietnam
ntthong@agu.edu.vn
² Vietnam National University Ho Chi Minh City, Vietnam
³ Faculty of Natural Resources - Environment, Kien Giang University, Vietnam

Abstract

The experiment aimed at investigating effects of the methods of drying and grinding on the crude protein solubility of foliage of Mimosa pigra and Water spinach, was carried out at Central Laboratory of An Giang University from March to May 2022.

The objectives were to determine the effects on the protein solubility in leaves of Mimosa pigra and foliage of water spinach of sun drying, oven-drying at 65^oC or 100^oC; and of e grinding the fresh foliage in a liquidizer.

Protein solubility was very much higher in leaves of water spinach than on leaves of mimosa. Solubility N is grinding the fresh foliage, followed by the sun dry and drying at 65^oC and lowest values for the drying at 100^oC treatment

Keywords: solution, nitrogen, legume, methods, environment

Introduction

Mimosa pigra (Mimosaceae) is originated from Central America (Lonsdale 1992). In Vietnam, local names of Mimosa pigra are Nguu Ma Vuong, Trinh Nu Nhon or Mac co. Mimosa pigra is an invasive legume that has colonized appreciable areas in Vietnam (Tran Triet et al 2007). The protein in the Mimosa pigra was of low solubility (10.1%) which is attributed to complexes formed with associated phenolic compounds such as tannins that are present in Mimosa pigra. It is hypothesized that the low solubility of the mimosa protein would favour its escape from the rumen ad the decrease in a fermentable substrate in the rumen would create conditions less favourable to the formation of methane (Nguyen Thi Thu Hong et al 2021).

Water spinach (Ipomoea aquatica) plays an important role for farmers in rural areas. The crude protein content in the leaves and stems can be as high as 32 and 18% in dry basis, respectively (Ly Thi Luyen 2003). However, the protein which is considered to be highly degradable by rumen microbes (Kongmanila et al 2007). The solubility of the protein was high in the water spinach with 70 -77.8%/CP (Ho Quang Do et al 2013; Nguyen Thi Ngoc Trang and Nguyen Thi Thu Hong 2021).

Ruminant production needs to strictly control methane emissions, which is one of the important factors contributing to the prevention of global warming. At the same time, reducing methane emissions also contributes to improving economic efficiency in livestock production by minimizing nutrient loss of feeds. Preston and Leng (2021) propose to refine the nomenclature for identifying protein sources that are of low solubility and that it is this characteristic that facilitates the partial escape of the protein from the rumen fermentation. This is optimize ruminant production and at the same time minimize emissions of methane in ruminants (Preston et al 2021).

Material and methods

Location

This experiment was carried out at An Giang University.

Design and treatments

The experiment was designed in a 2*2 factorial arrangement with 4 replications. The first factor was Mimosa or Water spinach. The second factor were methods : sun drying; drying at 65^oC or 100^oC; and grinding the fresh foliage in the liquidiser.

Measurements and chemical analysis

(1) For sun drying treatment: 100g fresh foliage/ treatment units (Mimosa or water spinach) was dry in the sun 2 days. After that, they was grinding to 1 mm screen

(2 and 3) The drying treatments: 100g fresh foliage/ treatment units (Mimosa or water spinach) was drying at 65^oC or 100^oC in the convection dryer. After that, they was grinding to 1 mm screen

For 1, 2 and 3 treatments, the solubility of the protein was determined by shaking 3 g of dried samples in 100 ml of 1M NaCl for 3h then filtering through Whatman No. 4 filter paper, and determining the N content of the filtrate (Whitelaw and Preston 1963).

(4) For grinding the fresh foliage in the 1M salt solution: 10g of the fresh foliage / treatment units (Mimosa or water spinach) was ground (Photo1) in 100ml of 1M salt solution to pass through a 1mm screen (Photo 2).

Photo 1. Grinding the fresh foliage along with 1M salt	Photo 2. Screening through a 1 mm sieve

After, they were submitted to shaking (Photo 3) for 3hours then filtered through Whatman No. 4 filter paper (Photo 4). Finally the were analyzed for nitrogen by AOAC (1990) method and determining the N content of the filtrate.

Photo 3. Shaking sample vessels	Photo 4. Filtered through Whatman No. 4 filter paper

The samples of Mimosa and water spinach were analyzed by AOAC (1990) methods for: dry matter (DM) by drying at 105⁰C for 24h; organic matter (OM) by ashing at 550⁰C for 4h; and crude protein (CP) by Kjeldahl technique. The condensed tannin content of feeds was determined by the Lowenthal method (AOAC 1936).

Statistical analysis

The data were analyzed by the general linear model in the Minitab software (Minitab 2010). Sources of variation were: treatments, repetitions and error.

Results and discussion

Both the foliages had high levels of crude protein (Table 1).

Soluble protein of the fresh water spinach leaves was 64.25% in CP (Table 2). This high value was also found by Ho Quang Do et al (2013) and Nguyen Thi Ngoc Trang and Nguyen Thi Thu Hong (2021).

The study showed that protein solubility in both mimosa and water spinach show the same trends with highest values for fresh leaves followed by drying at 65°C and lowest values for oven-drying at 100°C (Table 3).

Figure 1. Effect of method/temperature of drying on protein solubility of foliage from Mimosa pigra and water spinach

Conclusions

• The protein solubility of mimosa leaves was much lower than in leaves of water spinach
• In both species of leaves protein solubility was highest in fresh leaves followed by the sun dry and drying with lowest values oven-drying at 100^oC.

References

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