Physiological and biochemical analysis of peanut seeds ( Arachis hypogaea ) after storage using silica gel

. Peanuts contain high enough nutrients, especially protein and fat. The high fat and protein content in peanut seeds causes deteriorate faster during storage. Special treatment is required to reduce the deterioration. This study aimed to analyze the physiological and biochemical responses of peanut seeds after being stored using silica gel 120 days. This research used a completely randomized design and used the Pearson correlation test. Seeds were stored with different dosages of silica gels: control, 10gr, 20gr, and 30gr. The observed variables consisted of maximum growth potential, germination percentage, vigor index, relative growth speed, growth uniformity, seed water content, fat, and protein seeds. The results showed that storage using silica gel dosage had a significant response on maximum growth potential, germination percentage, vigor index, relative growth speed, and growth uniformity. Using silica gel treatment with a dose of 30g showed better seed viability and vigor values than other treatments. Based on the results of the correlation analysis of seed protein content, there was a strong correlation in the viability and vigor of seeds.


Introduction
Food crop commodities have a major role in meeting the needs of domestic food, feed, and industry.One of the potential food crop commodities to be developed in Indonesia after soybeans and green beans are peanuts.Peanuts contain high enough nutrients, especially protein and fat.According to the research 100g of raw peanuts contains about 25.8% of protein and 49.2% of fat [1].
Peanut production in Indonesia in 2019-2020 tends to decrease, in 2019 peanut production was 420,009 tons, but production in 2020 decreased by 7,562 tons [2].The availability of good quality seeds is one of the limiting factors in national peanut production, in that case, peanut seeds have a low storability.According to Sadjad [3] peanut seeds in a storage period of 3 months at room temperature of 300C and 14% of moisture content, cause a decline in the viability and vigor of the seed.Peanut seeds cannot be stored for long and cause a low interest for breeders in producing peanut seeds [4].
There are internal and external factors that affect seed viability and vigor during storage.Internal factors include the genetic characteristics of the seed, including the biochemical character of the peanut seed.Meanwhile, external factors include seed packaging conditions, gas composition, temperature, and storage place humidity [5].Seed viability and vigor decrease when the water content in the seeds is high during storage [6].Seeds have hygroscopic properties while the water content of the seeds will follow the level of humidity in the storage room [4].Seed moisture content is high enough to trigger the process of seed metabolism and respiration, under those circumstances, the rate of seed deterioration will increase, and the seeds will be easily infected with fungi, bacteria, or viruses.Proper treatments in storage can maintain the viability and vigor of seeds, hence overcoming these problems can be done by using desiccant materials.
Desiccant is a material needed to keep the seeds dry.In addition, the use of desiccants can maintain the humidity around the seeds, while the moisture content of the seeds can be maintained.Also, using desiccant material can maintain seed quality [7].There are several types of desiccants that can be used in seed storage, one of the desiccant materials is silica gel [8].Silica gel is a drying agent which can absorb high moisture in the seeds to avoid condensation, resulting in the water content in the seeds increasing [6].In addition, silica gel can absorb water content around the seeds, while the moisture content remains in a balanced state [9].
Based on research the desiccant or silica gel has the best water vapor absorption capacity compared to zeolite and alumina [8].Peanut seeds stored in aluminum foil bags lined with malathion and stored in polyvinyl bags with a desiccant using silica gel had the highest germination percentage [10].Furthermore, based on the results of research the use of silica gel as a storage package had a significant effect on the longevity potential of corn seeds compared to the control treatment (without silica gel), with storage in containers at a ratio of 1:1 (100 g gel/ 100 g seeds) can maximize the extension of storage life of corn seeds [11].Drying using silica gel was the best alternative to be used as a seed drying method, and also the results showed that the use of silica gel resulted in the highest germination percentage of 66.2% compared to drying using shade, sun, and seed dryer [12,13].Thus, this study aimed to analyze the physiological and biochemical responses of peanut seeds after being stored using silica gel for 120 days.

Research methods
This research was conducted at the Agrotechnology Seed Technology Laboratory, Faculty of Agriculture, Teuku Umar University.The analysis of the biochemical content was carried out at the Laboratory of Research and Industrial Standardization of Banda Aceh.The peanut seeds used were the Kelinci variety.This study used a non-factorial randomized block design consisting of 4 doses of silica gel, namely: 0gr, 10gr, 20gr, and 30gr.Peanut seeds totaling 150 grains were stored in airtight jars which were placed together with silica gel at room temperature (temperature 25-27 0 C and humidity 69-70%.)for 120 days.The physiological parameters of seeds consist of seed moisture content, maximum growth potential, germination power, vigor index, relative growth rate, and growth uniformity.Meanwhile, the observation parameters for seed biochemistry consisted of protein content using the Kjeldahl test method and seed fat content using the Soxhletation test method.Analysis of correlation between parameters using Pearson correlation analysis (Fig. 1).

Physiological response of seeds to the use of silica gel
The results of analysis of variance showed that the silica gel treatment had a very significant effect on the parameters of germination, vigor index, maximum growth potential (%), relative growth speed (%/Etmal) and growth uniformity, but had no significant effect on water content variables.The average physiological response of peanut seeds after being stored for 120 days using silica gel is presented in Table 1.Table 1 shows the maximum growth potential, germination, vigor index, growth uniformity, and the highest relative growth speed were found in the 30 g silica gel dose treatment (which was significantly different from the 10 g dose treatment but not significantly different from the control treatment and 20 g silica).The best treatment for the parameters of maximum growth potential, germination, vigor index, relative growth speed, and growth uniformity was discovered at a dose of 30 g of silica gel.This is in line with the role of silica gel, while the silica gel acts as a water vapor absorber causing the seed moisture content to be optimal, with optimal moisture content during storage the deterioration process will be slow.This result is in line with the research while silica gel has high moisture adsorption properties at high humidity levels.With the ability to absorb water vapor quickly, silica gel can be used for air drying in the seed storage room [14].The results showed that the use of silica gel as a storage package had a significant effect on the potential seeds' longevity compared to the control treatment (without silica gel) [11].Furthermore, the research also shows using silica gel was the best alternative to be used as a seed drying method [12].
The results also showed that the silica gel dose of 10 g tended to cause the water content of the seeds to be higher compared to other treatments (Fig. 4).This is presumably because the 10 g dose of silica gel is the smallest dose, so the absorption of water vapor by the silica gel also becomes lower.With the low absorption of water vapor during the storage period, the smallest dose of silica gel reaches the saturation point faster.These results are in line with the research results of silica gel will continue to absorb water vapor if it has not reached the saturation point [8].On the contrary, the absorption of silica gel will begin to decrease when the silica gel has reached the saturation point.The use of silica gel with a high ratio in peanut and corn seeds will be more effective than with a low ratio [15,11].

Biochemical response of seeds with the use of silica gel
Analysis of the protein and fat content of the seeds was carried out after the seeds were stored for 120 days, the average protein and fat content of the seeds were shown in Table 2.
Based on the data, Table 2 shows the average protein content of seeds increased by 0.20% after 120 days of storage.The increase in protein content is assumed to be due to the defense mechanism of the seeds against storage time.This result is also in line with the results of research ebony seeds stored for 8 weeks showed an increase in protein content which is a seed mechanism to survive under optimal conditions [13].In addition, according to Gifford [16], specific protein synthesis is needed to maintain embryonic dormancy.Also, the results of Sobari [17] study where cocoa seeds were stored for 4 weeks showed a higher protein content.
Meanwhile, seed fat content tends to decrease by an average of 0.155%.Fat content decreased and fatty acid levels increased [17].Decreased fat content in seeds due to the hydrolysis reaction of fat into fatty acids [18].Table 2 also shows that the 30g dose showed a relatively lower change compared to the other treatments.

Correlation Analysis between physiological and biochemical responses of seeds
Correlation values are presented in Table 3.Based on the Pearson correlation analysis between the physiological and biochemical responses of the seed, showed the water content of the seed had a moderate and positive correlation.On the other hand, the protein and fat content of the seeds variable were a moderate but negative correlation.This indicates that the fat content of the seed will decrease if there is an increase in the moisture content of the seed.Meanwhile, protein content also showed a strong correlation to the parameters of maximum growth potential, germination, relative growth speed, and growth uniformity.This indicates the protein content of the seed will affect the viability and vigor of the seed, whereas if there is damage to the protein content of the seed, it will cause a decreased viability and vigor value of the seed.

Conclusion
Using silica gel treatment had effect to phsyological and biochemical of seeds after being stored for 120 days.Silica gel dose of 30g showed better value on seed viability, vigor, protein and fat content than other treatments.Based on the results of the correlation analysis of seed protein content, there was a strong correlation in the viability and vigor of seeds.

Fig. 2 .
Fig. 2. Seed viability and vigor storage effect using silica gel for 120 days (a: control; b: 10gr dosage of silica gel, c: 20gr dosage of silica gel, d: 30 gr dosage of silica gel).

Table 1 .
Average seed viability and vigor storage effect using silica gel for 120 days.The line number followed by the same letter is not significantly different based on LSD test 5%.

Table 2 .
The effect of storage using silica gel on protein and fat content of soybean.