Agricultural Science Research Journal 4(2); pp. 39- 43, February 2014 Available online at http://www.resjournals.com/ARJ ISSN: 2026 – 6332 ©2014 International Research Journals

Full Length Research Paper

Performance study regarding dehydration and quality characteristics of Mushroom (Pleurotus ostreatus)

DEVENDRA KUMAR, LALMANI, RAJEEV SINGH

Baba Saheb Dr. Bhim Rao Ambedkar College of Agricultural Engineering and Technology, Etawah- 206001 Uttar

Pradesh, India

Faculty of Technology of Chandra Shekhar Azad University of Agriculture and Technology, Kanpur

*Corresponding Author’s Email: rajeev.abmcsa@gmail.com,Email: lalmani1859@rediffmail.com, devendrachaturvedi2008@gamil.com

Abstract

Mushrooms are the most edible fungus. They are soft, textural and highly perishable. They begin to deteriorate harvest owing to their most important causes namely microbes, enzymatic and chemical. Dehydration, canning and freezing have been found suitable for its preservation. Dehydration process is simple and economical. It reduces weight and volume by nearly 1/10 of its original. The performance study was undertaken to assess the effect of pre-treatment on dehydration characteristics of mushrooms at drying temperature of 50, 60 and 70

0C using air velocity of 1.5m/s. The study also

covered the effects of parameters on the quality characteristics of the dehydrated products. Dehydration characteristics of oyster pleurotus variety of mushroom were studied. Both untreated and treated ( steam blanching followed by sulphating and citric acid pre-treatment before drying) mushroom were dried in the thin layer set up at each of the drying air temperature 50, 60, and 70

0C for the air

velocity of 1.5 m/s. In thin layer drying mushroom dried under constant rate period for the short time at the beginning, subsequently it dried under falling rate period for the rest of the time. Rate of drying increases with the increase of drying air temperature of both treated and untreated mushrooms at particular air velocity. The quality characteristics of dehydrated mushrooms were analyzed. The colour and flavour of treated samples were appeared to be better. Rehydration ratio of untreated samples was found to be greater than those of the treated one. The texture of curry prepared from treated sample was a whole acceptable. Taking drying time and quality of the dehydrated product into account, a combination of drying air temperature of 60

0C and air velocity of 1.5 m/s appears to be suitable for

drying of both treated and untreated mushroom for good dehydrated products. Key Words: Mushroom, drying air temperature, air velocity, Rehydration ratio.

INTRODUCTION Mushrooms are saprophytic fungi. They are relished for their characteristics aroma and texture in the preparation of wide variety of dishes. Mushroom produces high quality of protein from worthless agro wastes. India is presently producing 50,000 tones mushroom per annum (Agro.Dutch, 2010). Mushrooms are soft textured and highly perishable. Dehydration, canning and freezing have been found to be suitable for its preservation. Dehydration and quality characteristics of mushrooms are most important to improve product quality. Dehydration is the process of removal of surplus water without destruction of cellular tissues or important of energy values. Removal of water from food helps preservation by preventing microbial spoilage (Kumar Devendra and

Prakash Vijay 2012). Air temperature, flow rate and relative humidity factors influenced rate of drying with higher temperature, lower relative humidity and higher air velocity condition yielding fastest drying rate with adversely affecting the product quality ( Bain, 1987). Preservation of aroma is an essential criterion of quality for processed mushroom products (Kompany, 1993). Microwave dried fruit slice exhibited lower rehydration capacity and faster absorption rate due to changes in the structure or texture of the slices (Maskan, 2003). Dehydration technique is simple and economical but major problem associated with air dehydration are considerable shrinkage caused by cell collapse following the loss of water, poor rehydration characteristics of the dehydrated products and the unfavorable change in the

40

Table 1. Rehydration of mushroom dried at 500C, 60

0C, and 70

0C after 20 days Storage under hot water condition

Soaking time (minute)

50,T 50, UT 60 T 60, UT 70,T 70, UT

ROR RR ROR RR ROR RR ROR RR ROR RR ROR RR

0 0.38 1 0.395 1 0.437 1 0.46 1 1.526 1 1.889 1

2 2.758 7.464 2.643 6.691 1.976 4.521 1.099 2.389 1.696 1.111 1.806 0.8

4 2.951 8.083 2.831 7.167 2.019 4.620 1.178 2.560 1.774 1.162 1.88 0.9

6 3.088 8.392 2.993 7.577 2.171 4.967 1.272 2.765 1.896 1.242 2.057 1.0

8 3.152 8.413 3.099 7.845 2.180 4.988 1.313 2.854 1.921 1.258 2.152 1.1

10 3.315 8.630 3.218 8.146 2.219 5.077 1.39 3.021 2.073 1.358 2.284 1.2

T= Treated, UT=Untreated, RR= Rehydration ratio,

ROR= Rate of rehydration (Kg. / kg of dry matter per minute)

Figure 1. variance of moisture content with drying time of untreated mushroom at different drying air temperature with air velocity of 1.5 m-s

Figure 2. Effect of drying air temperature on variation of drying rate (DR) with moisture content of treated mushroom

41

Figure 3. Effect of drying air temperature on variation of drying rate (DR) with moisture content o untreated mushroom

Figure 4. Moisture ration vs drying time at 60oC for untreated mushroom

colour, texture, flavour and nutritive caused by drying. Therefore the performance study was undertaken to assess the effect of pre-treatment on dehydration characteristics of oyster mushrooms at drying temperature of 50, 60 and 70

0C using air velocity of 1.5

m/s and quality of dehydrated products. MATERIALS AND METHODS Fresh mushrooms (Oyster Pleurotus) were purchased from local market and used for the study. Samples were subjected to successive steps of washing, sorting and trimming. The samples were steam blanched for 3 minutes followed by treatment with 0.5% sodium metabisulphite and 0.5% citric acid solution for 5 minutes according to Kumar Devndra and Prakash Vijay (2012).

Thin layer drying set up (model : M.D. B-1) was used for drying both treated and untreated mushrooms at each of the drying air temperature of 50 ,60, 70

0C for the air

velocity of 1.5 m/s. Drying was continued till the sample attained the desired moisture level. Dehydrated samples were kept in sealed airtight polyethylene bags and inspected for quality analysis i.e. rehydration ratio, colour, texture and flavour. The colour of the mushrooms was measured using a hunter lab colorimeter, model DP-9000 D25A in terms of hunter L (lightness ranging from 0 to 100, indicating black to white), a (+a redness and –a greenness) and b (+b yellowness and –b blueness). The texture of mushrooms was analyzed using Stevens LFRA texture analyzer with needle probe. The texture is expressed as the load in grams required penetrating the mushroom. Rehydration characteristics of untreated and treated samples were studied in both cold and hot water.

42

Figure 5. Effect of different drying air temperature on rehydration of treated and untreated mushroom. The dehydrated mushrooms were rehydrated and Indian style curries were prepared. The cooked mushroom samples were then sensory evaluated and compared with that of raw sample. RESULTS AND DISCUSSION Effect of drying air temperature Thin layer drying of both untreated and treated mushroom samples having initial moisture content by about 90% (wet basis) took place under constant- rate period for a short time followed by the falling – rate period. At any temperature there was initial adjustment of increasing the drying rate to higher level, which remained constant for 8 to 10 minutes. As drying air temperature increased, total drying time reduced for both untreated and treated samples. Rate of drying also increased with the increase of temperature but the effect was less pronounced at the later part of drying. At a drying air temperature of 50

oC , it took long

time to dry the material to the desired moisture level for both untreated and treated sample . It was seen that time required for drying of untreated and treated samples to the desired moisture level of 5% were 130 and 140 min respectively at 60

oC but at 70

0C, time required for

untreated and treated mushroom were 85 minute and 95 minute respectively for 1.5 m/s air velocity. Drying rate changes with pretreated mushroom were taken more time as compared to untreated for drying up to desired moisture level at various drying air temperature due to treatment effect. Similar results were reported by Ajibola (1999). It was found that the relationship between moisture content and drying time was exponential and was in decreasing order (Figure1). The drying air temperature has significant influence on loss of moisture. The reduction in moisture content of untreated samples was from 900%to 400% at 50

oC whereas from 900% to

150% at 60oC for air velocity of 1.5 m/s during first hours

drying. The effect of drying air temperature on variation of drying rate with moisture content of treated and untreated mushroom is shown in figure 2 and 3. Moisture ratio and drying time curve shows the linear relationship for treated and untreated mushroom at drying temperature of 60

0

C(Figure 4). Study of Quality characteristics The quality of rehydrated mushrooms in terms of colour, flavour and texture is highly important in a dehydrated product. Colour of raw and dehydrated mushroom was compared. Discoloration was more in samples dried at higher temperature. The shrinkage appeared to be more in case of treated samples than that of the untreated one. Under ambient storage condition discolouration was more in untreated samples than the treated one. In treated samples inactivation of polyphenol oxides by steam blanching and retardation of mallard reaction by sulphiting (treatment with sodium metabisulphite) helped it to maintain the colour as compared to the untreated one. Rehydration characteristics of treated and untreated samples were studied in hot water (100

oC). Rehydration

ratio of the untreated samples was found to be greater than that of the treated one (Table 1). Highest rehydration ratio (8.630) was obtained during drying air temperature of 50

0C for treated sample; whereas lowest rehydration

ratio (0.8) was obtained for drying air temperature of 700C

for untreated sample (Figure 5) initially the rate of rehydration was very fast up to 4 minute for both treated and untreated sample. Then the rehydration rate become very slowly and ultimately moisture content attained almost constant level. After 4 minute of rehydration in hot water, untreated and treated samples achieved final moisture content of 89.71 and 83.97% (wet basis) respectively. Rehydration rate of treated mushrooms increased at air drying temperature of 50 & 60

0C due to

treatment effect. Effect of different drying air temperature on rehydration of treated and untreated mushrooms is shown in figure 5. The texture and appearance of untreated samples after rehydration were better than those of the treated samples. The colour and flavour of the treated samples were better than those of the untreated ones. The results corroborate the findings of Maskan (2003). Sensory evaluations of curry prepared from raw, untreated and treated samples were carried out. The study indicated that the curry prepared from any untreated dehydrated sample was almost comparable to that of the raw one. The colour of curry prepared from untreated samples was relatively darker whereas the texture of the curry prepared from treated samples was a whole acceptable. Performance evaluation of dehydration and quality characteristics of mushroom was investigated and found that drying air temperature of 60

0C appears to be suitable

for both untreated and treated for a good dehydrated product. It was observed that untreated mushroom was dried at a faster rate than the treated one at all drying air temperatures. Rehydration ratio of untreated sample was found to be greater than those of treated one. After rehydration, texture and appearance of untreated mushrooms were better whereas the colour and flavour of the treated mushrooms were appeared to be better.

43 REFERENCES Agro.Dutch (2010). www.agro.dutch.com Ajibola Pabis S (1999). The initial phase of convention drying of

vegetables and mushrooms and the effect of shrinkage. Journal of Agricultural Engineering Research 72:187-195.

Bain GEB (1927). Air circulation in mushroom houses. Mushroom Journal 173: 151-169.

Kompany ER (1993). E Aroma retention of cultivated mushrooms (Agaricus bisporus) during the freeze drying process. Lebensmitted-Wissenschaft and Technology, 26: 524-528.

Kumar Devendra, Prakash Vijay (2012). Effect of pretreatment on dehydration and quality characteristics of mushroom. Journal of Current Advances in Agricultural Sciences 4(1):94-97.

Maskan Khalloufi S, Giasson J, Ratti C (2003). Water activity of dried mushrooms and berries. Canadian Agricultural Engineering, 42: 51-56.