4

Alexandra Smith1*, Brett Kenney1, Susan Slider1, Jacek Jaczynski1, Litha Sivanandan2, and Bryce MacAulay3. 1. Davis College of Agriculture, Natural Resources, and Design; West Virginia University, 2. WVU Extension Service, West Virginia University

2. 3. Statler College of Engineering and Mineral Resources.

EFFECT OF PROCESSING PARAMETERS ON DRIED BLUEBERRY YIELD

DISCUSSION AND CONCLUSION

Significantly higher yields of final product from: Higher sugar solution concentration (p<0.0001).o These blueberries experienced higher water

loss with subsequent sugar gain.Higher temperatures during osmotic dehydration (p=0.0004).o Increasing the temperature increases the

diffusion rate because energy is added to the particles.

Longer osmotic dehydration durations produces higher yield of the final product (p<0.0001).o Longer times allow for longer sugar transfer,

blueberries in the longer duration groups should have a higher sugar concentration, thus increasing the final product yield.

Final water activity was lowest when treated with 65°Brix and 25°C:

o Suggests that higher yields with higher temperatures may be due to inefficient water loss.

o Lower water activity better for product safety.

Application of the parameters could improve transfer rates, which may help cut costs and reduce product waste, and cause an increase in yield which will increase profit.

ACKNOWLEDGEMENTS

Funding: Partial support from National Science Foundation's ADVANCE IT Program under Award HRD-1007978. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.Partial support from Branch Banking and Trust Company’s CRA / Community Development Donation Fund.Acknowledgements: Ida Holaskova, Tammy Webster, West Virginia University.

45°Brix 65°Brix36.0

38.0

40.0

42.0

44.0

46.0

48.0

50.0

52.0

Effect of solution concentration on final percent yield after conventional

drying.

Solution Concentration in °Brix(p<0.0001, LS Mean Standard Error =0.00572)

Fin

al P

erce

nt

Yie

ld

25°C 50°C41.0

42.0

43.0

44.0

45.0

46.0

47.0

48.0

49.0

Effect of temperature on final percent yield after convention dehydration.

Temperature in Celsius(p=0.0004, LS Mean Standard Error=0.00572)

Fin

al P

erce

nt

Yie

ld

180 240 30040.0

41.0

42.0

43.0

44.0

45.0

46.0

47.0

48.0

49.0

Effect of osmotic dehydration duration on percent yield after conventional

dehydration.

Duration of OD in minutes(p<0.0001, LS Mean Standard Error=0.00701)

Fin

al P

erce

nt

Yie

ld

45°Brix/25°C

45°Brix/50°C

65°Brix/25°C

65°Brix/50°C

0.62

0.64

0.66

0.68

0.70

0.72

0.74

0.76

Effect of solution concentration and temperature on final water activity.

Solution Concentration*Temperature(p=0.0210, LS Means Standard Error=0.02019)

Fin

al W

ater

Act

ivit

y

Air Tank

Vacuum Pump

Vacuum Chamber

Osmotic Dehydration Chamber

1:3g/g Fruit to Solution

Schematic of the Pulsed Vacuum Osmotic Dehydration Apparatus.

OBJECTIVES

o Describe the influence of vacuum, temperature, osmotic solution concentration, and treatment duration on blueberry mass transfer phenomena.

METHODOLOGY

Experimental design was a 2*2*2*3 balanced incomplete block nested in °Brix. Three replicates were completed

for a total of 72 experiments.o 500g of scarified, frozen blueberries were placed in

sugar solution concentrations of 45°Brix and 65°Brix with a fruit to solution ratio of 1:3 g/g.

o All treatments were subjected to 1 of 2 different pressure treatments, normal atmospheric pressure (1,013.25 mbar or 760 torr) or pulsed vacuum (50 mbar or 37.5 torr for 15 minutes

o Fruit and solution were incubated at either 25°C or 50°C for 180, 240, or 300 minutes in an incubator on a shaker plate at 100 rpms.

o Weights and sugar content(°Brix) of fruit and solution were taken before and after treatments.

o Convention dehydration was used after osmotic dehydration at 135°F for 6.5 hours.

o Water Activity of final dehydrated product was assessed after cooling product for 1 day at room temperature.

o Final Percent Yield:

RESULTS

ABSTRACT

Fruit drying is energy intensive (thermal efficiency 25‑50%). Improved efficiency is possible if phase change is minimized during the process. To minimize phase change and increase product yield and quality, osmotic dehydration and pulsed-vacuum osmotic dehydration can be applied to maximize water removal before final drying. Objectives of this study were to 1) characterize the effect of vacuum, osmotic solution temperature and concentration, and treatment duration on blueberry mass transfer; and 2) achieve an operating condition that maximizes yield and minimizes processing time. Frozen blueberries were exposed to 2 temperatures (25 or 50°C), 2 sugar solution concentrations (45 or 65°Brix), 2 vacuum treatments (no vacuum or 50 mbar), and 3 duration treatments (180, 240, or 300 minutes). This design generated 24 treatment combinations that were nested in °Brix as a balanced incomplete block design. Following treatments, blueberries were conventionally dehydrated at 57.2°C for 6.5 hours. Higher concentration of osmotic solution increased blueberry sugar gains by 62% compared to sugar gains at the lower concentration. Time affected sugar gain at both concentrations (p<0.0001). Original blueberry °Brix was about 13.0°Brix and increased by 13.03, 17.29, and 17.68°Brix at 180, 240, and 300 minutes, respectively. Solution concentration, temperature, and time affected percent yield after conventional drying (p<0.0001, p=0.0004, p<0.0001, respectively). Higher temperatures increased yield of the final product compared to the lower temperature. Water activity appeared to be affected by an interaction between solution concentration and temperature (p=0.0210). Low temperature processes can be used commercially to reduce water activity of high moisture products and decrease the processing time; thereby, improving yield and producing minimally processed fruit products with marginal changes in color, texture, aroma, and flavor.