effect of extruder moisture and dryer processing temperature on vitamin c and e and astaxanthin...

8/9/2019 Effect of Extruder Moisture and Dryer Processing Temperature on Vitamin C and E and Astaxanthin Stability

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per kilogram of complete feed: vitamin A, 2400 IU; vitamin D3, 2000 IU; vitamin E (DL-a-tocopheryl acetate), 300 IU; vitamin K3, 10 mg; thiamin mononitrate, 25 mg;

riboflavin, 35 mg; pyridoxine, 30 mg; calcium D-pantothenate, 60 mg; cyanocobalamin,

0.1 mg; folic acid, 10 mg; niacin, 100 mg; D-biotin, 1 mg; vitamin C (ascorbyl-2-

monophosphate), 250 mg; astaxanthin, 60 mg; choline (chloride), 200 mg; inositol, 100;

S e (Na2SeO3), 0 .3 mg; C u (Cu SO45H2O ), 1 0 mg; I [Ca (IO3)2] , 5 mg; Mn(MnSO4H2O), 25 mg; Zn (ZnSO4), 75 mg. All supplemental vitamins were ROVIMIXRform vitamins.

The dry ingredients, including the vitamin trace mineral premix, were mixed andthen ground in a hammer mill to pass a 0.840-mm (1/32-in.) screen. The ingredients

were processed as described in Tables 1 and 2 to produce 6.0-mm-diameter pellets that

were approximately 8.0 mm in length. A Wenger X-85 single screw extruder (Wenger

Manufacturing, Sabetha, KS, USA), of 13.1:1 length to diameter ratio was used to

Table 2

Experimental processing conditions during the drying process

Process air temperature (jC) Low moisture High moisture

150 120 90 150 120 90

Dryer A

Retention time (min) 6 7.5 11 7 10 12

Moisture content (%)

Incoming 19.05 19.41 19.03 23.59 23.63 23.64

Discharge 2.17 7.91 9.04 15.40 11.44 12.26

Product temperature (jC)

Incoming 52 48 56 52 52 52

Discharge 84 72 62 74 75 59

Dryer B

Retention time (min) 6 7.5 11 7 10 12

Moisture content (%)

Incoming 2.17 7.91 9.04 15.40 11.44 12.26Discharge 0.93 2.19 4.21 4.67 3.79 6.03

Product temperature (jC)

Incoming 78 70 62 73 71 58

Discharge 134 112 81 116 98 78

Total retention time (min) 12 15 22 14 20 24

Table 3

Coefficient of variation (%) in mixed unground and ground feed samples

Ingredient Unground mash

(mixer)

Ground mash

Astaxanthin 6.8 5.7

Vitamin E 4.5 6.1

Vitamin C 4.4 7.6

J.S. Anderson, R. Sunderland / Aquaculture 207 (2002) 137149 139

Fig. 1. Effect of extruder discharge moisture (%) and dryer processing temperature (jC) on final product dry

matter (%).

Fig. 2. Effect of extruder moisture and dryer processing temperature on DL-a-tocopheryl acetate retention (%) in

the first stage of drying.

J.S. Anderson, R. Sunderland / Aquaculture 207 (2002) 137149140


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using a t-test (P= 0.05). Linear regression (Eq. (1)) was used to evaluate the effect of

extruder discharge moisture on vitamin stability.

Linear regression z y 0ax 1

Three nonlinear models (Eqs. (2)(4)) (Kleinbaum et al., 1988) were fit to the vitamin

retention data, where vitamin retention (%), extruder discharge moisture (%), and dryerprocessing temperature (jC) represented z, x, and y, respectively.

Plane z y 0axby 2

Gaussian z aexp

0:5

xx 0=b2 yy 0=c2

3

Lorentzian z a=

1 xx 0=b21 yy 0=c2

4

The adjusted R squared of the analyses was used to evaluate goodness of fit of the

models. Normality, constant variance, and power were also evaluated for each model. In

all cases, either a plane or Gaussian function was chosen as the appropriate model to

Fig. 5. Effect of extruder moisture and dryer processing temperature on DL-a-tocopheryl acetate retention (%) in

final product.


describe the effect of processing parameters on vitamin retention. Contour plots were

constructed by interpolation of the data using SigmaPlot (SPSS Science, Chicago, IL),

after the appropriate nonlinear model was determined.

3. Results

The mixer variation (coefficient of variation) for the ingredients of interest were

calculated for the unground and ground mash (Table 3). Extruder and dryer conditions

significantly influenced final product dry matter (Fig. 1). With the processing conditions

used in this study, average final product dry matter was 96.4% (range 93.599.1%).

3.1. Vitamin E

Both DL-a-tocopheryl acetate and DL-a-tocopherol were measured in the samples. Theamount of DL-a-tocopherol measured in the samples ranged from 1 to 7 ppm and was not

included in the retention calculations. When the term vitamin E is used in the following

text, it refers to DL-a-tocopheryl acetate. Grinding resulted in a significant vitamin E loss

of approximately 5% [437 IU vitamin E/kg of unground mash versus 416 IU vitamin E in

ground mash (t-test; P< 0.05)].

Fig. 6. Effect of extruder discharge moisture on ascorbyl-2-monophosphate retention in processed feed (95%

confidence interval included; P< 0.05).



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The combination of extruder discharge moisture and the dryer processing temperature

significantly influenced vitamin E retention (Fig. 2) in the first stage of the dryer. As both

moisture and temperature increased, less vitamin E was retained. Although, most of the

loss of vitamin E occurred in the extruder, regardless of extruder discharge moisture level

(Fig. 2). Samples containing higher levels of moisture resulted in more variation, thus

reducing the precision of the contour analyses. Extruder discharge moisture level had a

significant effect (P< 0.05) on vitamin E stability, but dryer processing temperature did

not significantly reduce retention in the final product (Figs. 3 and 4). Drying temperature

appeared to help stabilise the vitamin E loss in the final product (Fig. 5), up to a point,

then increased loss. An optimal dryer processing temperature of 125 jC was suggested.

The stabilising effect was likely due to the reduced moisture content in the final products

(Fig. 1). On average, 67% (range 5473%) of the vitamin E was retained after proces-

sing.

3.2. Vitamin C

Grinding did not appear to impact on AMP stability. Extruder discharge moisture

significantly affected AMP retention (98% versus 91%, P< 0.05) (Fig. 6).

Fig. 7. Effect of extruder moisture and dryer processing temperature on astaxanthin retention (%) in the first stage

of drying.


Extruder and dryer processing parameters did not have a significant ( P>0.05) influence

on AMP retention in the first stage nor in the second stage of the dryer. The power of the

regressions were low, at approximately 0.5, thus interpretation of the negative findings

should be done cautiously. On average, 93% (range 83103%) of the initially added AMP

was retained after processing to final feed.

3.3. Astaxanthin

Grinding did not result in a significant (t-test, P> 0.05) astaxanthin loss in the mash

samples. At the extruder, increased discharge moisture did significantly reduce astaxanthin

retention (89% versus 82%; t-test, P< 0.05).

In the first stage of the drying process, moisture spared the loss of astaxanthin, and an

optimal dryer processing temperature of 125 jC was suggested (Fig. 7). In the final

product, once the initial moisture level has been reduced, increased moisture removal

resulted in the destruction of astaxanthin (Fig. 8). An optimal dryer processing temperatureof 84 jC was suggested. On average, 86% (range 76102%) of the astaxanthin from

CAROPHYLLR Pink was retained after processing.

Fig. 8. Effect of extruder moisture and dryer processing temperature on astaxanthin retention (%) in the final

product.



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effect of extruder moisture and dryer processing temperature on vitamin c and e and astaxanthin...

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