INTRODUCTION
Processing of feed ingredients by sieving, grind-ing, cooking, and pelleting allows for the addition of value by increasing nutrient availability to an animal (Lund, 1984; Theurer et al., 1999). Specifically, pel-leting has been shown to improve finishing pig G:F by increasing ADG while decreasing ADFI (Medel et al., 2004). Whereas it is widely accepted that pel-leting improves G:F in modern swine genotypes by 4 to 8%, there is some dispute as to the source of this improvement (Miller, 2012). Pelleting provides both a degree of cook from the conditioner and a diet form change by pressing the hot mash through a pellet die, so it is difficult to isolate the individual effects of conditioning or pressing (Behnke, 1996). The pro-cess as a whole increas the percentage of gelati-nized starch or the quantity of starch molecules that have swollen during the heating process and are irre-versibly dissolved to allow for more hydrogen bond-
evaluation of conditioning time and temperature on gelatinized starch and vitamin retention in a pelleted swine diet1,2
L. L. Lewis,* C. R. Stark,* A. C. Fahrenholz,† J. R. Bergstrom,‡ and C. K. Jones*3
*Department of Grain Science and Industry, Kansas State University, Manhattan 66506; †Prestage De
partment of Poultry Science, North Carolina State University, Raleigh 27695; ‡DSM Nutritional Products, Parsippany, NJ 07054
ABSTRACT: Two key feed processing parameters, conditioning temperature and time, were altered to determine their effects on concentration of gelati-nized starch and vitamin retention in a pelleted finish-ing swine diet. Diet formulation (corn–soybean meal bad with 30% distillers dried grains with solubles) was held constant. Treatments were arranged in a 2 × 3 factorial design plus a control with 2 conditioning temperatures (77 vs. 88°C) and 3 conditioner retention times (15, 30, and 60 s). In addition, a mash diet not subjected to conditioning rved as a control for a total of 7 treatments. Samples were collected after condi-tioning but before pelleting (hot mash), after pelleting but before cooling (hot pellet), and after pelleting and cooling (cold pellet) and analyzed for percentage total starch, percentage gelatinized starch, and riboflavin, niacin, and vitamin D3 concentrations. Total percent-age starch was incread by greater conditioning tem-perature (P = 0.041) but not time (P > 0.10), whereas higher temperature and longer time both incread (P < 0.05) percentage gelatinized starch, with increasing time resulting in a linear increa in percentage starch gelatinization (P = 0.013). The interaction between conditioning temperature and time incread percent-age gelatinized starch (P = 0.003) but not percentage total starch (P > 0.10). Sample location also affecte
d both percentage total starch and gelatinized starch (P < 0.05), with the greatest increa in percentage gelatinized starch occurring between hot mash and hot pellet samples. As expected, the pelleting process incread percentage gelatinized starch (P = 0.035;
7.3 vs. 11.7% gelatinized starch for hot mash vs. hot pellet samples, respectively), but there was no differ-ence in total starch concentrations (P > 0.10). Finally, neither conditioning temperature nor time affected riboflavin, niacin, or vitamin D3 concentrations (P > 0.10). In summary, both increasing conditioning temperature and time effect percentage gelatinized starch, but not to the extent of forcing the diet through a pelleting die.
Keywords: conditioning, feed processing, gelatinization, pelleting, temperature
© 2015 American Society of Animal Science. All rights rerved. J. Anim. Sci. 2015.93:615–619 doi:10.2527/jas2014-8074
1Contribution number 14-348-J from the KS Agric. Exp. Stn.,
Manhattan 66506.
2Appreciation is expresd to DSM Nutritional Products for中国国家女子篮球队
in-kind vitamin analysis.
3Corresponding author: jonesc@k-state.edu
Received May 19, 2014.
Accepted November 20, 2014.
Published February 23, 2015
615
Lewis et al. 616
ing sites (Jenkins and Donald, 1998). It is important to evaluate both the processing step and conditions that maximize gelatinized starch so that the conditions may be optimized by feed processors in an attempt to maximize animal feed efficiency.
Whereas conditioning and pelleting ingredients can improve the availability of some nutrients, such
as with starch gelatinization, the potential negative effects of the conditions should also be consid
ered. This is particularly true regarding nutrients that may
be nsitive to heat, such as vitamins. Specifically, re-tention of some vitamins can be as low as 50% when subjected to extreme temperatures (Beetner et al., 1974; Guzman-Tello and Cheftel, 1990; Killeit, 1994). Therefore, the objectives of this experiment were to determine the effects of conditioning temperature and time on both concentration of gelatinized starch and vitamin stability as well as to determine the intermedi-
ate steps within the pelleting process that are most re-sponsible for altering the concentration of gelatinized starch.
MATeRIALS AND MeTHODS平行线定义
A late nurry swine diet with 30% distillers dried grains with solubles (Table 1) was manufactured ac-cording to 7 different methods in an effort to eluci-date differences in gelatinized starch concentrations and vitamin retention associated with pelleting and to further evaluate the individual process steps in which starch gelatinization occurs. Rearch was conduct-
ed at the North Carolina State University Feed Mill Educational Unit using a pellet mill (model PM1112-
2; California Pellet Mill Co., Crawfordsville, IN) fitted with a 28.6-mm die and a conditioner–feeder (model
C18LL4/F6; California Pellet Mill Co.). Treatments were arranged in a 2 × 3 factorial design plus a control with 2 conditioning temperatures (77 vs. 88°C) and 3
conditioner retention times (90, 60, and 30 rotations per minute to reprent 15, 30, and 60 s actual condi-tioning times). In addition, a mash diet not subjected to conditioning rved as a negative control for a total of 7 treatments. There were 3 manufacturing runs per treatment, run order was completely randomized, and the pellet mill and conditioner were completely shut off between each run. Treatment samples were ana-lyzed for proximate analysis, percentage total starch, percentage gelatinized starch, and riboflavin, niacin, and vitamin D3 concentration. In addition, samples were collected after mixing but before conditioning (cold mash), after conditioning but before pelleting (hot mash), after pelleting but before cooling (hot pel-let), and after pelleting and cooling (cold pellet) and the location samples were analyzed for percentage total starch and gelatinized starch.
Proximate analys were completed by wet chem-istry according to the AOAC International official methods 934.01 (moisture), 920.39 (crude fat), 990.03 (CP), and 978.10 (crude fiber; AOAC, 2006) a
nd the American Oil Chemists’ Society official method Ba 5b-68 (ash; AOCS, 2000). Total starch and gelati-nized starch were determined according to Mason et al. (1982). Briefly, one 0.5-g subsample was hydro-lyzed in 25 mL distilled water for 20 min at room tem-perature while a cond 0.5-g subsample was boiled with 25 mL distilled water for 20 min. The samples were allowed to cool to ambient temperature. Next, 10 mL of acetate buffer solution was added to each flask. Table 1. Ingredient composition and calculated nutri-ent analysis of basal diet (as-fed basis)1
平板游戏Ingredient, %Percent
Corn40.56 Soybean meal25.25
Corn distillers dried grains with solubles30.00
Poultry fat0.50 Monocalcium phosphate 1.03 Limestone 1.30
Salt0.35
l-lysine HCL0.45
dl-methionine0.07
l-threonine0.09 Vitamin premix20.25
Trace mineral premix30.15 Standardized ileal digestible (SID) AA, %
Lysine 1.26 Isoleucine:lysine65 Leucine:lysine156 Methionine:lysine33 Methionine and cysteine:lysine58 Threonine:lysine62 Tryptophan:lysine17
Valine:lysine74
Total lysine, % 1.47
ME, kcal/kg3,296
SID lysine:ME, g/Mcal 3.82
CP, %24.1
Ca, %0.76
P, %0.69 Available P, %0.41
1A single diet formulation was manufactured according to different feed processing parameters to determine effect of processing on percentage ge-latinized starch or vitamin retention.
2Provided per kilogram of diet: 11,023 IU vitamin A, 1,378 IU vitamin D3, 44 IU vitamin E, 4 mg vitamin K, 8 mg riboflavin, 28 mg pantothenic acid, 50 mg niacin, and 0.04 mg vitamin B12.
3Provided per kilogram of diet: 40 mg Mn from mangane oxide, 17 mg Fe from iron sulfate, 17 mg Zn from zinc sulfate, 2 mg Cu from copper sulfate, 0.30 mg I from calcium iodate, and 0.30 mg Se from sodium lenite.
Swine feed conditioning temperature and time617 Samples were hydrolyzed with 5 mL of glucoamlyla
and incubated at 40°C for 70 min. After incubation, 5
mL of trichloroacetic acid was added to halt hydroly-
sis and samples were cooled to room temperature and
then mixed with approximately 50 mL distilled water
to a final volume of 100 mL. Free D-gluco was then
measured using a YSI 2700 Gluco Analyzer (model
2700; YSI, Yellow Springs, OH). The resulting quanti-
ty of free gluco determined in the cold water hydro-
lyzed sample reprents the percentage of starch that
was gelatinized during processing whereas the cooked
sample reprents the percentage of total starch within
sample. Samples were analyzed for vitamin concen-
tration by DSM Nutritional Products (Parsippany, NJ)
by using a combination of HPLC and tandem mass
spectrometry according to Chen et al. (2009) for ribo-
flavin and niacin and according to Schadt et al. (2012)
for vitamin D3. The vitamins were chon for analy-
sis bad on preliminary unpublished data suggesting they were the most nsitive to degradation from low temperature and high moisture environments.
Data were analyzed as a completely randomized design using the GLIMMIX procedure of SAS (SAS Inst. Inc., Cary, NC) with run as the experimental unit. Conditioning temperature, time, and their interaction rved as fixed effects. The results were considered significant if P < 0.05 or a trend if P < 0.10.
ReSULTS AND DISCUSSION
Analyzed nutrient composition revealed no dif-ferences between mash and thermally procesd treat-ments (Table 2). There were also few differences in production rate or pellet durability throughout each processing run. Pellet mill production rate was rela-tively stable throughout all treatments and varied by no more than 3%. Pellet durability index was also con-sistent throughout all treatments. The high pellet qual-ity among treatments should be noted as one would traditionally expect incread conditioning time to re-sult in improved pellet quality.
Percentage total starch was incread by greater conditioning temperature (P = 0.041) but was not af-fected by time or the interaction between temperature and time (P> 0.10; Table 3). While significant, the total starch values due to temperature differences were numerically (35.2 and 36.1%) similar, so the biologi-cal significance of this difference is questionable. The literature indicates that total starch values should be the same throughout processing (Muir et al., 1995; Theurer et al., 1999).
However, significant differences (P < 0.05) in percentage gelatinized starch were obrved across all treatments, demonstrating that temperature and retention time are major factors affecting gelatiniza-tion. Both main effects and the interaction incread percentage gelatinized starch (P < 0.05), with increas-ing duration resulting in a linear increa in percent-age starch gelatinization (P = 0.013). Specifically, the treatment conditioned at 88°C for 60 s had greater (P < 0.05) percentage gelatinized starch than tho con-ditioned at 77°C for either 15 or 30 s. Stevens (1987) obrved an opposite effect, where a temperature increa during pelleting resulted in lower levels of gelatinization. This may be explained by the method ud to evaluate the percentage of gelatinized starch. Stevens (1987) ud differential scanning calorimetry, whereas the current study ud enzymatic methods for quantification of gelatinization. Differential scan-ning calorimetry is a robust method for evaluation of
starch gelatinization but is most reliable at detecting gelatinization in isolated starch compared with com-pound mixtures of ingredients (Sopade et al., 2004). Meanwhile, the method ud in the current study was developed specifically for finished feeds with multiple ingredients. Additionally, the method ud by Stevens (1987) ud a substantially smaller sample size (0.002 vs. 0.5 g). Therefore, sampling error may further af-fect the precision of the assay results compared with a larger batch of compound feed.
With respect to vitamin retention, there was no effect (P > 0.10) of temperature, time, or their inter-action on riboflavin, niacin, or vitamin D3 concentra-tions. This discrepancy was not altogether surprising becau processing up to 88°C for 60 s is not thought to affect vitamin stability. However, it has been argued that vitamin stability has not been thoroughly validated (Lešková et al., 2006). Niacin destruction occurs dur-ing the precooking process when it may leach into steep Table 2. Analyzed nutrient concentrations and manu-facturing production specifications
Nutrient,1 %Mash
Condition temperature, °C
7788
Condition retention, s
306090306090 Moisture11.311.511.611.411.611.411.4 Ether extract 4.1 5.2 4.8 5.1 4.7 5.3 4.7 Protein24.925.224.825.024.524.924.7 Fiber 5.2 5.1 4.9 4.9 4.7 5.2 5.1 Ash 3.7 3.7 3.7 3.6 3.6 3.7 3.6
P e llet mill
production
rate, kg/h
面试一定要问hr的6个问题–716719734725740737
P e llet durability
index
–89.695.091.093.092.693.0
1Analys were completed in duplicate according to the AOAC International official methods 934.01
(moisture), 920.39 (ether extract), 990.03 (CP), and 978.10 (crude fiber; AOAC, 2006) and the American Oil Chemists’ Society official method Ba 5b-68 (ash; AOCS, 2000).
Lewis et al. 618
water, but processing alone is not expected to destroy the vitamin (Lešková et al., 2006). However, cooking beef products to 57°C internal temperature has dem-onstrated a loss of both riboflavin and niacin (Dawson et al., 1988). Therefore, degradation of B vitamins can occur at low temperatures; however, conditioning times relevant to animal feed pelleting do not appear to be long enough to affect vitamin concentrations.
Finally, both percentage total starch and gelatinized starch were affected by processing step (P < 0.05; Table 4). Mash samples collected before conditioning or pel-leting had lower (P < 0.05) percentage total starch than conditioned mash or hot pellet samples. Meanwhile, both cold and hot mash samples had lower (P < 0.05) percentage gelatinized starch compared with hot or cold pellet samples. Notably, there was no difference in percentage gelatinized starch between cold mash and hot mash samples. This suggests that conditioning alone did not have a significant impact on degree of gelatinization. True starch gelatinization is thought to occur at temperatures above 70°C and moist
ure above 25% (Lund, 1984). Although the temperatures evalu-ated in the current experiment were above this point, the maximum moisture addition by a conditioner is expected to be only 6% (Leaver, 1988). This agrees with the moisture concentrations of cold mash and hot mash obrved in the current experiment, which were 11.1 and 17.1%, respectively. Moisture addition during conditioning is therefore below the 25% requirement for true starch gelatinization to occur, which confirms that conditioning alone has very little effect on starch gelatinization, regardless of temperature.
The difference in starch gelatinization between hot mash and hot pellet samples suggests that starch gelatinization does occur due to the frictional or me-chanical heat of the pelleting process. This is in agree-ment with Wang (1993), who showed that mechanical energy was effective at starch cooking during extru-sion processing at 50°C, and Skoch et al. (1981), who showed that when cold mash was pelleted without the addition of steam, a significant amount of starch dam-age was recorded due to frictional heat impod by die rolls and feed compression. Therefore, it appears that the pelleting process itlf results in starch gelatiniza-tion and not necessarily conditioning.
In summary, this rearch found that there were no biologically significant effects of conditioning tem-perature or time on total starch concentration or vi-tamin retention. Meanwhile, increasing conditioning temperature and duration incread percentage gela-tinized starch but to a lesr exten
t than that obrved from forcing feed through a pellet die.
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American Oil Chemists’ Society (AOCS). 2000. Official methods and recommended practices of the AOCS. 5th ed. Oil Chem.
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Association of Official Analytical Chemists (AOAC). 2006. Official Methods of Analysis. 18th ed. AOAC, Arlington, V A. Beetner, G., T. Tsao, A. Frey, and J. Harper. 1974. Degradation of thiamine and riboflavin during extrusion processing. J. Food Sci. 39:207–208. doi:10.1111/j.1365-2621.1974.tb01024.x
Table 3. Main effects of conditioning temperature (temp.) and time on starch and vitamin concentrations
Item
Conditioning temp.Conditioning time1,2P-value
77°C88°C SEM15 s30 s60 s SEM Temp.Time
Temp.
× time
Starch, %
Total35.236.10.4135.935.635.50.450.0410.4960.147 Gelatinized9.010.70.579.69.710.2 1.710.0010.0080.003 Vitamin concentration
Riboflavin, mg/kg8.47.70.777.97.98.20.950.5450.9710.980 Niacin, mg/kg52.252.5 3.3553.654.948.3 4.100.9520.4970.777 D3, IU1,3821,312117.51,3551,2851,400143.70.6760.8520.920 1Retention time was pret as specified conditioner screw rotations per minute during the manufacturing process and verified manually. The pret reten-tion speeds of 90, 60, and 30 rotations per minute resulted in actual retention times of 15, 30, and 60 s, respectively.
2Linear effect of conditioning time: total starch, P = 0.174; gelatinized starch, P = 0.013; riboflavin, P = 0.92; niacin, P = 0.39; and vitamin D
3
小学科学实验, P = 0.83.
Table 4. Effects of process step on percentage total
starch and gelatinized starch1
Item
Form
SEM P-value Cold
mash
Hot
mash
Hot
pellet
Cold
pellet
Total starch, %34.7a36.3b36.7b35.2ab0.390.001
G e latinized starch, %6.1a7.3a11.7b10.8b 1.020.001
a,b Means within a row that lack a common superscript differ (P < 0.05). 1Cold mash samples were collected after mixing but before condition-ing, hot mash samples were collected after conditioning but before pellet-ing, hot pellet samples were collected after pelleting but before cooling,
and cold pellet samples were collected after manufacturing was complete and pellets were completely cooled.
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