63 Winter 1988 Peeling Sugarbeets by Use of High Pressure Steam

Peeling Sugarbeets by Use of High Pressure Steaml

R.H. Edwards2 , J.M. RandalF and L.W. RodeP

2USDA-ARS, Western Regional Research Center, 800 Buchanan St., Albany, CA 94710, and 3Beet Sugar Development Foundation,

2301 Research Blvd., #107, Fort Collins, CO 80526

ABSTRACf

A high pressure steam peeling technique was used successfully to peel uncrowned and crowned sugar­beets. Treatments of 40-60 seconds with 1825 kPa (250 psig) steam followed by mechanical brushing with a stiff nylon brush produced uncrowned peeled beets with only minor amounts of skin or peel still intact. For these treatments, peeling weight losses of 3.5­5.8% were obtained resulting in losses of 1.8-2.8% of the sugar in the original beets to the peel fraction. Crowned beets could be peeled after a shorter steam treatment time (20-30 sec). For crowned beets, peel and sugar losses were 2.9-3.9% and 1.3-1.7%, respec­tively. The peeled beets were lower than the peel fraction by factors of 3 or more in ash, nitrogen, sodium, potassium, calcium, and magnesium con­tent. Brei juice and thin juice purities from peeled uncrowned and peeled crowned beets were up to 1.6% (relative) higher than extracts from the unpeeled control beets. Color values of thin juice from the peeled beets were not significantly different than those obtained from the control beets. All peel frae­tions were low in sugar (28-41%, dry basis) and pro­duced thin juice with low purities (53.2-75.5%) and high color values (2000-7500 ICUMSA).

Additional Key Words: Beta vulgaris, quality components, purity

ImpUrity levels are higher and sucrose levels lower in the skin or peel, and in the crown of a sugarbeet than in the main portion of the root. Removal of these parts should increase

ICooperative investigation of the U.S. Departrn~nt of Agriculture, Agricultural Research Service, and the Beet Sugar Development Foundation. The authors are, respectively, Research General Engineer and Research Chemical Engineer, USDA,' ARS, Western Regional Research Center, Albany, CA 94710, and Analytical Chemist, BSDF, Western Regional Research Center, Albany, CA 94710.

64 Journal of Sugar Beet Research Vol 26 No 1

the sugar content of the remaining root in comparison to that of the whole beet, and increase the purity of subsequent juice. Madsen et al. (7) found such a juice purity increase from hand peeled beets. Subsequently, a machine with rotating wire brushes which mechanically removed the skin was built (6). Test runs showed that the purity of thin juice could be increased by up to 2.3 purity points and extraction improved by as much as 1.6 percent absolute. The color level in thin juice from peeled beets was also significantly reduced. Large-scale mechanical peeling of root crops is not generally practiced today. Instead, most root crops such as potatoes, turnips, carrots, red beets and yams are peeled using high pressure steam. High pressure steam peeling is preferred because it maximizes peeled product yield and uses no toxic chemical compounds (e.g. lye), which are a disposal problem (5).

Commercial scale high pressure steam peeling works as fol­lows: The feed material is automatically loaded into a high pres­sure vessel by means of a weigh-belt conveyor. The vessel door closes and high pressure steam (690- 2070 kPa; 100-300 psig) is rapidly admitted. Steam pressure is maintained for 5-80 sec until the stearn has superheated water in the skin and a thin layer adjacent to it. The vessel is rotated during the steam application period to ensure uniform steam distribution. Then, steam is ven­ted rapidly from the vessel. During this time, superheated water flashes to stearn. The large volume increase due to the phase change loosens the heated layer from the rest of the product. The vessel stops rotating, and product is discharged. Usually a secondary peel removal device is used to separate loosened peel from the product. This generally is a machine containing sets of rotating brushes which lightly contact the surfaces of the stearn treated product. The entire operation is considered a batch-con­tinuous process. High pressure steam peeling technology should be readily adaptable to the beet sugar industry.

The objectives of this work were to determine the eff~cts of a high pressure steam peeling process on the yield and compos­ition of peeled beet and peel fractions, and on the quality of juices extracted from the beet fractions. Experiments were con­ducted with both uncrowned and crowned beets.

MATERIALS AND METHODS Sample Preparation and Treatment

Beet selection and sizing. Washed, uncrowned beets within the weight range 1350 g ± 10% were obtained at a nearby beet sugar factory. Beets were divided into lots of 10 beets each with a total weight of 13.5 kg ± 5%. Beets weighing 900 g ± 10% and 2050 g ± 10% were also collected for some experiments. Beets were sliced straight across at the first leaf Dode to produce crowned beets.

Hand peeling. Beets were peeled by hand using a typical

65 Winter 1989 Peeling Sugarbeets by Use of High Pressure Steam

kitchen vegetable peeler. A light peel was obtained by peeling the surface of the beet but not removing peel from depressed or pitted areas. In a heavy peel, skin in the cleft and in depressed and pitted areas was removed, using the pointed tip of the peeler if necessary. The lowest peel level was obtained by scraping the edge of a paring knife across the beet surface. Beets were weighed before and after peeling.

Steam peeling. A single beet in a wire mesh basket was placed in the high pressure peeling vessel and subjected to 1825 kPa (250 psig) steam for 15-80 sec. The vessel was depressurized, which required 15 sec, and the treated beet was removed. The hot beet was cooled by pouring about 500 ml of distilled water over the surface of the beet. The water was collected and re-used for all beets in a lot. The liquid was added to the peel fraction after the last beet was peeled. After cooling, the beet was scrub­bed with a stiff nylon brush (Kellog Brush Mfg. Co., grout and tile) to remove loosened peel. Peel which had fallen off in the basket was combined with peel from the beet. Beets were weighed before and after peeling.

Sampling. After peeling, the peeled beet or root fraction was cut into pieces and ground in the a laboratory grinder-press (Norwalk Mfg. Co., Model 200) and then mixed for 2 min with a kitchen mixer. A sample equal to 12 percent of the peeled beet weight was removed and frozen with dry ice. The fractional root samples from each of the 10 beets in a lot were combined and mixed to form a composite sample. The peel fraction from a1110 beets in a lot and any applicable wash water were combined, ground, and blended. Portions of the root and peel fractions were freeze dried and ground through a 20 mesh screen.

Brei juice. Two hundred grams of the ground, mixed beet fraction and 300 g of distilled water were heated to 75C while stirring. The hot mixture was transferred to a food blender con­tainer and blended for 5 min at high speed. The brei was poured into a fine weave nylon bag and the brei juice expressed through the cloth using the hydraulic press portion of the grinder-press (Norwalk Mfg. Co., Model 200).

Juice purification. Brei juice was clarified by filtration through Reeve Angel No. 226 paper after addition of basic lead acetate and filter aid. Laboratory thin juice was prepared by the Car­ruthers and Oldfield (3) modification of the Brown and Serro (2) procedure in which impurities are precipitated as phophates by the addition of phosphoric acid to lime-treated juice. Calcium hydroxide was added to brei juice at the level of 1.6% on weight of juice. Precipitates were removed by centrifugation (Sorvall, Model RC2B) for 3 min at 5000 RPM (Fmax = 4068 g) followed by filtration through Reeve Angel No. 226 paper.

Analyses. Sugar content. Sugar content of juices was determined by

polarization in a Rudolph Autopol III saccharimeter using a

66 Journal of Sugar Beet Research Vol 26 No 1

200mm tube. Sugar content in brei was determined by an ICUMSA method (8) using a 26.00 g sample.

Total dissolved solids. Dissolved solids content of sugar juices was determined by refractive index, by use of a Bellingham and Stanley RFM 81 digital refractometer.

Color. Color of laboratory thin juice was measured by an ICUMSA procedure (9). Solutions were adjusted to pH 7 with 1 N HCl and filtered through a 0.45 mm membrane before absor­bance was measured at 420 nm.

Dry matter. Dry matter content of brei was determined from weight lost after drying weighed samples for 16 hr at 10SC.

Ash and metal content. Ash content of freeze dried samples was determined by an AOAC method (1). Sodium, potassium, calcium, and magnesium were determined by atomic absorption, with a Perkin-Elmer 303 AA spectrophotometer. Samples were prepared by a modified dry ashing procedure of Chapman and Pratt (4).

Equipment. High pressure steam peeler. A high pressure steam peeler

(Odenberg K + K, Sacramento, CA, Model 100) with a volume of 100 1 was used for steam treatment of the beets. Steam treat­ment time and time delay before opening of the vessel door after release of steam pressure were controlled by a microprocessor.

Peeling baskets. Cylindrical baskets to hold a single beet were used to minimze unrecoverable losses of peel solids in the peeler. The baskets were 15 cm diameter x 30 cm long. The baskets were constructed of 20 mesh stainless steel wire cloth and had remov­able tops.

Calculations Peel loss. Percent peel loss (PL) was calculated as:

PL = (W/Wo) x 100 where Wp = beet weight loss on peeling, and Wo = original beet weight. '

Sugar loss. Percent sugar loss to the peel fraction (SLp) was calculated as: W x S . SL = p p x 100

p (Wpb x Spb) + (W p x Sp) where Wpb = peeled beet weight; Sp = peel sugar content; and Spb = peeled beet sugar content.

Apparent purity. Apparent purity (P) was calculated as

P 0.26 x Pol 100 RDSxD x

where Pol = saccharimeter reading; RDS = refractive dry solids; and 0 = apparent density.

RESULTS AND DISCUSSION Hand Peeled Uncrowned Beets. Preliminary experiments with

hand peeled beets wer~ conducted to obtain an indication of what changes peeling might produce without the complicating factor of having the high pressure steam in contact with the beet.

67

I

Wmter 1989 Peeling Sugarbeets by Use of High Pressure Steam

Table 1. Yield and quality of process fractions and sugar juices from hand peeled beets~

Beet Peel Loss (% orig wt) Sugar Loss Sugar(%) Beet Treatment Fraction (Mean ± S.D.) (Range) (%orig) (as is) (dry basis)

Control whole beet 16.0 71.5

Scraped root 1.4 ::!: 0.3 0.9-2.4 0.3 15.7 73.3 peel 3.8 16.8

Light peel root 3.6 ::!: 0.4 2.9-4.5 1.5 15.4 70. 7 peel 6.1 31.1

Heavy peel root 5.6::!: 0.6 3.9-7.2 2.7 16.1 72.4 peel 7.6 36.2

Very heavy peel root 7.3::!: 0.7 6.4-8.8 3.9 17. 6 73.3 peel 9.0 36.8

Average of two experiments

Brei Juice Thin Iuice Beet Purity Purity Purity Increase

Beet Treatment Fraction (%) (%) (% of control)2

Control whole beet 88.1 94.3

Scraped root 88.4 94.9 0.6 peel 38.0 52.8

Light peel root 89.6 95.2 1.0 peel 53.0 68.8

Heavy peel root 88.0 95.4 1.2 peel 55.3 70.2

Very heavy peel root 89.6 %.2 2.0 peel 58.0 72.4

, Relative percent

Results from these runs are shown in Table 1. Mean peel losses ranged from 1.4 to 7.30/0 of the original beet weight. Within treat­ments, there were large variations in peel loss on a beet k> beet basis, as indicated by the range and standard deviation figures. At the lowest peel losses, obtained by scraping the edge of the knife along the beet, the dry basis sugar content of the peel was very low (16.8%), but was higher (31.1-36.8%) at more normal peel losses. This is still only about half of the sugar content in the peeled root. The sugar lost to the peel fraction, which presumably would not be recovered as product sugar, ranged from 0.3 to 3.9%

(relative) of the sugar originally present in the beets. In general, peeling increased the measured sugar content in the peeled root fraction as compared to the original beet.

As expected, the apparent purities of brei juice and thin juice from the peel fractions were very low. Peeling increased the purities of both brei juice and thin juice made from the peeled root fractions. Apparent purity increases as much as 1.9% relative to the control beets were obtained.

68 Journal of Sugar Beet Research Vol 26 No 1

Steam Peeled Uncrmvned Beets. Photos of representative peeled beets subjected to high pressure steam for 20 to 80 sec are shown in Fig. 1. Material was most easily removed from the broad areas of the root. Skin in the cleft area was more difficult to remove, in part because it was anchored there by the hair roots growing in that region. Material from the crown was the most difficult to remove. After an 80 sec treatment, the only remaining skin was in some of the deeper pits. The thickness of the heat affected layers was 1.5-2, 2-4, 3-5, and 4-7 mm for 30,40,60 and 80 second steam treatments, respectively.

The results of three laboratory experiments using the steam peeler are shown in Table 2. Peel losses covered roughly the same range of values as in the hand peeled beet experiments.

Figure 1. Photograph of beets peeled by treatment with high pressure steam (1825 kPa) for various times.

69 Wmter 1989 Peeling Sugarbeets by Use of High Pressure Steam

7

6 c

I­3 5 iii <.9

c:r: 0 4 c

~ • iii

(/) 3 (/) I!I

0 -I

-I 2 w w Cl...

Ii

0 0 20 40 60 80

STEAM TIME (SEC)

Figure 2. Effect of stearn time on the amount of peel loss from high pressure steam peeling of uncrowned beets.

3 III

III

III

III (.!)-a:: 0 2 El

~ EI

111

en en 0 ---1

111

a:: III

« (.!)

:J 111

en EI

O+----~---~---~------r----~---~---~---~--------~

o 20 40 60 80 100

STEAM TIME (SEC)

Figure 3. Effect of steam time on the sugar loss to the peel fraction from high pressure steam peeling of uncrowned beets.

100

0.5 2.76 41.3 12.4

Table 2. Yield and of Beet Fractions after HiQ"h Pressure Steam PeelinQ" of Uncrowned Beets .~

40 root 3.5 ± 0.5 2.9-4.4 1.8 16.3 71.6 0,41 2.2 0.09 0.19 35.7 1.4 10.1 0.48 0.62

60 4.8 ±·1.0 3.1-6.4 2.4 16.4 73.8 0.47 2.1 0.16 0.09 0.18 I~~peel 36.0 1.5 10.2 0.36 1.7 0.45 0.62 ...

4.3 ± 0.6 3.5 -5.3 16.2 72.1 0.59 2.0 0.45 0.09 0.20 32.3 1.8 0.43 1.9 0.49 0.66

root 5.8 ± 0.7 5.0-6.9 16.7 72.9 0.26 2.0 0.16 0.45 0.11 0.17 3.90 33.8 1.3 11.5 0.70 1,4 0.51 0.63 "­

6.1 ± 0.8 5.0-7.0 2.7 16.5 73.4 0040 2.0 0.16 0,47 0.08 0.15 3.34 31.4 1.2 10.6 0,49 0.55

2 Control whole beet 15.8 71.4 0.50 2.2 0.11 0.20 20 root 2.3 ± 0.3 1.9-2.7 1.1 16.8 73.8 0.51 2.0 0.11 0.19

peel 2.87 35.7 10.0 0.57 0.62

30 root 3.4 ± 0.7 2,4-4.8 1.7 15.9 72.8 0.52 0.19 peel 3.15 35.6

40 root 4.0 ± 0.5 3.2-4.7 2.0 17.0 74.8 0.49 2.1 peel 3.35 37.0 9.3 1.9 0.54 0.57

60 root 4.9 ± 0.9 3.9-6.9 2.6 17.5 74.8 peel 3.75 38.0

3 Control whole beet 15.4 69.8 0.52 20 root 1.6 ± 0.6 1.2-3.0 71.0 0.53 2.3 0.21

2.34 35.1 12.1 0.72 30 root 2.7 ± 0.6 1.8-3.4 70.4 0.56 2.2 0.09 0.20

34.7 1.6 10.2 2.1 0.56 0.62

0

~ ~ 0

'" (f)

= ~ = II> ~

~ ID

~

Table 3. Quality of Juices Extracted from High Pressure Steam Peeled Uncrowned Beets Steam Peel Sugar Brei Juice Thin Iuice

Experiment Treatment Beet Loss Loss Purity Purity Purity Increase Color UNo. (sec) Fraction (% orig. wt.) (% orig.) (%) (%) (% of control) I (lCUMSA)

Control whole beet 87.3 93.9 140 20 root 1.0 0.6 89.3 94.4 0.5 150

peel 75.5 40 root 4.3 2.0 87.0 94.6 0.7 170 ~

peel 53.6 61.4 7500 !lS· ~60 root 5.8 2.8 88.0 95.2 1.4 140 (J)

peel 55.9 65.4 6800

! I:

80 root 6.l 2.7 89.8 95.2 1.4 140 peel 53.l 59.6 6300 ~

!1 0­'<

2 Control whole beet 89.8 95.2 130 20 root 2.3 1.1 89.1 95.3 0.1 220 c

~peel 53.8 70.2 a,

30 root 3.4 1.7 89.5 95.3 O.l 240 e;peel 57.2 67.9

~ 40 root 4.0 2.0 90.6 95.7 0.5 210 "0

~peel 56.6 71.2 ~ 60 root 4.9 2.6 90.4 96.0 0.8 250 ~

peel 57.3 70.9 ~ ~ ...

3 Control whole beet 87.7 94.6 150 9 20 root 1.6 0.8 87 .6 95.0 0.4 150

peel 53.2 65.9 2100 30 root 2.7 1.3 88.4 94.2 -0.4 150

peel 54.5 68.9 2000

40 root 3.5 1.8 90.0 95.6 1.1 120 peel 56.0 67.5 4100

60 root 4.8 2.4 89.1 95.2 0.6 140 peel 54.5 65.7 3700 1;::1

I Relative percent.

72 Journal of Sugar Beet Research Vol 26 No 1

Again the beet to beet variation of peel loss within treatments was large. This may have been due partly to beet to beet variation in the amount of crown area, or to possible variation between beet varieties, as seen during peeling of other root crops. Peel losses (Fig. 2) and sugar losses (Fig. 3) were roughly proportional to increasing treatment time. There was a straight line relation­ship between the peel loss and the sugar loss. This relationship is sugar loss (%) = 0.49 x (peel loss, %), R2 = 0.97. Thus, the sugar losses were essentially equal to one-half of the peel loss values. Sugar contents in the peel fractions, which ranged from 31.4-41.3 percent (dry basis), agreed well with those from the handpeeled values. The measured sugar content of the peeled roots was higher than those of the unpeeled controls and in­creased with increasing steam time.

The levels of impurities were significantly higher in the peel fractions than in the peeled roots or in the whole beet control samples. Compared to the peeled root, ash in the peel was higher by a factor of 4.6 5.9; nitrogen by 2.8-5.0; sodium by 1.7-4.0; potassium by 3.0-4.2; calcium by 4.6-6.2; and magnesium by 3.1-3.7. Since the peels are significantly higher in impurities than the whole beets, removal of the peel fractions must make the peeled beets lower in impurities than the control beets. This effect can be seen in Table 2. Impurity levels in the peeled beet fractions are generally lower than in the control beets, but these differences may not be statistically significant. There appeared to be little difference in peel composition as a function of steam treatment time, but the impurity levels in the peeled beet frac­tions showed an apparent decrease with increasing steam treat­ment time.

The quality of juices prepared from the same lots of peeled beets is shown in Table 3. In general, both brei and thin juice purities from the peeled beets were higher than those from the control beets. Apparent purity increases, compared to the un­peeled controls, of up to 1.4% relative were found for the peeled beet fractions. Purity increases usually became larger as the steam treatment time or degree of peeling increased. As expected, purities of juices from the peel fractions were considerably lower than those from the peeled roots. Peel fraction thin juice purities, ranging from 59.6-75.5%, were similar to those obtained by hand peeling. Maximum increases in peeled root thin juice purities, compared to the controls, were considerably lower than the 3.94­4.5% reported by Madsen and Nielson (6).

Unlike Madsen and Nielsen (6), we found little difference between thin juice color values from peeled and control beets. Color levels in thin juice from the peel fractions, however, were 13-53 times higher than those from the control beets. When the color levels in the peel and root fractions were recombined mathematically, the color levels in the whole beets thus created were considerably higher than those from the actual control beet

73 Wmter 1989 Peeling Sugarbeets by Use of High Pressure Steam

Table 4. Effect of Beet Size on Peeling Losses l

Target Beet Actual Mean Weight Beet Weight Peel Loss (% orig wt)

Beet Size (g) (g) (Mean) (Range)

Small 900 ± 10% 915 6.8 5.4-8.6 Medium 1350 ± 10% 1392 5.2 4.0-6.1 Large 2050 ± 10% 2081 4.7 3.2-5.6

J Beets treated for 60 sec wth 1825 kPa steam, then hand brushed; single experiment.

Table 5. High Pressure Steam Peeling Losses of Crown and Root Fractions l

Steam Whole Beet Crown Treatment Peel Loss2 Weight Peel Loss Peel Loss (sec) (% orig) (% orig whole beet) (%crownwt) (% oftotalloss)

Hand peeled 4.6 19.0 8.7 35.8 40 4.0 22.8 5.1 29.1 60 6.0 21.4 10.3 35.7 80 7.1 18.2 12.4 31.6

J Single experiment; steam 1825 kPa . , Crown plus root.

Steam Whole Beet Root Treatment Peel Loss2 Weight Peel Loss Peel Loss (sec) (% orig) (% orig whole beet) (%rootwt) (% of total loss)

Hand peeled 4.6 81.0 3.6 64.2 40 4.0 77.2 3.7 71.9 60 6.0 78.6 4.8 64.3 80 7.1 81.8 5.9 68.4

, Crown plus root.

lots. nus indicates that some colorants were formed in the peel fraction by the high pressure steam treatment.

Peeling losses were also dependent on beet weight. The amount of peel is proportional to the surface area, while the weight is a function of the volume. Thus, peel loss is a function of the surface area to volume ratio, and would be higher for small beets. TIUs was found to be the case. Table 4 shows that the peel loss increased by almost 50% when changing from large to small beets.

Steam Peeled Crowned Beets. Figure 1 showed that longer steam times were required to loosen the surface material on the crown. To examine this further, individual beets were cut into separate root and crown sections and then subjected to peeling. The results are shown in Table 5. To peel uncrowned beets, a greater percentage of the weight of the crown (8.7-12.4) than weight of the root (3.6-5.9) must be removed. This is because the crown has a higher surface

I :i;!

Table 6. Quality of Juices Extracted from High PressiIre Steam Peeled Crowned Beets!

Steam Brei Juice Thin Iuice Experiment Treatment Beet Peel Loss Sugar Loss Sugar Purity Purity Purity increase Color No. (sec) Fraction (% Olig. wt.) (% Olig.) (%, dry basis) (%) (%) (% of control» (lCUMSA)

Control whole Beet 73.1 86.0 91.8 130 20 root 2.9 1.3 73.7 87.2 93.1 1.4 140 C c

peel 32.3 45.4 60.1 4500 :3 ~

25 root 3.5 1.4 74.6 87.7 93.0 1.3 130 a, peel 30.0 43.5 57.9 3500 VI c

~30 root 3.6 1.5 75.0 86.3 93.3 1.6 140 el peel 30.6 45.1 57.3 6700 til

1"1>

!l­2 Control whole Beet 72.0 84.8 92.7 130 IS root 2.1 0.8 72.6 85.7 93.1 0.4 120

l ~

peel 28.2 42.4 62.3

20 root 2.9 1.3 72.9 86.3 92.9 0.2 110 peel 32.0 47.5 64.1 2000

25 root 3.5 1.6 73.5 86.1 93.0 0.3 120 peel 32.5 49.9 66.5 2300

30 root 3.9 1.7 73.9 86.6 93.7 1.1 110 peel 30.7 47.0 62.7 2500

I Steam 1825 kPa. I Relative percent.

~ !t z 0 ....

75 Wmter 1989 Peeling Sugarbeets by Use of High Pressure Steam

to volume ratio than the root. The surface material removed from the crown is also thicker than the skin on the root. While the peel losses as a percentage of the original crown and root weight in­creased with longer treatment times for both beet fractions, the ratio of the fractions was relatively constant. That is, peel from the crown always represented about 30-35% of the total peel weight of a whole beet.

Peeled roots were judged satisfactory after the 40 sec steam treatment where the root peel loss was 3.7 percent. The peeled crown was unsatisfactory until a 60 sec treatment which produced a crown peel loss of 10.3 percent, and a root peel loss of 4.8 percent. Since the root was satisfactory after a peel loss of 3.7 percent (40 sec treatment), the difference between the 4.8 and 3.7 weight per­cent of the root (60 sec minus 40 sec treatments) represents good root flesh which became part of the peel fraction only to achieve a satisfactory peeled crown area for the whole uncrowned beet.

Steam treatment times required to peel the crowned beets were about half those previously required for the uncrowned beets (Table 6) to reach the same degree of peel loss. Sugar losses were also lower for the crowned beets. The quality of brei and thin juices from crowned peeled beets were basically the same as from the peeled uncrowned beets. Thin juice purity increases of up to 1.6% (relative) were obtained, the same value as for the uncrowned beets. There was little difference in color values of thin juice from peeled and unpeeled beets.

ACKNOWLEDGMENTS

This project was a cooperative investigation with the Beet Sugar Development Foundation.

The authors thank Gary McDonald for analytical support, Judy Ikawa, Jeff McKee, and Sean Mullin for experimental help, and the Spreckels Sugar Div., Amstar Corp., for supplying sugarbeets and other assistance. .

Reference to a company and/or product named by the Depart­ment is only for purposes of information and does not imply ap­proval or recommendation of the product to the exclusion of others which may also be suitab~e.

LITERATURE CITED 1. Association of Analytical Chemists. 1980. Official methods of analysis, 13th

ed., Washington, D.C. 2. Brown, R. and R. Serro. 1954. A method for determination of thin juice purity

from individual mother beets. Proc. Am. Soc. Sugar Beet Techno!. 8(2): 274-278.

3. Carruthers, A. and J.ET. Oldfield. 1961. Methods for the assessment of beet quality. Int. Sugar J. 63: 72-74, 103-105, 137-139.

4. Chapman, H.D. and P.E Prah. 1961. Methods of analysis for soils, plants, and waters. University of California Press, Berkeley, CA.

5. Huxsol, c.c. and T. Smith. 1975. Peeling potatoes for processing. Pages 275-304. In Potato Processing. AVI Pub. Co., Westport, CT.

76 Journal of Sugar Beet Research Vol 26 No 1

6. Madsen, R.E and W.K. Nielsen. 1982. Methods of improving the recovery of sugar from sugar beets. U.S. Patent No. 4,326,892, April 27, 1982.

7. Madsen, R.E and W.K. Nielsen, B. Wintrom-Olsen, and T.E. Nielsen. 1979. Formation of color compounds in production of sugar from sugar beet. Sugar Tech. Rev., 6: 49-115.

8. Schneider, E (ed). Pages 14-17. In Sugar Analysis, ICUMSA methods. British Sugar Corp., Peterborough, England.

9. Ibid. Pages 125-128.