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Textural Analysis of Crystallized Honey Using Response Surface Methodology
Can. lnst. Food Sci. Technol. J. Vol. 23. No. 4/5, pp. 178-182, 1990
RESEARCH
Textural Analysis Of Crystallized Honey Using Response Surface Methodology l J.M. Shinn 2 and S.L. Wang3 Horticultural Products Laboratory Horticultural Research Institute of Ontario Vineland Station, Ontario LOR 2EO
Abstract
Introduction
Raw honey samples were selected for response surface experimental design based on their chemical composition. Selected batches of honey were then crystallized using the Dyce process. The effect of glucose/maltose fraction, moisture, percent seed, holding time and conditioning on texture was studied. Using a Voland/Stevens texture analyzer, textural parameters including peak force, yield force, adhesiveness and cohesiveness of the crystallized honey were measured. Response surface methodology was employed to establish the relationship between the chemical and processing factors and the textural parameters. Optimum chemical composition and processing conditions for maximum textural responses were estimated using mathematical model equations. These model equations can be used for predicting the final texture of crystallized honey with known levels of each factor, or for controlling the final texture by selecting suitable levels of chemical composition and processing conditions.
Honey is composed of carbohydrates, 95-99070 of which are sugars (Doner, 1977). The majority of the sugars are fructose and glucose which are present in approximately equal proportions, and a minor sugar, maltose, ranges generally from 5 to 9% (Austin, 1958; White, 1978). The specific saccharide level, and moisture content are influenced by floral source and variations in climatic as well as environmental conditions (White, 1978). Spontaneous crystallization which occurs after extraction tends to be coarse grained. To improve the texture of honey, fine seed crystal are introduced as nuclei for growth under a process of controlled crystallization (Dyce, 1931). Several factors have been implicated in affecting the texture of crystallized honey (Austin, 1958). A higher glucose to moisture ratio promotes spontaneous crystal growth in unprocessed honey. Other factors that affect the formation of glucose monohydrate crystals from liquid are: the concentration and state of supersaturation of the main sugars and minor components, the number and size of colloidal particles and temperature (Kaloyereas and Oertel, 1958). For creamed honey, the time allowed for setting under controlled storage conditions will affect final hardness (Guilbault, 1965). Texture, particularly graininess, can be controlled by conditioning the honey at 4°C for several hours according to Dyce (1931) and Guilbault (1965). The purpose of this study was to determine the effects of various chemical and processing factors on the textural properties of crystallized honey using response surface methodology, and to establish mathematical model equations for the prediction of the behaviour of crystallized honey.
Resume Des echantillons de miel cru furent selectionnes pour etudier les phenomenes de surface avec un plan experimental base sur leur composition chimique. Des lots de miel furent ensuite cristallises a l'aide du procede Dyce. La texture du miel fut etudiee en rapport avec la fraction glucose/maltose, I'humidite, Ie degre d'ensemencement, Ie temps de retention et Ie conditionnement. A l'aide d'un texturometre Voland/Stevens, on a mesure les parametres de texture dont la force maximale, la limite de resistance, I'adhesivite et la cohesivite du miel cristallise. La methodologie des phenomenes de surface fut employee pour etablir la relation entre les facteurs chimiques et de traitement et les parametres de la texture. La composition chimique optimale et les conditions de traitement optimales pouvant Ie plus influencer la texture furent evaluees a l'aide d'equations mathematiques modeles. Ces equations modeles peuvent servir a predire la texture finale du miel cristallise avec des niveaux connus pour chaque facteur, ou pour controler la texture finale par Ie choix des niveaux de composition chimique et de conditions de traitement.
I Presented, in part, at the 31st Annual Meeting of the Canadian Institute of Food Science and Technology, 1988, Winnipeg, Man. 2 Present Address: Prince Edward Island Food Technology Centre, P.O. Box 2000, Charlottetown, P.E.I. CIA 7N8 3 To Whom correspondence should be addressed.
Copyright <>
Materials And Methods Chemical Analyses A titratable sugar fraction (glucose and maltose fraction) was determined using an iodometric titra-
1m Canadian Institute of Food Science and Technology 178
tion (Lothrop and Holmes, 1941) without any correction. This glucose/maltose fraction (GMF) was used as a general guide for selecting honey. Sugar solid values were determined and converted to percent honey solids according to White (1978) using an Abbe refractometer (American Optical, Buffalo, NY). Percent moisture was calculated as the difference between 100070 and percent honey solids.
Response Surface Experimental Design The experiment was designed with a central composite rotatable response surface design according to Khuri and Cornell (1987) using four factors, i.e. glucose/maltose fraction, moisture, seed and holding time. Each of these factors was assigned five levels. An additional factor was randomly assigned to the treatments so that half the processed honey received a one-day conditioning treatment. Hence, this experiment consisted of five factors, eight star points and six centre points at levels shown in Table 1. Data were analyzed as a multiple regression analysis of variance (MANOVA) using software from SAS (1982). Initially, linear, quadratic and crossproduct terms for all five factors were included. Response models were then simplified by removing insignificant terms at the 15% level. Using SAS/GRAPH software, the response surface plots were generated by holding two factors constant and plotting the estimated response against the remaining two factors.
Processing Method Based on the response surface design, batches of honey with suitable GMF and moisture were selected for processing. Their moisture was adjusted either by adding de-ionized water or by evaporating under vacuum to the desired level. These batches of honey were divided into small lots and crystallized under various prescribed processing conditions. The crystallization procedure consisted of melting, pasteurization, seeding and holding at l2°C according to Dyce (1931). Seeding honey was prepared by blending creamed honey thoroughly before use. The seeded honeys were stored in small plastic tubs for textural analysis. Half of the sample lots were conditioned at 4°C for one day prior to holding at l2°C.
Table
I. Response surface design: Various levels of chemical and processing factors.
Factor Glucose/maltose fraction (G)(OJo) . Moisture (M)(%) Seed (S)(%) Holding time (H)(days at 12°C) Conditioning (F)(days at 4°C)
Can. Insl. Food Sci. Technol. J. Vol. 23, No.
Range of Levels
34 15 7 8 0
4/5,
36 16 9 10 1
1990
38 17 11 12
40 18 13 14
42 19 15 16
Textural Analysis Measurements were made with a Voland/Stevens TA1000 texture analyzer (Texture Technologies Corp., Scarsdale, NY). The resulting force-deformation curve was based on constant speed and linear deformation of the sample to a selected distance of penetration. Test parameters were chosen based on preliminary trials. A circular, flat-faced probe with 3 mm diameter was used to penetrate a honey sample once to a 7 mm depth, at a rate of 0.5 mm/s. Several textural parameters, including peak force, yield force and adhesiveness were measured with triplicated samples. Peak force was the maximum force during compression, yield force was the initial break point at the surface and adhesiveness was the maximum negative force registered during upstroke. The ratio between peak and adhesive forces, which relates the positive compression force and the negative pulling force, was calculated as cohesiveness. However, this was used here as a general indicator for the internal strength and was not equivalent to the values obtained from the a two-cycled compression test (Bourne, 1978). Table 2. Textural responses of crystallized honey to different chemical and processing conditions based on a response surface design.
p7 34.69 17.09 11 12 36.16 16.34 9 10 36.16 16.34 9 14 36.16 16.34 13 10 36.16 16.34 13 14 36.16 18.10 9 10 36.16 18.10 9 14 36.16 18.10 13 10 36.16 18.10 13 14 37.91 15.10 11 12 37.83 16.94 7 12 37.83 16.94 11 8 37.83 16.94 11 12 37.83 16.94 11 12 37.83 16.94 11 12 37.83 16.94 11 12 37.83 16.94 11 12 37.83 16.94 11 12 37.83 16.94 11 16 37.83 16.94 15 12 37.93 19.05 11 12 40.17 15.93 9 10 40.17 15.93 9 14 40.17 15.93 13 10 40.17 15.93 13 14 40.16 18.21 9 10 40.16 18.21 9 14 13 10 40.16 18.21 41.16 18.21 13 14 42.30 17.04 11 12 1G1ucose/maltose fraction 2Moisture (%) 3Seed (%) 4Holding (day) 5Conditioning (day) 6Yield force 7Peak force 8Adhesiveness 9Cohesiveness
1 I 0 0 1 0 1 1 0 0 1 0 0 0 0 I
1 1 1 0 1 0 1 1 0 1 0 0 1 0 (%)
11.83 14.95 2.58 6.71 12.72 16.02 5.46 10.04 31.87 34.42 20.58 23.30 15.35 20.33 15.24 16.38 29.53 35.14 29.52 32.60 32.13 37.58 16.92 17.04 80.00 89.33 93.17 93.23 88.00 93.17 76.25 78.03 78.67 84.02 80.55 81.50 142.0 159.4 127.0 130.5 193.7 216.5 27.82 31.75 109.5 137.7 102.8 126.3 202.7 219.6 174.3 182.3 249.7 287.5 200.0 240.8 335.7 331.0 526.7 498.7
18.72 11.67 23.30 14.93 39.61 25.57 21.75 19.00 36.50 39.58 42.40 21.82 97.33 99.00 101.0 83.62 91.88 90.25 110.4 108.8 90.8 40.57 121.2 115.8 126.2 103.7 101.7 100.2 109.7 113.7
0.80 0.58 0.69 0.67 0.87 0.91 0.93 0.86 0.96 0.83 0.89 0.78 0.92 0.94 0.92 0.93 0.91 0.90 1.44 1.20 2.38 0.78 1.13 1.09 1.74 1.76 2.83 2.41 3.02 4.39
Shinn and Wang / 179
Results and Discussion The texture responses including peak force, yield force, adhesiveness and cohesiveness of various crystallized honey samples are given in Table 2. Due to the wide range of textural values, the values were transformed by natural logarithmic functions. Statistical analysis of the transformed data showed that conditioning at 4°C for one day had no significant effect on any textural parameter. This result, obtained under a wide range of honey composition, does not support the previous finding by Guilbault ~1965).
Each textural parameter was then analyzed using MANOVA, and the insignificant terms were eliminated from the model. The high levels of probability (15070) were chosen because the experimental design required fewer replicated responses. This also ensured that factors which contributed only a small amount of variance would not be eliminated from the model. The final model statements obtained are as follows: In (peak force) = -62.64 + 0.52 G + 2.23 M + 1.40 S + 2.56 H -0.04 H*H - 0.08 M*S - 0.09 M*H; R2 = 0.94 (I) In (yield force) = -78.02 + 0.56 G + 2.98 M + 1.64 S + 2 3.44 H - 0.04 H*H - 0.09 M*S - 0.13 M*H; R = 0.94 (2) In (adhesiveness) = -151.78 + 4.26 G + 5.69 M + 0.67 S + 2.48H - ~.05 G*G - 0.14 M*M - 0.03 S*S - 0.05 H*H - 0.Q7 M*H; R = 0.91 (3) In (cohesiveness) = 112.83 - 4.11 G - 4.49 M - 0.54 H + 0.04 G*G + 0.08 M*M + 0.06 G*M + 0.01 G*S + 0.02 G*H 0.02 M*S; R2 = 0.98 (4) Where:
G = Glucose/maltose fraction Moisture, S=Seed, H = Holding Time
In order to analyse the changes of textural response with respect to each factor, the change of slope was calculated. For example, peak force changes with respect to glucose/maltose fraction, moisture, seeds and holding time could be expressed as d[ln(P)]/d(G), d[ln(P)]/d(M), d[ln(P)]/d(S) and d[ln(P)]/d(H) (P designates peak force). Analysis of changmg trend using derivatives of the model statement is more precise than using the three-dimensional graphs. However, some three-dimensional graphs are provided for visual illustration. The optimum value of each factor for maximum textural responses was calculated by solving the equations d[ln(P)]/d(G) = 0, d[ln(P)]/d(M) = 0, etc. . Due to the complexity of the experiment, which mvolves multiple textural responses to multiple factors, the effects of chemical and processing factors on the texture of crystallized honey are discussed separately.below.
Peak Force The optimum level of each factor for the highest peak force was computed and found to be: moisture = 18.7%; seed = 15.3%; and holding = 12.8 d. The glucose/maltose fraction was shown to increase 180 / Shinn and Wang
peak force continuously at a constant rate. A higher glucose/maltose fraction gave rise to a higher peak force regardless of the changes of other factors. However, the glucose/maltose fraction of a natural honey seldom exceeded 42% and therefore the optimum level realistically would be 42%. ' A three-dimensional graph was plotted to show the relationship between peak force, moisture and glucose/maltose fraction, assuming that the honey ?ad 11 % seed and 12d holding (Figure la). An mcrease of moisture is beneficial for increased peak force as long as holding time is kept at 12 d. In a graph showing the relationship between peak force moisture and holding, a holding time greater tha~ 12 d is unfavourable for peak force increase especially at high moisture levels (Figure Ib). Seed i~ ~nfluenced by moisture level and has a relatively small Impact on peak force.
Yield Force . The optimum level of each factor for the highest yIeld force was found to be that moisture = 18.6%, seed = 15.9%, holding = 12 d, and glucose/maltose fraction = 42% (for the same reason mentioned above). Yield force and peak force were shown to be similar in many aspects. Both had a similar model equation and an optimum value for each factor.
HOLDING
= 12, SEED = 11
iiJ ()
a:
ou.
10
7
~
«
4
.s
-2
~ 19
18
17
16
15
34
42 40 38 36 ~ clp
0~
MOISTURE % Fig. lb. Effect of moisture and holding time on peak force measurements.
SEED
iiJ
()
10
oU.
7
~
4
a:
«
-.s
= 11,
GMF
=42
16
~
14 -2~_
19
18
17
16
MOISTURE %
15
8
10
12
_I
'F' r~~
~~'
<;J-....
,?,OV
Fig. la. Effect of glucose/maltose fraction and moisture on peak force measurements. J. Inst. Can. Sci. Technol. Aliment. Vol. 23, No. 4/5, 1990
Also, peak force values and yield force values were identical in each measurement on the Voland/Stevens texture analyzer.
Adhesiveness The optimum level of each factor for the highest adhesiveness was found to be: moisture = 170/0; seed = 12.5%; holding = 13.5 d; and glucose/maltose fraction = 40.9%. In this model, all four factors were related with adhesiveness with significant quadratic functions. Changes in adhesiveness are affected, to a large extent, by glucose/maltose fraction, moisture and holding time. The response of adhesiveness to GMF is only affected by GMF. Assuming a holding of 12 d and a moisture content of 18%, the graph shows that adhesiveness increases with GMF and seed to a limit beyond which the response becomes negative (Figure 2). In other words, higher level of GMF and seed depresses the increase of adhesiveness under this condition. The response of adhesiveness to moisture or holding is affected by both moisture and holding. Higher moisture and longer holding times do not favour the increase of adhesiveness. It is interesting to note the effect of seed on adhesiveness is not dependent on moisture as are other textural responses.
Cohesiveness The optimum level of each factor: for the highest cohesiveness was found to be: moisture = 16.7%; seed = 9.5%; holding = 22 days and glucose/maltose fraction = 33.4%. These values indicate that cohesiveness is a difficult parameter to control. The optimum level of GMF and holding are theoretical values with which to achieve the highest cohesiveness, that is, in theory, a GMF level higher than 33.4% will nullify the effect of holding. However, at low GMF and moisture levels when holding = 12 d and seed = 11 %, the response of cohesiveness is negative
HOLDING
en
en
= 12.
MOISTURE
(Figure 3). Since higher levels of GMF and moisture are required for improved cohesiveness (Figure 3), relatively high GMF levels are preferred for processing applications. The level of moisture and seed tends to affect each other's ability to influence textural responses. Higher levels of seed improves the response of cohesiveness to moisture and vice versa. As a whole, the manifestation of the effect of various factors on cohesiveness is far more complicated with many significant interactions between factors. Based on the model equations and estimated optimum level of various factors for maximum textural responses, it is possible to predict the textural behaviour of crystallized honey under a given chemical and processing condition. If a processing condition is established, the textural behaviour can be predicted by the chemical composition of honey alone. The uniformity of crystallized honey was found to be excellent because only small differences between yield force and peak force were detected by the Voland/Stevens TA-lOOO texture analyzer. Also, the homogeneous texture was shown by the good reproducibility obtained from the replications of textural measurement using a small probe.
Conclusions In the process of inducing crystallization of liquid honey, two chemical factors and two processing factors were found to affect the final texture of the crystallized honey. The glucose/maltose fraction was used as a primary indicator for selecting sujtable honey for processing, since moisture was easy to adjust. The changes of hardness, yield force, adhesiveness and cohesiveness of crystallized honey were illustrated with mathematical model equations. Using the model equations, optimum values of each factor for highest textural response were estimated. if the levels of chemical factors are pre-selected and the
= 18
HOLDING
6
en
~
4r--_~
Z UJ
f3:::c C
« -
.so
SEED
= 11
-
UJ
Z
= 12.
f3
2
0 -2
~--15
4~2-~4lnO--=----"""- 7 9 38 36 34 GMF%
11
13
f;)c¥ ~«.,~
Fig. 2. Effect of glucose/maltose fraction and seed on adhesiveness measurements. Can. lnst. Food Sci. Technol. J. Vol. 23, No. 4/5, 1990
> en w :::c
o
~
5.0
3.5 2. 0 ~
0.5
-1.
0191-~---=::_---,..__ 18
17
16
1534
~
3638
~ c¥
Q>~
MOISTURE % Fig. 3. Effect of glucose/maltose fraction and moisture on cohesiveness values.
Shinn and Wang / 181
processing factors controlled, the final textural property of a crystallized honey can be predicted. At present, crystallized honey is made to provide a creamy and spreadable texture. Although creamed honey has been manufactured for many decades since the invention of the crystallization process by Dyce (1931), controlling the texture of a creamed honey is more or less an art to an experienced honey processor. They may know, through experience, that certain processing conditions may be favourable for making a soft and spreadable creamed honey, but sometimes a creamed honey with more rigid texture may result. This is because that chemical composition of honey is not considered in the manufacture of creamed honey by most small processors. In this investigation, the textural properties of the crystallized honey were defined by a texture analyser, thus providing quantifiable values to the changing texture of creamed honey. As long as the textural measurements of a honey product are available, the processor should be able to reproduce that product by manipulating the chemical and processing factors. While the factors can be controlled to yield a soft and spreadable texture, they can also be controlled to yield' a rigid texture. By properly blending honey to a desirable level of chemical composition and regulating the amount of seed and holding time, the final texture of the crystallized honey can be better controlled. It should be noted however, blending of honey must be done within the honey specification estab-
182 /
Shinn and Wang
lished by Health and Welfare Canada (1975), or other relevant regulations for exportation.
References Austin, G.H. 1958. Maltose content of Canadian honeys and its probable effect on crystallization. Proc. Int. Congr. Entomo!., 10th, 1956.4:1001. Montreal, P.Q. Bourne, M.C. 1978. Texture profile analysis. Food Techno!. 32(7):62. Doner, L.W. 1977. The sugars of honey - a review. J. Sci. Food. Agric. 28:443. Dyce, E. J. 1931. Fermentation and crystallization of honey. Bull. Cornell Agric. Exp. Sta. No. 528. Guilbault, J. 1965. Crystallization of Honey. Thesis. Ontario Agric. College, Guelph, Onto Health and Welfare Canada. 1975. Laws and Statures. Honey, Section B.18. 025-027. Khuri, A. I. and Cornell, J .A. 1987. Response Surfaces, Design and Analysis, Marcel Dekker, Inc. New York. p. 116. Kaloyereas, S.A. and Oertel, E. 1958. Crystallization of honey, The effect of ultrasonic treatment; the effect of the rate of freezing; and a new inhibitor of crystallization for honey. Proc. Int. Congr. Entomo!., 10th, 1956.4:1007. Montreal, P.Q. Lothrop, R.E. and Holmes, R.L. 1931. Determination of dextrose and levulose in honey by use of iodine-oxidation method. Ind. Eng. Chern., Anal. ed. 3:334. SAS. 1982. SAS User's Guide: Statistics, SAS Institute, Cary, NC White, J.W. Jr. 1978. Honey. In: Advances in Food Research. Academic Press Inc., New York. 24:288.
Submitted April 18, 1989 Revised February 22, 1990 Accepted May 31, 1990
J. Ins/. Can. Sci. Techno/. Aliment. Vol. 23. No. 4/5, 1990
RESEARCH
Textural Analysis Of Crystallized Honey Using Response Surface Methodology l J.M. Shinn 2 and S.L. Wang3 Horticultural Products Laboratory Horticultural Research Institute of Ontario Vineland Station, Ontario LOR 2EO
Abstract
Introduction
Raw honey samples were selected for response surface experimental design based on their chemical composition. Selected batches of honey were then crystallized using the Dyce process. The effect of glucose/maltose fraction, moisture, percent seed, holding time and conditioning on texture was studied. Using a Voland/Stevens texture analyzer, textural parameters including peak force, yield force, adhesiveness and cohesiveness of the crystallized honey were measured. Response surface methodology was employed to establish the relationship between the chemical and processing factors and the textural parameters. Optimum chemical composition and processing conditions for maximum textural responses were estimated using mathematical model equations. These model equations can be used for predicting the final texture of crystallized honey with known levels of each factor, or for controlling the final texture by selecting suitable levels of chemical composition and processing conditions.
Honey is composed of carbohydrates, 95-99070 of which are sugars (Doner, 1977). The majority of the sugars are fructose and glucose which are present in approximately equal proportions, and a minor sugar, maltose, ranges generally from 5 to 9% (Austin, 1958; White, 1978). The specific saccharide level, and moisture content are influenced by floral source and variations in climatic as well as environmental conditions (White, 1978). Spontaneous crystallization which occurs after extraction tends to be coarse grained. To improve the texture of honey, fine seed crystal are introduced as nuclei for growth under a process of controlled crystallization (Dyce, 1931). Several factors have been implicated in affecting the texture of crystallized honey (Austin, 1958). A higher glucose to moisture ratio promotes spontaneous crystal growth in unprocessed honey. Other factors that affect the formation of glucose monohydrate crystals from liquid are: the concentration and state of supersaturation of the main sugars and minor components, the number and size of colloidal particles and temperature (Kaloyereas and Oertel, 1958). For creamed honey, the time allowed for setting under controlled storage conditions will affect final hardness (Guilbault, 1965). Texture, particularly graininess, can be controlled by conditioning the honey at 4°C for several hours according to Dyce (1931) and Guilbault (1965). The purpose of this study was to determine the effects of various chemical and processing factors on the textural properties of crystallized honey using response surface methodology, and to establish mathematical model equations for the prediction of the behaviour of crystallized honey.
Resume Des echantillons de miel cru furent selectionnes pour etudier les phenomenes de surface avec un plan experimental base sur leur composition chimique. Des lots de miel furent ensuite cristallises a l'aide du procede Dyce. La texture du miel fut etudiee en rapport avec la fraction glucose/maltose, I'humidite, Ie degre d'ensemencement, Ie temps de retention et Ie conditionnement. A l'aide d'un texturometre Voland/Stevens, on a mesure les parametres de texture dont la force maximale, la limite de resistance, I'adhesivite et la cohesivite du miel cristallise. La methodologie des phenomenes de surface fut employee pour etablir la relation entre les facteurs chimiques et de traitement et les parametres de la texture. La composition chimique optimale et les conditions de traitement optimales pouvant Ie plus influencer la texture furent evaluees a l'aide d'equations mathematiques modeles. Ces equations modeles peuvent servir a predire la texture finale du miel cristallise avec des niveaux connus pour chaque facteur, ou pour controler la texture finale par Ie choix des niveaux de composition chimique et de conditions de traitement.
I Presented, in part, at the 31st Annual Meeting of the Canadian Institute of Food Science and Technology, 1988, Winnipeg, Man. 2 Present Address: Prince Edward Island Food Technology Centre, P.O. Box 2000, Charlottetown, P.E.I. CIA 7N8 3 To Whom correspondence should be addressed.
Copyright <>
Materials And Methods Chemical Analyses A titratable sugar fraction (glucose and maltose fraction) was determined using an iodometric titra-
1m Canadian Institute of Food Science and Technology 178
tion (Lothrop and Holmes, 1941) without any correction. This glucose/maltose fraction (GMF) was used as a general guide for selecting honey. Sugar solid values were determined and converted to percent honey solids according to White (1978) using an Abbe refractometer (American Optical, Buffalo, NY). Percent moisture was calculated as the difference between 100070 and percent honey solids.
Response Surface Experimental Design The experiment was designed with a central composite rotatable response surface design according to Khuri and Cornell (1987) using four factors, i.e. glucose/maltose fraction, moisture, seed and holding time. Each of these factors was assigned five levels. An additional factor was randomly assigned to the treatments so that half the processed honey received a one-day conditioning treatment. Hence, this experiment consisted of five factors, eight star points and six centre points at levels shown in Table 1. Data were analyzed as a multiple regression analysis of variance (MANOVA) using software from SAS (1982). Initially, linear, quadratic and crossproduct terms for all five factors were included. Response models were then simplified by removing insignificant terms at the 15% level. Using SAS/GRAPH software, the response surface plots were generated by holding two factors constant and plotting the estimated response against the remaining two factors.
Processing Method Based on the response surface design, batches of honey with suitable GMF and moisture were selected for processing. Their moisture was adjusted either by adding de-ionized water or by evaporating under vacuum to the desired level. These batches of honey were divided into small lots and crystallized under various prescribed processing conditions. The crystallization procedure consisted of melting, pasteurization, seeding and holding at l2°C according to Dyce (1931). Seeding honey was prepared by blending creamed honey thoroughly before use. The seeded honeys were stored in small plastic tubs for textural analysis. Half of the sample lots were conditioned at 4°C for one day prior to holding at l2°C.
Table
I. Response surface design: Various levels of chemical and processing factors.
Factor Glucose/maltose fraction (G)(OJo) . Moisture (M)(%) Seed (S)(%) Holding time (H)(days at 12°C) Conditioning (F)(days at 4°C)
Can. Insl. Food Sci. Technol. J. Vol. 23, No.
Range of Levels
34 15 7 8 0
4/5,
36 16 9 10 1
1990
38 17 11 12
40 18 13 14
42 19 15 16
Textural Analysis Measurements were made with a Voland/Stevens TA1000 texture analyzer (Texture Technologies Corp., Scarsdale, NY). The resulting force-deformation curve was based on constant speed and linear deformation of the sample to a selected distance of penetration. Test parameters were chosen based on preliminary trials. A circular, flat-faced probe with 3 mm diameter was used to penetrate a honey sample once to a 7 mm depth, at a rate of 0.5 mm/s. Several textural parameters, including peak force, yield force and adhesiveness were measured with triplicated samples. Peak force was the maximum force during compression, yield force was the initial break point at the surface and adhesiveness was the maximum negative force registered during upstroke. The ratio between peak and adhesive forces, which relates the positive compression force and the negative pulling force, was calculated as cohesiveness. However, this was used here as a general indicator for the internal strength and was not equivalent to the values obtained from the a two-cycled compression test (Bourne, 1978). Table 2. Textural responses of crystallized honey to different chemical and processing conditions based on a response surface design.
p7 34.69 17.09 11 12 36.16 16.34 9 10 36.16 16.34 9 14 36.16 16.34 13 10 36.16 16.34 13 14 36.16 18.10 9 10 36.16 18.10 9 14 36.16 18.10 13 10 36.16 18.10 13 14 37.91 15.10 11 12 37.83 16.94 7 12 37.83 16.94 11 8 37.83 16.94 11 12 37.83 16.94 11 12 37.83 16.94 11 12 37.83 16.94 11 12 37.83 16.94 11 12 37.83 16.94 11 12 37.83 16.94 11 16 37.83 16.94 15 12 37.93 19.05 11 12 40.17 15.93 9 10 40.17 15.93 9 14 40.17 15.93 13 10 40.17 15.93 13 14 40.16 18.21 9 10 40.16 18.21 9 14 13 10 40.16 18.21 41.16 18.21 13 14 42.30 17.04 11 12 1G1ucose/maltose fraction 2Moisture (%) 3Seed (%) 4Holding (day) 5Conditioning (day) 6Yield force 7Peak force 8Adhesiveness 9Cohesiveness
1 I 0 0 1 0 1 1 0 0 1 0 0 0 0 I
1 1 1 0 1 0 1 1 0 1 0 0 1 0 (%)
11.83 14.95 2.58 6.71 12.72 16.02 5.46 10.04 31.87 34.42 20.58 23.30 15.35 20.33 15.24 16.38 29.53 35.14 29.52 32.60 32.13 37.58 16.92 17.04 80.00 89.33 93.17 93.23 88.00 93.17 76.25 78.03 78.67 84.02 80.55 81.50 142.0 159.4 127.0 130.5 193.7 216.5 27.82 31.75 109.5 137.7 102.8 126.3 202.7 219.6 174.3 182.3 249.7 287.5 200.0 240.8 335.7 331.0 526.7 498.7
18.72 11.67 23.30 14.93 39.61 25.57 21.75 19.00 36.50 39.58 42.40 21.82 97.33 99.00 101.0 83.62 91.88 90.25 110.4 108.8 90.8 40.57 121.2 115.8 126.2 103.7 101.7 100.2 109.7 113.7
0.80 0.58 0.69 0.67 0.87 0.91 0.93 0.86 0.96 0.83 0.89 0.78 0.92 0.94 0.92 0.93 0.91 0.90 1.44 1.20 2.38 0.78 1.13 1.09 1.74 1.76 2.83 2.41 3.02 4.39
Shinn and Wang / 179
Results and Discussion The texture responses including peak force, yield force, adhesiveness and cohesiveness of various crystallized honey samples are given in Table 2. Due to the wide range of textural values, the values were transformed by natural logarithmic functions. Statistical analysis of the transformed data showed that conditioning at 4°C for one day had no significant effect on any textural parameter. This result, obtained under a wide range of honey composition, does not support the previous finding by Guilbault ~1965).
Each textural parameter was then analyzed using MANOVA, and the insignificant terms were eliminated from the model. The high levels of probability (15070) were chosen because the experimental design required fewer replicated responses. This also ensured that factors which contributed only a small amount of variance would not be eliminated from the model. The final model statements obtained are as follows: In (peak force) = -62.64 + 0.52 G + 2.23 M + 1.40 S + 2.56 H -0.04 H*H - 0.08 M*S - 0.09 M*H; R2 = 0.94 (I) In (yield force) = -78.02 + 0.56 G + 2.98 M + 1.64 S + 2 3.44 H - 0.04 H*H - 0.09 M*S - 0.13 M*H; R = 0.94 (2) In (adhesiveness) = -151.78 + 4.26 G + 5.69 M + 0.67 S + 2.48H - ~.05 G*G - 0.14 M*M - 0.03 S*S - 0.05 H*H - 0.Q7 M*H; R = 0.91 (3) In (cohesiveness) = 112.83 - 4.11 G - 4.49 M - 0.54 H + 0.04 G*G + 0.08 M*M + 0.06 G*M + 0.01 G*S + 0.02 G*H 0.02 M*S; R2 = 0.98 (4) Where:
G = Glucose/maltose fraction Moisture, S=Seed, H = Holding Time
In order to analyse the changes of textural response with respect to each factor, the change of slope was calculated. For example, peak force changes with respect to glucose/maltose fraction, moisture, seeds and holding time could be expressed as d[ln(P)]/d(G), d[ln(P)]/d(M), d[ln(P)]/d(S) and d[ln(P)]/d(H) (P designates peak force). Analysis of changmg trend using derivatives of the model statement is more precise than using the three-dimensional graphs. However, some three-dimensional graphs are provided for visual illustration. The optimum value of each factor for maximum textural responses was calculated by solving the equations d[ln(P)]/d(G) = 0, d[ln(P)]/d(M) = 0, etc. . Due to the complexity of the experiment, which mvolves multiple textural responses to multiple factors, the effects of chemical and processing factors on the texture of crystallized honey are discussed separately.below.
Peak Force The optimum level of each factor for the highest peak force was computed and found to be: moisture = 18.7%; seed = 15.3%; and holding = 12.8 d. The glucose/maltose fraction was shown to increase 180 / Shinn and Wang
peak force continuously at a constant rate. A higher glucose/maltose fraction gave rise to a higher peak force regardless of the changes of other factors. However, the glucose/maltose fraction of a natural honey seldom exceeded 42% and therefore the optimum level realistically would be 42%. ' A three-dimensional graph was plotted to show the relationship between peak force, moisture and glucose/maltose fraction, assuming that the honey ?ad 11 % seed and 12d holding (Figure la). An mcrease of moisture is beneficial for increased peak force as long as holding time is kept at 12 d. In a graph showing the relationship between peak force moisture and holding, a holding time greater tha~ 12 d is unfavourable for peak force increase especially at high moisture levels (Figure Ib). Seed i~ ~nfluenced by moisture level and has a relatively small Impact on peak force.
Yield Force . The optimum level of each factor for the highest yIeld force was found to be that moisture = 18.6%, seed = 15.9%, holding = 12 d, and glucose/maltose fraction = 42% (for the same reason mentioned above). Yield force and peak force were shown to be similar in many aspects. Both had a similar model equation and an optimum value for each factor.
HOLDING
= 12, SEED = 11
iiJ ()
a:
ou.
10
7
~
«
4
.s
-2
~ 19
18
17
16
15
34
42 40 38 36 ~ clp
0~
MOISTURE % Fig. lb. Effect of moisture and holding time on peak force measurements.
SEED
iiJ
()
10
oU.
7
~
4
a:
«
-.s
= 11,
GMF
=42
16
~
14 -2~_
19
18
17
16
MOISTURE %
15
8
10
12
_I
'F' r~~
~~'
<;J-....
,?,OV
Fig. la. Effect of glucose/maltose fraction and moisture on peak force measurements. J. Inst. Can. Sci. Technol. Aliment. Vol. 23, No. 4/5, 1990
Also, peak force values and yield force values were identical in each measurement on the Voland/Stevens texture analyzer.
Adhesiveness The optimum level of each factor for the highest adhesiveness was found to be: moisture = 170/0; seed = 12.5%; holding = 13.5 d; and glucose/maltose fraction = 40.9%. In this model, all four factors were related with adhesiveness with significant quadratic functions. Changes in adhesiveness are affected, to a large extent, by glucose/maltose fraction, moisture and holding time. The response of adhesiveness to GMF is only affected by GMF. Assuming a holding of 12 d and a moisture content of 18%, the graph shows that adhesiveness increases with GMF and seed to a limit beyond which the response becomes negative (Figure 2). In other words, higher level of GMF and seed depresses the increase of adhesiveness under this condition. The response of adhesiveness to moisture or holding is affected by both moisture and holding. Higher moisture and longer holding times do not favour the increase of adhesiveness. It is interesting to note the effect of seed on adhesiveness is not dependent on moisture as are other textural responses.
Cohesiveness The optimum level of each factor: for the highest cohesiveness was found to be: moisture = 16.7%; seed = 9.5%; holding = 22 days and glucose/maltose fraction = 33.4%. These values indicate that cohesiveness is a difficult parameter to control. The optimum level of GMF and holding are theoretical values with which to achieve the highest cohesiveness, that is, in theory, a GMF level higher than 33.4% will nullify the effect of holding. However, at low GMF and moisture levels when holding = 12 d and seed = 11 %, the response of cohesiveness is negative
HOLDING
en
en
= 12.
MOISTURE
(Figure 3). Since higher levels of GMF and moisture are required for improved cohesiveness (Figure 3), relatively high GMF levels are preferred for processing applications. The level of moisture and seed tends to affect each other's ability to influence textural responses. Higher levels of seed improves the response of cohesiveness to moisture and vice versa. As a whole, the manifestation of the effect of various factors on cohesiveness is far more complicated with many significant interactions between factors. Based on the model equations and estimated optimum level of various factors for maximum textural responses, it is possible to predict the textural behaviour of crystallized honey under a given chemical and processing condition. If a processing condition is established, the textural behaviour can be predicted by the chemical composition of honey alone. The uniformity of crystallized honey was found to be excellent because only small differences between yield force and peak force were detected by the Voland/Stevens TA-lOOO texture analyzer. Also, the homogeneous texture was shown by the good reproducibility obtained from the replications of textural measurement using a small probe.
Conclusions In the process of inducing crystallization of liquid honey, two chemical factors and two processing factors were found to affect the final texture of the crystallized honey. The glucose/maltose fraction was used as a primary indicator for selecting sujtable honey for processing, since moisture was easy to adjust. The changes of hardness, yield force, adhesiveness and cohesiveness of crystallized honey were illustrated with mathematical model equations. Using the model equations, optimum values of each factor for highest textural response were estimated. if the levels of chemical factors are pre-selected and the
= 18
HOLDING
6
en
~
4r--_~
Z UJ
f3:::c C
« -
.so
SEED
= 11
-
UJ
Z
= 12.
f3
2
0 -2
~--15
4~2-~4lnO--=----"""- 7 9 38 36 34 GMF%
11
13
f;)c¥ ~«.,~
Fig. 2. Effect of glucose/maltose fraction and seed on adhesiveness measurements. Can. lnst. Food Sci. Technol. J. Vol. 23, No. 4/5, 1990
> en w :::c
o
~
5.0
3.5 2. 0 ~
0.5
-1.
0191-~---=::_---,..__ 18
17
16
1534
~
3638
~ c¥
Q>~
MOISTURE % Fig. 3. Effect of glucose/maltose fraction and moisture on cohesiveness values.
Shinn and Wang / 181
processing factors controlled, the final textural property of a crystallized honey can be predicted. At present, crystallized honey is made to provide a creamy and spreadable texture. Although creamed honey has been manufactured for many decades since the invention of the crystallization process by Dyce (1931), controlling the texture of a creamed honey is more or less an art to an experienced honey processor. They may know, through experience, that certain processing conditions may be favourable for making a soft and spreadable creamed honey, but sometimes a creamed honey with more rigid texture may result. This is because that chemical composition of honey is not considered in the manufacture of creamed honey by most small processors. In this investigation, the textural properties of the crystallized honey were defined by a texture analyser, thus providing quantifiable values to the changing texture of creamed honey. As long as the textural measurements of a honey product are available, the processor should be able to reproduce that product by manipulating the chemical and processing factors. While the factors can be controlled to yield a soft and spreadable texture, they can also be controlled to yield' a rigid texture. By properly blending honey to a desirable level of chemical composition and regulating the amount of seed and holding time, the final texture of the crystallized honey can be better controlled. It should be noted however, blending of honey must be done within the honey specification estab-
182 /
Shinn and Wang
lished by Health and Welfare Canada (1975), or other relevant regulations for exportation.
References Austin, G.H. 1958. Maltose content of Canadian honeys and its probable effect on crystallization. Proc. Int. Congr. Entomo!., 10th, 1956.4:1001. Montreal, P.Q. Bourne, M.C. 1978. Texture profile analysis. Food Techno!. 32(7):62. Doner, L.W. 1977. The sugars of honey - a review. J. Sci. Food. Agric. 28:443. Dyce, E. J. 1931. Fermentation and crystallization of honey. Bull. Cornell Agric. Exp. Sta. No. 528. Guilbault, J. 1965. Crystallization of Honey. Thesis. Ontario Agric. College, Guelph, Onto Health and Welfare Canada. 1975. Laws and Statures. Honey, Section B.18. 025-027. Khuri, A. I. and Cornell, J .A. 1987. Response Surfaces, Design and Analysis, Marcel Dekker, Inc. New York. p. 116. Kaloyereas, S.A. and Oertel, E. 1958. Crystallization of honey, The effect of ultrasonic treatment; the effect of the rate of freezing; and a new inhibitor of crystallization for honey. Proc. Int. Congr. Entomo!., 10th, 1956.4:1007. Montreal, P.Q. Lothrop, R.E. and Holmes, R.L. 1931. Determination of dextrose and levulose in honey by use of iodine-oxidation method. Ind. Eng. Chern., Anal. ed. 3:334. SAS. 1982. SAS User's Guide: Statistics, SAS Institute, Cary, NC White, J.W. Jr. 1978. Honey. In: Advances in Food Research. Academic Press Inc., New York. 24:288.
Submitted April 18, 1989 Revised February 22, 1990 Accepted May 31, 1990
J. Ins/. Can. Sci. Techno/. Aliment. Vol. 23. No. 4/5, 1990