Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
2010
Volume 13
Issue 2
Topic:
Food Science and Technology
ELECTRONIC
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
Grujiæ S. , Grujiæ R. , Polja¹eviæ J. 2010. EFFECT OF FOOD ADDITIVES ON SENSORY CHARACTERISTICS OF THERMO-STABLE MARMALADE, EJPAU 13(2), #11.
Available Online: http://www.ejpau.media.pl/volume13/issue2/art-11.html

EFFECT OF FOOD ADDITIVES ON SENSORY CHARACTERISTICS OF THERMO-STABLE MARMALADE

Slavica Grujiæ1, Radoslav Grujiæ2, Jelena Polja¹eviæ1
1 Faculty of Technology, University of Banja Luka, Bosnia and Herzegovina
2 Faculty of Technology Zvornik, University of East Sarajevo, Bosnia and Herzegovina

 

ABSTRACT

On the market of Bosnia and Herzegovina there is no any available marmalade or similar finished product with ability to form stable gel after re-heating. Our work was designed in aim to create marmalade useful for filling, before sourdough doughnuts heating during baking in oven or preparing deep-fried products. Experiment was designed in two parts. Marmalades were prepared in laboratory conditions from frozen peach and apple purée (pulp) in two combinations, 8 samples with 70% peach : 30% apple (1 sample with min. 70%, 5 samples with min. 67%  and 2 samples with min. 45% dry matter) and 3 samples with 50% peach : 50% apple (samples with min. 67% dry matter). Other ingredients used for marmalade preparations are sugar and additives in different proportion: gelling agents from producers DANISCO-CULTOR (GRINSTED FB-850) and OBIPECTIN (PECTIN BROWN RIBBON J, PECTIN PURPLE RIBBON B, PECTIN PURPLE RIBBON D-075 X), firming agent calcium chloride (E 509), acidity regulator sodium citrates (E 331) and citric acid (E 330). Prepared samples were pasteurized and hot filled in glass jars and closed with twist-off caps. For quality and chemical composition control of marmalade, we determined dry matter, total acids and pH. After 20 days storing on room temperature, for sensory analysis and stability control of thermo-reversible gel, we prepared doughnuts filled with samples of marmalade and baked in home electric oven. Doughnuts were prepared from BERLINER MIX (IREKS AROMA D.O.O.) and according recommended recipe. After sensory analysis of 11 marmalade samples before and after re-heating, 4 samples were selected for further investigation and tried to make products acceptable quality and with minimally necessary quantity of additives. 12 marmalades were prepared with 70% peach : 30% apple purée (pulp) (3 samples with min. 70%, 9 samples with min. 67% dry matter). After sensory analysis before and after baking in doughnuts 2 marmalades were selected, marmalade produced with DANISCO-CULTOR (GRINSTED FB-850) gelling additive and other with OBIPECTIN PECTIN (BROWN RIBBON J). Both samples had expected sensory quality after re-heating and cooling on room temperature, orange-light-brown colour, specific aroma of peach and apple, and as the most important evaluated sensory attributes were appearance and texture of homogeneous, medium-strong firm gel, useful for filling of doughnuts baked in oven and similar products.

Key words: thermo-stable marmalade, additives, sensory characteristics.

INTRODUCTION

Sensory and product testing researches are often responsible for new product development and strengthening their position on the market. Developers of new food product often find motivation and ideas for new product from different sources, in-house suggestions, R&D applications, marketing trends, external consultants and even costumers. Consumers today demand high-quality products in various innovative forms and for competitive prices [5,8,12,18,19,20].

Producers are trying to relate consumers' expectations with sensory quality characteristics responsible for product preference. In the contest, food industry carry out different sensory analytical tests [4,10,11,21,23,26]. Food products introduced as 'new' to the market by food companies can be classified as new form of existing products or reformulation of existing products. That kind of products could be with better colour, more fibres, less fat or different physical properties. Development of those products may require a longer development time, but small changes in the manufacturing process, storage and handling would be at minimum costs [3,9].

Great care must be taken to insure that as wide a range of samples as reference standards is available, so that complete vocabulary is developed to describe and illustrate all possible food product samples. Most successful vocabulary is likely to be found when the assessors are carefully selected and then allowed to choose the terms they wish to use, with a personal interest in and familiarity with the product and common sense [6,22]. As result of conducted consumers test it was found that food texture had quality associations. Using consumers to measure hedonic acceptability and attribute intensities is a feasible and effective option for product optimisation [8]. Product texture could be related to the freshness and excellence of food preparation. Some concerns about health effects could be associated with off textures. Odour could be signal of spoiled food that may be injurious to consumer’s health when eaten. People like to be in full control of the food placed in their mouth. Gummy or slimy food, or those containing unexpected lumps or hard particles are rejected [16,26].

Historically, jams and jellies may have originated as an early effort to preserve fruit for consumption in the off-season. Processing of different fruit kinds into juice, marmalade, jam or dried products is important for insuring of fruits during all year. In the same time, it is important for bio-constituents recovery. The importance of state of ripening at harvest is important for its physico-chemical and sensory characteristics (appearance, smell and flavour). As result of ripening soluble sugar content groves, acidity decrease, modification of fruit texture and conversion of protopectin to pectin happens. Native pectin in plant cell walls plays as central role in the ripening, texture, and storage qualities of fruits and vegetables. The technological qualities of the products and jam processed thereof, vary with the variety of fruit and its physico-chemical characteristics [1,2,13,17].

Jellies, jams and marmalades are primary distinguished by the form from which their fruit is incorporated. Marmalades are basically jellies with fruit purée and sugar-acid-pectin gel or low-methoxyl pectin-calcium gels. Pectin is traditionally used in a wide range of fruit-based products in which it acts as a gelling agent.  Pectic substances are a group of polysaccharides, which occur in land plants and which have partially metoxylated polygalacturonic acid as their main constituent. Pectin is a subgroup among the pectic substances water-soluble, partially methoxylated polygalacturonan which is used as food ingredient and is capable forming gels under suitable conditions [14]. Pectin is a complex polysaccharide, which has a high molecular weight and is present in all plants. The composition of pectin varies with the source and conditions used in its isolation, so molecules have a molecular weight in the region 60 to 150000 and a degree of polymerisation of 60 to 800 units of galacturonic acid units per molecule. The molecular weight of pectic substances is important in determining of jellying properties. The pattern of methyl-esterification is also critical in determining rheological properties.

A pectin gel is formed when a linear polymer are crossed linked to form a three dimensional crystalline network in which water and solutes are trapped. Various factors determine gelling properties including temperature, pectin type, degree of methyl-esterification, degree of acetylation, pH, sugar and other solutes, and calcium [14, 27]. Both the degree of methyl-esterification and degree of acetylation have impact on functional properties and pectins are traditionally used as food additives categorised as high-ester with degree of methyl-esterification more of 50% or low-ester with degree of methyl-esterification less of 50%. In high-ester pectins the junction zones are formed by the cross-linking of hydrogen bridges and hydrophobic forces between methoxyl groups, both promoted by high sugar concentration and low pH. In low-ester pectins junction zones are formed by calcium cross-linking between free carboxyl groups. The gelling mechanism requiring the presence of calcium ions places low-ester pectins in the group with the alginate as distinguished from other gelling agents such as gelatine, agar, and carrageenans, which are independent of sugar + acid as well as calcium concentrations. A typical application of low-ester pectin is in reversible bakery jelly, where low-ester pectin could be melted before being applied to the pastry.

In food technology edible polymeric materials named hydrocolloids or hydrocolloid gums are used in food systems as additives, because of their hydrating and colloidal function and especially gelling function. They are produced from natural products such as gelatine, exudates of trees, seaweeds, plant seeds, fruits, fermentation products or cellulose. One of the basic functionality features of the hydrocolloids is their capability of modifying the behaviour of water in the food systems. This is affected mainly through the immobilization of a portion of the waters molecules. As a result, water will be held more effectively in the food structure, and stabilization of the textural properties will be obtained. Alginates or alginic acid derivates or their salts are hydrocolloids produced from seaweed. Chemically, the alginic acids are linear polymers of beta-D-mannuronic acid units linked to each other in 1-4 positions [14]. Alginic acid salts or esters are widely used in the food industry for their water-binding, gel-forming and emulsion-stabilizing power. The gradual reaction of algin derivatives with calcium is the basis of their use for suspension and stabilizing of fine chopped insoluble fruit pulp particles in products with different viscous level or in gelled products strengthening their resistance against syneresis. For achieving better functional properties of gelled food systems, often are used mixtures of two or more substances with gelling function.

Working on new product usually stars with experimental design, which lies down on different combinations of the elements. The objective of our study was to create marmalade useful for filling, before final heating of sourdough doughnuts baked in oven, deep-fried products or cakes. Experiment was designed in two parts. Marmalades from frozen peach and apple purée (pulp) with sugar and additives in different proportion were prepared in laboratory. Prepared samples were pasteurised, hot filled in glass jars and closed. After 20 days storing on room temperature, for sensory analysis and stability control of thermo-reversible gel, doughnuts filled with samples of marmalade were prepared and baked in home electric oven. The products with expected sensory quality were selected from variety of prepared samples.

MATERIALS AND METHODS

Marmalade preparation
Initial qualitative trials established the composition and recipes necessary for the various marmalade samples preparation. The aim of the marmalade models preparation was to make marmalade according to the food regulations demands [24] and with acceptable sensory characteristics, especially gel texture. Marmalade must have minimally 67% soluble dry matter (DM), of what min. 7% from fruit and maximally 60% from sugar. According to the EU Directive (2001/113/EC) [25] marmalades and similar products must have soluble dry matter content 60% or more as determined by refractometer, what is different of legal regulations in Bosnia and Herzegovina, or 65% according to the CODEX STAN (79–1981) [7].

Marmalades from frozen peach and apple purée (pulp) in two combinations were prepared in laboratory conditions in open pot, under normal atmospheric pressure. One model marmalade contained fruit purée (edible fruit part) in 1000 g marmalade, with proportional share of fruit purée 70% peach purée (10.60% DM) and 30% apple purée (9.0% DM). Another model marmalade contained fruit purée in 1000g marmalade, with proportional share of fruit purée 50% peach purée (10.60% DM) and 50% apple purée (9.0% DM) as shown in Table 1.

In first step of experimental work 11 marmalade samples signed M.1-M.5 were manufactured, signed as M.1.1, M.1.2, M.1.3, M.2.1, M.2.2, M.2.3, M.3, M.4.1, M.4.2, M.5.1, M.5.2 (Table 1), 8 marmalade samples were with proportional share of fruit purée 70% peach and 30% apple (1 sample with min. 70% DM, 5 samples were with min. 67% DM, 2 samples with min. 45% DM) and 3 samples with proportional share of fruit purée 50% peach and 50% apple (samples with min. 67% DM). The ingredients used for marmalade preparations were peach and apple purée, sugar, tap water and additives in different proportion.

In second step of experiment, 12 different marmalade samples were manufactured (Table 1), with proportional share of fruit purée 70% peach and 30% apple purée, 3 samples with min. 70% DM (M.3, M.3.a, M.3.b) and 9 samples with min. 67% DM (M.1.1, M.1.1.a, M.1.1.b, M.4.1, M.4.1.a, M.4.1.b, M.4.2, M.4.2.a, M.4.2.b), as shown in Table 1.

Used additives were: commercial gelling agents from producers DANISCO-CULTOR (GRINSTED FB-850, made of pectin E 440 and sodium alginate E 401 mixture); and OBIPECTIN (PECTIN BROWN RIBBON J, high methoxyl pectin; PECTIN PURPLE RIBBON B, low methoxyl pectin E 440; PECTIN PURPLE RIBBON D-075 X, low methoxyl amidated pectin E 440); firming agent calcium chloride (E 509), acidity regulator sodium citrates (E 331) and citric acid (E 330), as shown in Table 2.

Sweetness was varied and related products with lower dry meter content were prepared with appropriate gelling and firming agents. The acidity of marmalades prepared according to the actual formulation with different concentrations of additives were adjusted to the pH = 3.2–3.6 by citric acid addition. The gelling agents, acidity regulator and firming agent calcium chloride, were mixed with five parts of sugar and dispersed in hot water (80°C), as appropriate. The dispersion was mixed until completely dissolved and gelling agents had hydrated (approximately 30 min). The remaining sugar and fruit puree were homogenized and heated in open pot until reached 60% DM (~°Brix). Then, gelling agent dispersion was added, dry meter and pH controlled or corrected, and if all quality parameters are fulfilled, marmalade was hot filled in glass jars after pasteurization in pot (30 min on 80°C). Prepared samples were closed with twist-off caps and stored on room temperature. One unopened capped jar of every manufactured marmalade sample were placed to the refrigerator on +4 to +8°C and kept 6 month for control.

The use of calcium salts
Pectin is a high value functional food ingredient widely used as a gelling agent and stabilizer. Low methoxyl pectins gel by reacting with polyvalent cations. In fruit this is above all native calcium. However, in most cases this calcium content is not sufficient to cover the characteristic need of some of the pectins. Defined quantities of calcium are, therefore, added in the form of calcium salts. The recipe suggestions for our products in experiment are based on laboratory trials. Since the specific conditions vary from one user to another, adaptation may be necessary.

The use of buffering salts
Buffer salts are used to lower the gelling temperature and, in the case of low methoxyl pectins, the reaction with calcium can be delayed. Thus buffering salts are also called retarding agents. Obipektin AG recommends buffer salts if the solids content is very high or in combination with calcium-reactive pectins. The buffer salt is dry-mixed with the pectin or added to the fruit/water mixture.

Chemical and physical analysis
Soluble dry matter was determined on 20°C with Leica Abbe Mark II Refractometer Model 10480, Leica, USA; total acidity (titration with 0.1 M NaOH) expressed as percentage of citric acid; pH was measured with pH-meter (ISKRA) for chemical and physical quality control of marmalade.

Control of marmalade stability after reheating
After minimally 20 days storing on room temperature (25–28°C), for sensory analysis and stability control of thermo-reversible gel, doughnuts filled with samples of marmalade were prepared and baked in home electric oven (CANDY, heating temperature 220°C max.). Doughnuts were prepared (as carrier for marmalades sensory evaluation) from flour, eggs and other ingredients mix for doughnuts BERLINER MIX (IREKS AROMA D.O.O.), adding margarine, yeast, tap water as recommended in producers’ recipe. For dough mixing laboratory electrical mixer (CLATRONIC), 2 kg dough maximal capacity was used. Doughnuts approximately 50 g. dough weight were prepared by hand, filled with 15 g marmalade samples, proofed in casserole with 12 holes (55 mm diameter and 35 mm highs) and baked.

Sensory evaluation of marmalade samples
The whole sensory assessment took place at the Laboratory for sensory analysis on Faculty of Technology, Banja Luka, Bosnia and Herzegovina. The panel was composed of five panellists, experts in food production and quality control, trained persons previously screened for capability, who received extensive training in quantitative descriptive sensory analysis of marmalades and similar products.

Marmalade samples were stored at room temperature (25–28ºC) during the whole study. One soupspoon of marmalade, approximately 30g, was presented on coded white plates and teaspoon for samples evaluation. Marmalade samples were presented to the assessors on the same time with filled baked doughnuts (after cooling to the room temperature). Marmalade texture was evaluated by compressing with a teaspoon, cutting with teaspoon and in mouth. Sensory analyses were conducted under white light in separate booths. Bottled water (room temperature) was provided as palate cleanser.

In initial preparation of the marmalade sensory analysis coefficient of significance – Cs was determined for every sensory characteristics (sum of them are 20). Appropriate coefficient of significance – Cs was multiplied with score given after sensory evaluation of each selected attribute (in scale from 5 for very good quality, to 1 for very bad, unacceptable quality) and after that addition of all results for evaluated sensory attributes gives corrected score expressed as percentage of maximum possible product quality, or 100%  for the best quality. For marmalade the most important evaluated sensory attributes were appearance and texture (Cs = 8), after that taste and aroma (Cs = 5), than colour (Cs = 4) and odour (Cs = 3). The scoring forms (questionnaire) with attributes definition and possible defects for appearance and texture, colour, odour and aroma were delivered to the panellists with every sample. Panellists were instructed to evaluate intensities for all offered attributes using 5-point scoring system, from five for very good quality, to one for very bad, unacceptable quality. Marmalade appearance and colour evaluation were done visually. Texture evaluations were judged by sight, with fingers, coffee spoon and in the mouth. Odour was evaluated before putting portion of sample in the mouth, and after that, oral tactile texture, taste and aroma were measured, before samples were swallowed.

RESULTS AND DISCUSSION

Composition and descriptive characteristics of the samples
The objective of our study was creating marmalade useful for filling, before final heating of sourdough doughnuts baked in oven, deep-fried products or cakes. Experiment was designed in two parts. In laboratory, marmalades were prepared from frozen, in industrial conditions produced, fine mashed peach and apple purée with sugar and additives in different proportion.

Product quality could be defined in many ways. For sensory quality of marmalade, important attributes are orange colour with reddish tinge, pleasant fruity odour and aroma, balance of sweetness and sourness and medium firm gel. Important contributor of marmalade optimal quality is texture. Gel texture depends of a few factors. For gel formation in marmalade, different pectin preparations or some other substances as gelling agent are added. During marmalade preparation, in optimal conditions, pectin chains aggregate and form a polymer network, a gel [2,23]. The gelling properties of pectin are well known to home jam makers and industrial producers. In the food industry pectin is known primarily as a gelling agent and is widely used in the production of jams and jellies, fruit juice, confectionary products and bakery fillings.

Pectin consists primarily of a chain of galacturonic acid units forming a long molecular chain in which are linked by α-1,4 glucosidic bonds. As a gel forms, the molecules develop three-dimensional network which traps solution in the interstices. If molecules are too short, or some of parameters are out of optimal values, the network is not continuous in many spots, and result in soft gel. The galacturonic acid chains are partially esterified as methyl esters or are amidated, so the functional properties of pectin are also largely determined by the degree of esterification of the pectin molecules. Pectins with a degree of esterification of 50% or more are known as high-ester pectins and are capable of forming gels in aqueous systems with high contents of soluble solids and low pH values. These pectins are mainly used in high sugar jams and confectionery jellies.

Formulations containing different gelling agents and their combinations can be used to create product with controlled textural properties. The texture of marmalade depends of structural and micro-structural features, the expression of inter-atomic and inter-molecular interactions. As result of texture attributes quantifying, it is possible to obtain product just-as-expected, not too much hard and nor soft [23,27]. The marmalade samples for experiment were prepared from the same raw material, frozen peach and apple purée in two combinations, 8 samples with proportional share of fruit purée 70% peach and 30% apple and different soluble dry matter (DM), 1 sample with min. 70% DM, 5 samples with min. 67% DM  and 2 samples with min. 45% DM (Table 1).

Table 1. Average content of fruit purée and sugar in 1000g marmalade sample

Sample mark

Soluble
dry matter
[%]

Soluble
dry matter
from fruit
[%]

Fruit
purée
[g]

Proportional share
of fruit purée

Soluble
dry matter
from sugar
[%]

Sugar
[g]

peacha
[%]

appleb
[%]

M.1.1

67.30

7

700

70

30

60

600

M.1.2

67.20

7

700

70

30

60

600

M.1.3

67.10

7

700

70 

30

60

600

M.2.1

67.50

7

720

50

50

60

600

M.2.2

67.20

7

720

50

50

60

600

M.2.3

67.00

7

720

50

50

60

600

M.3

70.60

7

1000

70

30

60

600

M.4.1

67.60

7

700

70

30

60

600

M.4.2

67.00

7

700

70

30

60

600

M.5.1

45.10

7

700

70

30

38

380

M.5.2

45.20

7

700

70

30

38

380

M.1.1.a

67.40

7

700

70

30

60

600

M.1.1.b

67.60

7

700

70

30

60

600

M.3.a

70.00

7

1000

70

30

60

600

M.3.b

70.10

7

1000

70

30

60

600

M.4.1.a

67.10

7

700

70

30

60

600

M.4.1.b

67.00

7

700

70

30

60

600

M.4.2.a

67.00

7

700

70

30

60

600

M.4.2.b

67.10

7

700

70

30

60

600

a Soluble dry matter of peach purée = 10.60%.
b Soluble dry matter of apple purée = 9.0%.

Hydrocolloids can be used to create gels or gel-based texturized foods with different specific rheological characteristics, as strength or degree of elasticity. Relatively slight variations in a hydrocolloids mixture composition or hydrocolloid concentration can produce substantial changes in mechanical properties of gel and modify the texture of gel. Mixture of pectines and sodium salt of alginic acid, sodium alginate, is used in the food industry as a gelling agent of fruit-based products in which it improves its thermal stability [14].

Fig. 1. Marmalade samples in doughnuts after baking

Samples M.1.1, M.1.2 and M.1.3 (Table 1) were made on the same production method, with proportional share of fruit purée 70% peach and 30% apple, with GRINSTED FB-850 (DANISCO-CULTOR) gelling agent made of pectin and sodium alginate mixture, and different amount of firming agent (CaCl2) as shown in Table 2. Acidity was corrected with addition of crystal citric acid dissolved in small water amount, until optimal pH was reached. The marmalade sample M.1.1 had the best sensory quality of evaluated samples, scored as 92% of maximally possible sensory quality (Table 3) after marmalade sensory analyse before baking and after baking trial in doughnuts. The marmalade sample M.1.1 was produced with the least amount of CaCl2 (0.5 g/kg), as shown in Table 2. Gel texture of samples M.1.2 and M.1.3 were scored as firmer than expected and different from previous (both samples were scored as 80% of maximally possible sensory quality), so they were refused from further investigation (Fig. 1).

Table 2. Gelling agent, firming agent and acidity regulator used as additives for 1000 g marmalade sample

Sample
mark

Gelling agent
commercial name
[g]

Firming agent
calcium chloride
[g]

Acidity regulator
sodium citrates [g]

M.1.1

11.00

GRINSTED FB 850

0.50

not used

M.1.2

11.00

GRINSTED FB 850

0.83

not used

M.1.3

11.00

GRINSTED FB 850

1.00

not used

M.2.1

11.00

GRINSTED FB 850

0.50

not used

M.2.2

11.00

GRINSTED FB 850

0.83

not used

M.2.3

11.00

GRINSTED FB 850

1.00

not used

M.3

8.00

PECTIN BROWN RIBBON J

not used

not used

M.4.1

8.00

PECTIN PURPLE RIBBON B

0.30

0.50

M.4.2

9.00

PECTIN PURPLE RIBBON D-075X

0.30

0.25

M.5.1

9.00

PECTIN PURPLE RIBBON B

0.30

not used

M.5.2

10.00

PECTIN PURPLE RIBBON D-075X

0.28

not used

M.1.1.a

11.00

GRINSTED FB 850

0.25

not used

M.1.1.b

11.00

GRINSTED FB 850

not used

not used

M.3.a

6.00

PECTIN BROWN RIBBON J

not used

not used

M.3.b

4.00

PECTIN BROWN RIBBON J

not used

not used

M.4.1.a

8.00

PECTIN PURPLE RIBBON B

0.15

0.25

M.4.1.b

8.00

PECTIN PURPLE RIBBON B

not used

not used

M.4.2.a

9.00

PECTIN PURPLE RIBBON D-075X

0.15

0.15

M.4.2.b

9.00

PECTIN PURPLE RIBBON D-075X

not used

not used

The diversity of fruit constituents content results in different gel firmness during marmalades, jams or jelly preparation. Divalent calcium ions (Ca2+) normally occur in fruit tissue, but not always in enough amounts. To obtain gel formation in a system containing low ester pectin, the presence of calcium ions is crucial. For gel formation and its stability at all temperatures, it is important to insure optimal pH range 2.5-4.5 with acid and acidity regulator sodium citrate addition [2,22,25]. Acids should be added to the batch as late as possible, after the boiling temperature has been reached, prior to the product filling, to prevent early gelling.

In aim to produce marmalade with relative smaller part of peach and bigger part of apple (as cheaper fruit), 3 marmalade samples with proportional share of fruit purée 50% peach and 50% apple (samples with min. 67% DM) were prepared (Table 1). Samples M.2.1, M.2.2 and M.2.3 were made on the same production method as previous group of samples, with GRINSTED FB-850 (DANISCO-CULTOR) gelling agent made of pectin (E 440) and sodium alginate (E 401) mixture, and different amount of firming agent CaCl2 (Table 2), but with proportional share of fruit purée 50% peach and 50% apple. It is known that fruit particle changes during preparation are not completely controlled. During the process of fruit growth and ripening, protopectin is gradually transformed into water-soluble pectin [14,25,27]. With apple purée, some amount of pectin and other constituents were taken in product, what results with firmer than expected gel texture in marmalade samples M.2.1, M.2.2 and M.2.3. This can be explained as one of reasons that gel construction was firmer than expected in the formulations. These samples M.2.1, M.2.2 and M.2.3 had weak fruity aroma, especially peach aroma. For all that reasons sample M.2.1 were scored as 80% of maximally possible quality, and samples M.2.2 and M.2.3 with 63% of maximally possible sensory quality (Table 3) and refused from further investigation (Fig. 1).

Table 3. Order marmalade samples ranked after first sensory analysis

Rank*

Sample
mark

Sensory scores expressed as
percentage of maximal possible quality

Soluble
dry matter

(%)

Gelling agent

1.

M.1.1

92%

67.30

GRINSTED FB 850

2.

M.3

92%

70.60

PECTIN BROWN RIBBON J

3.

M.4.2

92%

67.00

PECTIN PURPLE RIBBON D-075X

4.

M.4.1

88%

67.60

PECTIN PURPLE RIBBON B

5.

M.1.2

80%

67.20

GRINSTED FB 850

6.

M.1.3

80%

67.10

GRINSTED FB 850

7.

M.2.1

80%

67.50

GRINSTED FB 850

8.

M.2.3

63%

67.00

GRINSTED FB 850

9.

M.2.2

63%

67.20

GRINSTED FB 850

10.

M.5.2

56%

45.20

PECTIN PURPLE RIBBON D-075X

11.

M.5.1

56%

45.10

PECTIN PURPLE RIBBON B

12.

K.1c

53%

67.00

PEKTIN (E 440)

* Marmalade samples ranked after sensory analysis from the best at 1st place, to worst.

Only marmalade sample M.3 (Table 1) were produced with proportional share of fruit purée 70% peach and 30% apple and higher dry matter content (70.60%), gelling additive PECTIN BROWN RIBBON J (OBIPECTIN), which is high methoxyl pectin, and without firming agent and acidity regulator addition (Table 2). The marmalade sample, signed as M.3, scored as 92% of maximally possible sensory quality (Table 3), had expected medium-strong texture, pleasant light sour and refreshing taste.

Pectins with the degree of esterification of less than 50% are known as low-ester pectins. This group of pectins is divided into two sub-groups, low-ester pectin and amidated low-ester pectin. Both sub-groups are characterised by their ability to form gels in the presence of calcium in systems with lower solids content and a wide pH range.

Formulations for M.4.1 and M.4.2 marmalade samples had min. 67% DM and were different from previous in gelling agent and acidity regulator content (Table 2). Gelling agent producers suggested use of firming agent (CaCl2) and acidity regulator (three-sodium citrate two-hydrate) with OBIPECTIN PECTIN PURPLE RIBBON B (low methoxyl pectin) and PECTIN PURPLE RIBBON D-075 X (low methoxyl amidated pectin). After sensory analysis, these marmalade samples, scored as 88% of maximally possible quality (Table 3), were characterised as marmalade with specific pleasant fruit aroma, homogenous medium-firm satisfactory gel texture. Sample M.4.1 (scored as 80% of maximally possible quality) as shown in Table 3, had for a little darker colour than M.4.2 marmalade sample (scored as 92% of maximally possible quality).

Marmalades structure, appearance and mouthfeel results from a complex interaction between pectin level and functionality, pH, sugar type and content, setting temperature, and in the case of low-methoxyl pectin gels, calcium content [2]. More than 40% of total weight of marmalade made according to the classic formulation is sugar. Its addition significantly affected marmalade sweet taste. In any case, some optimal amount of sugar is necessary to obtain expected or required gel strength. Sugar is necessary for the formation of pectin gels and must be present in a minimum concentration. Low ester pectins are able to form gels in the presence of small amount of divalent ions of calcium in low percent of solids or sugar in medium. So, added divalent ions react with carboxyl group of two molecules of pectic acid and forming a bridge between them impact on marmalade texture. As result of taste sensory analysis, marmalade samples made according to the classic formulation were scored as very sweet, but specific for the product. To produce marmalade with medium sweet taste, two samples M.5.1 and M.5.2 were made as lower-energy products with 45% DM in final product and lower sugar content (Table 1), on the same production method as previous. Gelling additives PECTIN PURPLE RIBBON B (OBIPECTIN) and PECTIN PURPLE RIBBON D-075X (OBIPECTIN) and CaCl2 as firming agent were used (Table 2). These samples had specific colour, pleasant peach aroma, and acceptable medium sweet and sour taste. However, these samples in glass jars had too-soft unacceptable gel and signs of syneresis. After baking in doughnuts marmalade was viscose, almost liquid consistency, unacceptable for this purpose (Fig. 1). They got relative law scores after sensory analysis, both scored as 56% of maximally possible quality, the lowest scores in this group of 11 prepared samples, as shown in Table 3.

As control marmalade sample (signed as K.1) was used marmalade made from peach, apple and sugar, with min. 67% DM and with pectin (E 440) as additive with gelling properties, produced as classic spreadable product. It had specific light-brown colour with reddish orange tinge and light peach aroma, but sweater taste than it could be. It had very firm, spreadable gel texture before baking, but after baking in doughnuts, marmalade were quite liquid and unacceptable for doughnuts feeling and baking (Fig. 1). Results of the control marmalade sample K.1 sensory evaluation, showed bad quality (scored as 53% of maximally possible quality), and that it is not acceptable for use as product filling for baking purpose (Table 3). This marmalade was very soft, almost liquid after re-heating and different from model samples. The pectin used for this marmalade preparation had irreversible gelling property and therefore influenced on the marmalade property after reheating.

After sensory analysis of all (11) marmalade samples, before and after doughnuts filling and baking, calculated results were ranked as shown in Table 3. Four formulations (M.1.1, M.3, M.4.1, M.4.2) with best quality score, more than 90% of possible sensory quality, were select for further investigations (Table 3).

In the second part of the study, some changes on the selected samples formulations were made. The point of this research part was product optimization and trying to make products with acceptable quality and minimally necessary quantity of additives. Modification of selected formulations resulted in 12 different marmalades for sensory analysis, prepared with proportional share of fruit purée 70% peach and 30% apple purée, 3 samples with min. 70% DM (M.3, M.3.a, M.3.b) and 9 samples with min. 67% DM (M.1.1, M.1.1.a, M.1.1.b, M.4.1, M.4.1.a, M.4.1.b, M.4.2, M.4.2.a, M.4.2.b), as shown in Table 1.

Marmalade samples M.1.1.a and M.1.1.b had in CaCl2 content modified formulations of M.1.1 marmalade production formulation (Table 2). They were with smaller CaCl2 content in sample M.1.1.a and without CaCl2 content in sample M.1.1.b. As result of that modification, both marmalades had colour and aroma similar to the other products, but gel texture was softer than expected. Sample M.1.1.b had pH=3.57 (total acidity 0.84) and a little less sour taste than sample M.1.1.a with pH=3.58 (total acidity 0.83). Both samples were scored as 84% of maximally possible quality, as shown in Table 3.

Table 4. Order marmalade samples ranked after second sensory analysis

Rank*

Sample
mark

Sensory scores
expressed as
percentage of maximal
possible quality

Soluble
dry matter
(%)

Gelling agent

1.

M.1.1

92%

67.30

GRINSTED FB 850

2.

M.3.a

92%

70.00

PECTIN BROWN RIBBON J

3.

M.3

92%

70.60

PECTIN BROWN RIBBON J

4.

M.4.1.b

92%

67.10

PECTIN PURPLE RIBBON B

5.

M.4.1.a

92%

67.00

PECTIN PURPLE RIBBON B

6.

M.4.2.b

92%

67.10

PECTIN PURPLE RIBBON D-075X

7.

M.4.2.a

92%

67.00

PECTIN PURPLE RIBBON D-075X

8.

M.4.2

92%

67.00

PECTIN PURPLE RIBBON D-075X

9.

M.4.1

88%

67.60

PECTIN PURPLE RIBBON B

10.

M.1.1.b

84%

67.60

GRINSTED FB 850

11.

M.1.1.a

84%

67.40

GRINSTED FB 850

12.

M.3.b

76%

70.10

PECTIN BROWN RIBBON J

* Marmalade samples ranked after sensory analysis from the best at 1st place, to worst.

Marmalade samples M.3.a and M.3.b had, in gelling agent content modified formulations of M.3 marmalade production formulation (Table 2). Marmalade M.3.a had all expected quality characteristics, scored as 92% of maximally possible quality, the same as samples M.3 and M.1.1 (Table 4), orange colour with light-brown tinge (Fig. 2). Peach aroma was light, but similar as in other products. Gel texture was medium firm and homogenous. According to the all analyzed sensory quality characteristics and economy of production, from these three samples marmalade signed as M.3.a was the best (Table 4). Sample M.3.b had darker orange-light brown colour with reddish tinge (scored as 76% of maximally possible quality). It could be explained as result of cooking method. Texture of these samples was softer than expected, so the marmalade was scored as with unacceptable quality.

Fig. 2. Marmalade samples in doughnuts after baking

Marmalade samples M.4.1.a and M.4.1.b, the same as samples M.4.2.a and M.4.2.b were produced with smaller amount of firming agent, acidity regulator and citric acid than in M.4.1 and M.4.2 sample (Table 2). All these marmalade samples had satisfactory specific colour and peach aroma and (scored as 92% of maximally possible quality), as shown in Table 4. Samples made with smaller amount of additives had satisfactory uniform and medium-firm gel texture (Fig. 2). Marmalades with smaller amount of additives (Table 2) were selected as cheaper for production.

After sensory analysis before and after baking in doughnuts, two marmalades (scored as 92% of maximally possible quality) were selected as cheaper for production (Table 4). One marmalade sample M.1.1 produced with GRINSTED FB-850 (DANISCO-CULTOR) gelling additive made of pectin (E 440) and sodium alginate (E 401) mixture and 0.50 g CaCl2/kg marmalade, and other sample M.3.a with BROWN RIBBON J (OBIPECTIN) high methoxyl pectin (Table 2). Both samples had expected sensory quality after re-heating and cooling on room temperature, orange-light-brown colour, specific aroma of peach and apple, uniform and medium-firm gel useful for filling of doughnuts baked in oven and similar products. For this study marmalades were cooked on electric heater in open pot, under normal atmospheric pressure, so in industrial conditions marmalade with better colour could be expected.

Peach and apple purée contents had major impact on flavour and fruity aroma. They were scored as good in prepared marmalade samples. For doughnuts or cakes filling, marmalade aroma could be stronger and corrected with small amount of natural peach flavour adding during marmalade production. Storage time and temperature (products cooled on +4ºC or room temperature) during extended investigation of several months did not affect quality of the marmalade. The quality of all produced marmalade samples were compared with similar fruit content and chemical composition commercial marmalade (signed as K.1) bought at local shop.

Chemical composition
Marmalades were formulated taking into account many factors, such as different peach and apple purée content, the dry matter, pH, sugar, pectin and other additives content. The average composition of marmalade samples is shown in Table 1. Marmalades samples had composition and quality characteristics in accordance with defined in food regulations for marmalade quality in Bosnia and Herzegovina [24].

Prepared marmalade samples could be grouped in dependence of peach and apple purée content and based on minimal soluble dry matter (DM) content.

The marmalade samples were prepared from the same raw material, frozen peach and apple purée in two combinations: 8 marmalade samples with proportional share of fruit purée 70% peach and 30% apple (M.1.1, M.1.1.a, M.1.1.b, M.1.2, M.1.3, M.3, M.3.a, M.3.b, M.4.1, M.4.1.a, M.4.1.b, M.4.2, M.4.2.a, M.4.2.b, M.5.1, M.5.2) and 3 marmalade samples with proportional share of fruit purée 50% peach and 50% apple (M.2.1, M.2.2 and M.2.3), as shown in Table 1.

Prepared marmalade samples had different soluble dry matter (DM), 3 sample with min. 70% DM (M.3, M.3.a, M.3.b), 14 samples with min. 67% DM (M.1.1, M.1.1.a, M.1.1.b, M.1.2, M.1.3, M.3, M.3.a, M.3.b, M.4.1, M.4.1.a, M.4.1.b, M.4.2, M.4.2.a, M.4.2.b)  and 2 samples with min. 45% DM (M.5.1, M.5.2).

Factors with impact on gelling properties of marmalade, pectin type, sugar content and calcium and/or acidity regulator content are added during samples preparation so combined to achieve optimal quality of product. Physical and chemical characteristics of marmalade samples are shown in Table 5. Ranges of pH values observed in samples were optimal, between 3.16 (in samples M.3.a and M.3.b) and 3.58 (in sample M.1.1.a). The same, total acidity values expressed as % of citric acid were in optimal range, from 0.72 (in samples M.2.2 and M.2.3) to 1.20 (in samples M.3.a and M.3.b).

Table 5. Physical and chemical characteristics of marmalade samples

Sample mark

Soluble
dry matter
(%)

pH

Acidity*
(%)

M.1.1

67.30

3.48

0.82

M.1.2

67.20

3.50

0.76

M.1.3

67.10

3.50

0.77

M.2.1

67.50

3.50

0.73

M.2.2

67.20

3.51

0.72

M.2.3

67.00

3.55

0.72

M.3

70.60

3.22

1.02

M.4.1

67.60

3.25

1.01

M.4.2

67.00

3.25

1.12

M.5.1

45.10

3.25

1.12

M.5.2

45.20

3.18

1.01

M.1.1.a

67.40

3.58

0.83

M.1.1.b

67.60

3.57

0.84

M.3.a

70.00

3.16

1.20

M.3.b

70.10

3.16

1.20

M.4.1.a

67.10

3.48

0.91

M.4.1.b

67.00

3.48

0.91

M.4.2.a

67.00

3.52

0.91

M.4.2.b

67.10

3.53

0.91

* Total acidity expressed as percentage of citric acid

After comparing and evaluating quality of produced samples two were selected as the best. For marmalade the most important evaluated sensory attributes were appearance and texture. The first selected marmalade sample (M.1.1) was produced with 11 g gelling additive (GRINSTED FB-850, DANISCO-CULTOR) for kilogram marmalade and 0.50 g CaCl2/kg marmalade. Dry matter in the marmalade sample was approximately 67% and pH = 3.48 (Table 5). Second marmalade sample (M.3.a) was produced with 6g gelling additive (BROWN RIBBON J, OBIPECTIN) for kilogram marmalade. Dry matter in the marmalade sample was approximately 70%, pH = 3.16 (Table 5).

CONCLUSIONS

Consumers today demand high-quality products in various innovative forms at competitive prices. Developing and designing of such products with desired attributes should result with new high quality product. Methods of descriptive sensory analysis are useful tool for quality and acceptability measuring of peach and apple fruit marmalades. The doughnuts were used as excellent carrier for the marmalades sensory evaluation.

After sensory evaluation series of model-marmalades produced with selected combinations of content food additives responsible for marmalade jelly texture properties, among all analysed, two marmalade samples produced with different commercial gelling additive were selected as the best.

As a result of the marmalade production with 11g gelling additive mixture pectin and sodium alginate GRINSTED FB-850 used for kilogram marmalade and optimal content of calcium chloride (0.50 g CaCl2/kg marmalade), water was held effectively in the product structure, and stabilization of the textural properties were obtained after reheating product during baking in electric oven doughnuts filled with samples of marmalade. Dry matter in the marmalade sample was approximately 67% and pH = 3.48.

Sensory analysis and stability control of thermo-reversible gel in doughnuts filled with samples of marmalade showed that sample produced with 6g gelling additive BROWN RIBBON J, high methoxyl pectin (OBIPECTIN) for kilogram marmalade had expected high quality, also. Dry matter in the marmalade sample was approximately 70% and pH = 3.16.

Both marmalade samples had expected sensory characteristics after re-heating and cooling on room temperature, orange-light-brown colour, specific light aroma of peach and apple, homogeneous and medium-firm gel useful for filling of doughnuts baked in oven and for similar products.

The study shows that development of this marmalade and including as new product would not be problem. New product processing and preparing ingredients for the production are not significantly different from usual classic marmalade production, so investment for introduction of this marmalade as new product would be at minimum costs and can be recommended. 

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Accepted for print: 10.05.2010


Slavica Grujiæ
Faculty of Technology,
University of Banja Luka, Bosnia and Herzegovina

email: grujicslavica@yahoo.com

Radoslav Grujiæ
Faculty of Technology Zvornik, University of East Sarajevo, Bosnia and Herzegovina


Jelena Polja¹eviæ
Faculty of Technology,
University of Banja Luka, Bosnia and Herzegovina


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