Ice cream is a very favourite dairy product among all sections of the people because of its palatable nature and nutritious nature. The use of new ingredients fat replacement is a new concept and is finding wide application in the food industry recently. In this regard, a study was carried out to prepare low fat fibre enriched ice cream by incorporating insulin and fructo-oligosaccharides. Different treatments of fibre enriched ice cream prepared by incorporating insulin or fructo-oligosaccharides at 0, 3, 5 and 7 per cent levels. The mean values of pH and titratable acidity of control and treatment ice cream after preparation and during the 5 weeks storage period at -230 C showed no significant difference. However, a highly significant (P < 0.01) difference was noticed in specific gravity, viscosity, melt down and over run values between different ice cream with a proportional increase to the increase in percent of and fructo-oligosaccharides. Among the different ice cream prepared, the low fat fibre enriched ice cream with 3% insulin and low fat ice cream with 3% fructo-oligosaccharides recorded the highest scores for appearance, sweetness, flavor and overall acceptability, comparable to that of control. Dietary fibre inclusion at 7% level in the ice cream recorded higher viscosity, specific gravity, meltdown and over run in comparison with the low fat control ice cream.
Ice cream is very popular among all sections of the people because of the food and health aspects ranging from ‘taste delight to nutrient delivery (Sukumar De, 1980). A typical compositional range for the components used in ice cream mix is milk fat 10-16%,milk solids not fat 9-12%, sucrose 9-12%, stabilizers/emulsifiers 0-0.5%, total solids 36-45% and water 55-64% (Goff, 1997). Fat is the main ingredient in ice cream and the type used is saturated fat. In India, an ice cream has to contain a minimum 10 per cent of butter fat, cream or milk to match food industry specifications (BIS 1980). Generally, high dietary fat intake is associated with an increase in the risk of many diseases, such as obesity, some types of cancer, high blood cholesterol and coronary heart disease (Rothstein, 2006). Most of the consumers prefer food products with therapeutic value for their health aspects over its palatability. The primary difficulties to overcome in low fat or fat free products include improving the mouth feel and flavour perception to resemble that of full-fat products. Fat replacers have been used to replace fat in food systems due to their properties and the improvement of textural quality of such foods (Akoh, 1998). Fat replacer currently used in low–fat formulation are bulking agents based on carbohydrates, such as cellulose, gum, starch, pectin, maltodextrin and polydextrose (Roland et al., 1998).
In addition, like any other dairy products, ice cream also lacks in dietary fibre content. Insulin and fructo-oligosaccharides (oligofructose) are natural ingredients, having functionality similar to other carbohydrates called fructans, those polymers containing fructose but provides less energy. Insulin and Fructo–oligosaccharides possess some characteristics of dietary fibre. The physiological actions promoted by fibre addition (insulin and fructo–oligosaccharides) in foods include the maintenance of gastrointestinal health, reduction of intestine transit time, protection against colon cancer, lowering of total and low-density lipoprotein cholesterol in the blood serum, reduction of post prandial blood glucose levels, increase of calcium bioavailability and reinforcement of the immunological system (Tungland and Meyer, 2002).
Thus, incorporation of dietary fibre would add value to the ice cream not only in terms of variety but also their enhanced healthfulness. Hence, an attempt has been made in the development of low fat fibre enriched ice cream by incorporating dietary fibres like insulin and fructo-oligosaccharides with the objectives of preparing low fat fibre enriched ice cream by incorporating insulin and fructo-oligosaccharides and to determine the nutritional value of the product.
Materials and Methods
The following equipments were used during the present study.
Procedure for the Preparation of Low Fat Fibre Enriched Ice cream
Low fat Ice cream mixes were prepared by pasteurizing (680 C for 30 min) a mix containing skim milk, cream, skim milk powder, sugar, stabilizer and emulsifiers. Fibre enriched ice cream were prepared by incorporating insulin or fructo-oligosaccharides at 3, 5 and 7 per cent levels in two different lots. The mixes were then homogenized at 2000 / 500 psi and ice cream mix were kept for ageing at 40 C for 4 hours and for freezing at – 40 C. After packing the ice cream were kept for hardening and storage at -230 C.
Flow Chart for the Preparation of Treatment Ice Cream Mix
Selection of Ingredients
(Skim milk, cream, skim milk powder, sugar, insulin or
fructo-oligosaccharides, stabilizers emulsifiers and flavour)
Figuring the mix
Making the mix
Pasteurizing the mix (68.5⁰ C for 30 min)
Homogenizing the mix (150 kg / cm 2 & 30 kg / cm 2 at 65⁰ C)
Cooling and ageing the mix (4 ± 1⁰ C for 4 hrs)
Freezing the mix (– 4 to – 5⁰ C)
Packaging of Ice Cream
Hardening and storage of Ice cream (– 23 to – 29°C)
Design of Experiment
FFIM – Full fat ice cream mix
LFIM – Low fat ice cream mix
LFIMI1 -Low fat ice cream mix with incorporation of 3% insulin.
LFIMI2 -Low fat ice cream mix with incorporation of 5% insulin.
LFIMI3 -Low fat ice cream mix with incorporation of 7% insulin.
LFIMF1 -Low fat ice cream mix with incorporation of 3% FOS
LFIMF2 -Low fat ice cream mix with incorporation of 5% FOS
LFIMF3 -Low fat ice cream mix with incorporation of 7% FOS
The ingredients used per litre of different treatment ice cream mixes given comprehensively in Table1.
Table1: Ingredients used per litre of different treatment ice cream mixes
|Types of ice cream mixes||Incorporation of dietary fibre (%)||Skim Milk (ml)||Cream with their % of fat (g)||SMP||Sugar||Dietary fibre||Stabilizer & Emulsifier (g)||Flavour (ml)|
|Full-fat ice cream||0||700 (Whole milk)||120 (40%)||40||140||0||5||3|
|Low-fat ice cream||0||711||102 (40%)||40||150||0||7||3|
|Low-fat ice cream||3||712||111(40%)||40||110||30||7||3|
|Low-fat ice cream +||3||712||111(40%)||40||110||30||7||3|
|Fructo –oligosaccharides||5||713||80 (45%)||40||110||50||7||3|
Estimation of Physic-Chemical Properties of Ice Cream
The pH of ice cream was estimated using a digital pH meter. The titratable acidity of ice cream was estimated as per the procedure of BIS (1980). The specific gravity of ice cream mix was estimated by weighing a known volume of mix using specific gravity bottle on a gravimetric balance (Sommer, 1951)
The meltdown time was estimated following the procedure outlined by Rajor et al. (1982). One hundred grams of ice cream was carefully placed on a four square inch glass plate rested on the brim of five inches glass funnel, fitted on a metal stand with its tail end leading into a 100 ml graduated cylinder. The time taken to complete meltdown was recorded. The relative viscosity formula given hereunder, the viscosity of ice cream mix was calculated, keeping the viscosity water (1.005 cp) as standard.
no topo no – Viscosity of water in CP
= n1 – Viscosity of ice cream mix
n1 t1 p1 t1 – Time of flow of ice cream mix
topo to – Time of flow of water
n1 = no po – Sp. gravity of water
t1p1 p1 – Sp. gravity of ice cream mix
Overrun in ice cream was calculated as per the procedure outlined by Sukumar De (1980).
Organoleptic evaluation of prepared ice cream using 9- point hedonic scale (Amerine et al., 1965) was carried out by panel of judges comprising five members. All the samples were appropriately coded before subjected for sensory evaluation.
Results and Discussions
The comprehensive results for various physiochemical parameters discussed here under for different treatment of ice cream are given in Table2.
Table 2: Physico chemical properties of different treatment of ice cream (Mean ± SE)@
|Treatment ice cream mixes||Physico chemical properties|
|pH||Titratable acidity||Specific gravity||Viscosity (centipoises)||Melt down (minutes)||Over run|
|FFIM||6.460 a ± 0.024||0.247 a ± 0.00||1.086a ± 0.002||172.80a ± 0.374||10.00a ± 0.00||41.60a ± 0.927|
|LFIM||6.400 a ± 0.031||0.247 a ± 0.00||1.046cd ± 0.0024||160.40e ± 0.244||8.00b ± 0.00||31.80e ± 0.800|
|LFIMI1||6.440 a ±0.024||0.246 a ± 0.00||1.042 d ± 0.003||163.00d ± 0.316||8.40b ± 0.24||36.00c ± 0.316|
|LFIMI2||6.360 a ± 0.024||0.247 a ± 0.00||1.054bc ± 0.002||164.80 bc ± 0.200||8.60b ± 0.24||37.00 c ± 0.447|
|LFIMI3||6.400 a ± 0.000||0.246 a ± 0.00||1.066 b ± 0.002||165. 60b ± 0.244||9.60a ± 0.24||38.00 bc ± 0.316|
|LFIMF1||6.400 a ± 0.036||0.246 a ± 0.00||1.050bc ± 0.003||160.60d ± 0.024||8.60b ± 0.24||34.20d ± 0.374|
|LFIMF2||6.380 a ± 0.049||0.246 a ± 0.00||1.060b ± 0.004||163.60bcd ± 0.244||8.80b ± 0.24||36.00c ± 0.316|
|LFIMF3||6.440 a ± 0.025||0.247 a ± 0.00||1.068b ± 0.003||165.60b ± 0.244||9.40ab ± 0.40||38.00b ± 0.316|
|F value||1.34 NS||0.88 NS||22.45**||209.77**||8.29 **||29.89 **|
pH and Titratable Acidity
There was no significant (P > 0.05) difference with regard to pH and titratable acidity between different treatment groups of ice cream. This was in close agreement with the findings of Zhu (2004), Guven et al. (2005), Akalin and Erisir (2008) and Karaca et al. (2009) whose findings revealed that insulin / fructo-oligosaccharides incorporation did not influence pH and titratable acidity of ice cream / yoghurt.
There was highly significant (P < 0.01) difference in specific gravity values of different treatment ice cream. The mean value shows different treatments of ice cream have lower specific gravity than full fat control ice cream (FFIM), but higher than low fat control ice cream (LFIM). Among the treatment ice cream, higher specific gravity was observed in LFIMI3, LFIMF3, where dietary fibre was included at 7 % level. The density of ice cream depends on two factors viz., the density of the ingredient mixture and the expansion or “overrun” that occurs due to freezing and introduction of air. As the density of cream is very close to that of water – on the order of 1.008 Kg/L for heavy cream, the other ingredients, such as sugar, flavouring, and other additives may increase or decrease the density. Dietary fibre like insulin and oligofructose has a specific gravity of about 1.35 and an average molecular weight of about 1,600. Being highly hygroscopic nature, insulin / fructo-oligosaccharides would bind with water and in addition to other components that form gel like network in ice cream mixes. Hence, addition of dietary fibres increases the specific gravity in low fat treatment ice cream when compared with low fat control ice cream.
Statistical analysis showed that there was a highly significant (P < 0.01) difference with regard to viscosity of different ice cream. The mean value shows different treatments of ice cream have lower viscosity than full fat control ice cream (FFIM), whereas, higher than low fat control ice cream (LFIM). Among the different treatment ice cream prepared, inclusion of 7% dietary fibre (LFIMI3, LFIMF3) showed higher viscosity. Viscosity values slightly increased with increasing insulin or oligofructose levels. These findings were in consistent with the findings of Schaller and Smith (1999), EL-Nagar et al. (2002), Hauly et al. (2005) and Akalin and Erisir (2008) and Karaca et al. (2009). The increase in viscosity upon addition of insulin or oligofructose in comparison with low fat ice cream can be explained by the interactions of the dietary fibre and liquid components of ice-cream. Insulin and oligofructose, being highly hygroscopic, would bind water and increases the viscosity.
Meltdown is an important attribute of ice cream which influences its sensory quality. Ice cream with more cream will generally melt at a slower rate to a liquid of smooth consistency. It is also very important that the ice cream is not too hard or should not melt quickly. There was a highly significant difference (P < 0.01) with regard to meltdown characteristic of different treatments of ice cream. The mean value shows increasing meltdown time was observed when the level of dietary fibre inclusion increases. The highest meltdown value was observed in 7% inclusion of dietary fibre when compared other level of ice cream. These findings were in close accordance with the findings of Akalin and Erisir (2008), who reported that the addition of insulin and fructo-oligosaccharides increasing melting time of ice cream. El-Nagar et al. (2002) and Akin (2005) also demonstrated that insulin supplementation reduced the melting rate and increased firmness in yog-ice cream. The result for melting characteristics suggests that insulin and oligofructose may act as stabilizers due to its capacity for binding water. Because of this property, the water molecules become immobilized and were unable to move freely among other molecules of the mixture. Furthermore, the delayed melting in the treatment ice-cream may also be ascribed to the retarded movement of molecules, as Insulin or oligofructose may have the ability to reduce the free movement of water molecules in the mix.
Overrun, which is directly related to the amount of air in ice cream, is very important, because, it contributes to the quality of the product and also to the profit margin. There was a highly significant (P < 0.01) difference in overrun percentage between different treatment ice cream. At the ideal incorporation level of 3% dietary fibre, Insulin had higher overrun when compared to oligo fructose. This concurred with the findings of Karaca et al. (2009), who reported that Insulin-containing ice creams possessed higher overrun values than other fat replacers. The mean value scores of increasing overrun was observed, when the level of dietary fibre inclusion increases, attributing to increased air incorporation in ice cream mixes. Accordingly, among the different treatment categories, ice cream prepared with either 7% insulin or fructo-oligosaccharides had higher overrun per cent. This was in close agreement with the findings of Akalin and Erisir (2008), who observed highest overrun value upon incorporation of insulin or FOS in the making of low fat probiotic ice cream.
Further, the sensorial attributes have also been carried out and the results are discussed here under-
Appearance of Different Treatment Ice Cream at Different Storage Period
Table 3: Appearance scores of different treatment ice cream at different storage period
|Treatment ice cream mix||Appearance scores at different storage periods||Mean ± SE|
|0 week||1st week||2nd week||3rd week||4th week||5th week|
|FFIM||8.58||8.57||8.55||8.56||8.52||8.52||8.550a ± 0.010|
|LFIMI1||8.58||8.58||8.58||8.58||8.58||8.58||8.580 a ± 0.000|
|LFIMI2||7.84||7.83||7.84||7.83||7.82||7.83||7.831b ± 0.003|
|LFIMI3||7.59||7.58||7.59||7.59||7.57||7.59||7.585c ± 0.003|
|LFIMF1||8.59||8.58||8.57||8.58||8.56||8.58||8.576a ± 0.004|
|LFIMF2||7.83||7.83||7.83||7.83||7.83||7.83||7.830b ± 0.000|
|LFIMF3||7.66||7.66||7.65||7.66||7.65||7.64||7.653c ± 0.003|
Table 3 shows the result of appearance of control and low fat fibre enriched ice cream. Statistical analysis indicated that there was no significant (P>0.05) difference for appearance score in different storage periods. Full fat control ice cream (FFIM) had highest (P < 0.01) appearance scores than low fat control ice cream (LFIM). Whereas, ice cream containing either 3% insulin (LFIMI1) or 3 % fructo-oligosaccharides (LFIMF1) were awarded significantly higher appearance scores (P < 0.01), when compared to their counter parts. This was in close agreement with the reports of Devereux et al. (2003), who prepared ice cream using insulin and oligofructose.
The mean value scores of appearance decreased when level of addition of dietary fibre increases. Owing to the highest water holding and emulsion properties, when Insulin and fructo-oligosaccharides are mixed with water or another aqueous liquid, they form a particle gel network resulting in a white creamy structure with a short spreadable texture. Because of this reason, if the concentration of dietary fibre is increased there will be negative impact on the appearance scores of ice cream. This was in agreement with the findings of Guven et al.(2005), who observed that found that appearance scores of yoghurt decreased with increasing insulin concentration over 15 days of storage time. Aryana et al. (2007) also reported that the over 22 days of storage the desirable appearance scores were obtained in yoghurt with insulin
Flavour of Different Treatment Ice Cream at Different Storage Period
There was no significant (P>0.05) difference for flavour score in different storage periods of ice cream. The panel members gave significantly highest flavour score (P < 0.01) for full fat control ice cream (FFIM) when compared to low fat control ice cream (LFIM). Ice cream with either 3% insulin (LFIMI1) or 3 % fructo-oligosaccharides (LFIMF1) received significantly higher scores (P < 0.01) (Table 4).
Table 4: Flavour scores of different treatment ice cream at different storage period
|Treatment Ice cream mix||Flavour scores at different storage periods||Mean ± SE|
|0 week||1st week||2nd week||3rd week||4th week||5th week|
|LFIM||7.15||7.16||7.17||7.16||7.15||7.16||7.158f ± 0.003|
|LFIMI2||7.85||7.83||7.84||7.83||7.85||7.83||7.838c ± 0.005|
There was a decrease in the mean value scores of flavour upon increase in the level of dietary fibre. As Insulin and fructo-oligosaccharides are soluble dietary fibres, oligofructose has 30% to 50% of the sweetness of sugar and insulin is of bland taste, increased concentration of dietary fibre inclusion in ice cream will result in decreased flavour scores. El-Nagar et al. (2002) reported that addition of insulin / FOS to low-fat yog-ice cream improved the flavour as high-fat product. Aryana et al. (2007) also reported that the desirable flavour scores were obtained in yoghurt containing insulin and FOS. However, Issariyachaikul (2008) observed that there was no significant difference in appearance, flavour, texture and overall acceptability among full fat formula and the majority of insulin added modified fat ice cream.
Sweetness of Different Treatment Ice Cream at Different Storage Period
Statistical analysis showed that there was no significant (P>0.05) difference for sweetness score during different storage periods of ice cream. These findings were in consistent with the reports of Schaller and Smith (1999), who reported that the sweetness intensity remained relatively consistent over the 6week of storage period. The panel members awarded highest sweetness for full fat control ice cream (FFIM) than low fat control ice cream (LFIM), which was highly significant (P < 0.01). In case of different treatments, ice cream with 3% insulin (LFIMI1) and 3% fructo-oligosaccharides (LFIMF1) separately had significantly higher scores (P < 0.01). It was observed that the mean value scores of sweetness decreased as the level of addition of dietary fibre increases (Table 5).
Table5: Sweetness scores of different treatment ice cream at different storage period
|Treatment Ice cream mix||Sweetness scores at different storage periods||Mean ± SE|
|0 week||1st week||2nd week||3rd week||4th week||5th week|
|LFIM||7.44||7.42||7.42||7.41||7.41||7.42||7.420f ± 0.004|
|LFIMI3||7.83||7.82||7.83||7.8||7.81||7.83||7.820d ± 0.005|
|LFIMF1||8.83||8.84||8.82||8.83||8.8||8.82||8.823a ± 0.005|
|LFIMF2||8.37||8.36||8.36||8.36||8.35||8.36||8.360c ± 0.002|
|LFIMF3||7.76||7.76||7.75||7.75||7.74||7.74||7.750e ± 0.003|
As insulin has a bland neutral taste, and fructo -oligosaccharide has a sweetness of about 35% in comparison with sucrose and without any off-flavour or aftertaste, its sweetening profile closely approaches that of sugar. By increasing per cent of inclusion of insulin and fructo-oligosaccharides in ice cream there will be negative effect on the scores of sweetness because of bland neutral taste of insulin and less sweetness of FOS. This is in agreement with the reports of Guven et al. (2005) who found that taste and aroma scores of set-type low-fat yoghurt decreased with increasing insulin concentration over 15 days of storage time.
Overall Acceptability of Different Treatment Ice Cream at Different Storage Period
Statistical analysis revealed there was no significant (P>0.05) difference for overall acceptability score during different storage periods of ice cream. There was a highly significant (P < 0.01) difference in overall acceptability scores between different treatments of ice cream. The full fat ice cream mixes (FFIM) followed by low fat ice cream with 3% insulin (LFIMI1) and 3% incorporation of FOS(LFIMF1) had the highest overall acceptability scores, when compared with other treatments of ice cream. The lowest overall acceptability scores were recorded in low fat control ice cream (LFIM) among different treatments of low fat ice cream (Table 6).
Table 6: Overall acceptability scores of different treatment ice cream at different storage period
|Treatment Ice cream mix||Overall acceptability scores at different||Mean ±SE|
|0 week||1st week||2nd week||3rd week||4th week||5th week|
|FFIM||8.66||8.65||8.65||8.66||8.65||8.65||8.653 a± 0.002|
|LFIM||6.83||6.83||6.84||6.83||6.83||6.83||6.831f ± 0.001|
|LFIMI1||8.66||8.66||8.65||8.66||8.65||8.65||8.650a ± 0.002|
|LFIMI2||7.85||7.85||7.84||7.83||7.83||7.85||7.841b ± 0.004|
|LFIMI3||7.79||7.79||7.78||7.78||7.78||7.79||7.785d ± 0.002|
|LFIMF1||8.66||8.66||8.66||8.66||8.66||8.66||8.650 a± 0.001|
|LFIMF2||7.79||7.79||7.79||7.79||7.79||7.79||7.790c ± 0.002|
This was in accordance with the findings of Issariyachaikul (2008), who reported that there was no significant difference in appearance, flavour, texture and overall acceptability among full fat formula and the majority of insulin added modified fat ice cream.
The results of this study show that the supplementation of insulin and fructooligosaccharides may be employed to produce lowfat fibre enriched ice cream with no difference in pH and titratable acidity of control ice cream. However, a highly significant (P < 0.01) difference was noticed in specific gravity, viscosity, melt down and over run values between different ice cream with a proportional increase to the increase in percent of insulin and fructo-oligosaccharides. The low fat ice cream with 3% of insulin , low fat ice cream with 3% of fructo-oligosaccharides recorded the highest appearance, sweetness, flavor and overall acceptability scores as like that of control full fat ice cream(FFIM) than the different treatment ice cream. Therefore, both insulin and fructooligosaccharide can be used to prepare low fat fibre enriched ice cream. Further, owing to its lower calorific value and low cost of production, ice cream with fructo-oligosacchrides seems to be the ideal choice recommended for production of low fat fibre enriched ice cream.