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Evaluation of textural and sensory characteristics of three types of low-fat goat milk ice cream
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Evaluation of textural and sensory characteristics of three types of low-fat goat milk ice cream夽 Christopher E. McGhee, Jolethia O. Jones, Young W. Park ∗ Georgia Small Ruminant Research & Extension Center, Fort Valley State University, Fort Valley, GA 31030-4313, USA
a r t i c l e
i n f o
Article history: Received 6 October 2014 Received in revised form 6 December 2014 Accepted 8 December 2014 Available online xxx Keywords: Goat milk Ice cream Texture Sensory properties Storage
a b s t r a c t Three types of low-fat soft-serve goat milk ice creams were manufactured using whole milk (3.64% fat), 2% fat and skim (0.71% fat) goat milk, and evaluated for textural and sensory characteristics of the caprine ice cream products. A commercial powdered vanilla flavor pre-mix containing 0.25% fat (Alpha Freeze, D466-A9047, Tampa, FL, USA) was formulated into the three types of goat milk base for the manufacture of the ice creams, and textural and sensory properties of the products were determined at 0, 2, 4, 8 weeks of frozen-storage at −18 ◦ C. Additional textural traits at 0, 1 and 56 days of storage were compared among the three types of low-fat caprine ice creams using a texture analyzer (TA-XT2 Texture Technologies Corp., Scarsdale, NY, USA). The results showed that approximately threefold increases in firmness and consistency of all three types of soft-serve low-fat goat ice creams after 1 day frozen-storage. The similar trend of elevation was observed in cohesiveness and index of viscosity for all tested products, probably due to the hardening of the texture of the frozen products after 1 day storage. Regardless of fat level treatments of the low-fat goat ice creams, all textural properties after 56 days frozen-storage revealed substantial elevations especially in firmness and consistency traits compared to those of the original soft-serve ice creams with extreme high variations. In sensory quality, storage period significantly affected the flavors of cooked (P < 0.01), sweetness (P < 0.05), freshness (P < 0.05), rancidity (P < 0.05), whey (P < 0.05) and oxidized (P < 0.05), but not in acid flavor. There was a general trend of a slight decline in overall acceptability of the three types of low-fat goat ice creams as storage period advanced. It was concluded that the textural and sensory qualities of the low-fat goat milk ice creams were still acceptable by the sensory panel after 8 weeks frozen-storage. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Ice cream is one of the main frozen desserts made primarily from cow milk in the US, but it can be manufactured from different dairy species milk such as caprine milk. Ice
夽 Mention of brand names does not imply endorsement by Fort Valley State University nor NIFA/US Department of Agriculture over similar products not mentioned in the paper. ∗ Corresponding author. Tel.: +1 478 827 3089; fax: +1 478 825 6376. E-mail address: [email protected] (Y.W. Park).
cream market amounted to 1.52 billion gallons (5.75 billion liters) (USDA, 2012). It comprised 86.7% of the total volume of all frozen desserts, and the rest of the market primarily consists of frozen yogurt, water/fruit ices, and sherbet (Kilara and Chandan, 2013). While ice cream is a popular food around the world, high fat foods are discouraged, since dietary fat has been implicated with coronary heart diseases, diabetes and other health problems (WHO, 2010; Nouira et al., 2011). Consumption of reduced or low fat dairy products has been increasingly popular among health-conscientious consumers in recent years (Thayer, 1992; Johnson et al.,
http://dx.doi.org/10.1016/j.smallrumres.2014.12.002 0921-4488/© 2014 Elsevier B.V. All rights reserved.
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2009). The sales of light ice cream have been increased by 9% in 1997, while the sales of both low fat and fat free had declined (Markgraf, 1997). Although ice cream typically contains 10–16% fat, the dairy industry recently has developed a variety of low-fat and fat-free ice cream products (Giese, 1996; Marshall et al., 2003). Compared with traditional ice creams, the low-fat ice creams have problems of low flavor and low textural qualities (Akahm et al., 2008). Texture plays an important role in sensory quality and consumer acceptability of ice cream, while reduction in milk fat can cause serious textural and flavor defects such as coarseness and iciness, crumbly body, shrinkage and flavor defects in dairy foods including ice cream products (Berger, 1990; Drake and Swanson, 1995; Marshall and Arbuckle, 1996; Johnson et al., 2009). Overall acceptability of low-fat foods is determined more by texture than by flavor of the products (Devereux et al., 2003). This fact has led a practice for the ice cream manufacturers to use milk fat replacers in order to produce their products that meet the demands of health-conscious consumers (Akahm et al., 2008). The structure of the ice cream has been identified as a three component foam made up of a network of fat globules and ice crystals dispersed in a high viscosity aqueous phase (Dickinson, 1992; Prentice, 1992). This challenge in working with low fat ice creams is attributed to the fact that the fat globule network would either be disrupted or absent and this could seriously impact the texture of the product (Aime et al., 2001). Goat milk has shown to possess better health and therapeutic values than cow milk counterpart (Park and Haenlein, 2006). Compared to bovine milk, caprine milk contains more minerals and vitamins A, B and C, lower cholesterol, and higher smaller and medium chain fatty acids (MCT) and has better digestibility due to the smaller fat globule size of goat milk (Park, 2006). Goat milk is oversupplied with protein, Ca, P, vitamin A, thiamin, riboflavin, niacin and pantothenate in relation to the FAOWHO requirements to a human infant (Jenness, 1980; Park, 2006). Goat milk ice cream may have certain nutritional advantages over cow milk counterparts due to the differences in nutrient composition between bovine and caprine milk (Park, 2006). Even though many studies of the nutritional, chemical, rheological, and sensory characteristics of cow milk ice creams have been documented, very few scientific reports have been available on goat milk ice cream products due to the lack of governmental, industry and academia supports and interests, the lack of an infrastructure, seasonal milk production, and paucity of research data (Park, 2000). Therefore, the objectives of this study were to: (1) evaluate textural and sensory properties of three types of low fat goat milk ice creams made with whole milk, 2% fat and skim goat milk and (2) compare the effect of 0, 2, 4, and 8 weeks frozen-storage at −18 ◦ C on textural and sensory characteristics among these samples. 2. Materials and methods 2.1. Experimental design The study was conducted in a 3 × 3 × 4 factorial experiment. Three batches of goat milk ice creams were manufactured using three
different levels of low fat goat milk as skim (0.71% fat), 2% fat, and whole milk (3.64% fat). The three levels of low fat goat milk ice creams were manufactured and stored at −18 ◦ C for four different storage periods as 0, 2, 4 and 8 weeks. The effects of two main factors and their interactions on nutritional, textural, and sensory characteristics of the experimental goat milk ice cream were evaluated. All experimental ice cream samples were packaged in 227 g (8 ozoz) styrofoam cups until further analysis for basic nutrient contents, lipolysis, textural and sensory characteristics.
2.2. Manufacture of ice creams 2.2.1. Manufacture of whole and skim milk ice creams 2.2.1.1. Whole goat milk ice cream. The experimental goat milk used was taken from the bulk tank milk collected from the milking goat herd of the Georgia Small Ruminant Research & Extension Center (GSRREC), Fort Valley State University (FVSU), Fort Valley, GA, USA. One gallon (3.76 L) of whole goat milk was pasteurized at 64 ◦ C for 30 min using a Hoegger Table Top pasteurizer (54M-5, Fayetteville, IN, USA). After pasteurization, 1.3 kg of commercial vanilla mix (Alpha Freeze, D466-A9047, Tampa, USA) powdered ice cream pre-mix was added to the pasteurized whole milk, and mixed thoroughly using a hand mixer. Due to the unavailability of 100% goat milk-based ice cream pre-mix, a commercial ice cream premix was used in this study. The commercial ice cream mix was composed of sugar, corn syrup solids, coconut oil, natural flavor, sodium caseinate, sodium and potassium phosphate, guar gum, mono and diglycerides, xanthan gum, and soy lecithin. The total fat content of the commercial ice cream mix was 0.25%. The mixture of milk and powder ice cream pre-mix was poured into two separate tanks in the Sani Serv ice cream machine (A5223P, Mooresville, IN, USA), where the mixture was frozen and blended until the soft serve ice cream was formed. The soft serve ice cream was packaged into 227 g (8 oz) styrofoam cups, labeled, and stored in a chest freezer (Frigidaire, Model GLFC2528FW, Raleigh, NC) at −18 ◦ C for 0, 2, 4, and 8 weeks for the analyses of chemical, textural and sensory characteristics. The ice cream was made at the dairy plant of the GSRREC, FVSU, Fort Valley, GA, USA.
2.2.1.2. Skim goat milk ice cream. For the skim goat milk ice cream manufacture, cream was first separated prior to pasteurization by an electric cream separator (125 L/h, Clair Co. Model 17584, Althofen, Austria), cream was removed, and then only skim goat was used to make the skim milk ice cream. The manufactured skim milk ice cream was packaged and was received the same experimental treatments as the whole milk ice cream.
2.2.1.3. Manufacture of 2% fat goat ice cream. The 2% fat goat milk ice cream was manufactured using the skim goat milk and goat cream produced from the separation of the whole goat milk. Accurate amount of goat milk cream was calculated using the Pearson square method. The accurately measured amounts of cream and skim milk were combined and the 2% milk was produced. The percentage of the 2% fat milk was determined by using a Milk-O-Scan (Model FT2, Hillerod, Denmark). The 2% milk was pasteurized and 2% fat ice cream was made as the same way as the whole milk and skim milk ice creams, and assigned the same experimental treatments as the other two types of ice creams, and performed all the same corresponding analyses.
2.3. Basic nutrient analysis 2.3.1. Fat content The percent fat of all experimental ice cream samples was determined using the Babcock procedure (Richardson, 1985). The ice cream was melted at room temperature and then 9 g of the ice cream was weighed and transferred into the Babcock bottle for the analysis. Fat and other basic nutrients for original milk samples were tested by the Milk-O-Scan machine (Model FT2, Hillerod, Denmark).
2.3.2. Protein content Protein content was determined using a carbon/nitrogen analyzer (Vario MAX CN Elementar Americas, Inc., Mt. Laurel, NJ, USA). Nitrogen contents of the ice cream samples were first determined by the Vario MAX CN analyzer according to the manufacturer’s instruction, and the %N was multiplied by 6.38 to calculate protein contents of the ice creams.
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2.3.3. Dry matter and ash content Dry matter was determined by oven drying method at 105 ◦ C overnight (AOAC, 1985). Amounts of ash of ice cream samples were analyzed by dry ashing method (AOAC, 1985). A 2 g sample was placed in a muffle furnace at 600 ◦ C for overnight, and cooled to room temperature in a desiccator before determining the ash contents. 2.4. Acid degree value (ADV) The ADV refers to measure of the amount of free fatty acids present in a fat sample, which is a quantitative index of hydrolytic lipolysis in dairy products. ADV was determined by the Standard Methods for the Examination of Dairy Products (Richardson, 1985). Approximately 10 g of sample were grated, homogenized, and placed into a Babcock cheese bottle for fat extraction; 1 mL of the final extracted fat was titrated against the standard alcoholic 0.02 N KOH solution. Calculation of ADV was performed using the following formula: ADV = mL KOH for sample − mL KOH for blank × N × 100 weight of fat (g)
Fig. 1. Comparison of changes in ADV values among three experimental goat milk ice creams stored at −18 ◦ C for 0 to 8 weeks.
3. Results and discussion
where N is the normality of KOH solution in methanol. 2.5. Texture analysis Textural characteristics of the ice cream were evaluated using a texture analyzer (TA-XT2 Texture Technologies Corp., Scarsdale, NY, USA). A cylindrical probe was used for detecting shear force (g) which was made of acrylic material and 2.5 cm in diameter and 3.5 cm in height. The undisturbed sample was loaded on the analyzer in suitable beaker (50 mL) for g force measurement to prevent disturbing its physical and textural states. The speed of the probe was set at 2 mm/s as the recommended procedure of Guinard et al. (1997) and Tunick (2000). 2.6. Sensory evaluation An eight member sensory panel composed of faculty and graduate students from College of Agriculture, Family Sciences and Technology at Fort Valley State University, Fort Valley, GA evaluated the sensory properties of goat milk ice creams. Panelists assessed the flavor, body and texture, and color and appearance properties of the goat ice cream products using the USDA scorecard (1976) and ADSA Collegiate Dairy Products Evaluation Ice Cream scorecard. Recent references (Carunchia Whetstine and Drake, 2006; Alvarez, 2009) were used as the standard for ratings for all sensory descriptors. The panelists were trained for sensory scoring practice of goat ice creams for four times prior to the sensory experiment and also at the time of sensory testing periods (0, 2, 4 and 8 weeks). Panelists were presented the instructions of descriptive languages, lexicon of flavor and the score card at the training of sensory testing for the ice creams using the descriptive languages and lexicon of dairy goat products illustrated by Carunchia Whetstine and Drake (2006). At the sensory laboratory windows, one half ounce (14.18 g) of ice cream samples in small plastic cups (30 mL size) from each treatment groups without tempering, a glass of water for mouth washing, small sampling spoon, crackers, napkins, the descriptive language instructions and score cards were given to each panelist for sensory evaluation. The flavor properties evaluated on the 10-point intensity scale hedonic scores were: cooked, sweetness, freshness, rancid, whey, high acid, and oxidized. Body/texture and color and appearance were both scored on the 5-point intensity scale, and the body/texture parameters evaluated were: coarse/icy, crumbly, fluffy, gummy, sandy, soggy, and weak body. The only parameters scored for color and appearance was tested on hedonic scores of the color and overall acceptability of the ice creams. 2.7. Statistical analysis All experimental data of three batches of goat milk ice creams made with three levels of milk fat (whole, 2%, and skim) were analyzed for the effect of main factors and their interactions on nutritional, lipolytic, textural, and sensory characteristics by the method of Steel and Torrie (1960). All data were also analyzed by analysis of variance, Duncan’s multiple mean comparisons between main factors using general linear model of SAS program (1994).
3.1. Basic nutrient composition of three types of ice creams The results of proximate analysis of the three types low fat experimental goat milk ice creams are shown in Table 1. As expected, there were significant differences (P < 0.05) between the levels of fat in the three different types of ice creams, where the actual fat contents (wet basis) of the skim, 2%, and whole goat milk ice cream were 1.87%, 3.84%, and 5.31%, respectively. Carbohydrate content of the whole milk ice cream was slightly lower than those of skim and 2% milk ice creams probably due to the differences in the sugar content of the pre-mix as well as lactose content of the original goat milk. However, no differences were found among the three types of low fat goat milk ice creams in the other basic nutrient contents such as total solids, protein and ash contents. The original whole caprine milk base used in this study contained 12.2% total solids, 3.64% of fat, 3.59% of protein, and 0.81% ash, which has a similar composition reported by Park (2006), indicating that fat removal in the original goat milk, and the addition of the commercial powder mix and sugar made differences in the basic nutrients contents of the experimental goat milk ice creams. 3.2. Effect of frozen storage on lipolysis of goat milk ice creams Acid degree value (ADV) is the measurement of the amount of free fatty acid in a dairy product, which is an index of lipolysis of a sample (Richardson, 1985; Park, 2001; Nouira et al., 2011). It determines the degree of lipolysis in a food product, whereby it estimates the shelf life of the food product in question. Fig. 1 illustrates the differences of changes in ADV values among the three different experimental goat milk ice creams during 0, 2, 4, 6, and 8 weeks storage period. Although the differences were not statistically significant, there was a trend of slight increase in lipolysis up to 4 weeks frozen-storage, where the order of increase in ADV values were 2% milk, whole milk and skim milk ice creams. This might be attributed to the release and activation of lipase from the disrupted fat globule membranes during the cream separation processes from the goat milk used. There was a sudden drop in ADV values
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Table 1 Basic nutrient contents (%) of three types of low-fat goat milk ice creams. Fat type
Dry matter (%)
Skim 2% Whole a,b,c
Ash (%)
Fat content (%)
Protein (%)
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
32.11ab 34.15a 33.28ab
0.40 1.7 1.70
1.54a 1.58a 1.58a
0.05 0.18 0.08
1.87c 3.84b 5.31a
0.40 0.13 0.57
2.87a 2.80ab 2.90a
0.15 0.16 0.24
24.81ab 25.94a 23.47ab
0.12 0.06 0.12
Means with different superscript within a column are significantly different (P < 0.05). SD: standard deviation. Whole milk
4000
2% milk
Skim milk
450
3000 2500
Whole milk 2000
2% milk
1500
Skim milk
1000
Cohesiveness (g force)
3500
Firmness (g force)
Carbohydrate (%)
400 350 300 250 200 150 100 50
500
0
0 0 day
1 day
0 day
56 days
1 day
56 days
S to r a g e p e r io d
Fig. 2. Comparison of firmness of three types of goat milk ice creams during three different frozen-storage periods.
at 6 weeks frozen storage and then slight increases at 8 weeks storage. The reasons for these reductions in ADV are not clear, while certain indigenous lipolytic enzymes in the original milk and/or the ice creams mix, as well as lipases from psychrotropic bacteria (Deeth and FitzGerald, 1976; Park, 2001) in the ice cream ingredients might have been reduced in lipolytic conditions during the 6 weeks frozenstorage conditions. In addition, autooxidation of the fat in the ice cream might have been reduced at this 6 weeks frozen-storage period. 3.3. Effect of frozen-storage on textural properties of goat milk ice creams The results of textural properties on the three types of experimental low-fat goat milk ice creams are shown in Figs. 2–5. The mean values (g force) of firmness and consistency for freshly made soft serve whole milk, 2% and skim milk goat ice creams were: 208.7, 297.3; 182.8, 261.8; 183.5, 255.0, respectively (Figs. 2 and 3). These data show that the firmness and consistency values of all freshly made
Fig. 4. Comparison of changes in cohesiveness of three types of goat milk ice creams during three different frozen-storage periods.
three low-fat goat ice were increased significantly (P < 0.01) (almost threefold) after 1 day frozen-storage at −18 ◦ C. The trend of elevation of the textural values was same for all tested indices probably due to the hardening of the texture of the frozen products for 1 day frozen-storage compared to the soft-serve samples. In addition, all three types of low-fat ice goat creams revealed that there were substantial increases in all tested textural properties from 0 day to 56 days (8 weeks) of frozen-storage (Figs. 2 and 3). The firmness and consistency of whole milk ice cream after 56 days were more than twofold greater than those of skim and 2% milk ice cream (Figs. 2 and 3), indicating that the higher milk fat in the whole milk ice cream may have contributed to these outcomes. Texture plays an important role in consumer acceptability of a food product (Drake and Swanson, 1995; Tunick, 2000; Park et al., 2006; Park, 2007). Changes in fat composition can have serious influence on textural and flavor characteristics of ice cream, which may in turn affect the consumer acceptability (Berger, 1990; Akahm et al., 2008). It has been also reported that goat milk can be used Whole milk
18000
Skim milk
300
14000 12000 10000
Whole milk
8000
2% milk
6000
Skim milk
4000 2000
Index of viscosity
Consistency (g force)
2% milk
350
16000
250 200 150 100 50
0 -2000
0 day
1 day S to r a g e p e r io d
56 days
Fig. 3. Comparison of consistency of three types of goat milk ice creams during three different frozen-storage periods.
0 0 day
1 day
56 days
Fig. 5. Comparison of changes in the index of viscosity of three types of goat milk ice creams during three different frozen-storage periods.
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Table 2 Mean flavor property scores of three different types of low-fat goat milk ice creams during 8-week storage period evaluated by the sensory panel. Cooked Mean
Sweet
Fresh
Rancid
Whey
High acid
Oxidized
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Whole milk ice cream Week 0 9.50b 9.67a Week 2 9.42bc Week 4 9.29c Week 8
0.25 0.19 0.14 0.07
8.83bc 9.29ab 9.13ab 9.29ab
0.52 0.44 0.13 0.19
9.17ab 9.42ab 9.33ab 9.21ab
0.26 0.19 0.31 0.07
9.38ab 9.42ab 9.42ab 9.25b
0.13 0.31 0.07 0.33
8.71c 9.42a 9.17ab 9.04b
1.15 0.29 0.29 0.07
9.42a 9.42a 9.42a 9.25ab
0.31 0.26 0.31 0.13
9.46ab 9.50ab 9.50ab 9.33b
0.29 0.25 0.22 0.07
2% milk ice cream Week 0 9.46bc 9.58ab Week 2 9.50b Week 4 9.33c Week 8
0.29 0.14 0.13 0.14
8.88bc 9.38a 9.25ab 9.25ab
0.13 0.22 0.13 0.25
9.33ab 9.54a 9.29ab 9.13ab
0.44 0.14 0.31 0.38
9.21b 9.71a 9.38ab 9.17b
0.36 0.14 0.00 0.26
8.79c 9.46a 9.21ab 9.25ab
0.38 0.19 0.07 0.13
9.21ab 9.54a 9.33ab 9.33ab
0.31 0.14 0.14 0.29
9.42ab 9.67a 9.42ab 9.21b
0.36 0.19 0.07 0.19
Skim milk ice cream 9.42bc Week 0 9.71a Week 2 9.46bc Week 4 Week 8 9.38c
0.19 0.07 0.07 0.13
9.04b 8.88bc 8.67c 9.04b
0.07 0.33 0.19 0.26
9.33ab 9.38ab 9.42ab 9.04b
0.07 0.38 0.07 0.36
9.33ab 9.63a 9.38ab 9.50ab
0.38 0.22 0.00 0.25
9.00b 9.33ab 8.96bc 9.25ab
0.22 0.31 0.19 0.33
9.25ab 9.42a 9.42a 9.50a
0.25 0.07 0.07 0.22
9.46ab 9.71a 9.46ab 9.42ab
0.40 0.07 0.07 0.29
a,b,c 1
Means with different superscripts within a same column are different (P < 0.05 or 0.01). All mean values are average of 8 panelists.
to produce a softer texture ice cream with a more desirable melting quality (Riberio and Riberio, 2010). Regardless of fat level treatments of the experimental low-fat goat milk ice creams in the present study, all textural properties after 8 weeks (56 days) frozen storage, especially in firmness and consistency traits, were substantially increased compared to those of the original fresh ice cream (Figs. 2 and 3). However, the variations in the textural property values between the soft-serve and frozen-stored ice cream samples as well as between and within samples, especially after the 8 weeks frozen-storage were substantially high (Figs. 2 and 3), which may be attributed to the extended hardening of the samples during the 56 days storage compared to the fresh soft serve samples. The high variability of textural properties values in hardened ice creams may also be due to the differences in the sensitivity of the texture analyzer (TA-XT2 Texture Technologies Corp.) used between the soft serve samples and the extended hardened ice cream samples (Figs. 2 and 3). It is also likely attributed to the fact that the hardened ice cream might have exerted completely different thermophysical and colloidal profiles compared to those of the fresh soft-serve ice cream samples drawn from the freezer. The mean cohesiveness values of fresh and 8 weeks frozen stored whole milk, 2% and skim milk ice cream samples were: 88.4, 95.1, 92.4; 385.6, 258.4, 184.6, respectively (Fig. 4), and index of viscosity values of fresh and 56 days frozen stored skim, 2%, and whole goat milk ice cream were: 49.3, 54.0, 45.4; 300.4, 178.0, 140.5, respectively (Fig. 5). There was a general trend that cohesiveness and index of viscosity values increased with the advanced storage time. The whole goat milk ice cream showed significantly (P < 0.01) higher cohesiveness and index of viscosity values than those of skim and 2% goat milk ice cream as storage time extended to 8 weeks frozen-storage (Figs. 4 and 5), suggesting that the fat content of the lowfat ice cream products also affected or increased these two textural indices of the goat milk ice creams in our study (Figs. 4 and 5). Beyond the fat content of the milk used
in ice cream manufacture, other factors contributing ice cream texture include stabilizers and emulsifiers (Aime et al., 2001). In a research with full fat ice cream, JimenezFlores et al. (1993) have shown that stabilizers promoted viscosity development in the aqueous phase and controlled ice crystal growth (Stanley et al., 1996). Since the powder ice cream pre-mix used in our study contained stabilizers and emulsifiers, they may have increased the values of cohesiveness and index of viscosity.
3.4. Effect of frozen storage on sensory characteristics The mean flavor characteristics scores of the three types of low-fat experimental goat ice creams for 8 weeks storage periods are presented in Table 2. The mean body/texture characteristics scores of the same low-fat goat ice creams evaluated by the sensory panel for the same experimental periods are also shown in Table 3. In general, most of flavor characteristics were affected by the frozen-storage periods, while the frozen-storage effect was minimal on body/texture scores except sogginess and fluffiness up to 8 weeks storage at −18 ◦ C. The analysis of variance (F values) on the effects of main factors and interactions on flavor characteristics are summarized in Table 4. For the main factors, storage period had significant influences on the flavors of cooked (P < 0.01), sweetness (P < 0.05), freshness (P < 0.05), rancidity (P < 0.05), whey (P < 0.05) and oxidized (P < 0.05), but not in acid flavor. The multiple mean comparison revealed one prominent results that the 2 weeks frozen-stored ice cream samples showed the highest scores of all flavor traits. This may indicate that the 2 weeks frozen goat ice creams were better in flavor characteristics compared to the fresh soft serve ice creams. As far as the other main factor (the fat types) goes, no fat type effect was found in any of the flavor characteristics. In light of batch effect, the batch 3 had significantly (P < 0.01) higher rancidity value than the batches 1 and 2, while other flavor characteristics were not affected by fat type and type x storage interaction effects (Table 4).
Please cite this article in press as: McGhee, C.E., et al., Evaluation of textural and sensory characteristics of three types of low-fat goat milk ice cream. Small Ruminant Res. (2014), http://dx.doi.org/10.1016/j.smallrumres.2014.12.002
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Table 3 Mean body/texture characteristics scores of three different types of low-fat goat milk ice creams during 8-week storage period by the sensory panel. Coarse/icy Mean
Crumbly
Fluffy
Gummy
Sandy
Soggy
Weak body
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Whole milk ice cream Week 0 4.63 4.29 Week 2 4.25 Week 4 4.25 Week 8
0.13 0.26 0.13 0.33
4.75 4.67 4.54 4.21
0.13 0.07 0.26 0.19
4.58ab 4.58ab 4.45ab 4.58ab
0.07 0.36 0.07 0.07
4.71 4.75 4.75 4.50
0.14 0.22 0.22 0.22
4.58 4.71 4.63 4.46
0.26 0.07 0.13 0.29
4.29b 4.58ab 4.63a 4.46ab
0.47 0.26 0.13 0.14
3.92 4.54 4.50 4.38
0.79 0.19 0.66 0.45
2% milk ice cream Week 0 4.42 4.67 Week 2 4.38 Week 4 4.50 Week 8
0.19 0.26 0.22 0.33
4.67 4.54 4.50 4.38
0.07 0.19 0.22 0.22
4.46ab 4.67a 4.33b 4.75a
0.19 0.31 0.14 0.22
4.63 4.67 4.67 4.75
0.25 0.07 0.14 0.13
4.46 4.75 4.63 4.54
0.07 0.22 0.13 0.07
4.33b 4.63a 4.63a 4.50ab
0.38 0.13 0.13 0.25
4.38 4.63 4.67 4.38
0.63 0.00 0.26 0.13
Skim milk ice cream 4.38 Week 0 4.38 Week 2 4.50 Week 4 Week 8 4.46
0.00 0.43 0.38 0.14
4.46 4.58 4.63 4.67
0.29 0.19 0.33 0.07
4.54ab 4.54ab 4.42ab 4.71a
0.14 0.19 0.26 0.19
4.54 4.50 4.71 4.54
0.26 0.13 0.07 0.40
4.54 4.33 4.50 4.66
0.19 0.07 0.13 0.19
4.33b 4.58ab 4.71a 4.54ab
0.19 0.29 0.19 0.29
4.38 4.29 4.50 4.50
0.33 0.19 0.22 0.33
a,b 1
Means with difference superscripts within a same column are different (P < 0.05). Differences were found only in fluffy and soggy properties. All mean values are average of 8 panelists.
Table 4 Effects of main factors and interactions on flavor characteristics of the three types of low fat goat milk ice creamsa .
Batch Type Storage Type × storage a * **
Cooked
Sweetness
Freshness
Rancid
Whey
Acid
Oxidized
0.83 0.12 6.00** 0.34
0.03 0.15 3.57* 0.96
1.74 0.18 2.13* 0.40
4.52* 0.57 2.84* 1.01
1.19 0.42 1.94* 0.24
1.00 0.03 0.59 0.58
2.56 0.35 2.74* 0.37
All numbers are F values from the analysis of variance of the experimental data. Significant at P < 0.05 Significant at P < 0.01
Table 5 Pooled data of two selected body/texture traits showing significant differences between frozen-storage periods by Duncan’s multiple mean comparison. Sogginess 4 wk 2 wk 8 wk 0 wk
Fluffiness 4.654 4.599 4.503 4.321
A A AB B
8 wk 2 wk 0 wk 4 wk
4.683 4.600 4.531 4.432
A AB AB B
Means with different letters within a same column are different (P < 0.05).
Among body and texture properties, only two characteristics had shown significant (P < 0.05) differences among the four different storage periods in the experimental low fat goat milk ice creams (Tables 3 and 5). Sogginess and fluffiness were the only two properties shown the differences between the storage periods among all body and texture properties. The descending order of sogginess values were 4, 2, 8 and 0 week samples, while the corresponding descending order of fluffiness traits were 8, 2, 0 and 4 week samples (Table 5). The amount of fat in the ice creams influenced on consumers perception of the goat ice cream product, where the fat type of the low fat goat ice cream products were associated with sweetness perception of the products, showing the 2% fat ice cream had higher (P < 0.05) sweetness value than the whole milk and skim milk ice cream samples. Fig. 6 depicts the overall acceptability of the three experimental goat ice creams scored by the sensory panel.
Fig. 6. Comparison of changes in mean overall acceptability scores of three types of goat milk ice creams during 8 weeks frozen-storage.
The average overall acceptability scores of the whole milk, 2% milk, and skim goat milk ice creams were: 4.30, 4.34, 4.29, respectively, implying that the skim goat milk ice cream exhibited slightly higher overall acceptability than those of the other two ice creams after 8 weeks frozenstorage. For color change scores, no detectable changes were found in all three types of the goat milk ice creams up to 8 weeks frozen-storage. However, it was observed that there was a general trend of slightly declining overall acceptability of the three experimental low-fat goat ice creams in the present study (Fig. 6). Although our results
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on overall acceptability of the experimental goat ice creams for 8 weeks were not affected, Aime et al. (2001) reported that their trained panel rated the low-fat and fat free ice creams to have lower viscosity, smoothness and mouth coating properties, while the sensory attributes of the light samples were comparable to the regular cow milk vanilla ice cream. They also observed that there was good correlation between the instrumentally determined firmness values and the sensory results. Compared with traditional ice creams, the low-fat or reduced fat ice creams are expected to have lower flavor and textural quality (Berger, 1990; Marshall et al., 2003; Akahm et al., 2008).
4. Conclusions All three types of the experimental low-fat soft-serve goat milk ice creams showed substantial increases in textural properties especially in firmness and consistency after 8 weeks frozen-storage. High variations in elevation of the textural characteristics of the frozenstored ice cream samples appeared to be attributed to the hardening of the products during the frozen-storage, as well as the difference in sensitivity of the texture analyzer between soft serve and hardened ice cream samples. The flavors of the low-fat goat ice creams were significantly influenced by storage period in cooked, sweetness, freshness, rancidity, whey and oxidized flavors, but not in acid flavor. Among body and texture properties, sogginess and fluffiness were the only two properties affected by the storage periods. Although there was a slight decrease in overall acceptability of the three experimental low-fat goat ice creams during 8 weeks storage, textural and sensory qualities of the three types of low-fat goat milk ice creams were acceptable. Even though the commercial ice cream pre-mix contains minor ingredient (sodium caseinate) derived from cow milk, their effects were expected to be identical and equally canceled out from all three different goat milkbased experimental ice creams, whereby the comparison of textural and sensory qualities between the products would be valid. However, further studies may be necessary to determine textural and sensory qualities using the premix containing only goat milk ingredients, when it becomes available.
Conflict of interest There is no conflict of interest.
Acknowledgements This research was supported by the 1890 Capacity Building Grants of the USDA/NIFA Grant No. 2010-02049. Authors appreciate Carlton Green, Schauston Miller and Ruby Ragan for preparation of goat milk and other commercial powdered ice cream premix for the ice cream manufacture.
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References Aime, D.B., Arntfield, S.D., Malcolmson, L.J., Ryland, D., 2001. Textural analysis of fat reduced vanilla ice cream products. Food Res. Int. 34, 237–246. Akahm, A.S., Karagozlu, C., Unal, G., 2008. Rheological properties of reduced-fat and low-fat ice cream containing whey protein isolate and inulin. Eur. Food Res. Technol. 227, 889–895. Alvarez, V.B., 2009. Ice cream and related products. In: Clark, S., Costello, M., Drake, M., Bodyfelt, F. (Eds.), The Sensory Evaluation of Dairy Products. , 2nd ed. Springer, pp. 271–332. AOAC, 1985. Official Methods of Analysis. 14th Ed. Assoc. Offic. Anal. Chem. Washington, DC. No. 43.292. 7.001, 7.009, 7.006. Berger, K.G., 1990. In: Larsson, K., Friberg, S.E. (Eds.), Ice Cream in Food Emulsions. , 2nd ed. Marcel Dekker, Inc., New York, p. 367. Carunchia Whetstine, M.E., Drake, M.A., 2006. Flavor characteristics of goat milk and other minor species milk products. In: Park, Y.W., Haenlein, G.F.W. (Eds.), Handbook of Milk of Non-Bovine Mammals. Blackwell Publishers, Ames, Iowa and Oxford, England, pp. 107–120. Deeth, H.C., FitzGerald, C.H., 1976. Lipolysis in dairy products: a review. Aust. J. Dairy Technol. 31, 53–64. Devereux, H.M., Jones, G.P., McCormack, L., Hunter, W.C., 2003. Consumer acceptability of low fat foods containing inulin and oligofructose. J. Food Sci. 68 (5), 1850–1854. Dickinson, E., 1992. An Introduction to Food Colloids. Oxford University Press. Drake, M.A., Swanson, B.G., 1995. Reduced- and low-fat cheese technology: a review. Trends Food Sci. Technol. 6, 366–369. Giese, J., 1996. Fats, oils, and fat replacers. Food Technol. 50 (4), 48–83. Guinard, J.-X., Zoumas-Morse, C., Mori, L., Uatoni, B., Panyam, D., Kilara, A., 1997. Sugar and fat effects on sensory properties of ice cream. J. Food Sci. 62, 1087–1094. Jenness, R., 1980. Composition and characteristics of goat milk: review 1968–1979. J. Dairy Sci. 63, 1605–1630. Jimenez-Flores, R., Klipfel, N.J., Tobias, J., 1993. Ice cream and frozen desserts. In: Hui, Y.H (Ed.), Dairy Science and Technology Handbook. Product Manufacturing, vol. 2. VCH Publishers, Inc., New York, pp. 57–157. Johnson, M.E., Kapoor, R., McMahon, D.J., McCoy, D.R., Narasimmon, R.G., 2009. Reduction of sodium and fat levels in natural and processed cheeses: scientific and technological aspects. Compr. Rev. Food Sci. Food Safety 8, 252–268. Kilara, A., Chandan, R.C., 2013. Frozen dairy products. In: Park, Y.W., Haenlein, G.F.W. (Eds.), Milk and Dairy Products in Human Nutrition. Wiley-Blackwell Publishers, pp. 435–457. Markgraf, S., 1997. Annual ice cream report: indulgence supreme. Dairy Foods 99 (3), 82–84. Marshall, R.T., Arbuckle, W.S., 1996. Ice Cream, 5th ed. Chapman & Hill, New York. Marshall, R.T., Goff, H.D., Hartel, R.W., 2003. Ice Cream, 6th ed. Kluwer/Plenum Publ., New York, pp. 18, 23, 34, 93, 203. Nouira, W., Park, Y.W., Guler, Z., Terrill, T.H., 2011. Comparison of free fatty acid composition between low-fat and full-fat goat milk cheeses stored for 3 months under refrigeration. Open J. Anim. Sci. 2, 17– 23. Park, Y.W., 2000. Comparison of mineral and cholesterol composition of different commercial goat milk products manufactured in USA. Small Rumin. Res. 37, 115–124. Park, Y.W., 2001. Proteolysis and lipolysis of goat milk cheese. J. Dairy Sci. 84 (E. Suppl.), E84–E92. Park, Y.W., 2006. Goat milk – chemistry and nutrition. In: Park, Y.W., Haenlein, G.F.W. (Eds.), Handbook of Milk of Non-Bovine Mammals. Blackwell Publishers, Ames, Iowa and Oxford, England, pp. 34–58. Park, Y.W., 2007. Rheological characteristics of goat milk and sheep milk. Small Rumin. Res. 68, 73–87. Park, Y.W., Gerard, P.D., Drake, M.A., 2006. Impact of frozen storage on flavor of caprine milk cheeses. J. Sens. Stud. 21, 654–663. Park, Y.W., Haenlein, G.F.W., 2006. Therapeutic and hypo-allergenic values of goat milk and implication of food allergy. In: Park, Y.W., Haenlein, G.F.W. (Eds.), Handbook of Milk of Non-Bovine Mammals. Blackwell Publ., Oxford, England, pp. 121–136. Prentice, J.H., 1992. Dairy Rheology: A Concise Guide. VCH Publishers, Inc., New York. Riberio, A.C., Riberio, S.D.A., 2010. Specialty products made from goat milk. Small Rumin. Res. 89 (2–3), 225–233. Richardson, 1985. Standard Methods for the Examination of Dairy Products, 15th ed. American Public Health Association, Washington, DC. SAS, 1994. User’s Guide. SAS Inst., Inc., Cary, NC.
Please cite this article in press as: McGhee, C.E., et al., Evaluation of textural and sensory characteristics of three types of low-fat goat milk ice cream. Small Ruminant Res. (2014), http://dx.doi.org/10.1016/j.smallrumres.2014.12.002
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ARTICLE IN PRESS C.E. McGhee et al. / Small Ruminant Research xxx (2014) xxx–xxx
Stanley, D.W., Goff, H.D., Smith, A.K., 1996. Texture–structure relationships in foamed dairy emulsions. Food Res. Int. 29, 1–13. Steel, R.G.D., Torrie, J.J., 1960. Principles and Procedures of Statistics. McGrow-Hill Co., Inc., New York, NY. Thayer, A.M., 1992. Food additives. Chem. Eng. News 70, 26. Tunick, M.H., 2000. Rheology of dairy foods that gel, stretch, and fracture. J. Dairy Sci. 83, 1892–1898.
USDA, 1976. Judging and Scoring Milk and Cheese Farmer’s Bulletin No. 2259. United State Dept. of Agriculture, Washinton, DC. USDA, 2012. National Agriculture Statistics Service, 16 July 2012. US Department of Agriculture http://www.idfa.org/news–views/ media-kits/ice-cream/ice-cream-sales-and-trends/ WHO, 2010. Global Health Indicator Tables and Footnotes Part 2. World Health Statistics http://www.who.int/whosis/whostat/2010/en/
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Evaluation of textural and sensory characteristics of three types of low-fat goat milk ice cream夽 Christopher E. McGhee, Jolethia O. Jones, Young W. Park ∗ Georgia Small Ruminant Research & Extension Center, Fort Valley State University, Fort Valley, GA 31030-4313, USA
a r t i c l e
i n f o
Article history: Received 6 October 2014 Received in revised form 6 December 2014 Accepted 8 December 2014 Available online xxx Keywords: Goat milk Ice cream Texture Sensory properties Storage
a b s t r a c t Three types of low-fat soft-serve goat milk ice creams were manufactured using whole milk (3.64% fat), 2% fat and skim (0.71% fat) goat milk, and evaluated for textural and sensory characteristics of the caprine ice cream products. A commercial powdered vanilla flavor pre-mix containing 0.25% fat (Alpha Freeze, D466-A9047, Tampa, FL, USA) was formulated into the three types of goat milk base for the manufacture of the ice creams, and textural and sensory properties of the products were determined at 0, 2, 4, 8 weeks of frozen-storage at −18 ◦ C. Additional textural traits at 0, 1 and 56 days of storage were compared among the three types of low-fat caprine ice creams using a texture analyzer (TA-XT2 Texture Technologies Corp., Scarsdale, NY, USA). The results showed that approximately threefold increases in firmness and consistency of all three types of soft-serve low-fat goat ice creams after 1 day frozen-storage. The similar trend of elevation was observed in cohesiveness and index of viscosity for all tested products, probably due to the hardening of the texture of the frozen products after 1 day storage. Regardless of fat level treatments of the low-fat goat ice creams, all textural properties after 56 days frozen-storage revealed substantial elevations especially in firmness and consistency traits compared to those of the original soft-serve ice creams with extreme high variations. In sensory quality, storage period significantly affected the flavors of cooked (P < 0.01), sweetness (P < 0.05), freshness (P < 0.05), rancidity (P < 0.05), whey (P < 0.05) and oxidized (P < 0.05), but not in acid flavor. There was a general trend of a slight decline in overall acceptability of the three types of low-fat goat ice creams as storage period advanced. It was concluded that the textural and sensory qualities of the low-fat goat milk ice creams were still acceptable by the sensory panel after 8 weeks frozen-storage. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Ice cream is one of the main frozen desserts made primarily from cow milk in the US, but it can be manufactured from different dairy species milk such as caprine milk. Ice
夽 Mention of brand names does not imply endorsement by Fort Valley State University nor NIFA/US Department of Agriculture over similar products not mentioned in the paper. ∗ Corresponding author. Tel.: +1 478 827 3089; fax: +1 478 825 6376. E-mail address: [email protected] (Y.W. Park).
cream market amounted to 1.52 billion gallons (5.75 billion liters) (USDA, 2012). It comprised 86.7% of the total volume of all frozen desserts, and the rest of the market primarily consists of frozen yogurt, water/fruit ices, and sherbet (Kilara and Chandan, 2013). While ice cream is a popular food around the world, high fat foods are discouraged, since dietary fat has been implicated with coronary heart diseases, diabetes and other health problems (WHO, 2010; Nouira et al., 2011). Consumption of reduced or low fat dairy products has been increasingly popular among health-conscientious consumers in recent years (Thayer, 1992; Johnson et al.,
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2009). The sales of light ice cream have been increased by 9% in 1997, while the sales of both low fat and fat free had declined (Markgraf, 1997). Although ice cream typically contains 10–16% fat, the dairy industry recently has developed a variety of low-fat and fat-free ice cream products (Giese, 1996; Marshall et al., 2003). Compared with traditional ice creams, the low-fat ice creams have problems of low flavor and low textural qualities (Akahm et al., 2008). Texture plays an important role in sensory quality and consumer acceptability of ice cream, while reduction in milk fat can cause serious textural and flavor defects such as coarseness and iciness, crumbly body, shrinkage and flavor defects in dairy foods including ice cream products (Berger, 1990; Drake and Swanson, 1995; Marshall and Arbuckle, 1996; Johnson et al., 2009). Overall acceptability of low-fat foods is determined more by texture than by flavor of the products (Devereux et al., 2003). This fact has led a practice for the ice cream manufacturers to use milk fat replacers in order to produce their products that meet the demands of health-conscious consumers (Akahm et al., 2008). The structure of the ice cream has been identified as a three component foam made up of a network of fat globules and ice crystals dispersed in a high viscosity aqueous phase (Dickinson, 1992; Prentice, 1992). This challenge in working with low fat ice creams is attributed to the fact that the fat globule network would either be disrupted or absent and this could seriously impact the texture of the product (Aime et al., 2001). Goat milk has shown to possess better health and therapeutic values than cow milk counterpart (Park and Haenlein, 2006). Compared to bovine milk, caprine milk contains more minerals and vitamins A, B and C, lower cholesterol, and higher smaller and medium chain fatty acids (MCT) and has better digestibility due to the smaller fat globule size of goat milk (Park, 2006). Goat milk is oversupplied with protein, Ca, P, vitamin A, thiamin, riboflavin, niacin and pantothenate in relation to the FAOWHO requirements to a human infant (Jenness, 1980; Park, 2006). Goat milk ice cream may have certain nutritional advantages over cow milk counterparts due to the differences in nutrient composition between bovine and caprine milk (Park, 2006). Even though many studies of the nutritional, chemical, rheological, and sensory characteristics of cow milk ice creams have been documented, very few scientific reports have been available on goat milk ice cream products due to the lack of governmental, industry and academia supports and interests, the lack of an infrastructure, seasonal milk production, and paucity of research data (Park, 2000). Therefore, the objectives of this study were to: (1) evaluate textural and sensory properties of three types of low fat goat milk ice creams made with whole milk, 2% fat and skim goat milk and (2) compare the effect of 0, 2, 4, and 8 weeks frozen-storage at −18 ◦ C on textural and sensory characteristics among these samples. 2. Materials and methods 2.1. Experimental design The study was conducted in a 3 × 3 × 4 factorial experiment. Three batches of goat milk ice creams were manufactured using three
different levels of low fat goat milk as skim (0.71% fat), 2% fat, and whole milk (3.64% fat). The three levels of low fat goat milk ice creams were manufactured and stored at −18 ◦ C for four different storage periods as 0, 2, 4 and 8 weeks. The effects of two main factors and their interactions on nutritional, textural, and sensory characteristics of the experimental goat milk ice cream were evaluated. All experimental ice cream samples were packaged in 227 g (8 ozoz) styrofoam cups until further analysis for basic nutrient contents, lipolysis, textural and sensory characteristics.
2.2. Manufacture of ice creams 2.2.1. Manufacture of whole and skim milk ice creams 2.2.1.1. Whole goat milk ice cream. The experimental goat milk used was taken from the bulk tank milk collected from the milking goat herd of the Georgia Small Ruminant Research & Extension Center (GSRREC), Fort Valley State University (FVSU), Fort Valley, GA, USA. One gallon (3.76 L) of whole goat milk was pasteurized at 64 ◦ C for 30 min using a Hoegger Table Top pasteurizer (54M-5, Fayetteville, IN, USA). After pasteurization, 1.3 kg of commercial vanilla mix (Alpha Freeze, D466-A9047, Tampa, USA) powdered ice cream pre-mix was added to the pasteurized whole milk, and mixed thoroughly using a hand mixer. Due to the unavailability of 100% goat milk-based ice cream pre-mix, a commercial ice cream premix was used in this study. The commercial ice cream mix was composed of sugar, corn syrup solids, coconut oil, natural flavor, sodium caseinate, sodium and potassium phosphate, guar gum, mono and diglycerides, xanthan gum, and soy lecithin. The total fat content of the commercial ice cream mix was 0.25%. The mixture of milk and powder ice cream pre-mix was poured into two separate tanks in the Sani Serv ice cream machine (A5223P, Mooresville, IN, USA), where the mixture was frozen and blended until the soft serve ice cream was formed. The soft serve ice cream was packaged into 227 g (8 oz) styrofoam cups, labeled, and stored in a chest freezer (Frigidaire, Model GLFC2528FW, Raleigh, NC) at −18 ◦ C for 0, 2, 4, and 8 weeks for the analyses of chemical, textural and sensory characteristics. The ice cream was made at the dairy plant of the GSRREC, FVSU, Fort Valley, GA, USA.
2.2.1.2. Skim goat milk ice cream. For the skim goat milk ice cream manufacture, cream was first separated prior to pasteurization by an electric cream separator (125 L/h, Clair Co. Model 17584, Althofen, Austria), cream was removed, and then only skim goat was used to make the skim milk ice cream. The manufactured skim milk ice cream was packaged and was received the same experimental treatments as the whole milk ice cream.
2.2.1.3. Manufacture of 2% fat goat ice cream. The 2% fat goat milk ice cream was manufactured using the skim goat milk and goat cream produced from the separation of the whole goat milk. Accurate amount of goat milk cream was calculated using the Pearson square method. The accurately measured amounts of cream and skim milk were combined and the 2% milk was produced. The percentage of the 2% fat milk was determined by using a Milk-O-Scan (Model FT2, Hillerod, Denmark). The 2% milk was pasteurized and 2% fat ice cream was made as the same way as the whole milk and skim milk ice creams, and assigned the same experimental treatments as the other two types of ice creams, and performed all the same corresponding analyses.
2.3. Basic nutrient analysis 2.3.1. Fat content The percent fat of all experimental ice cream samples was determined using the Babcock procedure (Richardson, 1985). The ice cream was melted at room temperature and then 9 g of the ice cream was weighed and transferred into the Babcock bottle for the analysis. Fat and other basic nutrients for original milk samples were tested by the Milk-O-Scan machine (Model FT2, Hillerod, Denmark).
2.3.2. Protein content Protein content was determined using a carbon/nitrogen analyzer (Vario MAX CN Elementar Americas, Inc., Mt. Laurel, NJ, USA). Nitrogen contents of the ice cream samples were first determined by the Vario MAX CN analyzer according to the manufacturer’s instruction, and the %N was multiplied by 6.38 to calculate protein contents of the ice creams.
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2.3.3. Dry matter and ash content Dry matter was determined by oven drying method at 105 ◦ C overnight (AOAC, 1985). Amounts of ash of ice cream samples were analyzed by dry ashing method (AOAC, 1985). A 2 g sample was placed in a muffle furnace at 600 ◦ C for overnight, and cooled to room temperature in a desiccator before determining the ash contents. 2.4. Acid degree value (ADV) The ADV refers to measure of the amount of free fatty acids present in a fat sample, which is a quantitative index of hydrolytic lipolysis in dairy products. ADV was determined by the Standard Methods for the Examination of Dairy Products (Richardson, 1985). Approximately 10 g of sample were grated, homogenized, and placed into a Babcock cheese bottle for fat extraction; 1 mL of the final extracted fat was titrated against the standard alcoholic 0.02 N KOH solution. Calculation of ADV was performed using the following formula: ADV = mL KOH for sample − mL KOH for blank × N × 100 weight of fat (g)
Fig. 1. Comparison of changes in ADV values among three experimental goat milk ice creams stored at −18 ◦ C for 0 to 8 weeks.
3. Results and discussion
where N is the normality of KOH solution in methanol. 2.5. Texture analysis Textural characteristics of the ice cream were evaluated using a texture analyzer (TA-XT2 Texture Technologies Corp., Scarsdale, NY, USA). A cylindrical probe was used for detecting shear force (g) which was made of acrylic material and 2.5 cm in diameter and 3.5 cm in height. The undisturbed sample was loaded on the analyzer in suitable beaker (50 mL) for g force measurement to prevent disturbing its physical and textural states. The speed of the probe was set at 2 mm/s as the recommended procedure of Guinard et al. (1997) and Tunick (2000). 2.6. Sensory evaluation An eight member sensory panel composed of faculty and graduate students from College of Agriculture, Family Sciences and Technology at Fort Valley State University, Fort Valley, GA evaluated the sensory properties of goat milk ice creams. Panelists assessed the flavor, body and texture, and color and appearance properties of the goat ice cream products using the USDA scorecard (1976) and ADSA Collegiate Dairy Products Evaluation Ice Cream scorecard. Recent references (Carunchia Whetstine and Drake, 2006; Alvarez, 2009) were used as the standard for ratings for all sensory descriptors. The panelists were trained for sensory scoring practice of goat ice creams for four times prior to the sensory experiment and also at the time of sensory testing periods (0, 2, 4 and 8 weeks). Panelists were presented the instructions of descriptive languages, lexicon of flavor and the score card at the training of sensory testing for the ice creams using the descriptive languages and lexicon of dairy goat products illustrated by Carunchia Whetstine and Drake (2006). At the sensory laboratory windows, one half ounce (14.18 g) of ice cream samples in small plastic cups (30 mL size) from each treatment groups without tempering, a glass of water for mouth washing, small sampling spoon, crackers, napkins, the descriptive language instructions and score cards were given to each panelist for sensory evaluation. The flavor properties evaluated on the 10-point intensity scale hedonic scores were: cooked, sweetness, freshness, rancid, whey, high acid, and oxidized. Body/texture and color and appearance were both scored on the 5-point intensity scale, and the body/texture parameters evaluated were: coarse/icy, crumbly, fluffy, gummy, sandy, soggy, and weak body. The only parameters scored for color and appearance was tested on hedonic scores of the color and overall acceptability of the ice creams. 2.7. Statistical analysis All experimental data of three batches of goat milk ice creams made with three levels of milk fat (whole, 2%, and skim) were analyzed for the effect of main factors and their interactions on nutritional, lipolytic, textural, and sensory characteristics by the method of Steel and Torrie (1960). All data were also analyzed by analysis of variance, Duncan’s multiple mean comparisons between main factors using general linear model of SAS program (1994).
3.1. Basic nutrient composition of three types of ice creams The results of proximate analysis of the three types low fat experimental goat milk ice creams are shown in Table 1. As expected, there were significant differences (P < 0.05) between the levels of fat in the three different types of ice creams, where the actual fat contents (wet basis) of the skim, 2%, and whole goat milk ice cream were 1.87%, 3.84%, and 5.31%, respectively. Carbohydrate content of the whole milk ice cream was slightly lower than those of skim and 2% milk ice creams probably due to the differences in the sugar content of the pre-mix as well as lactose content of the original goat milk. However, no differences were found among the three types of low fat goat milk ice creams in the other basic nutrient contents such as total solids, protein and ash contents. The original whole caprine milk base used in this study contained 12.2% total solids, 3.64% of fat, 3.59% of protein, and 0.81% ash, which has a similar composition reported by Park (2006), indicating that fat removal in the original goat milk, and the addition of the commercial powder mix and sugar made differences in the basic nutrients contents of the experimental goat milk ice creams. 3.2. Effect of frozen storage on lipolysis of goat milk ice creams Acid degree value (ADV) is the measurement of the amount of free fatty acid in a dairy product, which is an index of lipolysis of a sample (Richardson, 1985; Park, 2001; Nouira et al., 2011). It determines the degree of lipolysis in a food product, whereby it estimates the shelf life of the food product in question. Fig. 1 illustrates the differences of changes in ADV values among the three different experimental goat milk ice creams during 0, 2, 4, 6, and 8 weeks storage period. Although the differences were not statistically significant, there was a trend of slight increase in lipolysis up to 4 weeks frozen-storage, where the order of increase in ADV values were 2% milk, whole milk and skim milk ice creams. This might be attributed to the release and activation of lipase from the disrupted fat globule membranes during the cream separation processes from the goat milk used. There was a sudden drop in ADV values
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Table 1 Basic nutrient contents (%) of three types of low-fat goat milk ice creams. Fat type
Dry matter (%)
Skim 2% Whole a,b,c
Ash (%)
Fat content (%)
Protein (%)
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
32.11ab 34.15a 33.28ab
0.40 1.7 1.70
1.54a 1.58a 1.58a
0.05 0.18 0.08
1.87c 3.84b 5.31a
0.40 0.13 0.57
2.87a 2.80ab 2.90a
0.15 0.16 0.24
24.81ab 25.94a 23.47ab
0.12 0.06 0.12
Means with different superscript within a column are significantly different (P < 0.05). SD: standard deviation. Whole milk
4000
2% milk
Skim milk
450
3000 2500
Whole milk 2000
2% milk
1500
Skim milk
1000
Cohesiveness (g force)
3500
Firmness (g force)
Carbohydrate (%)
400 350 300 250 200 150 100 50
500
0
0 0 day
1 day
0 day
56 days
1 day
56 days
S to r a g e p e r io d
Fig. 2. Comparison of firmness of three types of goat milk ice creams during three different frozen-storage periods.
at 6 weeks frozen storage and then slight increases at 8 weeks storage. The reasons for these reductions in ADV are not clear, while certain indigenous lipolytic enzymes in the original milk and/or the ice creams mix, as well as lipases from psychrotropic bacteria (Deeth and FitzGerald, 1976; Park, 2001) in the ice cream ingredients might have been reduced in lipolytic conditions during the 6 weeks frozenstorage conditions. In addition, autooxidation of the fat in the ice cream might have been reduced at this 6 weeks frozen-storage period. 3.3. Effect of frozen-storage on textural properties of goat milk ice creams The results of textural properties on the three types of experimental low-fat goat milk ice creams are shown in Figs. 2–5. The mean values (g force) of firmness and consistency for freshly made soft serve whole milk, 2% and skim milk goat ice creams were: 208.7, 297.3; 182.8, 261.8; 183.5, 255.0, respectively (Figs. 2 and 3). These data show that the firmness and consistency values of all freshly made
Fig. 4. Comparison of changes in cohesiveness of three types of goat milk ice creams during three different frozen-storage periods.
three low-fat goat ice were increased significantly (P < 0.01) (almost threefold) after 1 day frozen-storage at −18 ◦ C. The trend of elevation of the textural values was same for all tested indices probably due to the hardening of the texture of the frozen products for 1 day frozen-storage compared to the soft-serve samples. In addition, all three types of low-fat ice goat creams revealed that there were substantial increases in all tested textural properties from 0 day to 56 days (8 weeks) of frozen-storage (Figs. 2 and 3). The firmness and consistency of whole milk ice cream after 56 days were more than twofold greater than those of skim and 2% milk ice cream (Figs. 2 and 3), indicating that the higher milk fat in the whole milk ice cream may have contributed to these outcomes. Texture plays an important role in consumer acceptability of a food product (Drake and Swanson, 1995; Tunick, 2000; Park et al., 2006; Park, 2007). Changes in fat composition can have serious influence on textural and flavor characteristics of ice cream, which may in turn affect the consumer acceptability (Berger, 1990; Akahm et al., 2008). It has been also reported that goat milk can be used Whole milk
18000
Skim milk
300
14000 12000 10000
Whole milk
8000
2% milk
6000
Skim milk
4000 2000
Index of viscosity
Consistency (g force)
2% milk
350
16000
250 200 150 100 50
0 -2000
0 day
1 day S to r a g e p e r io d
56 days
Fig. 3. Comparison of consistency of three types of goat milk ice creams during three different frozen-storage periods.
0 0 day
1 day
56 days
Fig. 5. Comparison of changes in the index of viscosity of three types of goat milk ice creams during three different frozen-storage periods.
Please cite this article in press as: McGhee, C.E., et al., Evaluation of textural and sensory characteristics of three types of low-fat goat milk ice cream. Small Ruminant Res. (2014), http://dx.doi.org/10.1016/j.smallrumres.2014.12.002
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Table 2 Mean flavor property scores of three different types of low-fat goat milk ice creams during 8-week storage period evaluated by the sensory panel. Cooked Mean
Sweet
Fresh
Rancid
Whey
High acid
Oxidized
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Whole milk ice cream Week 0 9.50b 9.67a Week 2 9.42bc Week 4 9.29c Week 8
0.25 0.19 0.14 0.07
8.83bc 9.29ab 9.13ab 9.29ab
0.52 0.44 0.13 0.19
9.17ab 9.42ab 9.33ab 9.21ab
0.26 0.19 0.31 0.07
9.38ab 9.42ab 9.42ab 9.25b
0.13 0.31 0.07 0.33
8.71c 9.42a 9.17ab 9.04b
1.15 0.29 0.29 0.07
9.42a 9.42a 9.42a 9.25ab
0.31 0.26 0.31 0.13
9.46ab 9.50ab 9.50ab 9.33b
0.29 0.25 0.22 0.07
2% milk ice cream Week 0 9.46bc 9.58ab Week 2 9.50b Week 4 9.33c Week 8
0.29 0.14 0.13 0.14
8.88bc 9.38a 9.25ab 9.25ab
0.13 0.22 0.13 0.25
9.33ab 9.54a 9.29ab 9.13ab
0.44 0.14 0.31 0.38
9.21b 9.71a 9.38ab 9.17b
0.36 0.14 0.00 0.26
8.79c 9.46a 9.21ab 9.25ab
0.38 0.19 0.07 0.13
9.21ab 9.54a 9.33ab 9.33ab
0.31 0.14 0.14 0.29
9.42ab 9.67a 9.42ab 9.21b
0.36 0.19 0.07 0.19
Skim milk ice cream 9.42bc Week 0 9.71a Week 2 9.46bc Week 4 Week 8 9.38c
0.19 0.07 0.07 0.13
9.04b 8.88bc 8.67c 9.04b
0.07 0.33 0.19 0.26
9.33ab 9.38ab 9.42ab 9.04b
0.07 0.38 0.07 0.36
9.33ab 9.63a 9.38ab 9.50ab
0.38 0.22 0.00 0.25
9.00b 9.33ab 8.96bc 9.25ab
0.22 0.31 0.19 0.33
9.25ab 9.42a 9.42a 9.50a
0.25 0.07 0.07 0.22
9.46ab 9.71a 9.46ab 9.42ab
0.40 0.07 0.07 0.29
a,b,c 1
Means with different superscripts within a same column are different (P < 0.05 or 0.01). All mean values are average of 8 panelists.
to produce a softer texture ice cream with a more desirable melting quality (Riberio and Riberio, 2010). Regardless of fat level treatments of the experimental low-fat goat milk ice creams in the present study, all textural properties after 8 weeks (56 days) frozen storage, especially in firmness and consistency traits, were substantially increased compared to those of the original fresh ice cream (Figs. 2 and 3). However, the variations in the textural property values between the soft-serve and frozen-stored ice cream samples as well as between and within samples, especially after the 8 weeks frozen-storage were substantially high (Figs. 2 and 3), which may be attributed to the extended hardening of the samples during the 56 days storage compared to the fresh soft serve samples. The high variability of textural properties values in hardened ice creams may also be due to the differences in the sensitivity of the texture analyzer (TA-XT2 Texture Technologies Corp.) used between the soft serve samples and the extended hardened ice cream samples (Figs. 2 and 3). It is also likely attributed to the fact that the hardened ice cream might have exerted completely different thermophysical and colloidal profiles compared to those of the fresh soft-serve ice cream samples drawn from the freezer. The mean cohesiveness values of fresh and 8 weeks frozen stored whole milk, 2% and skim milk ice cream samples were: 88.4, 95.1, 92.4; 385.6, 258.4, 184.6, respectively (Fig. 4), and index of viscosity values of fresh and 56 days frozen stored skim, 2%, and whole goat milk ice cream were: 49.3, 54.0, 45.4; 300.4, 178.0, 140.5, respectively (Fig. 5). There was a general trend that cohesiveness and index of viscosity values increased with the advanced storage time. The whole goat milk ice cream showed significantly (P < 0.01) higher cohesiveness and index of viscosity values than those of skim and 2% goat milk ice cream as storage time extended to 8 weeks frozen-storage (Figs. 4 and 5), suggesting that the fat content of the lowfat ice cream products also affected or increased these two textural indices of the goat milk ice creams in our study (Figs. 4 and 5). Beyond the fat content of the milk used
in ice cream manufacture, other factors contributing ice cream texture include stabilizers and emulsifiers (Aime et al., 2001). In a research with full fat ice cream, JimenezFlores et al. (1993) have shown that stabilizers promoted viscosity development in the aqueous phase and controlled ice crystal growth (Stanley et al., 1996). Since the powder ice cream pre-mix used in our study contained stabilizers and emulsifiers, they may have increased the values of cohesiveness and index of viscosity.
3.4. Effect of frozen storage on sensory characteristics The mean flavor characteristics scores of the three types of low-fat experimental goat ice creams for 8 weeks storage periods are presented in Table 2. The mean body/texture characteristics scores of the same low-fat goat ice creams evaluated by the sensory panel for the same experimental periods are also shown in Table 3. In general, most of flavor characteristics were affected by the frozen-storage periods, while the frozen-storage effect was minimal on body/texture scores except sogginess and fluffiness up to 8 weeks storage at −18 ◦ C. The analysis of variance (F values) on the effects of main factors and interactions on flavor characteristics are summarized in Table 4. For the main factors, storage period had significant influences on the flavors of cooked (P < 0.01), sweetness (P < 0.05), freshness (P < 0.05), rancidity (P < 0.05), whey (P < 0.05) and oxidized (P < 0.05), but not in acid flavor. The multiple mean comparison revealed one prominent results that the 2 weeks frozen-stored ice cream samples showed the highest scores of all flavor traits. This may indicate that the 2 weeks frozen goat ice creams were better in flavor characteristics compared to the fresh soft serve ice creams. As far as the other main factor (the fat types) goes, no fat type effect was found in any of the flavor characteristics. In light of batch effect, the batch 3 had significantly (P < 0.01) higher rancidity value than the batches 1 and 2, while other flavor characteristics were not affected by fat type and type x storage interaction effects (Table 4).
Please cite this article in press as: McGhee, C.E., et al., Evaluation of textural and sensory characteristics of three types of low-fat goat milk ice cream. Small Ruminant Res. (2014), http://dx.doi.org/10.1016/j.smallrumres.2014.12.002
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Table 3 Mean body/texture characteristics scores of three different types of low-fat goat milk ice creams during 8-week storage period by the sensory panel. Coarse/icy Mean
Crumbly
Fluffy
Gummy
Sandy
Soggy
Weak body
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Whole milk ice cream Week 0 4.63 4.29 Week 2 4.25 Week 4 4.25 Week 8
0.13 0.26 0.13 0.33
4.75 4.67 4.54 4.21
0.13 0.07 0.26 0.19
4.58ab 4.58ab 4.45ab 4.58ab
0.07 0.36 0.07 0.07
4.71 4.75 4.75 4.50
0.14 0.22 0.22 0.22
4.58 4.71 4.63 4.46
0.26 0.07 0.13 0.29
4.29b 4.58ab 4.63a 4.46ab
0.47 0.26 0.13 0.14
3.92 4.54 4.50 4.38
0.79 0.19 0.66 0.45
2% milk ice cream Week 0 4.42 4.67 Week 2 4.38 Week 4 4.50 Week 8
0.19 0.26 0.22 0.33
4.67 4.54 4.50 4.38
0.07 0.19 0.22 0.22
4.46ab 4.67a 4.33b 4.75a
0.19 0.31 0.14 0.22
4.63 4.67 4.67 4.75
0.25 0.07 0.14 0.13
4.46 4.75 4.63 4.54
0.07 0.22 0.13 0.07
4.33b 4.63a 4.63a 4.50ab
0.38 0.13 0.13 0.25
4.38 4.63 4.67 4.38
0.63 0.00 0.26 0.13
Skim milk ice cream 4.38 Week 0 4.38 Week 2 4.50 Week 4 Week 8 4.46
0.00 0.43 0.38 0.14
4.46 4.58 4.63 4.67
0.29 0.19 0.33 0.07
4.54ab 4.54ab 4.42ab 4.71a
0.14 0.19 0.26 0.19
4.54 4.50 4.71 4.54
0.26 0.13 0.07 0.40
4.54 4.33 4.50 4.66
0.19 0.07 0.13 0.19
4.33b 4.58ab 4.71a 4.54ab
0.19 0.29 0.19 0.29
4.38 4.29 4.50 4.50
0.33 0.19 0.22 0.33
a,b 1
Means with difference superscripts within a same column are different (P < 0.05). Differences were found only in fluffy and soggy properties. All mean values are average of 8 panelists.
Table 4 Effects of main factors and interactions on flavor characteristics of the three types of low fat goat milk ice creamsa .
Batch Type Storage Type × storage a * **
Cooked
Sweetness
Freshness
Rancid
Whey
Acid
Oxidized
0.83 0.12 6.00** 0.34
0.03 0.15 3.57* 0.96
1.74 0.18 2.13* 0.40
4.52* 0.57 2.84* 1.01
1.19 0.42 1.94* 0.24
1.00 0.03 0.59 0.58
2.56 0.35 2.74* 0.37
All numbers are F values from the analysis of variance of the experimental data. Significant at P < 0.05 Significant at P < 0.01
Table 5 Pooled data of two selected body/texture traits showing significant differences between frozen-storage periods by Duncan’s multiple mean comparison. Sogginess 4 wk 2 wk 8 wk 0 wk
Fluffiness 4.654 4.599 4.503 4.321
A A AB B
8 wk 2 wk 0 wk 4 wk
4.683 4.600 4.531 4.432
A AB AB B
Means with different letters within a same column are different (P < 0.05).
Among body and texture properties, only two characteristics had shown significant (P < 0.05) differences among the four different storage periods in the experimental low fat goat milk ice creams (Tables 3 and 5). Sogginess and fluffiness were the only two properties shown the differences between the storage periods among all body and texture properties. The descending order of sogginess values were 4, 2, 8 and 0 week samples, while the corresponding descending order of fluffiness traits were 8, 2, 0 and 4 week samples (Table 5). The amount of fat in the ice creams influenced on consumers perception of the goat ice cream product, where the fat type of the low fat goat ice cream products were associated with sweetness perception of the products, showing the 2% fat ice cream had higher (P < 0.05) sweetness value than the whole milk and skim milk ice cream samples. Fig. 6 depicts the overall acceptability of the three experimental goat ice creams scored by the sensory panel.
Fig. 6. Comparison of changes in mean overall acceptability scores of three types of goat milk ice creams during 8 weeks frozen-storage.
The average overall acceptability scores of the whole milk, 2% milk, and skim goat milk ice creams were: 4.30, 4.34, 4.29, respectively, implying that the skim goat milk ice cream exhibited slightly higher overall acceptability than those of the other two ice creams after 8 weeks frozenstorage. For color change scores, no detectable changes were found in all three types of the goat milk ice creams up to 8 weeks frozen-storage. However, it was observed that there was a general trend of slightly declining overall acceptability of the three experimental low-fat goat ice creams in the present study (Fig. 6). Although our results
Please cite this article in press as: McGhee, C.E., et al., Evaluation of textural and sensory characteristics of three types of low-fat goat milk ice cream. Small Ruminant Res. (2014), http://dx.doi.org/10.1016/j.smallrumres.2014.12.002
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on overall acceptability of the experimental goat ice creams for 8 weeks were not affected, Aime et al. (2001) reported that their trained panel rated the low-fat and fat free ice creams to have lower viscosity, smoothness and mouth coating properties, while the sensory attributes of the light samples were comparable to the regular cow milk vanilla ice cream. They also observed that there was good correlation between the instrumentally determined firmness values and the sensory results. Compared with traditional ice creams, the low-fat or reduced fat ice creams are expected to have lower flavor and textural quality (Berger, 1990; Marshall et al., 2003; Akahm et al., 2008).
4. Conclusions All three types of the experimental low-fat soft-serve goat milk ice creams showed substantial increases in textural properties especially in firmness and consistency after 8 weeks frozen-storage. High variations in elevation of the textural characteristics of the frozenstored ice cream samples appeared to be attributed to the hardening of the products during the frozen-storage, as well as the difference in sensitivity of the texture analyzer between soft serve and hardened ice cream samples. The flavors of the low-fat goat ice creams were significantly influenced by storage period in cooked, sweetness, freshness, rancidity, whey and oxidized flavors, but not in acid flavor. Among body and texture properties, sogginess and fluffiness were the only two properties affected by the storage periods. Although there was a slight decrease in overall acceptability of the three experimental low-fat goat ice creams during 8 weeks storage, textural and sensory qualities of the three types of low-fat goat milk ice creams were acceptable. Even though the commercial ice cream pre-mix contains minor ingredient (sodium caseinate) derived from cow milk, their effects were expected to be identical and equally canceled out from all three different goat milkbased experimental ice creams, whereby the comparison of textural and sensory qualities between the products would be valid. However, further studies may be necessary to determine textural and sensory qualities using the premix containing only goat milk ingredients, when it becomes available.
Conflict of interest There is no conflict of interest.
Acknowledgements This research was supported by the 1890 Capacity Building Grants of the USDA/NIFA Grant No. 2010-02049. Authors appreciate Carlton Green, Schauston Miller and Ruby Ragan for preparation of goat milk and other commercial powdered ice cream premix for the ice cream manufacture.
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References Aime, D.B., Arntfield, S.D., Malcolmson, L.J., Ryland, D., 2001. Textural analysis of fat reduced vanilla ice cream products. Food Res. Int. 34, 237–246. Akahm, A.S., Karagozlu, C., Unal, G., 2008. Rheological properties of reduced-fat and low-fat ice cream containing whey protein isolate and inulin. Eur. Food Res. Technol. 227, 889–895. Alvarez, V.B., 2009. Ice cream and related products. In: Clark, S., Costello, M., Drake, M., Bodyfelt, F. (Eds.), The Sensory Evaluation of Dairy Products. , 2nd ed. Springer, pp. 271–332. AOAC, 1985. Official Methods of Analysis. 14th Ed. Assoc. Offic. Anal. Chem. Washington, DC. No. 43.292. 7.001, 7.009, 7.006. Berger, K.G., 1990. In: Larsson, K., Friberg, S.E. (Eds.), Ice Cream in Food Emulsions. , 2nd ed. Marcel Dekker, Inc., New York, p. 367. Carunchia Whetstine, M.E., Drake, M.A., 2006. Flavor characteristics of goat milk and other minor species milk products. In: Park, Y.W., Haenlein, G.F.W. (Eds.), Handbook of Milk of Non-Bovine Mammals. Blackwell Publishers, Ames, Iowa and Oxford, England, pp. 107–120. Deeth, H.C., FitzGerald, C.H., 1976. Lipolysis in dairy products: a review. Aust. J. Dairy Technol. 31, 53–64. Devereux, H.M., Jones, G.P., McCormack, L., Hunter, W.C., 2003. Consumer acceptability of low fat foods containing inulin and oligofructose. J. Food Sci. 68 (5), 1850–1854. Dickinson, E., 1992. An Introduction to Food Colloids. Oxford University Press. Drake, M.A., Swanson, B.G., 1995. Reduced- and low-fat cheese technology: a review. Trends Food Sci. Technol. 6, 366–369. Giese, J., 1996. Fats, oils, and fat replacers. Food Technol. 50 (4), 48–83. Guinard, J.-X., Zoumas-Morse, C., Mori, L., Uatoni, B., Panyam, D., Kilara, A., 1997. Sugar and fat effects on sensory properties of ice cream. J. Food Sci. 62, 1087–1094. Jenness, R., 1980. Composition and characteristics of goat milk: review 1968–1979. J. Dairy Sci. 63, 1605–1630. Jimenez-Flores, R., Klipfel, N.J., Tobias, J., 1993. Ice cream and frozen desserts. In: Hui, Y.H (Ed.), Dairy Science and Technology Handbook. Product Manufacturing, vol. 2. VCH Publishers, Inc., New York, pp. 57–157. Johnson, M.E., Kapoor, R., McMahon, D.J., McCoy, D.R., Narasimmon, R.G., 2009. Reduction of sodium and fat levels in natural and processed cheeses: scientific and technological aspects. Compr. Rev. Food Sci. Food Safety 8, 252–268. Kilara, A., Chandan, R.C., 2013. Frozen dairy products. In: Park, Y.W., Haenlein, G.F.W. (Eds.), Milk and Dairy Products in Human Nutrition. Wiley-Blackwell Publishers, pp. 435–457. Markgraf, S., 1997. Annual ice cream report: indulgence supreme. Dairy Foods 99 (3), 82–84. Marshall, R.T., Arbuckle, W.S., 1996. Ice Cream, 5th ed. Chapman & Hill, New York. Marshall, R.T., Goff, H.D., Hartel, R.W., 2003. Ice Cream, 6th ed. Kluwer/Plenum Publ., New York, pp. 18, 23, 34, 93, 203. Nouira, W., Park, Y.W., Guler, Z., Terrill, T.H., 2011. Comparison of free fatty acid composition between low-fat and full-fat goat milk cheeses stored for 3 months under refrigeration. Open J. Anim. Sci. 2, 17– 23. Park, Y.W., 2000. Comparison of mineral and cholesterol composition of different commercial goat milk products manufactured in USA. Small Rumin. Res. 37, 115–124. Park, Y.W., 2001. Proteolysis and lipolysis of goat milk cheese. J. Dairy Sci. 84 (E. Suppl.), E84–E92. Park, Y.W., 2006. Goat milk – chemistry and nutrition. In: Park, Y.W., Haenlein, G.F.W. (Eds.), Handbook of Milk of Non-Bovine Mammals. Blackwell Publishers, Ames, Iowa and Oxford, England, pp. 34–58. Park, Y.W., 2007. Rheological characteristics of goat milk and sheep milk. Small Rumin. Res. 68, 73–87. Park, Y.W., Gerard, P.D., Drake, M.A., 2006. Impact of frozen storage on flavor of caprine milk cheeses. J. Sens. Stud. 21, 654–663. Park, Y.W., Haenlein, G.F.W., 2006. Therapeutic and hypo-allergenic values of goat milk and implication of food allergy. In: Park, Y.W., Haenlein, G.F.W. (Eds.), Handbook of Milk of Non-Bovine Mammals. Blackwell Publ., Oxford, England, pp. 121–136. Prentice, J.H., 1992. Dairy Rheology: A Concise Guide. VCH Publishers, Inc., New York. Riberio, A.C., Riberio, S.D.A., 2010. Specialty products made from goat milk. Small Rumin. Res. 89 (2–3), 225–233. Richardson, 1985. Standard Methods for the Examination of Dairy Products, 15th ed. American Public Health Association, Washington, DC. SAS, 1994. User’s Guide. SAS Inst., Inc., Cary, NC.
Please cite this article in press as: McGhee, C.E., et al., Evaluation of textural and sensory characteristics of three types of low-fat goat milk ice cream. Small Ruminant Res. (2014), http://dx.doi.org/10.1016/j.smallrumres.2014.12.002
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ARTICLE IN PRESS C.E. McGhee et al. / Small Ruminant Research xxx (2014) xxx–xxx
Stanley, D.W., Goff, H.D., Smith, A.K., 1996. Texture–structure relationships in foamed dairy emulsions. Food Res. Int. 29, 1–13. Steel, R.G.D., Torrie, J.J., 1960. Principles and Procedures of Statistics. McGrow-Hill Co., Inc., New York, NY. Thayer, A.M., 1992. Food additives. Chem. Eng. News 70, 26. Tunick, M.H., 2000. Rheology of dairy foods that gel, stretch, and fracture. J. Dairy Sci. 83, 1892–1898.
USDA, 1976. Judging and Scoring Milk and Cheese Farmer’s Bulletin No. 2259. United State Dept. of Agriculture, Washinton, DC. USDA, 2012. National Agriculture Statistics Service, 16 July 2012. US Department of Agriculture http://www.idfa.org/news–views/ media-kits/ice-cream/ice-cream-sales-and-trends/ WHO, 2010. Global Health Indicator Tables and Footnotes Part 2. World Health Statistics http://www.who.int/whosis/whostat/2010/en/
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