4.3.1. Effect of sterilization on color of product
The score of color of products which applied different regimes of heat sterilization was shown in Fig. 4.5.
Fig. 4.5. Effect of sterilization on color of product
Note: S1=1100C/5min, S2=1100C/7min, S3=1100C/10min, S4=1100C/15 min, S5=1150C/5 min, S6=1150C/7min, S7=1150C/10min, S8=1150C/15min, S9=1210C/5min, S10=1210C/7min,
S11=1210C/10min and S12=1210C/15min 8,75 8,69 8,66
0 1 2 3 4 5 6 7 8 9 10
S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12
Score
Product
The figure obtained indicated that score of color significantly declined with increase in sterilized temperature from 1100C to 1210C.
The four samples which sterilized at 1100C (group A) achieved the highest score of color. The color of S1 was close to milk white with score of 8.75 followed by S2 (8.69), S3 (8.66) and S4 (8.41) in that order. The Tukey multiple comparisons of means (Appendix 5) indicated that color differences between the samples in group A were not statistically significant (alpha=0.05). The color of samples sterilized at 1150C (group B) was changed visibly in compare with group A. The score of S5 and S6 was smaller of 6.38 and 6.28 respectively. The color of the left samples (S7, S8) in group B reduced to 5.81 that observed difference is statistically significant in compare with S5. The sharp drop observed in group C (temperature of 1210C) that score of S9 and S12 were 3.44 and 1 respectively. Considering these observations, the higher the sterilization temperature was, the darker the color of the product was.
The significant increase in colour intensity (which caused a reduction in the colour score of group B and C) could be due to Millard reactions, which usually occur between reducing sugars and amino groups in proteins and amino acids.
These reactions are encouraged by increase in temperature, pH and concentration of reactants and are accompanied by destruction of some essential amino acids (Alais and Linden, 1991).
4.3.2. Effect of sterilization on microbiological quality
Three products which sterilized at temperature of 1100C in 5 minutes, 7 minutes and 10 minutes analyzed microbiological criteria including total aerobic microorganism, yeast and mold and coliform after 10 day insulation at 370C. The numerous of microbe shown in the table 4.6
Table 4.6: The number of microbe of sample sterilized at 1100C (CFU/ml)
Microbiological
criteria Sterilization time (min)
Number of microbe
The maximum
limit a
Reference
Aerobic
microorganism
5 95
100
TCVN 4884:2005
7 79
10 68
Yeast and mold 5 11
10
TCVN 8275- 1:2010
7 9
10 5
Coliform 5 9
10
TCVN 6848:2007
7 8
10 5
Source: a National technical regulation for soft drinks (2010 )(Ministry of Health) It could be seen from this table that total aerobic microorganism, yeast and mold and coliform significantly decreased when the time of sterilization increased from 5 min to 10 min. The numerous of aerobic microorganism found in the product sterilized in 5 min was 95 CFU/ml (Table 4.6). It sharply reduced to 68 CFU/ml when the time of sterilization extended in 10 min. This number was greatly less than the maximum limit (100 CFU/ml). Besides, the number of yeasts and molds presented in the product sterilized in 5 min was 11 CFU/ml which exceeded the maximum limit (10 CFU/ml). However, this numerous remarkably reduced to 5 CFU/ml when the product sterilized in 10 min.
Furthermore, there was a dramatically decrease in the numerous of coliform in the product sterilized in 10 min (5 CFU/ml). This number was half the maximum limit (10CFU/ml). Considering these observations, total aerobic microorganisms, yeasts and molds and coliform as well in the sample sterilized in 10 min was within the acceptable limits as given in table 4.6. To be sure that this sample ensures microbiological quality and safety in consuming, microbiological criteria including Staphylococcus aureus, Clostridium perfringen, E. Coli, Streptococcus
faecalis and Pseudomonas aeruginosa were analyzed at National Institute for Food Control under Ministry of Health. These microbes have not been detected in the sample (LOD = 1 CFU/ml). The result of numerous of microbes which must be evaluated according QCVN 6-2:2010/BYT is indicated in the table 4.7.
Table 4.7: The numerous of microbe of sample sterilized at 1100C in 10min (CFU/ml)
Microbiological criteria Experimental data
The maximum limit a
Reference
Aerobic microorganism 68 100 TCVN 4884:2005
Yeast and mold 5 10 TCVN 8275-1:2010
Coliform 5 10 TCVN 6848:2007
Staphylococcus aureus n.d 0 TCVN 4830-1:2005
Clostridium perfringen n.d 0 TCVN 4991:2005
E. Coli n.d 0 TCVN 7924-2:2008
Streptococcus faecalis n.d 0 TCVN 6189-2:1996
Pseudomonas aeruginosa n.d 0 ISO 16266:2006
Source: a National technical regulation for soft drinks (2010) (Ministry of Health) Considering these observations, the sample sterilized at 1100C in 10 min was the best which successfully met requirements about microbiological criteria according National technical regulation for soft drinks, 2010 (QCVN 6- 2:2010/BYT).
4.3.3. Consumer sensory evaluation
The results of liking evaluation on 2 products (quinoa milk and Korean rice milk) were illustrated in Fig. 4.6 following
Fig. 4.6. Distribution of response level on hedonic scale
It could be seen that the percentage of people who extremely liked quinoa milk was about 2% which was smaller than those of rice milk (5%). However, quinoa milk received three times as the responses “like very much” as rice milk.
In general, the number of people who liked rice milk accounted for 75% of this group, while this number of quinoa milk was slightly smaller making up 67%.
Although quinoa milk is quite new in the market, it was highly appreciated in comparison with rice milk by the panel.
The “dislike” responses of quinoa milk accounted for 5% while those of rice milk were slightly higher constituting for 6.67%. None showed the “dislike very much” or “dislike extremely” response in both products. The lowest score of rice milk was given by the panel was 3 (dislike moderately), whereas 4 (dislike slightly) was the lowest score of quinoa milk.
2 5
15 5
28 30
22 35
28 18
5 1.675
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Quinoa milk Korean Rice milk
Rate of panelist
Product
Like extremely Like very much Like moderately Like slightly Neither like nor dislike Dislike slightly Dislike moderately Dislike very much Dislike extremely
Fig. 4.7. Average scores of quinoa milk and rice milk
The average scores of both product's quinoa milk and rice milk that were in the range from “like extremely” to “dislike extremely” were 6.25 and 6.22 respectively (Fig. 4.7). A one-way ANOVA (Appendix 4) indicated that hedonic differences between the products were not statistically significant (alpha=0.05, F(2,60)=0.02, p=0.88). The similar likelihood between a commercial product and researched product demonstrated the potential of quinoa milk which can reach into beverage market.
4.3.4. Building the process of producing quinoa milk
From the above studies, the process of producing quinoa milk was proposed with the attached technological parameters (Fig 4.8).
5 5,2 5,4 5,6 5,8 6 6,2 6,4 6,6 6,8 7
Average score
Quinoa milk Rice milk
6.25 6.22
Fig. 4.8. Flow chart of producing process of quinoa milk with the attached technological parameters.
Quinoa seed
Grinding
Enzymatic treatment (0.12
%, 91.90C, 69.6min) Starch gelatinizing
(800C/10min) Water (500%)
Enzyme Termamyl
Filtrating
Mixing
Sweetened condensed milk (5%), Vanilla
(0.05%) Filling into glass bottle,
sealing
Sterilising (1100C/10min)
Product