Food Biotechnology
Soheyl Reyhani Poul; Sakineh Yeganeh; Zeynab Raftani Amiri
Abstract
Introduction Since heat treatments and special standards are not used in the production of traditional (homemade) tomato paste, fungal and bacterial spoilage in the product occurs extensively during storage in the refrigerator (4°C). Astaxanthin extracted from aquatics has antimicrobial activity ...
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Introduction Since heat treatments and special standards are not used in the production of traditional (homemade) tomato paste, fungal and bacterial spoilage in the product occurs extensively during storage in the refrigerator (4°C). Astaxanthin extracted from aquatics has antimicrobial activity and color similar to tomato and can probably be effective in preventing spoilage of tomato paste. In addition, astaxanthin has other properties in the field of preventing and controlling diseases and maintaining human health, which justifies its use in food formulations as an enrichment. Since heat, enzyme, acid, etc. treatments are practiced during the production of tomato paste, these factors may change the structure and thus the function of astaxanthin. For this reason, astaxanthin nanoencapsulation is necessary for its use in tomato paste formulation. Materials and Methods In this research, first, astaxanthin was extracted from Haematococcus pluvialis microalgae using the acid-acetone combined method. Then, this pigment was nanoencapsulated using maltodextrin-sodium caseinate coating and the resulting nanocapsules were used together with the pure form of astaxanthin in the formulation of tomato paste. The research treatments were control, tomato pastes containing 3 and 6% astaxanthin (A and B, respectively) and also 3, 6 and 9% nanocapsules carrying the pigment (C, D and E, respectively). These treatments were kept at refrigerator for 28 days and were evaluated (on days 0, 7, 14, 21 and 28) in terms of the total number of fungi, Howard's number (HMC), pH, fungal flora, total bacteria count, amount of lactic acid bacteria and sensory properties. This research was conducted in a completely randomized design. Data were analyzed by One-way Anova and the difference between the means was evaluated by Duncan's test at 95% confidence level. Results and Discussion The results showed that the fungi proliferation, total count and lactic acid bacteria were slower than the control during the storage period in the treatments containing astaxanthin and its carrying nanocapsules, and the minimum number of the mentioned microorganisms and Howard's number were related to treatments D and E (p>0.05). Treatments C, B and A were ranked next in this respect (p<0.05). The number of fungi in two treatments D and E from day 0 to 28 varied from 128 to 332 cfu/gr. Also, the Howard number of these treatments was recorded from 18 to 34% in the mentioned time period. However, these two indices in the control ranged from 121 to 792 cfu/gr and 18 to 91%, respectively, during the storage period. The count of total bacteria and the amount of lactic acid bacteria in the control on day 28 were equal to 8.9 cfu/gr and 311 mg/kg, respectively, but these two values were recorded in the E and D treatments on the same day, about 4.8 cfu/gr and 110 mg/kg, respectively. Counting the total number of fungi, bacterias and also Howard's number in control and other treatments showed that the effect of nanocapsules carrying astaxanthin on microbial growth and proliferation is significantly greater than pure astaxanthin (p<0.05). The pH of the treatments varied from 3.9 to 5.8 during the storage period and the most standardized pH (3.9-4.4) was recorded in C, D and E (p>0.05) treatments (p<0.05). The pH of two treatments A and B (p>0.05) was higher than the three mentioned treatments and lower than the control (p<0.05). This finding showed that nanocapsules carrying astaxanthin have a greater effect on controlling the pH of tomato paste than pure astaxanthin during storage at refrigerator (p<0.05). The identification of the fungal flora of the treatments on the 28th day confirmed that two genus of Penicillium and Aspergillus form the main flora of the product. The results of the sensory evaluation of the treatments on day 0 showed that adding astaxanthin and its carrier nanocapsules does not change the color, aroma, taste and texture indicators (subsequently the general acceptance) of tomato paste (p>0.05). On the 28th day, the mentioned sensory indices only in the two treatments D and E were not significantly different from the 0 day, but they changed negatively in the other treatments (p<0.05). Conclusion According to the findings of the present research, astaxanthin extracted from Haematococcus pluvialis microalgae has the ability to inhibit fungal and bacterial spoilage and stabilize the sensory properties of tomato paste stored at refrigerator. This properties were improved by adding nanoencapsulated pigment using maltodextrin-sodium caseinate combined coating. Since there were no significant differences between the two treatments containing 6% and 9% of nanocapsules carrying astaxanthin (D and E) in terms of quality indices and microbial spoilage, therefore, the treatment containing 6% nanocapsules is introduced as the optimal treatment.
Minoo Rastegar; Seyed Esmaeil Razavi; Pouneh Ebrahimi
Abstract
Introduction: White button mushroom (Agaricus bisporus) has a high moisture content (~90%) which makes it more vulnerable to the germs and chemical reactions. The contents of fungus coating are beneficial for shelf-life extension of mushroom. Coated mushrooms loss less moisture and have firmness, better ...
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Introduction: White button mushroom (Agaricus bisporus) has a high moisture content (~90%) which makes it more vulnerable to the germs and chemical reactions. The contents of fungus coating are beneficial for shelf-life extension of mushroom. Coated mushrooms loss less moisture and have firmness, better appearance and color features than uncoated mushrooms (Zahedi et al., 1390). Application of food coatings is widely used in order to extend the shelf-life of foods including mushrooms. These methods include improved packaging methods, coated treatment with a solution of anti-microbial, plant extracts and anti-browning agents. The essential oil of thyme plant (Zataria multiflora) contains derivatives of phenol such as carvacrol and thymol (Aligiannis et. al, 2001). The interaction of essential components with each other plays an important role in determining antimicrobial effect. Therefore, the synergistic antimicrobial effects of thymol and carvacrol are enhanced (Didry et. al, 1994). It is worth noting that carvacrol through changes in permeability of H+/K+ ion channel in the cell membrane leads to the suppression of cell dysfunction and ultimately death (Ultee et al, 1999).
Materials and methods: Cap of button mushroom was coated by carboxymethyl cellulose, glycerol and thyme extract. In order to identify the thyme components, GC Mass model VARIAV CP3800 and VF5MS column was used. Also to measure the amount of thymol in thyme extract, HPLC method was used. The cap of button mushroom was sampled in three days (first day, seventh and fourteenth) and cultured in the food culture of PDA and NA.
Results and discussion: The results showed that the bacteria Psudomonas sp. and the mold Aspergillus sp. in various stages of maintenance of the control samples are observed in the warheads. The coating with thyme extract reduced the population of bacteria and mold. The results also showed that the medium level of microbial density was reduced with increasing concentrations of thyme extract. Therefore, the bacteria and mold did not grow in the extract concentration of 5.187 mgL-1. Thymol in a concentration of 70 and 105 ppm inhibited the growth of bacteria and mold, respectively. According to the results, 5.187 ppm thyme extract and 105 ppm thymol are suitable for coating and prevent the growth of bacteria and mold. The population of bacteria and mold in the treated and untreated samples of mushroom cap were identical. It was much more in the control sample with increasing storage time and was maximum at the end of the fourteenth day. The population of bacteria and mold in the coated samples and thyme extracts was lower than control samples. The direct relationship was observed with increasing storage time in the population growth of bacteria and mold. Lyzhyans et al. (2001) showed that the amount of phenolic oil is higher, the more antibacterial activity. The extract of thyme also contain phenolic compounds of thymol and carvacrol which have the most important role in creating antioxidant properties.
