Preparation and characterisation of avocado cream cheese : effects of different treatments and ratios of avocado puree : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Auckland, New Zealand
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Date
2021
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Massey University
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Abstract
Cream cheese fortified with the addition of avocado puree to improve its nutritional value has not been developed in the food industry, although some studies have researched the possibility of mixing cream cheese products with other fruits. This research study initially aimed to develop a novel cream cheese fortified with avocado puree by finding the appropriate concentration level and a proper processing condition to preserve avocado puree from colour degradation. Four levels of avocado puree (0, 10, 20 and 30%) were investigated in this research to figure out the effect of avocado puree concentrations on cream cheese quality and stability during 28-day storage to select one proper avocado concentration. Then, three different treatments of avocado puree were used for preserving avocado puree in this research, such as i) addition of ascorbic acid, ii) use of high-pressure processing (HPP), and iii) a combination of HPP and ascorbic acid, to investigate whether these treatments had any effects on the avocado puree fortified cream cheese quality and stability during the storage at 4°C for 4 weeks. This research characterised several essential properties of cream cheese, including textural properties, colour stability, microbiological safety, rheological properties, and microstructure. This research aimed to determine the impacts of avocado puree and treated avocado puree on cream cheese's formation, properties, and stability. The cream cheese samples prepared in this research were analysed weekly after preparation and during storage. After researching these basic cream cheese properties, a comprehensive sensory evaluation was conducted to determine consumers preferred avocado puree concentration and processing condition. The results revealed that adding 20% (w/w) of avocado puree in cream cheese and treating it with HPP with the addition of ascorbic acid was the most suitable approach to developing an avocado-fortified cream cheese with desired sensory properties and stability. All physicochemical properties of avocado-fortified cream cheese produced in this research appeared to be significantly affected by avocado levels, especially at 30% concentration, and the different methods of treatment applied to avocado puree had a slight impact on the cream cheese’s properties compared to the control sample (cream cheese with untreated avocado puree, i.e. without HPP and ascorbic acid). As mentioned above, the most appropriate avocado puree concentration in cream cheese was 20% in this study. To be specific, cream cheese added with 20% avocado puree showed relatively stable textural and rheological properties during storage for 4 weeks at 4°C. The sensory evaluation results showed that participants preferred cream cheese containing 20% avocado puree among the four levels of avocado puree (0, 10, 20 and 30%). As for the effects of avocado puree’s processing conditions, adding ascorbic acid as an additive in HPP-treated avocado puree was found to contribute better to lowering colour changes and syneresis in cream cheese samples. This treatment also showed a relatively small impact on changes in the cream cheese’s textural properties and the flow behaviour during storage at 4°C compared to other treatments. Also, it helped cream cheese containing avocado puree only had a slight change in colour with the total colour change (∆E) value of 1.31 and less syneresis (2.63%) after the storage period compared to the other samples. Besides, more than 50% of participants had positive opinions on this sample from sensory evaluation. However, this project did not research other possible concentrations of avocado puree and their treatments, such as adding other kinds of antioxidants, chelating agent and hydrocolloids. These other variables are recommended to investigate for further development. This project provides vital insight into developing a novel avocado-fortified cream cheese and suitable processing to protect avocado puree from degradation in cream cheese during storage.