Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Has files: YesSubject: search.filters.subject.High pressure processing

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Innovative yoghurts: novel processing technologies for improving acid milk gel texture
    (Elsevier, 2013) Loveday, SM; Singh, Harjinder; Sarkar, Anwesha
    Consumers are demanding low-fat yoghurts without hydrocolloid stabilisers, but they are unwilling to compromise on texture for the sake of a ‘clean label’. Producing high quality low-fat yoghurt without stabilisers is challenging, and there is a need for new processing technologies to address consumer demand. Here we examine four technologies that can potentially improve the texture of yoghurt: high-pressure processing (HPP), high-pressure homogenisation (HPH), ultrasonic processing (USP) and protein crosslinking with the enzyme transglutaminase (TG). The benefits of HPH and USP depend on fat content, whilst HPP and TG work best in combination with other processes, and have strong potential for improving protein ingredients.
  • Thumbnail Image
    Item
    Effects of high pressure processing and ethyl lauroyl arginate on the shelf-life of ready-to-eat chicken breast roast : a thesis submitted in partial fulfillment of the requirements for the degree of Master of Food Technology, Massey University, Albany, New Zealand
    (Massey University, 2011) Seemeen, Sadia; Seemeen, Sadia
    High pressure processing (HPP) is becoming increasingly popular in commercial food processing as it offers great potential within the food industry. The popularity of the technology is driven by the need to provide minimally processed foods which are safe, wholesome and have extended shelf-life that challenge traditional methods of food processing. High pressures of upto 900 MPa can be used to kill or inhibit microorganisms without changing the nutritional and sensory properties of the food. However, the inherent high resistances of bacterial endospores and food enzymes are the major challenges for the broader application of HPP. Therefore, a hurdle approach is almost axiomatic for significant widespread use of HPP in commercial food processing. Therefore, several antimicrobial compounds have been used in conjunction with HPP in a hurdle approach to improve the overall quality of the products. Ethyl lauroyl arginate (LAE) has not been investigated in combination with HPP. LAE is a novel antimicrobial compound derivative of lauric acid, L-arginine and ethanol, all of which are naturally occurring substances. LAE can extend the shelf-life of products due to its antimicrobial action on spoilage microorganisms during refrigerated storage. Therefore, the objective of this study was to investigate the effects of HPP and LAE on the shelf-life of ready-to-eat (RTE) cooked chicken breast roast during storage at 4°C for 16 weeks. The RTE cooked chicken breast roast was prepared using portions (samples) of freshly marinated chicken breasts, which were cooked to an internal temperature of 75°C for 5 minutes, and then cooled (4°C), sliced (60 mm) and vacuum-packaged. The study was conducted in two phases, each carried out for 16 weeks. The first phase comprised of fourteen unique treatments which were screened by microbial and instrumental analysis. Based on the results of the first phase, five treatments were selected for further work. Similar tests were carried on these treatments, in addition to sensory evaluation. The effects of HPP at 450 MPa and 600 MPa pressures at 1 min, 3.5 min and 5 min hold times respectively, on the shelf-life of RTE sliced chicken breast roast were studied for 16 weeks during storage at 4°C. HPP in combination with LAE (200 ppm) was also investigated using similar treatment pressures, hold times and storage conditions. The effects of LAE (200 ppm & 315 ppm) alone on the shelf life of RTE sliced chicken breast roast was studied for 16 weeks when stored at 4°C. RTE sliced chicken breast roast samples without any preservative and/or HPP treatment served as the controls. Aerobic plate counts (APCs), lactic acid bacteria (LAB) and yeasts and moulds (Y&M) were analyzed in five samples from each of the treatments at regular intervals for upto 16 weeks. Instrumental analyses of color and texture were also conducted on the samples to determine any significant changes during storage at 4°C. Five sample treatments were selected after screening and evaluated by consumer sensory analysis using a 9-point hedonic scale. Analyses for APCs, LAB, Y&M, color and texture were also conducted on the selected samples during refrigerated storage. Survival analysis methodology was used to estimate the consumer sensory shelf-life of the selected treatments at 25% and 50% rejection probability. The results showed the potential of using HPP to extend the microbiological and consumer sensory quality of the products. Samples treated with HPP alone, and HPP in combination with LAE (200 ppm) at 600 MPa inhibited the growth of APCs for 16 weeks when stored at 4°C. However, there was no significant (P>0.05) difference in the microbial shelf-life of samples treated with 200 ppm or 315 ppm LAE. No significant (P>0.05) changes in color and texture were detected in all the treatments. Further, no LAB or Y&M were detected in all the sample treatments for the entire storage period at 4°C. Samples treated with HP at 600 MPa for 1 min and 5 min, HPP+LAE (200 ppm) at 600 MPa for 1 min, LAE at 200 and 315 ppm were evaluated by a consumer sensory panel at different storage times. The results of the consumer sensory analysis showed no changes in color, texture, flavour and freshness of the HP-treated and HPP+LAE (200 ppm)-treated samples. LAE-treated (200 and 315 ppm) samples were not acceptable by a consumer panel at week 12. A maximum sensory shelf-life of >16 weeks at 50% and 13.8 weeks at 25% rejection probability was obtained for samples treated with HPP at 600 MPa for 1 min. Therefore, samples treated at 600 MPa for 1 min had stable sensory properties and were well-accepted by a consumer panel. Also, the samples had good microbiological quality.
  • Thumbnail Image
    Item
    Effects of high pressure processing on carrot tissue : a microstructure approach : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand
    (Massey University, 2011) Trejo Araya, Ximenita Isabelle
    High pressure processing (HPP) has the potential of extending the shelf life of fruits and vegetables whilst preserving nutrients and, importantly, many sensory attributes. Although there is a developing body of literature identifying the advantages of this technology for specific products under specific conditions, it is important to gain further understanding of why undesirable quality changes can also be enhanced by this process. For this reason, this work focused on the changes that HPP promotes within the microstructure of the product (carrots, Daucus carota L.) considering that macroscopic quality is determined at a cellular level. This project was part of a government funded flagship programme at CSIRO Australia, where carrots were chosen as a model product of study. The effects of HPP on this commodity were studied for a range of pressures (100-600 MPa) applied for different holding times (2, 10 and 30 minutes) at ambient temperatures (20 °C). The effects were measured qualitatively and quantitatively by using several microscopy techniques, textural, physiological, biochemical and sensory analysis and through comparison with unprocessed (raw), frozen and heat processed (boiled, steamed and sous vide) carrots. The information collected provided understanding of how different pressure levels affected the physical and physiological responses of carrots based on cellular changes. It also allowed HPP to be positioned within the range of other preservation techniques and to identify relationships between quantitative and sensory quality attributes. The key findings of the study can be divided into HPP effects below and above 200 MPa, as near this pressure a “tissue break point” was identified. Pressures below 200 MPa only slightly affected the cellular structure arrangement according to microscopy techniques, which explained small textural changes, but there was an interesting shift in the metabolic response from aerobic to anaerobic metabolism, presumably due to stress. Above 200 MPa, cell structures became less organized and more disrupted resulting in significant loss of textural characteristics such as hardness and cutting forces compared to raw carrots. This texture loss was related to cellular leakage and loss of turgidity. Considering that ii texture is one of the most important quality attributes in carrots, this study searched for ways of ameliorating the impact of pressure by manipulating turgidity before and after the HPP process. One possibility was by weight loss prior to high pressure processing, but this approach did not help to overcome texture losses after HP treatments above 200 MPa, as structures were irreversibly damaged. Below 200 MPa, cells were still able to regain some turgor pressure (pressure of the cell content against the cell wall); however changes in cell permeability were evident. The addition of calcium chloride solutions in samples high pressure treated at above 200 MPa showed no quantitative texture improvements, confirming membrane damage as the principle mechanism and limited influence of biochemical reactions (pectin degradation by pectin methylesterase) affected cell walls at the conditions studied. Sensory perception by a trained panel showed a positive response toward HPP carrots treated at 600 MPa for 2 minutes. It was interesting to observe no significant differences in many sensory attributes in comparison to raw and sous vide samples, while boiled carrots showed low acceptability due to loss of most volatiles, texture and colour attributes. Storage trials confirmed that high pressure treated samples retained higher quality after 14 days at 4°C by supporting a lower count of lactic acid bacteria and consequently having less ethanol and acetic acid production in the pack. Overall, this research has provided a greater understanding of the application of high pressure on whole vegetable pieces by following microstructural changes. Based on this work, HPP can be considered equivalent to other ‘lightly processed’ technologies such as sous vide and may offer benefits as a complementary process to this or other similar preservation techniques. Future opportunities could be investigated taking advantage of the changes observed in cell permeability (< 200 MPa) for diffusion processes such as salting and candying. Health benefits arising from nutrients being more exposed and preserved after pressure treatments should be further studied by following nutrient availability and body absorption. Furthermore, studies on altering rates of compression or decompression and various pressure cycling effects could assist in optimisation of future commercial HPP applications.