In this study, a number of experiments were undertaken to investigate possible methods for effective improvement of the texture and flavour of canned late-run chum salmon. These included removal of the skin and bones from the fish, processing of the boneless-skinless steaks in retort pouches, brine treatment using two washes with an 8% salt solution for one hour each time, and a precanning treatment in which the boneless-skinless steaks were soaked in a solution of 10% tripolyphosphate and 2% brine for two minutes. Only fish of advanced sexual maturity were used. The canned salmon was steam processed at 120°C for 65 minutes in an FMC laboratory retort. This was based on a known commercial process for 307 x 115 cans. Heat penetration studies were carried out to design the process schedules for the pouched samples. It was found that the pouched product required 48% less thermal processing time than the canned product to achieve similar lethality. Sensory results showed that the removal of the skin and bones did not produce any significant improvement in the flavour and acceptability of the fish. There was no significant difference between the polyphosphate/brine samples and the untreated (control) samples for all attributes tested. The brine treatment also did not improve the texture of the samples. However, there was less detection of late-run flavour in the brine treated samples when compared to the control. Comments offered by panelists described these samples as having a salty/briny flavour. Pouched samples had a firmer, drier and more fibrous texture than the canned product. They also scored better in terms of late-run flavour. Acceptance of the fish however was only moderate. As a consequence, although this study demonstrated an improvement in the texture and flavour of the pouched late-run chum in comparison to the canned product, it was concluded that a more acceptable pouched product could probably be obtained by using late-run salmon of less advanced sexual maturity. Results of linear regression analysis showed that significant relationships were obtained between sensory firmness, fibrousness and chewiness and instrumental hardness, maximum slope and chewiness. However, none of the sensory parameters were well predicted by the instrumental results. / Land and Food Systems, Faculty of / Graduate

This diploma thesis deals with the determination of some metals in fruit compotes packed in cans. There is described the production of fruit compotes and metal packaging legislation relating to the studied issues, the possibility of contamination of food packaging components, packaging corrosion, metal migration from packaging and techniques used for the analysis of metals in the food industry. Concentrations of metals in 14 different fruit compotes from a commercial network in the Czech Republic were determined by ICP-MS technique in the experimental part. Concentrations of metals were detected only in the juice of stewed fruit, because the juice is in direct contact with the surface of packaging, and metals are transferred first into it. The measured values were compared with the maximum permissible levels of metals in fruit compote determined by European legislation. In some cases there were found higher concentrations of tin, but other metals did not exceed the allowable amounts. Concentrations of metals in the compote varied depending on the kind of compote, which could be due to a different chemical composition of compotes depending on the origin of food and process of the fruit production, or a different cans coating material.

This master’s thesis deals with the issue of the release of tin in canned fruit of used packaging. The theoretical part of the thesis is described canning fruit as raw material, its composition, methods of preservation, basic technological operations fruit processing, manufacture of compote, manufacture of metal packaging, marches corrosive metal packaging, chemical behavior of tin in foods and toxicity, methods for the determination of tin in foods with a focus on optical emission spectrometry with inductively coupled plasma. I the experimental part of the thesis was first ICP-OES optimized before to analysis of the 20 different samples compote purchased in chain stores. Tin concentration was determined by a fixed proportion compote. Measured concentration of tin were compared with the maximum permissible value in canned foods, which is allowed by European legislation. The tin content in all analyzed compote did not exceed the legislative limit of 200 mg/kg. The highest concentration of tin has been measured in sample conserved apricots namely 88,6 ± 2,8 mg/kg.

No description available.

No description available.

No description available.

Shelf-stable canned butter is currently available in retail stores, and many home-preservationists promote home-canning of butter. Non-cultured butter is a low-acid canned food, which would presumably require thermal processing. The lack of a thermal process step in canned butter products raises questions of potential safety, because they are hermetically sealed and generally exhibit anaerobic growth conditions, which are optimal for Clostridium botulinum growth. Without thermal processing, low-acid canned foods (LACF) must have inhibitory factors present to prevent C. botulinum growth. Some potential intrinsic inhibitory factors, or "hurdles", within butter include: reduced water activity (aw), acidity (pH) in cultured products, elevated salt content, and the micro-droplet nature of the aqueous phase in the butter emulsion. It was hypothesized that a normal intact butter emulsion would have sufficient "hurdles" to prevent C. botulinum growth, while a broken butter emulsion would result in a larger aqueous phase that would allow for growth. Butter was prepared using a batch churn method with either inoculated or uninoculated cream. Butter samples with four different salt amounts (0, 0.8, 1.6, & 2.4% added NaCl) were prepared and placed in coated aluminum cans for storage. Samples were stored for 1 or 2 week periods at either 22°C or 41°C and then plated for C. sporogenes growth. Samples stored at 41°C showed a significant increase over those stored at 22°C. This growth increase occurred due to incubation near the optimal growth temperature for C. sporogenes and damage to emulsion structure. Furthermore, sodium chloride (NaCl) addition was found to have a significant effect on C. sporogenes growth, with 0.8 % NaCl promoting more growth than 0%, but with decreases in growth beyond 0.8%. Uninoculated control plates were also found to have bacterial growth. This growth was attributed to other anaerobic bacteria present within the cream. It was concluded that removal of the butter structure "hurdle" could result in C. botulinum growth even at elevated salt levels and therefore home preparation of canned butter is not advisable. It is also possible that commercially canned butter, if heat abused, could potentially allow for C. botulinum growth and therefore consumption is not recommended.

M.S.

No description available.

M.S.