The application of continuous system of ultraviolet light on various dairy products: Investigation of the formation of undesirable flavors associated with oxidation and revealing the applicability of UV light on a product basis by associating it with shelf life and the impacts of antioxidant activity

Project no. 21883 · Status: Kapanmış (Yayın bekleniyor) · 2020

Summary

Ultraviolet light (UV) is one of the innovative technologies that can be used to ensure food safety without use of chemicals. However, UV light treatment may cause sensory and chemical quality degradation depending on the doses. In this project, dairy products where the mold problem is mentioned by producers and consumers in our country, it is firstly aimed to determine the limit doses on a product basis by using the industry-compatible continuous UV light system and then to reveal the oxidation mechanisms and compounds that cause this undesirable flavor with both chemical and descriptive sensory analyses. In addition, it is aimed to determine its effects on storage period and the usage of antioxidants on this process.  The effects of UV application at different doses for three different dairy product groups (fermented milk product, cheese and high-fat dairy product) were examined in detail. Experiments were conducted on homogenised yoghurt and yoghurt with cream as a fermented dairy product, butter and clotted cream as a high fat dairy product, and ultrafiltrated cheese and kashar cheese (both packaged and unpackaged) as a cheese group. The study was carried out in four stages: 1) Consumer tests was applied to determine the limit doses after the application of different UV light doses to each dairy product, 2) To determine the volatile and flavour compounds, composition, pH, color analysis, ipid and protein oxidation, volatile compounds, descriptive sensory analysis were applied on samples exposed to UV light at low, limit and high doses 3) Chemical and sensory changes during storage were monitored, 4) Chemical and sensory interactions were examined on the antioxidant added product.  High doses UV light application retarded the mold growth during storage. However, high doses application caused high foreign flavour scores and low total impression scores. With high dose application, strong differences were observed in the nutty and creamy taste in homogenised yoghurts, burned protein flavour in yoghurt with cream, almond flavour in clotted cream, cardboard, margarine flavour in butter, burnt feather/burnt protein flavour in cheeses. Differences were observed in PCA diagrams especially in terms of aldehyde content in yoghurts exposed to high doses of UV light and ketones in yoghurts exposed to limit and low doses of UV light. Butter showed a clear separation in terms of ketones, aldehydes and alcohols. It was determined that lipid oxidation levels (TBARS) and carbonyl values indicating protein oxidation degree increased with increasing UV doses in all products during the storage period. Only in butter, the change in protein oxidation level is negligible.  The relationship between the addition of antioxidant (BHA) in different concentration and UV light doses were examined in homogenised yoghurt. The addition of antioxidant limited the lipid oxidation degree of yoghurt, while increased antioxidant activities. Protein oxidation changes in these samples were observed depending on storage time and light dose. However, the foreign flavor was perceived due to the added antioxidant and this could be restricted the the use of antioxidant. As a result, high doses of UV treatment inhibited the growth of mold and yeast, but caused significant foreign flavor formation. Although mold and yeast growth cannot be controlled at doses where undesirable flavor developments are limited, the visual mold growth can be delayed. Therefore, it could be concluded that UV application can be used in dairy products not for the purpose of completely inactivating mold and yeast, but as a support for good hygiene practices.

View details