Valuation of strawberry tree fruits (Arbutus unedo L.): from chemical characterization to the development of new products

• Autor(a) principal: Fonseca, Daniela Filipa da Silva
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/13924
• topic: Bioquímica alimentar; Produtos alimentares; Compostos bioactivos - Plantas; Medronho

The strawberry tree (A. unedo L.) is native from the Mediterranean region and it is implanted all over the Portuguese territory. In Portugal, A. unedo fruits have been used in the production of spirit, liqueurs and jam. Considering the wide distribution through Portuguese territory and the limited number of applications, it becomes crucial to value A. unedo fruits. For this purpose it is necessary to understand the chemical composition of A. unedo fruits, particularly during maturation and storage. Therefore, some quality parameters of A. unedo fruits were studied throughout maturation, particularly ºBrix, pH, titratable acidity, total phenolic content and antioxidant activity. In addition, the lipophilic extractives profile was assessed in ripen fruits. To promote the consumption of A. unedo fresh fruits it was studied the effect of cold storage (≈ 5 ºC) using fruits from two different ripeness degrees (19 and 21 ºBrix). The final phase of this thesis was focused on innovation and development of new food products based on A. unedo fruits. This study allowed us to conclude that throughout maturation, the ºBrix content and pH increased, whereas titratable acidity, total phenolic content and the antioxidant activity exhibited no remarkable tendency. Moreover, 41 lipophilic compounds were identified in A. unedo fruits, which belong to 5 chemical families: triterpenoids, fatty acids, sterols, tocopherols and long chain aliphatic alcohols. Triterpenoids represent the major group of identified compounds, (ca. of 70 % of the total amount after alkaline hydrolysis), accounting for between 3196-5494 mg.kg-1 dry weight (dw)). Sterols account for between 217-805 mg.kg-1 dw and fatty acids content varies between 587-2954 mg.kg-1 dw (of which 50 to 78 % corresponded to unsaturated fatty acids). Tocopherols content range between 21-115 mg.kg-1 dw and the long-chain aliphatic alcohols are present in a broader range of 30-453 mg.kg-1 dw. Regarding the effect of cold storage using fruits from two different ripeness degrees, this study shows that the ripen-harvested fruits (21 ºBrix) can be stored up to 17 days while the unripen-harvested fruits (19 ºBrix) can be stored up to 20 days. At the best eating-point, berries from both sampling moments presented similar sensory and chemical characteristics. However, the unripen-harvested fruits were less pasty in the mouth and had significantly lower levels of ethanol. These results suggest that the fruits harvested with ca. of 19 ºBrix, pH 2.7 and titratable acidity of 1 g malic acid per 100 g fresh fruit, contribute to increase their shelf-life while maintaining the firmness and reduced ethanol content. The final phase of this thesis included several stages, namely research on consumer habits of A. unedo fruits by the Portuguese population, the assessment of market opportunities for this type of product, and the design of some novel products that are in line with current market trends. Thus, they were conceived and tested over several formulations of cookies, yoghurts, cereal bars and chocolates. In conclusion, the results obtained are relevant regarding the general chemical characterization of the Serra da Beira region strawberry tree fruits, with emphasis to the lipophilic compounds. The presence of the compounds with reported health benefits, particularly ω-3 and ω-6 fatty acids, phytosterols and triterpenoids, can be a crucial factor on the valuation of A. unedo fruits. Assessing the impact of maturation and cold storage on fresh fruits can be used as a decision tool to support A. unedo fruits producers, in order to reach new consumers and new markets. The last phase of this work also confirms that this fruit has numerous applications in the food area, which are in line with the current market trends.