Quality of pasteurised pineapple juice in the context of the Beninese marketing system

This study is a result of the interdisciplinary project Co-Innovation for Quality in African Food Chains (CoQA). The objective of the research was to improve the quality of pasteurised pineapple juice taking the characteristics of the Beninese pineapple marketing system into account. The specific objectives were to: (i) evaluate the adaptation of Beninese pineapple marketing system to the introduction of the pasteurised pineapple juice business; (ii) assess the extent to which pineapples with physical damage (i.e., of potential less quality) can be used for pineapple juice production; (iii) review the present state-of-the-art on the effect of processing on pineapple juice quality and (iv) evaluate the effect of pasteurisation on the microbiological, physicochemical and nutritional quality of pineapple juice. Chapter 2 of this thesis revealed that wholesalers are the main suppliers to both consumer-merchants and juice manufacturers. However, juice manufacturers’ preferences are different from those of consumer-merchants. More specifically, juice manufacturers prefer large pineapples from 'Kona Sugarloaf' variety and believe that pineapples with physical damage can be used to produce pasteurised pineapple juice. This offers wholesalers the opportunity to sell pineapples that are not demanded by consumer-merchants, but it was found that wholesalers are not engaged in any specific sorting and grading activities to fulfill the wants of the pineapple juice manufacturers. We learned that the reason for the lack of adaptation of the system is caused by the lack of responsiveness of wholesalers due to such factors. The results imply that, in the development context, the adaptation of the marketing system to a development intervention needs to be managed and the effects of interventions need to be considered beyond the primary target group. In other words, complementary marketing interventions should focus on the other actors of the marketing system. As juice manufacturers considered pineapples with physical damage as a possible raw material for pineapple juice production, the possibility of using pineapples with physical damage for pineapple juice production was investigated in chapter 3. Experiments were designed to simulate different types of physical damage and the damaged pineapples were stored for up to 9 days. Physically damaged pineapples stored for up to 9 days at 20 °C showed no adverse effects on the physicochemical characteristics and vitamin C content of fresh pineapple juice (Chapter 3). This suggests that pineapples with those characteristics are suitable for the production of pasteurised juice. Pasteurisation is widely used in juice production. Yet, few studies have investigated the effect of pasteurisation on the quality of pineapple juice (Chapter 4). Due to insufficient proof that pasteurisation has a negative effect on the pineapple juice quality as demonstrated in other juices (Chapter 4), the effect of pasteurisation on the microbiological (mainly yeasts), physicochemical (pH, degree Brix, organic acids, sugars content) and nutritional (vitamin C) quality was investigated in the range of 55 °C to 95 °C. It was found that yeast inactivation in pineapple juice could be described by the Weibull model. The desired 6 log reduction was achieved at 65 °C for 2 min. This result proved that pineapple juice does not need to be pasteurised at a high temperature (85 °C - 20 min) as it is generally applied in Benin and other countries to ensure juice safety. While not expected, vitamin C, the most important nutritional compound in pineapple juice, proved to be stable under the heat treatments investigated in this research. Actually, the degradation rate of vitamin C was below 20 %. Because of this stability, it was not possible to do a kinetic analysis. The physicochemical attributes of pineapple juice, such as pH, degree Brix, organic acid content, were not affected by the pasteurisation treatment. However, at 95 °C, a decrease of sucrose and a simultaneous increase of fructose and glucose contents was noticed, which will probably increase the sweetness of the juice but at the same time favour the Maillard reaction. The fact that HMF was detected in pineapple juice after 30 min at 95 °C, illustrates that the Maillard reaction can affect pineapple juice quality at higher temperatures and longer heat treatments (Chapter 5). Ultimately, pineapple juice should be pasteurised for 2 min at 65 °C to preserve its nutritional (vitamin C) and sensorial quality (colour, taste). Finally, all findings were integrated in chapter 6 and were discussed from an integrative perspective. The thesis has implications for further developing the industry. Currently, the pineapple juice industry is segmented because juice manufacturers differ in many ways. They are living in different locations, have different financial capabilities, different knowledge about juice processing techniques and as a result, they produce pasteurised pineapple juice that is variable in quality. In order to improve their pineapple juice quality and to increase their market access, juice manufacturers can be trained on better pineapple sourcing and pasteurisation techniques. Working more closely together, they can produce products at comparable quality levels using their own equipment. Juice manufacturers who are not willing to collaborate that way can continue to produce and improve their pineapple juice quality by taking the recommendations from this thesis into account.