The Monthly Digest – Food Waste October 2017

Food wastes and by-products
R & D abstracts – October 2017


Putting together the puzzle of consumer food waste: Towards an integral perspective (review)

Although consumer food waste has increasingly received attention in both the public and the scientific domain, its complex nature is far from unraveled. This study aimed to contribute to an integral understanding of possible causal pathways of consumer food waste, by means of a configurative systematic literature review of potential factors of consumer food waste. Insights from 59 scientific articles have been systematically analysed and synthesised. Consumer food waste research is characterised by fragmentation, lack of differentiation, and a relative scarcity of explanatory research into causal mechanisms. Potential factors of consumer food waste have been identified and categorised into behavioural, personal, product and societal factors and subclusters of these categories. On the basis of a synthesised overview of 116 factors, a framework has been developed that conceptualises the generation of consumer food waste in relation to stages of the household food chain. This review sheds light on the context-dependent ways in which proposed factors may be related to food waste and the possibility of parallel causal routes. Food waste factors might exert their influence in unexpected, indirect or multiple ways, possibly explaining contradictory findings. They might interact with other factors or form a condition for other factors to play a role, or might be correlated with food waste without playing a causal role. The framework may facilitate an integral and context-sensitive systems perspective, thereby promoting studies that account for the complexity of consumer food waste and intervention programmes that are better targeted.

Roodhuyzen DMA et al (2017) Trends in Food Science & Technology 68:37-50


Bioplastics of native starches reinforced with passion fruit peel (research)

Industrial passion fruit juice production generates a large amount of passion fruit waste, which contains about 60% of fibers when dried and could be used as reinforcement of thermoplastic starch. This study aimed to develop an extruded starchy bioplastic reinforced with passion fruit peel (Pfp) (0, 4, 10, 16, and 20%), glycerol (60, 64, 70, 76, and 80 wt%), and starch mix (55% corn and 45% cassava) that were processed at varied screw speeds (66, 80, 100, 120, and 134 rpm). The response surface methodology was applied to analyze the effects of Pfp, glycerol, and screw speed. Mechanical properties, contact angle, and water permeability and solubility were the response variables. Addition of Pfp, up to 4%, improved the bioplastic mechanical properties. High addition of Pfp (16 and 20%) combined with the lowest screw speed (66 rpm) reduced bioplastic water solubility. Water vapor permeability slightly increased with the combination of increasing glycerol content and screw speed. Contact angle was not statically affected by the independent variables. The extrusion showed as an interesting tool that provided greater homogeneity of Pfp incorporated in starch bioplastic, though the mix would benefit from finer Pfp particle size distribution.

Moro TMA et al (2017) Food and Bioprocess Technology 10:1798-1808

Pilot scale fermentation coupled with anaerobic digestion of food waste – Effect of dynamic digestate recirculation (research)

The anaerobic digestion in double stage is a known and adopted system, but the process productivity and optimization still remain an aspect to investigate. The accumulation of organic acids (produced during fermentative metabolism) in the first stage generally decrease the pH below the optimal values (5.5). A pre-evaluation strategy by control charts for further pH control is proposed. The process combines in series the 1st Fermentation process and the 2nd Anaerobic Digestion process, using the recirculation of the anaerobic digestion effluent, rich in buffer agents, to control the pH in the 1st stage. The recycle ratio becomes a further operating parameter that should be properly managed. A proper management as dynamic recirculation flow allows to maintain the pH of the first phase to values higher than 5. Specific hydrogen production, specific methane production and volatile fatty acid production; 170 L/kgTVS at 40% H2, 750 L at 67% CH4 and 14 gCOD/L VFA were obtained respectively.

Gottardo M et al (2017) Renewable Energy 114 B:455-463

Effects of organic composition on the anaerobic biodegradability of food waste (research)

This work investigated the influence of carbohydrates, proteins and lipids on the anaerobic digestion of food waste (FW) and the relationship between the parameters characterising digestion. Increasing the concentrations of proteins and lipids, and decreasing carbohydrate content in FW, led to high buffering capacity, reduction of proteins (52.7–65.0%) and lipids (57.4–88.2%), and methane production (385–627 mLCH4/g volatile solid), while achieving a short retention time. There were no significant correlations between the reduction of organics, hydrolysis rate constant (0.25–0.66 d−1) and composition of organics. Principal Component Analysis revealed that lipid, C, and N contents as well as the C/N ratio were the principal components for digestion. In addition, methane yield, the final concentrations of total ammonia nitrogen and free ammonia nitrogen, final pH values, and the reduction of proteins and lipids could be predicted by a second-order polynomial model, in terms of the protein and lipid weight fraction.

Li Y et al (2017) Bioresource Technology 243:836-845

Effects of organic composition on mesophilic anaerobic digestion of food waste (research)

Anaerobic digestion of food waste (FW) has been widely investigated, however, little is known about the influence of organic composition on the FW digestion process. This study aims to identify the optimum composition ratios of carbohydrate (CA), protein (CP) and lipid (EE) for maintaining high methane yield and process stability. The results show that the CA–CP–EE ratio was significantly correlated with performance and degradability parameters. Controlling the CA–CP–EE ratio higher than 1.89 (CA higher than 8.3%, CP lower than 5.0%, and EE lower than 5.6%) could be an effective way to maintain stable digestion and achieve higher methane production (385–627 mL/g VS) and shorter digestion retention (196–409 h). The CA-CP-EE ratio could be used as an important indicator for digestion performance. To effectively evaluate organic reduction, the concentration and removal efficiency of organic compositions in both solid phases and total FW should be considered.

Li Y et al (2017) Bioresource Technology 244:213-224